sensory, nervous system*

Episodic memory (explicit, declarative)

Medial temporal lobes, thalamus, fornix, prefrontal cortex memory storage: minutes to years Remembering what you had for breakfast, and what vacation you took last summer

Arrange the following terms to describe the sequence of events after a neurotransmitter binds to a receptor on a postsynaptic neuron.

-Chemical-gated channels open. -graded potential occurs -local current flows -axon hillock reaches threshold -action potential fires at the axon hillock -voltage-gated Na+ channels open -voltage-gated K+ channels open -saltatory conduction occurs -voltage gates Ca+2 channels ope -exocytosis

Acetylcholinesterase (AChE)

1.AChE is an enzyme that inactivates ACh activity shortly after it binds to the receptor. AChE is bound to the postsynaptic membrane. 2.Hydrolyzes ACh into acetate and choline, which are taken back into the presynaptic cell for reuse (reuptake). doc

Lens Accommodation

1.Accommodation: the ability of the lens to keep an object focused on the retina as the distance between the eye and the object moves or changes. a.Contraction of the ciliary muscle allows the suspensory ligaments to relax and the lens to thicken and roundup; for close vision. b.Relaxation of the ciliary muscle pulls on the suspensory ligaments, causing the lens to thin and flatten; for distant vision 2.Near point of vision - the minimum distance from the eyes that an object can be brought into focus 3.Presbyopia - loss of accommodation with age a.Reduced flexibility of the lens a)The lens is flattened for distant vision when the ciliary relaxes and the suspensory ligament is taut. b)The lens is more spherical for close-up vision when the ciliary muscle contracts and the suspensory ligament is relaxed doc The ability of a person's eyes to accommodate can be measure by the near point of vision which is the minimum distance from the eyes at which an object can brought into focus. This distance increases with age; after the age of 45 accommodation is significantly impaired. Loss of accommodation with age is called presbyopia and could be because of reduced flexibility of the lens.

Sensory Coding

Coding: Conversion of stimulus energy into a signal that conveys the relevant information to the CNS and the CNS must distinguish 4 properties of a stimulus: If all stimuli are converted to action potentials in sensory neurons and all action potentials are identical, how the CNS tell the difference between, say, heat and pressure, or between a pinprick to the toe and one to the hand? The attributes of the stimulus must somehow be preserved once the stimulus enters the nervous system for processing. This means that the CNS must distinguish four properties of a stimulus: its nature or modality, Each receptor type is most sensitive to a particular modality of stimulus. 1)Modality: nature of the signal; according to the law of specific nerve energies (a sensory receptor has an appropriate stimulus that it responds to), sensation evoked by sensory neuron is that produced by its normal or "adequate" stimulus. E.g. - a punch to the eye, photoreceptors are stimulated and the brain perceives it as a flash of light. -modality of a stimulus is indicated by which sensory neurons are activated and by where the pathways of the activated neurons terminate in the brain. 2)Intensity: 2 features- frequency of APs elicited by the stimulus and how many receptors are activated and sending signals (population coding) 3)Location:-The location of a stimulus is coded according to which receptive fields are activated. The receptive field for a receptor is a specific physical area that activates that sensory receptor. For example, a touch sensitive neuron in the skin responds to pressure that falls within its receptive field. oSize of the receptive field (2-point threshold) oCoded by the site of the receptor where the signal is originating. oAPs from each receptor travel along unique pathways to a specific region of the CNS. These distinct anatomical pathways are called labeled lines. 4)Duration: Tonic vs. Phasic receptors. Duration of the stimulus is coded by the duration of the Aps in the sensory neuron. In general, a longer stimulus generates more frequent APs. However, some receptors tend to adapt, or cease to respond. They could be phasic or tonic.

Which of the following is NOT an action needed for glutamate to open ion channels?

Cl - must pass through the open channel.

Semantic memory (explicit, declarative)

Inferior temporal lobes memory storage: minutes to years Knowing facts such as what city is the capital, your mother's maiden name, and the different uses of a hammer and a saw

At what region of the neuron are action potentials first produced?

Initial segment of an axon

Dynamic Disequilibrium in the Concentration of Ions in Intracellular and Extracellular Fluids

Inside the cell: more K+ Outside the cell: more Na+ More Cl outside the cell

occitpital lobe

Integration of movements in focusing the eye; correlation of visual images with previous visual experiences and other sensory stimuli; conscious perception of vision

temporal lobe

Interpretation of auditory sensations; storage (memory) of auditory and visual experiences

Comparison of Nicotinic and Muscarinic ACh Receptors

Iontropic: nicotinic Ach receptor, much faster Metalotropic: muscarinic, longer doc*

receptors for itch

Itch Sensation: distinct from pain a.Acute itch (mosquito bite) stimulated by histamine release from mast cells and basophils -can be treated by antihistamines b.Chronic itch stimulated by other chemicals (respond to molecules other than histamine) and does not respond to antihistamines c.Receptors stimulate unmyelinated sensory axons that conduct to the spinal cord

During repolarization of a neuron

K+ leaves the neuron

Match the ganglion cell response to the location of the light stimulus.

Light only shines on the center of an off-center visual field ganglion cell:inhibited Light only shines on the center of an on-center visual field ganglion cell:excited Light only shines on the surround of an off-center visual field ganglion cell: excited Diffuse light shines on both center and surround of an on-center visual field ganglion cell: weak response

Long Term Memory

Long-term memory can be classified into: a)Nondeclarative (implicit): memory of simple skills, how to do things b)Declarative (explicit): memory of things that can be verbalized. People with amnesia have impaired declarative memory; further broken into: 1)Semantic: facts 2)Episodic: events

Central Nervous System

Made up of the brain and the spinal cord Receives input from sensory neurons and directs activity of motor neurons innervating muscles and glands. CNS: integrating center PNS: Afferent division: to nervous system Efferent: away from nervous system

tonic receptor

Maintain a high firing rate as long as the stimulus is applied. E.g. pain -maintain their rate of firing the entire time a stimulus is present

Schwann cells

PNS Also called neurolemmocytes, produce the myelin sheaths around the myelinated axons of the peripheral nervous system; surround all PNS axons (myelinated and nonmyelinated) to form a neurilemmal sheath

Satellite cells

PNS Support functions of neurons within sensory and autonomic ganglia

Receptors for Pain

Pain Receptors: Pain may be produced by nociceptors that are free sensory neuron endings of either myelinated or unmyelinated fibers. Nociceptors a.Nociceptors can be myelinated or unmyelinated. oSudden, sharp pain is transmitted by rapidly conducting myelinated A delta axons of medium diameter neurons. oDull, persistent pain is transmitted by slower conducting thin unmyelinated C axons neurons These afferent neurons synapse in the spinal cord, with glutamate or substance P as the neurotransmitter. Nociceptors initiate protective responses. b.Nociceptors may be activated by chemicals released by damaged tissues, such as ATP, or by pH change or mechanical stimuli

a.Emotional response to pain occurs when information is sent from the thalamus to the anterior cingulate gyrus (part of the limbic system).

Pain is a subjective perception, the brain's interpretation of the sensory information transmitted along pathways beginning at nociceptors. Pain is highly individual and multidimensional, and may vary with a person's emotional state.

Comparison of the Sympathetic and Parasympathetic Divisions

Red: sympathetic Blue: parasympathetic Solid line: pre ganglion Dotted lines: post ganglion neuron Dual innovation: every organ gets sympathetic and parasympathetic (gas and brake) doc

Choose the statement that correctly describes the structure or function of dendrites

Transmit graded electrochemical impulses toward the cell body

Hypothalamus

a.Very important for maintaining homeostasis and regulating the autonomic system. Contains centers for: 1)Hunger/satiety and thirst 2)Regulation of body temperature 3)Regulation of sleep and wakefulness 4)Sexual arousal and performance 5)Emotions of fear, anger, pain, and pleasure 6)Control of the endocrine system 7)Controls hormone secretion from the pituitary gland -Most regulatory power in brain Critical for homeostasis and autonomic nervous system doc

Heroin causes similar, but much stronger effects to the nervous system as endogenous opioids. Heroin's mechanism of action might be that it acts as an

agonist to the endogenous opioid receptors

somatic motor

effector organs: skeletal muscles no ganglia number of neurons from CNS to effector:one type of neuromuscular junction: specialized motor end plate effect of nerve impulse of muscle: excitatory only type of nerve fibers: fast-conducting, thick (9 to 13 um), and myelinated effect of denervation: flaccid paralysis and atrophy

Sympathetic nervous system and preganglionic and postganglionic neuron

preganglionic neuron: - thoracic and lumbar segments of the spinal cord - short axon - neurotransmitter: ACh which acts on nicotinic receptors postganglionic neuron -long axon (or no axon: in adrenal medulla) - neurotransmitter: NE (E, NE, and DA released from the adrenal medulla)

parasympathetic nervous system and preganglionic and postganglionic neuron

preganglionic neuron: - sacral segment of the spinal cord and nuclei of cranial nerves -long axon - neurotransmitter: ACh which acts on nicotinic receptors postganglionic neuron - short axon - neurotransmitter: ACh which acts on muscarinic receptors

The most nearly correct sequence of activation of brain areas when one responds in writingto a verbal command is

primary auditory cortex, Wernicke's area, Broca's area, primary motor cortex.

If a neuron has receptors for a particular neurotransmitter, it will also

respond in a similar way to an agonist of that neurotransmitter

What event(s) could cause presynaptic inhibition?

All of the choices are correct.

Sensory Adaptation: Receptors can be categorized based on how they respond to a stimulus. Phasic Receptors

1)Phasic: respond with a burst of activity when stimulus is first applied but quickly adapt to the stimulus (stimulus continues) by decreasing response -This is called adaptation. The receptor adapts to the stimulus. a)May deliver another burst when stimulus is removed to provide on and off information b)Alert us to changes in the environment c)Allow sensory adaptation - cease to pay attention to constant stimuli. E.g. - smell, touch, temperature -An example is a Pacinian corpuscle, a pressure receptor in the skin. doc 2

Rods and Cones

1. Each rod and cone have an outer and an inner segment a.Outer segment; hundreds of flattened membranous sacs or discs with photopigment molecules -the photopigments required for vision are located in these discs -the photoreceptors continue to add discs at the base of the outer segment as the tips lose their discs to the retinal pigment epithelium through phagocytosis. b.Inner segment that contains the cell organelles 2.Retinal Pigment Epithelium (very important for vision) a.A single layer of cells b.Located under the rods and cones c.Help vision by: oPhagocytozing shed outer discs -cells of the RPE are the most phagocytically active cells in the body and routinely remove 10% of the outer segments every day oAbsorbing scattered light in the retina oDelivering nutrients to the photoreceptors, rods and cones oSuppressing immune attack in retina (making the retina an immunologically privileged site) oParticipating in visual cycle of retinal and contributing to vision oStabilizing ionic concentrations surrounding the photoreceptors doc

Introduction to the Synapse

1.A synapse is the functional connection between a neuron and its target cell a.In the CNS, this second cell will be another neuron. b.In the PNS, the second cell will be a muscle or gland; often called myoneural or neuromuscular junctions 2.When one neuron is signaling another neuron, the 1st is presynaptic neuron, and the 2nd is postsynaptic neuron. a.A presynaptic neuron can signal the dendrite, cell body, or axon of a second neuron. b.There are axodendritic, axosomatic, and axoaxonic synapses. c.Most synapses are axodendritic and are 1 direction 3.Synapses can be electrical or chemical Second cell: target cell? Action potential: presynaptic, axon terminal, postsynaptic neuron

Acetylcholine (ACh)

1.ACh is a neurotransmitter that opens ion channels either directly or indirectly when it binds to its receptor and causes depolarization. 2.Two Types of Acetylcholine Receptors a.Nicotinic ACh receptors, nAChR 1)Can be stimulated by nicotine; ligand-gated ion channel 2)Found in the neuromuscular junction of skeletal muscle, in autonomic ganglia, and in some parts of the CNS 3)Curare is an antagonist b.Muscarinic ACh receptors, mAChR; GPCR 1)Can be stimulated by muscarine (from poisonous mushrooms) 2)Found in CNS and plasma membrane of smooth and cardiac muscles and glands innervated by autonomic motor neurons 3)Atropine is an antagonist

Response to Cholinergic Stimulation

1.ACh released from preganglionic neurons of both the sympathetic and parasympathetic division is stimulatory. 2.ACh from postganglionic parasympathetic neurons is usually stimulatory, but some are inhibitory, depending on receptors. 3.In general, sympathetic and parasympathetic effects are opposite 4.Cholinergic Receptors a.Nicotinic: found in autonomic ganglia oStimulated by Ach from preganglionic neurons oServe as ligand-gated ion channels for Na+ & K+ oBlocked by curare b.Muscarinic: found in visceral organs and stimulated by release of Ach from postganglionic neurons oUse G-proteins and second messenger system oBlocked by atropine

Ganglion

Grouping of neuron cell bodies located outside the CNS

Taste

1.Also called gustation 2.Receptors are called taste buds - each taste bud consists of 50 to 100 specialized epithelial cells with long microvilli that extend out through the pore in the taste bud to the external environment of the mouth where they are bathed in saliva taste buds: Taste evoked by barrel-shaped taste buds. These are located primarily on the dorsal surface of the tongue 3.Taste Cells of Taste Buds: Specialized epithelial cells a)Cells behave like neurons by depolarizing and producing action potentials. b)Cells release neurotransmitters onto sensory neurons. c)Microvilli come into contact with chemicals. d)Each taste bud has taste cells sensitive to each category of tastes. doc Although these sensory epithelial cells are not neurons, they depolarize when stimulated appropriately, produce action potentials, and release neurotransmitters that stimulate sensory neurons associated with the taste buds. Because if these properties these cells are called neuroepithelial cells. Information regarding taste is carried by cranial nerve VII and cranial nerve IX to the medulla oblangata where they synapse. From there, the 2nd order neurons project to the thalamus which is the relay station for most of the senses. Third order neurons from the thalamus convey taste information to the primary gustatory cortex in the insula and to the somatosensory cortex of the postcentral gyrus devoted to the tongue. Information is also sent to the prefrontal cortex, which is important for taste associations and perception of flavor.

Action Potentials

1.At threshold membrane potential (−55mV), voltage-gated Na+ channels open, and Na+ rushes in. As the cell depolarizes, more Na+ channels open, and the cell becomes more and more permeable to Na+. a.This is a positive feedback loop. b.Causes an overshoot of the membrane potential c.Membrane potential reaches +30mV. d.This is called depolarization

Memory

1.Brain Areas a.Studies of people with amnesia reveal that areas of the temporal lobe, hippocampus, caudate nucleus, and dorsomedial thalamus are involved in memory. b.The amygdala is important in learning fear responses. c.The prefrontal cortex may be involved in complex problem solving and working memory-very short-term memory. . Left inferior frontal lobe - mathematical calculations e.Hippocampus is the critical component 1)Acquire new information 2)Consolidation of short-term memory to long-term memory f.Inferior temporal lobe - storage of long-term visual memories -Sleep important for memory Amygdala: learning fear responses Short term: a phone number someone just told you Long term: locker combination, long term associated with learning 2.Types of Memory a.Short-term memory: recent events; transferred to long-term memory through process of memory consolidation 1)Memory consolidation occurs in the medial temporal lobe, hippocampus, and amygdala. 2)Sleep is needed for optimum memory consolidation. b.Long-term memory: Requires actual structural change - Activation of genes, synthesis of mRNA, production of proteins, and formation of new synapses

Neuroglia (Glial Cells)

1.Cells that are non-conducting but support neurons 2.Two types are found in the PNS: a.Schwann cells (neurolemmocytes): form myelin sheaths around peripheral axons b.Satellite cells (ganglionic gliocytes): support cell bodies within the ganglia of the PNS 3.Four types are found in the CNS: a. Oligodendrocytes: form myelin sheaths around the axons of CNS neurons b. Microglia: migrate around CNS tissue and phagocytoze foreign and degenerated material c. Astrocytes: regulate the external environment of the neurons d. Ependymal cells: line the ventricles and secrete cerebrospinal fluid doc

Ion Gating in Axons

1.Changes in membrane potential are controlled by changes in the flow of ions through channels. a.K+ has two types of channels: o Not gated (always open); sometimes called K+ leakage channels o Voltage-gated K+ channels; open when a particular membrane potential is reached; closed at resting potential b.Na+ has mostly voltage-gated channels that are closed at rest; the membrane is less permeable to Na+ at rest. 2.Voltage-Gated Na+ Channels a.These channels open if the membrane potential depolarizes to −55mV. b.This is called the threshold. c.Sodium rushes in due to the electrochemical gradient. d.Membrane potential climbs toward sodium equilibrium potential. e.These channels are deactivated at +30mV. 3.Voltage-Gated K+ Channels a.At around +30mV, voltage-gated K+ channels open, and K+ rushes out of the cell following the electrochemical gradient. b.This makes the cell repolarize back toward the potassium equilibrium potential.

Adrenergic and Cholinergic Synapses

1.Cholinergic Synaptic Transmission a.Acetylcholine (ACh) is the neurotransmitter used by all preganglionic neurons (sympathetic and parasympathetic) b.It is also the neurotransmitter released from most parasympathetic postganglionic neurons. c.Some sympathetic postganglionic neurons (those that innervate sweat glands and skeletal muscle blood vessels) release ACh. d.These synapses are called cholinergic. 2.Adrenergic Synaptic Transmission a.Norepinephrine is the neurotransmitter released by most sympathetic postganglionic neurons. b.These synapses are called adrenergic. doc

Cerebrospinal Fluid

1.Choroid plexus: epithelial cells surrounding capillaries and connective tissue 2.Project into the roofs of the ventricles 3.Secrete cerebrospinal fluid (CSF) into the ventricles and central canal of the cord. 4.CSF is made from blood and is returned to blood Choroid plexus release cerebrospinal fluid, fluid continuous turned over doc

Cones and Color Vision

1.Cones are less sensitive than rods to light; but provide color vision and greater visual acuity. There are 3 different photopsins that give each type of cone the unique ability to absorb light in different wavelengths. 2.Trichromatic vision involves three types of cones. a.S: short wavelengths, blue b.M: medium wavelengths, green c.L: long wavelengths, red -trichromatic color vision, being able to see the primary colors red, blue, and green, and is seen in humans, chimpanzees, gorillas and gibbons. Each type of cone absorbs maximally at different wavelengths or colors. An individual cone's response to light depends on both the wavelength and its intensity. The color we perceive is dependent upon neural computations of the effects of light on the different types of cones. This provides us with the multitude of colors we can perceive. 3.Instead of opsins, photopigments have photopsins with retinene 4.Photopsins vary in each type cone. 5.Cone response depends on wavelength and intensity of light In bright light, the rods are bleached out and color vision with high acuity is provided by the cones. Each type of cone contains retiniene or retinal, like in rhodopsin, but in the cones it is associated with photopsin instead of opsins. Color blindness is caused by the congenital lack of one or more types of cones and is more common in men than women as these genes are on the X chromosomes. People with this condition have only two functioning types of cones (are dichromats), have trouble distinguishing red from green.

Nucleus

Grouping of neuron cell bodies within the CNS

Summary of the Specificity of Sensory Pathways

1.Each receptor is most sensitive to a specific stimulus (adequate stimulus). 2.Each stimulus above threshold initiates APs that are then sent to the CNS. 3.Stimulus intensity and duration are coded in the pattern of APs reaching the CNS. 4.Stimulus location and modality are coded by the type of receptors activated. 5.Each sensory pathway projects to a specific region of the cerebral cortex dedicated to a particular receptive field based on a map of our body in the brain. The size of the cortex dedicated to a body part depends on the sensitivity of the part. 6.Each pathway has a sequence of 3 neurons doc-pic of brain with each body part

Electrical Synapses

1.Electrical synapses occur in smooth muscle and cardiac muscle, between some neurons of the brain, and between glial cells. 2.Cells are joined by gap junctions. doc

Emotions and Memory

1.Emotions sometimes strengthen and other times weaken memory formation. a.If the memory has an emotional component, the amygdala is involved in memory formation. b.Stress impairs memory consolidation in the hippocampus and working memory function of the prefrontal cortex. c.Posttraumatic stress disorder may result in hippocampal atrophy. d.Memories are stored but retrieval is hindered 2.The amygdala and hippocampus have receptors for stress hormones, such as cortisol. a.It is thought that cortisol may strengthen emotional memory formation via the amygdala but weaken hippocampal memory formation and memory retrieval.

Amino Acids as NTs

1.Excitatory NT-glutamate a.An amino acid used as the major excitatory neurotransmitter in the brain b.Produces EPSPs in 80% of the synapses in the cerebral cortex c.Energy required for all the EPSPs constitutes the major energy use in the brain d.Astrocytes take glutamate from the synaptic cleft to increase glucose uptake and increase blood flow by vasodilation e.Glutamate Receptors: All are ion channels; NMDA receptors, AMPA receptors, etc.. NMDA and AMPA work together in Long Term Potentiation Glutamate: amino acid, excitatory Long term potentiation: how learning works, how we learn 2.Inhibitory NTs a.Glycine 1)Produces IPSPs 2)Binding of glycine opens Cl− channels, causing an influx of Cl−. 3)Makes it harder to reach threshold 4)Important in the spinal cord for regulating skeletal muscle movement. This allows antagonistic muscle groups to relax while others are contracting (for example, biceps relax while triceps contract). 5)Also important in the relaxation of the diaphragm, which is necessary for breathing. The poison strychnine blocks glycine receptors, which produces death by asphyxiation. b.GABA

Response to Adrenergic Stimulation Can be Excitation or Inhibition

1.From epinephrine in the blood or norepinephrine from sympathetic nerves 2.Can stimulate or inhibit, depending on receptors a.Stimulation: heart, dilatory muscles of the iris, smooth muscles of many blood vessels (causes vessel constriction) b.Inhibition: Bronchioles in lungs, other blood vessels; inhibits contraction and causes dilation of these structures 3.α and β Adrenergic Receptors a.Two types of α(alpha) - α1 and α2 (prefer norepinephrine) b.Two types of β(beta) - β1 and β2 (prefer epinephrine) c.All act using G-proteins and second messenger systems. 1)β receptors use cAMP. 2)α receptors use a Ca2+ second messenger system.

Classification of Neurons and Nerves

1.Functional classification of neurons-based on direction impulses are conducted a.Sensory neurons: conduct impulses from sensory receptors to the CNS (afferent) b.Motor neurons: conduct impulses from the CNS to target organs (muscles or glands; efferent) doc c.Association/interneurons: located completely within the CNS and integrate functions of the nervous system

Neural Pathways from the Retina

1.Geniculostriate System a.Axons from ganglion cells synapse on the lateral geniculate nucleus of the thalamus by way of the optic chiasma b.Neurons from the thalamus synapse on the striate cortex of the occipital lobe. c.Carries information of "what" is seen Due to refraction of light by the cornea and lens, the right half of the visual field is projected to the left half of the retina of both eyes. The left half of the visual field is projected to the right half of the retina of both eyes. Axons from ganglion cells in the left half of the left retina pass to the left lateral geniculate nucleus of the thalamus. Axons from ganglion cells of the right half of the right retina cross over (decussate) in the X-shaped optic chiasma, also to synapse in the lateral left lateral geniculate body. The left lateral geniculate thus receives input from both eyes that relates to the right half of the visual field. The right lateral geniculate body, similarly, receives input from both eyes that relate to the left half of the visual field. Neurons in both lateral geniculate bodies of the thalamus in turn project to the striate cortex of the occipital lobe. -About 70 to 80% of the axons from the retina are involved in answering the question What is it? And 20 to 30% are involved in answering the questions where is it? doc

Brain

1.Gray matter forms the cortex and deep nuclei; white matter is deep forming tracts 2.The adult brain has 100 billion neurons. 3.It weighs about 1.5 kg (3 to 3.5 pounds). 4.It receives 15% of the total blood flow to the body per minute. 5.Scientists have demonstrated neurogenesis (the formation of new brain cells from neural stem cells) in adult brains within the hippocampus and the lateral ventricles Gray matter is outer, bridges and grooves -unmyelinated axons -processing White matter is inside -axons cover by myelin sheath -connections

The Limbic System

1.Group of brain regions responsible for emotional drives a.Areas of the cerebrum included: cingulate gyrus, amygdala, hippocampus, septal nuclei, anterior insula b.The hypothalamus and thalamus (in the diencephalon) are also part of this system Emotions controlled by the limbic system: a.Aggression: areas in the amygdala and hypothalamus b.Fear: amygdala and hypothalamus c.Hunger/satiety: hypothalamus d.Sex drive: the whole system e.Goal-directed behaviors: hypothalamus and other regions Different structures that are connected together that are responsible for emotional drives

Norepinephrine as a Neurotransmitter

1.In both the CNS and PNS 2.Sympathetic neurons of the PNS use norepinephrine on smooth muscles, cardiac muscles, and glands. 3.Used by neurons of the CNS in brain regions associated with arousal 4.Amphetamines work by stimulating norepinephrine pathways in the brain.

Thalamus and Epithalamus

1.Thalamus a.Paired masses of gray matter b.Relay center through which all sensory information, except smell, is passed to the cerebrum c.Considered to be important for focus and concentration 2.Epithalamus a.Contains the choroid plexus over the third ventricle where cerebrospinal fluid is produced b.Also contains the pineal gland, which secretes the hormone melatonin that helps regulate circadian rhythms Thalamus size of robins egg

Autonomic Neurons

1.Innervate and regulate organs that are not under voluntary control. Effectors include cardiac muscle, smooth muscle, and glands. 2.Unlike somatic motor neurons, autonomic neurons work in chains of 2 neurons. Pre-ganglionic and post-ganglionic -2 neuron chain Autonomic ganglion: where pre and post come together doc Autonomic Neurons 1)Preganglionic neurons: originate in the midbrain or hindbrain or from the thoracic, lumbar, or sacral spinal cord 2)Postganglionic neurons: originate in ganglion Autonomic ganglia are located in the head, neck, and abdomen as well as in chains along either side of the spinal cord Neurotransmitters a.Somatic motor neurons release only acetylcholine which is always excitatory. b.Autonomic neurons release mainly acetylcholine and norepinephrine but may be excitatory or inhibitory

Cerebrum

1.Largest portion of the brain - 80% of the mass 2.Responsible for higher mental functions 3.Consists of a right and left cerebral hemisphere connected internally by the corpus callosum Two hemispheres Most functions are in cerebrum -most highly evolved -large -right and left hemisphere each with 4 lobes Hemispheres connected by corpus callosum doc

Introduction to Vision

1.Light energy transduced into nerve impulses 2.Only a limited part of the electromagnetic spectrum can excite photoreceptors. The eyes transduce energy in the visual range of the electromagnetic spectrum into nerve impulses. Only wavelengths between 400 and 700 nm can be perceived by our photoreceptors. Light: cornea (transparent), pupil (color portion), retina (lies interior surface): retinal pigment epithelium and neural retina (rods (low light) and cones (color and spatial resolution): outer, middle, retinal ganglion cells and those form optic nerve) optic tracts around brain stem to lateral geniculate nuclei, thalamus in optic radiations, primary visual cortex in occipital lobe-perceived as image

Control of ANS by Higher Brain Centers

1.Many visceral functions are regulated by autonomic reflexes. a.Sensory input is sent to brain centers (usually by the vagus nerve), which integrate the information and modify the activity of preganglionic neurons. b.Medulla oblongata controls many cardiovascular, pulmonary, urinary, reproductive, and digestive functions. 2.Regulation by the Medulla a.Higher brain regions regulate the medulla. oHypothalamus: major regulatory center of the ANS - body temperature, hunger, thirst, pituitary gland oLimbic system: responsible for autonomic responses during emotional states (blushing, pallor, fainting, cold sweating, racing heart rate) oCerebellum - motion sickness nausea, sweating, cardiovascular changes oFrontal & temporal lobes - emotion and personality -medulla least evolved?

Basal Nuclei

1.Masses of gray matter located deep in the white matter of the cerebrum 2.Degeneration of dopaminergic neurons from the substantia nigra to the corpus striatum causes Parkinson's disease 3.Involved in maintaining the balance between excitatory and inhibitory motor circuits -Gray matter: mainly cerebral cortex, but some scatter in pockets of cerebrum Loss of dopaminergic neurons in the basal nuclei cause symptoms of Parkinsons Parkinsons: excessive movement of skeletal muscles When one muscle contracts, the partner muscle of joint has to be inhibited (relaxed) -inhibitory and excitatory needed for muscle contraction Most complex thing brain does is regulation of voluntary skeletal muscles doc

Monoamine Neurotransmitters

1.Monoamines are derived from amino acids a.Catecholamines: derived from tyrosine; include dopamine, norepinephrine, and epinephrine b.Serotonin: derived from L-tryptophan c.Histamine: derived from histidine 2. Monoamine Action and Inactivation a.Made in the presynaptic axon, released via exocytosis, diffuse across the synapse, and bind to specific receptors. b.They are quickly taken back into the presynaptic cell (called reuptake) and degraded by monoamine oxidase (MAO). doc

Chemical Synapses

1.Most synapses involve the release of a chemical called a Neurotransmitter (NT) from the axon's terminal boutons. 2.The synaptic cleft is very small, and the presynaptic and postsynaptic cells are held close together by cell adhesion molecules (CAMs). 3.Release of NT a.NT is in synaptic vesicles in the axon terminal. oWhen the action potential reaches the end of the axon, voltage-gated Ca2+ channels open. oCa2+ stimulates the fusion of synaptic vesicles to the plasma membrane and exocytosis of NT. oA greater frequency of action potential results in more secretion of NT and thus greater stimulation of the postsynaptic neuron. Entry of calcium stimulates diffusion of synaptic vesicles and then exocytosis of stored neurotransmitter doc 4.Actions of NT a.NT diffuses across the synapse, where it binds to a specific receptor protein. This results in the opening of chemically regulated ion channels (also called ligand-gated Ion channels). b.Graded Potential oWhen ligand-gated ion channels open, the membrane potential changes depending on which ion channel is open. -Opening Na+ or Ca2+ channels results in a graded depolarization called excitatory postsynaptic potential (EPSP). Moves the membrane potential closer to threshold. -Opening K+ or Cl− channels results in a graded hyperpolarization called inhibitory postsynaptic potential (IPSP). Moves the membrane potential away from threshold doc Neurotransmitter: presynaptic neuron and postsynaptic neuron flow chart *synaptic potentials, integration, impulse conduction

Dual Innervation

1.Most visceral organs are innervated by both sympathetic and parasympathetic neurons. 2.Most of the time these systems are antagonists: a.Heart rate - sym increases, para decreases b.Digestive functions - sym decreases, para increases c.Pupil diameter - sym dilates, para constricts 3.Complementary Effects a.Occur when both divisions produce similar effects on the same target b.Example - Salivary gland secretion: Parasympathetic division stimulates secretion of watery saliva; sympathetic constricts blood vessels so the secretion is thicker. Parasympathetic: constrict pupils Sympathetic: dilate pupils 4.Cooperative Effects a.Occur when both divisions produce different effects that work together to promote a single action. b.Example - Urination: Parasympathetic division aids in urinary bladder contraction; sympathetic helps with bladder muscle tone to control urination.

Myelin sheath in PNS

1.Myelin sheath in the PNS a.All axons in the PNS are surrounded by a sheath of Schwann cells. b.Gaps between Schwann cells, called nodes of Ranvier, are left open. c.Myelinated axons propagate APs faster.

Organs Without Dual Innervation

1.The following organs are innervated by the sympathetic division only: a.Adrenal medulla b.Arrector pili muscles in skin c.Sweat glands in skin d.Most blood vessels 2.Regulated by increase and decrease in sympathetic nerve activity Is this tonic or antagonistic control? 3.Important for body temperature regulation through blood vessels and sweat glands

Synaptic Integration

1.Neural pathways a.Divergence of neural pathways: Axons have collateral branches, so one presynaptic neuron can form synapses with several postsynaptic neurons. b.Convergence of neural pathways: Several different presynaptic neurons (up to a thousand) can synapse on one postsynaptic neuron. 2.Summation a.Spatial summation occurs due to convergence of signals onto a single postsynaptic neuron. All the EPSPs and IPSPs are added together at the axon hillock. -different stimuli arrive at same part of the postsynaptic neuron, EPSPS and IPSPS added together and if sufficient then overcome threshold then action potential b.Temporal summation is due to successive waves of NT release that add together at the initial segment of the axon. -Different stimuli coming together in sufficient amount of time before graded potentials are dissipated

Dopamine as a Neurotransmitter

1.Neurons that use dopamine (dopaminergic neurons) are highly concentrated in the midbrain. 2.Nigrostriatal Dopamine System a.Neurons from the substantia nigra (part of the basal nuclei) of the brain send dopaminergic neurons to the corpus striatum. b.Important step in the control and initiation of movements c.Parkinson disease is caused by degeneration of these neurons. Patients are treated with L-dopa and MAOIs (monoamine oxidase inhibitors). 3.Schizophrenia is associated with excess dopamine. Drugs used to treat are antagonists. L-dopa can cross blood brain barrier Dopamine can't cross blood brain barrier so just giving someone more dopamine didn't help parkinsons

Polypeptides as Neurotransmitters

1.Neuropeptides a.Many chemicals used as hormones or paracrine signals are also found in the brain acting as neurotransmitters. 1)CCK: involved in a feeling of satiety after a meal 2)Substance P: mediates sensations of pain b.Neuromodulators 1)Neurons that release a classical NT like Ach or norepinephrine along with a polypeptide 2)Can release either under different conditions 3)Called synaptic plasticity-capacity for alteration at the molecular level Neuromodulators: long term, modifies how neuron/post synaptic neuron responding to different signal molecules 2.Endogenous Opioids a.Opioid receptors were discovered to bind with drugs such as opium and morphine, resulting in pain relief. b.Endogenous opioids are polypeptides produced by the brain and pituitary gland; includes enkephalin, β-endorphin, and dynorphin c.Opioids also produce euphoria so they may mediate reward pathways; may be related to feeling of well-being after exercise 3.Neuropeptide Y a.Most abundant neuropeptide in the brain b.Plays a role in stress response, circadian rhythms, and cardiovascular control c.Powerful stimulator of hunger; leptin inhibits neuropeptide Y release to suppress appetite d.Works by inhibiting the release of glutamate in the hippocampus (excess glutamate release can cause convulsions)

Endocannabinoids

1.Neurotransmitters that bind to the same receptors that bind to the active ingredient in marijuana (THC) 2.Short fatty acids produced in the dendrites and cell bodies and released directly from the plasma membrane (no vesicle) 3.Retrograde NTs released from the postsynaptic neuron; inhibit further NT release from the presynaptic axon 4.Endocannabinoids can inhibit IPSP-producing NTs from one neuron so EPSP-producing NTs from another neuron can have a greater effect. 5.Endocannabinoids may enhance learning and memory and have been shown to induce appetite; depolarization-induced suppression of inhibition 6.Marijuana use impairs learning and memory because the action of THC is widespread and not controlled.

Nitric Oxide

1.Nitric Oxide a.A gas produced by some neurons in the CNS and PNS from the amino acid L-arginine b.Diffuses across the presynaptic axon plasma membrane (no vesicle) c.Diffuses into the target cell and activates the production of cGMP as a second messenger d.Causes blood vessel dilation and helps kill bacteria e.May also act as a retrograde NT f.In the PNS, nitric oxide is secreted by autonomic neurons onto cells in the digestive tract, respiratory passages, and penis, causing muscle relaxation. oResponsible for an erection oThe drug Viagra works by increasing NO release. High frequency events: rereading notes, same info over and over again- long term potentation

Cranial Nerves

1.Part of the PNS 2.Nerves that arise directly from nuclei in the brain 3.Twelve pairs 4.Most are mixed nerves with both sensory and motor neurons (somatic and parasympathetic) 5.Those associated with vision, olfaction, and hearing are sensory only and have their cell bodies in ganglia located near the sensory organ.

Spinal Nerves

1.Part of the PNS 2.Nerves that arise directly from the spinal cord 3.31 pairs: 8 cervical, 12 thoracic, 5 lumbar, 5 sacral, 1 coccygeal 4.All are mixed nerves that separate near the spinal cord into a dorsal root carrying sensory fibers and a ventral root carrying motor fibers. a.The dorsal root ganglion houses the sensory neuron cell bodies. b.Motor neuron cell bodies are in the ventral gray horns

Diencephalon

1.Part of the forebrain that includes the epithalamus, thalamus, hypothalamus, part of the pituitary gland, and the third ventricle 2.Surrounded by the cerebral hemispheres Third ventricle is where cerebrospinal fluid is produced doc

Synaptic Inhibition

1.Postsynaptic inhibition is produced by inhibitory neurotransmitters such as glycine (spinal cord) and GABA (brain). 2.Hyperpolarizes the postsynaptic neuron and makes it less likely to reach threshold voltage at the axon hillock

Parasympathetic Division

1.Preganglionic neurons come from the brain or sacral region of the spinal cord. a.Also called the craniosacral division b.They synapse on ganglia located near or in effector organs; called terminal ganglia c.Preganglionic neurons do not travel with somatic neurons (as sympathetic postganglionic neurons do). 2.Terminal ganglia supply very short postganglionic neurons to the effectors

Sympathetic Division

1.Preganglionic neurons come from the thoracic and lumbar regions of the spinal cord. Aka the thoracolumbar division 2.Preganglionic neurons synapse in sympathetic ganglia that run parallel to the spinal cord. a.These are called the paravertebral ganglia. b.These ganglia are connected, forming a sympathetic chain of ganglia (sympathetic trunk). doc -Both sides of spinal cord Convergence and Divergence a.Because preganglionic neurons can branch and synapse in ganglia at any level, there is: 1)Divergence: One preganglionic neuron synapses on several postganglionic neurons at different levels. 2)Convergence: Several preganglionic neurons at different levels synapse on one postganglionic neuron. b.Allow the sympathetic division to act as a single unit through mass activation and to be tonically active

Release of neurotransmitter requires

A+B an action potential Ca2+ entry

Lateral Inhibition

1.Receptors where touch is the strongest are stimulated more than areas where touch is lighter 2.Receptors that are most strongly stimulated inhibit those around them. 3.This allows us to perceive well-defined sensations at a single location instead of a "fuzzy" border -When a blunt object touches the skin, many receptive fields are activates, some more than others. The receptive fields closest to where the touch is strongest will be stimulated more than those in neighboring fields. What we perceive is not a fuzzy sensation that you might expect. Instead, only a single touch with well defined borders is felt. This is due to lateral inhibition. Lateral inhibition enhances contrast and makes a stimulus easier to perceive. Lateral inhibition occurs within the CNS. Those sensory neurons whose receptive fields are stimulated most strongly inhibit-via interneurons that pass laterally within the CNS- sensory neurons that serve neighboring receptive fields. Lateral inhibition is a common theme in physiology. In vision, neurons have receptive fields in the retina, and lateral inhibition helps the brain more sharply distinguish borders of light and darkness. In olfaction, lateral inhibition helps the brain more clearly distinguish closely related odors. doc

Synaptic Plasticity

1.Repeated use of a neuronal pathway may strengthen or reduce synaptic transmission in that pathway. 2.When repeated stimulation enhances excitability, it is called long-term potentiation (LTP). a.Found in the hippocampus of the brain where memories are stored b.Associated with insertion of AMPA glutamate receptors c.Improves the efficacy of synaptic transmission that favors transmission along frequently used pathways d.Seen in learning and memory in the hippocampus 3.Long-term depression (LTD) occurs when glutamate-releasing presynaptic neurons stimulate the release of endocannabinoids. -Hippo: short term memories become long term memories -AMPA-Ion channel recepters 4.Both LTP and LTD depend on a rise in calcium ion concentration within the postsynaptic neuron a.Rapid rise leads to LTP b.Smaller but prolonged rise leads to LTD 5.Synaptic plasticity involves enlargement or shrinkage of dendritic spikes -Dendritic spikes: never seen on axons, only on dendrites -Appearance of spikes may correlate with memory

Receptive Fields and Sensory Acuity

1.Sensory neurons are activated by stimuli from a specific physical area called neuron's 'receptive field'. In the simplest case, one receptive field is associated with one sensory neuron also known as the primary sensory neuron which synapses on one CNS neuron known as the secondary sensory neuron. Primary and secondary sensory neurons are also known as first order and second order neurons. Receptive fields frequently overlap with neighboring receptive fields. a.The size of a receptive field depends on the density of receptors in that region of skin. The receptive fields tend to overlap b.There are few receptors in the back and legs, so the receptive fields are large. c.There are many receptors in the fingertips, so the receptive fields are small. d.The more receptors, the smaller the field, the larger the area of the somatosensory cortex e.A small receptive field = greater acuity (sharpness of the sensation) Small receptive fields are found in more sensitive areas of the body. When the receptive fields are smaller there are more sensory neurons and the CNS can more easily pinpoint where the stimulus is originating from leading to a sharper sensation.

ACh in the PNS

1.Somatic motor neurons form interactions called neuromuscular junctions with muscle cells. 2.The area on the muscle cell with receptors for neurotransmitter is called the motor end plate. a.EPSPs formed here are often called end plate potentials (EPP). b.End plate potentials open voltage-gated Na+ channels, which result in an action potential. c.This produces muscle contraction. 3.Interruption of Neuromuscular Transmission a.Certain drugs can block neuromuscular transmission. b.Curare is an antagonist of acetylcholine. It blocks ACh receptors so muscles do not contract. i.Leads to paralysis and death (due to paralyzed diaphragm) ii.Used clinically as a muscle relaxant. 4.Alzheimer Disease Associated with loss of cholinergic neurons that synapse on the areas of the brain responsible for memory 5. Myasthenia Gravis a.Myasthenia gravis an autoimmune disease caused by antibodies that block the nicotinic ACh receptors, particularly in the skeletal muscle cells. b.This produces muscle weakness, especially in the eyes, eyelids, and face. c.Neostigmine and related drugs, which block AChE in the synaptic cleft, can help treat symptoms. d.Treatment may also include steroids. neuromuscular junction

Presynaptic Inhibition

1.Sometimes a neuron synapses on the axon of a second neuron, inhibiting the release of excitatory neurotransmitter from the second neuron. 2.Calcium ion channels are inactivated -Seen in the action of endogenous opioids in pain reduction; inhibits the release of substance P that promotes pain transmission

Neurons

1.Structural and functional units of the nervous system 2.General functions a.Respond to chemical and physical stimuli b.Conduct electrochemical impulses c.Release chemical regulators d.Enable perception of sensory stimuli, learning, memory, and control of muscles and glands 3.Most can not divide, but can repair 4.General Structure of Neurons a.Neurons vary in size and shape, but they all have: i) A cell body that contains the nucleus, and other organelles; cluster in groups called nuclei in the CNS and ganglia in the PNS ii) Dendrites: receive impulses and conducts a graded impulse toward the cell body iii)Axon: conducts action potentials away from the cell body b.Axons i) Vary in length from a few millimeters to a meter ii) Connected to the cell body by the axon hillock where APs are generated at the initial segment of the axon. iii) Can form many branches called axon collaterals iv)Covered in myelin with open spots called nodes of Ranvier 5.Axonal Transport a)Active process to move organelles and proteins from cell body to axon terminals b) Anterograde transport- from cell body to dendrites and axon; c) Retrograde transport- from dendrites and axon to the cell body

General Functions

1.Sympathetic Functions a.The sympathetic division activates the body for "fight or flight" through the release of norepinephrine from postganglionic neurons and the secretion of epinephrine from the adrenal medulla. b.Prepares the body for intense physical activity in emergencies by increasing heart rate and blood glucose levels and by diverting blood to skeletal muscles c.Tonically regulates heart, blood vessels, and other organs 2.Parasympathetic Functions a.The parasympathetic division is antagonistic to the sympathetic division. b.Allows the body to "rest and digest" through the release of ACh from postganglionic neurons c.Slows heart rate, and increases digestive activities

Resting Membrane Potential (RMP 1)

1.The membrane potential of a cell not producing any impulses depends on: a.Ratio of the concentrations of each ion on either side of the membrane b.Specific permeability to each ion 2.K+, Na+, Ca2+ and Cl− contribute to the resting potential. 3.RMP is the Membrane potential of a cell not producing any impulses: a.Since the membrane is most permeable to K+, it has the most influence. b.Change in the permeability of the membrane for any ion will change the RMP. c.A change in the concentration of any ion inside or outside the cell will change the RMP. d.Key to how neurons work. -Potassium ion has the most influence -RMP: negative inside and positive outside -70 Sodium outside Potassium inside =gradient -Leak channels allow sodium or potassium to diffuse down their conc gradient -If potassium was only moving it would stabilize at -90 -Pumps compensate and maintain RMP

Cerebral Cortex

1.The outer region of the cerebrum composed of 2 to 4 mm gray matter with underlying white matter. 2.Characterized by raised folds called gyri separated by depressed grooves called sulci; together called convolutions 3.Each hemisphere is divided by deep sulci or fissures into 4 lobes - Frontal, Parietal, Temporal, Occipital 4.Frontal and Parietal Lobes a.Separated by the central sulcus b.The precentral gyrus is located in the frontal lobe and is responsible for motor control; neurons called upper motor neurons c.The postcentral gyrus is in the parietal lobe and is responsible for somatesthetic sensation (coming from receptors in the skin, muscles, tendons, and joints); called the somatosensory cortex 5.Temporal, and Occipital Lobes a.Temporal lobe: auditory centers b.Occipital lobe: vision and coordination of eye movements c.Insula: encoding of memory and integration of sensory information with visceral responses; receives olfactory, gustatory, auditory, and pain information doc

Spinal Cord

1.The spinal cord is composed of white matter surrounding a gray matter core The gray matter is arranged with a left and right dorsal horn and a left and right ventral horn. 2.The white matter is composed of ascending and descending fiber tracts. a.Ascending tracts carry sensory impulses and are given the prefix spino- with a suffix that indicates the brain region it synapses on; ex - lateral spinothalamic tract b.Descending tracts carry motor impulses and are given the suffix -spinal, and the prefix indicates the brain region they come from; ex - anterior corticospinal tract -Thickness of pinkie finger -Tapering: thinner as it goes down -Opposite composition of gray and white matter -Ascending: sensory impulse from body to cerebral cortex

Reticular Activating System

1.To fall asleep, we must tune out sensory stimuli. When awake, we are alert to sensory stimuli. 2.This depends on the activation and inhibition of the reticular activating system (RAS). -Includes the pons and reticular formation of the midbrain; Many drugs act on the RAS to promote either sleep (Benedryl® and Ambien®) or wakefulness (caffeine). -Loss of these neurons leads to narcolepsy. network of neurons doc

Descending Tracts

1.Two major groups: a.Corticospinal or pyramidal: descend directly without synaptic interruption from the cerebral cortex to the spinal cord b.Extrapyramidal motor tracts: Originate in the brain stem and are controlled by the motor circuit structures of the corpus striatum. Affected in Parkinson's disease. From primary cortex to wherever it needs to go Parkinsons: extrapyramidal symptoms doc

Reflex Arc

1.Unconscious motor response to a sensory stimulus 2.Parts of an arc a.Sensory receptor b.Sensory neuron c.Association neuron in CNS d.Motor neuron e.Effector - muscle or gland that responds 3.Types of arcs a.Somatic reflex - effectors are skeletal muscles b.Autonomic reflex - effectors are smooth muscle, cardiac muscle, or glands -Also known as spinal or cranial reflexes Most reflexes are somatic Reflex are faster cause integrated in spinal cord and info does go to cerebral cortex but response has already gone out from spinal cord doc

ATP and Adenosine as NTs

1.Used as cotransmitters released via vesicles with another neurotransmitter 2.Classified chemically as purines; bind to purinergic receptors a.P1 receptor for ATP b.P2 receptor for adenosine 3.Released with norepinephrine to stimulate blood vessel constriction and with ACh to stimulate intestinal contraction 4.Released by nonneural cells; act as paracrine regulators in blood clotting, taste, and pain

Serotonin as a Neurotransmitter

1.Used by neurons in the raphe nuclei (middle region of brain stem) a.Implicated in mood, behavior, appetite, and cerebral circulation b.The drug LSD and other hallucinogenic drugs may be agonists. c.Serotonin specific reuptake inhibitors (SSRIs) are used to treat depression. E. g. Prozac, Paxil, Zoloft 2.Over a dozen known receptors allow for diversity of serotonin function. 3.Different drugs that target specific serotonin receptors could be given for anxiety, appetite control, and migraine headaches.

Problems of Refractionand the Corrections

1.Visual Acuity: Sharpness of vision - the ability to distinguish between two closely spaced objects; measured at 20 feet with the Snellen Eye Chart -This depends on the resolving power of the visual system, meaning the ability of the visual system to distinguish between two closely related dots. When a person with a normal visual acuity stands 2 ft from a Snellen eye chart, the line of letters marked 20/20 can be read. 2.Myopia - nearsightedness a.Distant images are brought to a point of focus in front of the retina. -If a person has myopia or nearsightedness, this line will appear blurred because the image will be brought to a focus in front of the retina, rather than on the retina. b.Often due to an elongated eyeball; Corrected by concave lens eyeglasses that cause the light to diverge, so that the point of focus is farther from the lens and closer to the retina. 4.Hyperopia - farsightedness a.Distant images are brought to a point of focus behind the retina. -If the eyeball is too short, the line marked 20/20 will appear blurred because the focal length of the lens is longer than the distance to the retina. Thus the focus of the image would have been behind the retina. b.Often due to a short eyeball; corrected by lenses that are convex lenses that converge the light rays, so that the point of focus is brought to the retina. 5.Astigmatism a.Asymmetry of the cornea and/or lens curvatures b.Get several points of focus on the retina; corrected by cylindrical lenses to compensate for the asymmetry of the cornea and lens. doc

Conduction of Nerve Impulses 1+2

1.When an action potential occurs at a given point on a neuron membrane, voltage- gated Na+ channels open as a wave down the length of the axon. 2.The action potential at one location serves as the depolarization stimulus for the next region of the axon. DOC

Refraction of Light & Visual Fields

1.When light passes from one medium to another with a different density, it bends (refraction). -The degree of refraction depends on the density of the cornea, and in addition, the curvature of the cornea. a.Curvature at the point of entry can also bend light. -The curvature of the cornea is constant but the curvature of the lens can vary. b.Greatest refraction is at the air-cornea interface c.Changing the curvature of the lens allows fine control of focus. d.The humors will also contribute to the refraction e.The image is flipped upside down and right to left -The refractive properties of the lens can be a fine control for focusing light on the retina. As a result of refraction, the image formed on the retina is upside down and right to left. a.Visual fields are the part of the external world projected onto the retina is reversed in each eye because of refraction. b.The right side is projected onto the left side of the retina. c.The left side is projected onto the right side of the retina. -The cornea and the lens focus the right half of the visual field onto the left half of the retina of each eye, while the left half of the visual is focused on the right half of each retina. doc

Two Point Touch

2.Two-point Touch Threshold a.Receptive fields can be measured by seeing at what distance a person can perceive two separate points of touch. Sensitivity to touch is shown by a two-point discrimination test. In some areas of skin, such as that on the arms and legs, two pins places within 20 mm of each other are interpreted by the brain as a single pinprick. In contrast, on more sensitive areas of the skin such as the fingertips, two pins separated by as little as 2mm can be perceived as two separate touches. b.Measures tactile acuity c.Important in spacing the raised dots in Braille symbols -This tactile acuity or the sharpness of touch perception is utilized in reading of Braille. Braille symbols are formed by raised dots on the page that are separated from each other by 2.5 mm which is slightly greater than the 2mm two point discrimination threshold in the fingertips. Experienced Braille readers can scan words at about the same speed a sighted person can read aloud- a rate of about 100 words per minute.

Nicotinic ACh Receptors

3. Ligand-Gated Ion Channels a.The receptor protein is also an ion channel; binding of the neurotransmitter directly opens the ion channel. 2 binding sites for Ach b.Binding of 2 acetylcholine molecules opens a channel that allows both Na+ and K+ passage. oNa+ flows in, and K+ flows out. oDue to electrochemical gradient, more Na+ flows in than K+ out. doc

Temperature Receptors

3.Cold Receptors a.There are many more receptors (far more free dendritic endings) that respond to cold than to hot. b.Located in upper region of the dermis close to the epidermis c.Stimulated by cold and inhibited by warm d.Some cold receptors also respond to menthol -Membrane ion channels have recently been discovered that respond to both menthol and cold in the 8 to 28 C range. These are known as transient receptor potential channels or TRP channels. 4.Warm Receptors a.Located deeper in the dermis b.Excited by warming and inhibited by cooling c.Different from receptors that detect painful heat 5.Hot Receptors: Activated at 43⁰C or higher a. Heat experienced as pain by a special nociceptor called capsaicin receptor (membrane protein) -Capsaicin receptor is both an ion channel and a receptor for capsaicin the molecule in chili peppers that causes sensation of heat and pain.

Monoamine Oxidase (MAO) Inhibitors

3.Monoamine Oxidase (MAO) Inhibitors a.Monoamine oxidase (MAO) inhibitors are drugs that block the degradation of monoamine neurotransmitters. b.MAO inhibitors are useful in the treatment of depression, as well as of panic disorder, anxiety, and Parkinson's disease. c.MAO inhibitors have potentially dangerous interactions with over-the-counter tryptophan, St. John's Wort, and foods such as that contain the tyramine. Such interactions could provoke a hypertensive crisis. 4. Monoamine Action a.GPCR b.Cyclic adenosine monophosphate (cAMP) is the most common second messenger for catecholamines.

Midbrain

Also called the mesencephalon. Includes: Sites of visual reflexes, auditory reflexes; connects the cerebrum and cerebellum; involved in motor coordination Substantia nigra: important part of the motor circuit; part of the dopaminergic nigrostriatal system Involved in the behavioral reward system and has been implicated in addiction and psychiatric disturbances The positive reinforcement from abused drugs involves the release of dopamine by axons of the mesolimbic dopamine system. These axons arise in the midbrain and terminate in the nucleus accumbens of the forebrain. Nicotine, opioids (heroin and morphine), cannabinoids (from marijuana), benzodiazepines(Valium and zolpidem), cocaine, and amphetamines are examples of drugs that affect the dopamine systems.

Which is FALSE about the equilibrium potential of a given ion across a membrane? It is a function of the concentration of that ion on both sides of the membrane. It is the potential at which there is no net movement of that ion across the membrane. It is the potential difference across the membrane at which an electric force favoring movement of the ion in one direction is equal in magnitude and opposite in direction to the diffusion force provided by the concentration difference of the ion across t A permeable ion will move in the direction that will tend to bring the membrane potential toward that ion's equilibrium potential. An anion that is in higher concentration inside the cell than outside the cell will have a negative equilibrium potential.

An anion that is in higher concentration inside the cell than outside the cell will have a negative equilibrium potential.

Procedural memory (explicit or implicit; nondeclarative)

Basal nuclei, cerebellum, supplementary motor areas Minutes to years Knowing how to shift gears in a car and how to tie your shoelaces

Effects of Light on the Retina

Bipolar cells can now stimulate ganglion cells. cGMP is required to keep the sodium channels open, and the channels will close of the cGMP is converted into GMP. When a photopigment absorbs light, 11 cis retinal is converted into the all trans form and dissociates from opsin, causing opsin to change its conformation. Each opsin is associated with over a 100 regulatory G proteins known as transducins. Change in opsin conformation by light causes the alpha subunit of the transducin to dissociate, The alpha subunits activate previously inactive cGMP phosphodiesterase enzymes which convert cGMP into GMP. This causes the fall in the concentration of cGMP which closes the sodium channels. Even a single photon of light can block the entry of more than a million sodium ions causing Aps. doc

Which of the following statements related to the visual system is CORRECT?

Bipolar cells spontaneously depolarize in the absence of neurotransmitter secretion from the photoreceptor cells.

Somatic versus Autonomic System

Blue: rest/digest Red: fight/flight Ganglion closer to spinal cord Post ganglion is longer than pre Medulla: anaxonix: epinephrine and nonepinephrine

There are two type of photoreceptors: rods and cones.

Both contain pigment molecules that undergo dissociation in response to light, and it is this photochemical reaction that eventually results in the production of action potentials conducted through the optic nerve.

Hyperpolarization in the postsynaptic cell is caused by

Both inhibitory postsynaptic potentials and movement of K + out of the cell are correct.

Taste and Smell

Both involve Chemoreceptors -Chemoreceptors involved in taste and smell are exteroceptors as they respond to changes in the external environment. Type of exteroceptors as they detect changes from outside the body 1)Taste responds to chemicals dissolved in food and drink. 2)Smell responds to chemical molecules from the air. 3)Olfaction greatly influences gustation -However, odorant molecules have to dissolve in olfactory mucosa before the sense of smell can be stimulated. Also, we are all aware that the sense of olfaction influences the sense of taste. The sense of taste also requires that the food molecules are dissolved in saliva before they can be detected.

Drugs that Affect the Neural Control of Skeletal Muscles

Botulinum toxin Produced by Clostridium botulinum (bacteria) Inhibits release of acetylcholine (ACh) Curare Resin from a South American tree Prevents interaction of ACh with its nicotinic receptor proteins α-Bungarotoxin Venom of Bungarus snakes Binds to ACh receptor proteins and prevents ACh from binding Saxitoxin Red tide (Gonyaulax) algae Blocks voltage-gated Na+ channels Tetrodotoxin Pufferfish Blocks voltage-gated Na+ channels Nerve gas Artificial Inhibits acetylcholinesterase in postsynaptic membrane Neostigmine Nigerian bean Inhibits acetylcholinesterase in postsynaptic membrane Strychnine Seeds of an Asian tree Prevents IPSPs in spinal cord that inhibit contraction of antagonistic muscles

Central nervous system (CNS)

Brain and spinal cord Integration and command center

Respiratory Control Centers in the Brain Stem

Brain stem: pons and medulla

Astrocytes

CNS Cover capillaries of the CNS and induce the blood-brain barrier; interact metabolically with neurons and modify the extracellular environment of neurons 1.Most abundant glial cell 2.Processes with end-feet associate with blood capillaries and axon terminals doc Astrocyte Functions a.Take up K+ from the extracellular environment to maintain ionic environment for neurons b.Take up extra neurotransmitter released from axon terminals, particularly glutamate. Chemicals are recycled. c.Can store glycogen and produce lactate for neurons to use e.Needed for the formation of synapses in the CNS f.Regulate neurogenesis in regions of the adult brain g.Form the blood-brain barrier h.Release transmitter molecules (gliotransmitters) that can stimulate or inhibit neurons; includes glutamate, ATP, adenosine, D-serine 6.Blood-Brain Barrier a.Capillaries in the brain do not have pores between adjacent cells but are joined by tight junctions. b.Substances can only be moved by very selective processes of diffusion through endothelial cells, active transport, and bulk transport c.Movement is transcellular not paracellular d.Astrocytes influence the production of ion channels and enzymes that can destroy toxic substances by secreting glial-derived neurotrophic factor. e.Creates problems with chemotherapy of brain diseases because many drugs can not penetrate the blood-brain barrier.

Oligodendrocytes

CNS Form myelin sheaths around central axons, producing "white matter" of the CNS

Ependymal cells

CNS Form the epithelial lining of brain cavities (ventricles) and the central canal of the spinal cord; cover tufts of capillaries to form choroid plexuses—structures that produce cerebrospinal fluid

Microglia

CNS Phagocytose pathogens and cellular debris in the CNS

Nerve

Cable-like collection of many axons in the PNS; may be "mixed" (contain both sensory and motor fibers)

Nervous System

Central nervous system: brain and spinal cord Peripheral nervous system: cranial and spinal nerves Nervous Tissue is composed of two types of cells: a.Neurons that conduct impulses but generally can not divide. b.Glial cells (neuroglia) that support the neurons and can not conduct impulses but can divide.

Of which categories of receptor types are nociceptors?

Chemoreceptors and Mechanoreceptors

Hindbrain

Composed of pons, cerebellum, and medulla oblangata Has cardiovascular and respiratory control centers The pons houses sensory and motor tracts heading from/to the spinal cord. 1)The trigeminal, abducens, facial, and vestibulocochlear nerves arise from the pons 2)Respiratory control centers are found here 3)Surface fibers connect to the cerebellum Cerebellum 1)Second largest brain structure; gray matter outside, white matter inside 2)Receives input from proprioceptors in joints, tendons, and muscles 3)Works with the basal nuclei and motor cortex to coordinate movement 4)Important for memory, motor learning, emotion and higher functions Medulla oblangata All ascending and descending tracts between the brain and spinal cord pass through the medulla. -Cranial nerves rise from pons Muscle memory: cerebellum

Which of the following statements regarding the precision of locating a somatic stimulus is FALSE?

Convergence of afferent neurons onto common ascending pathways increases acuity.

Current Treatments for AD

Current treatments 1)Acetylcholinesterase inhibitors 2)Antagonists of glutamate 3)Drugs for depression 4)Many others are in clinical trials

Graded Potentials

Depolarization occurs when positive ions enter the cell (usually Na+). Excitatory Hyperpolarization occurs when positive ions leave the cell (usually K+) or negative ions (Cl−) enter the cell. Inhibitory -Once it reaches threshold -55, it fires action potential it's committed -All or none- it will fire a action potential or not -Hyper: brings beyond threshold DOC

Demyelinating Diseases

Diseases in which the myelin sheaths are specifically attacked. •Guillain-Barre syndrome: the T cells of the immune system attack the myelin sheaths of the PNS. This produces rapid onset of symptoms that include muscle weakness. •Multiple sclerosis (MS): produced by an autoimmune attack by T lymphocytes causing lymphocytes and monocyte-derived macrophages to enter the brain and target the myelin sheaths. causing demyelination.

Drugs that Mimic Adrenergic Stimulation

Drugs that mimic adrenergic responses a.Agonists - drugs that promote the process stimulated by the NT b.Antagonists - drugs that block the action of the NT c.Many are useful in medical applications

If there was an increased concentration of K+ outside of the neuron, which would be TRUE?

During an action potential, the neuron would repolarize slowly or stay depolarized. she said Neurons would spontaneously depolarize.?

The Neural Basis of Learning and Memory Long Term Potentiation

During normal low-frequency transmission, glutamate interacts with NMDA and non-NMDA (AMPA) and metabotropic receptors. With high-frequency stimulation other events occur. For LTP to last (Late LTP) the events of Fig. B must also lead to changes in protein synthesis and to formation of new synaptic connections -Eric kandel NMDA and AMPA are both iontropic receptors and when glutamine binds to receptors they open ion channel AMPA: net entry of sodium into post synaptic neuron that results in depolarization of membrane and results in net entry of diusm and expulsion of Mg from NMDA receptor so calcium can enter post synaptic neuron, kinase -new gene transcription and translation... NMDA: calcium ion channels, receptor blocked by magnesium ion Same event happening many times Increase glutamine Increased receptor in post synaptic neuron Increased bind glutamine to ? NMDA receptors Increased depolarization of post synap Increased of calcium in post synap Increased gene translation and transcription Increase synapses being formed Physically changes the brain

Visual Acuity and Sensitivity

Each eye is oriented to ensure that the image falls within the fovea centralis. The fovea is a pinhead-sized pit within the yellow macula region of the retina. The pit or fovea is formed as a result of the displacement of neural layers around the periphery; so that the light falls directly on photoreceptors in the center. The convergence in the fovea is 1:1. The photoreceptors are distributed such that the fovea contains only cones, whereas more peripheral regions of the retina contain both rods and cones. Approximately 4000 cones in the fovea provide input to about 4000 ganglion cells, therefore each ganglion cell has a private line to the visual field. Because of this, the only part of the visual field that is seen very clearly is the tiny part that falls on the fovea. We are usually not aware of this due to very rapid eye movements that continually shift different parts of the visual field onto the fovea. 1.Vision is best at the fovea centralis within the macula lutea a.Here, other layers of the retina are pushed aside, so light falls directly on a group of cones. b.Each cone has a 1:1 relationship with a ganglion cell (usually it is 105:1), which allows great visual acuity. c.Only works in good light. 2.Convergence of lots of rods onto a single ganglion cell increases light sensitivity.

ElectroEncephaloGram

Electroencephalogram (EEG): Electrodes on the scalp detect synaptic potentials produced by cell bodies and dendrites in the cerebral cortex. 1)Four patterns are usually seen: a)Alpha waves: active, relaxed brain. Seen most in frontal and parietal lobes b)Beta waves: produced with visual stimulation and mental activity. Seen most in frontal lobe c) Theta waves: seen during sleep; most from occipital and temporal lobes d) Delta waves: also seen in sleep, from all over the cerebrum doc -Synaptic potentials: graded potentials -have to be strong enough to pass through layers of cerebral cortex, mengigies, skull, scalp, hair, and then detected by electrodes; need to be strong signals -Excitatory or inhibitory Alpha: awake, eyes closed Beta: higher freq than alpha, eyes open and strong mental activity Theta and delta lower freq, delta higher amplitude and lowest freq: slow wave, slow wave sleep: deep sleep that's important for homeostasis

Neurotransmitters and Receptors of Sympathetic and Parasympathetic Pathways

Exceptions: Sympathetic post-ganglionic neurons to sweat glands secrete Ach instead of norepinephrine Sympathetic cholinergic neurons

Muscarinic ACh Receptors

G-Protein Coupled Channels a.The neurotransmitter receptor is separate from the protein that serves as the ion channel. Binding at the receptor opens ion channels indirectly by using a G-protein. Binding of acetylcholine opens K+ channels in some tissues (IPSP) or closes K+ channels in others (EPSP). doc!

tract

Grouping of axons that interconnect regions of the CNS

Pathways for Somatic Perception Project to the Cortex and Cerebellum

How does the information from the primary sensory neuron arrive at the brain? There are ascending pathways in the spinal cord-dorsal column and spinothalamic tract The information from the 4 somatosensory modalities of touch, temperature, proprioception, and nociception travels through the ascending tracts of the spinal cord. The dorsal column and the spinothalamic tract are the 2 main pathways. dorsal: The dorsal column begins with the axon of the first neuron entering the dorsal root and joining the dorsal column white matter in the spinal cord. The axons in the dorsal column terminate in the nuclei of the medulla, where each synapses with the 2nd neuron in the pathway. The 2nd neuron decussates or crosses the midline of the medulla. These axons then continue to ascend the brain stem and terminate in the thalamus, where each neuron synapses with the third neuron in the pathway. The 3rd neuron projects its axons to the postcentral gyrus of the cerebral cortex, where somatosensory stimuli are initially processed, and the conscious perception of the stimulus occurs. spinothalamic tract: also begins with neurons in a dorsal root ganglion, These neurons extend their axons to the dorsal horn where they synapse with the 2nd neuron in the pathway. The name spinothalamic comes from this 2nd neuron, which has its cell body in the spinal cord gray matter and connects to the thalamus. The axon from the 2nd neuron then decussates within the spinal cord and ascend to the brain and enter the thalamus, where it synapses with the 3rd neuron in its pathway. The neuron from the thalamus then projects to the somatosensory cortex. Many pathways also send branches to the cerebellum so that cerebellum can coordinate balance and movement. The different modalities each follow a specific pathway, consisting of a sequence of 3 neurons. doc

Generator (Receptor) Potential

In response to a stimulus, the sensory endings produce local graded changes in the membrane potential. 1.Receptors behave very similarly to dendrites of neurons. 2.Stimuli produce depolarizations called generator potentials. a.Similar to EPSPs; Light touch on a Pacinian corpuscle in the skin produces a small generator potential. -Sensory neurons are pseudounipolar and the Aps produced in response to generator potentials are conducted continuously from the periphery to the CNS. b.Increasing the pressure increases the magnitude of the generator potential until threshold is met and an AP occurs. 3.Pacinian corpuscles are phasic receptors, so if pressure is maintained, generator potential is diminished. -The Pacinian corpuscle in the skin is a pressure receptor. When there is a light touch, a small depolarization or generator potential is produced. Increasing the pressure on Pacinian corpuscle increases the magnitude of the generator potential until the threshold is reached doc 3. When a tonic receptor is stimulated it produces a generator potential that is proportional to the intensity of the stimulus. a.Increased intensity results in increased frequency of action potential after threshold is reached. After a threshold depolarization, increases in the amplitude of the generator potential result in increases in the frequency of Aps. Acting through changes in AP frequency, tonic receptors thus provide information about the intensity of the stimulus.

Ganglion Cell Receptive Fields

In the dark, ganglion cell fires spontaneously at a low rate. When the lights are turned on, firing rate of many ganglion cells increases. But some ganglion cells fire at a greater rate when the light is targeted at the middle of the receptive field. 1.Area of the retina with photoreceptors that send input to that ganglion cell 2.Some ganglion cells have on-center fields: a.A light in the center of the receptive field stimulates the ganglion cell strongly. b.A light toward the edge of the receptive field inhibits the ganglion cell. 3.Some ganglion cells have off-center fields: a.A light in the center of the receptive field inhibits the ganglion cell. b.A light toward the edge of the receptive field stimulates the ganglion cell. 4.This allows enhancement of edges, improving visual clarity doc Each ganglion cell receives information from a particular area of the retina. These areas or receptive fields are roughly circular and are divided into sections: a round center an doughnut shaped surround. This organization allows each ganglion cell to use contrast between the center and the surround to interpret visual information. Strong contrast between the center and surround elicits a strong excitatory response (a series of Aps) or a strong inhibitory response (no Aps). There are 2 types of ganglion cell receptive fields. Some ganglion cells have on-center receptive fields, and they respond strongly when the light is brightest in the center. If the light is brightest in the surround, these ganglion cells are inhibited. The reverse happens in ganglion cells with off-center receptive fields.

Language

Most of the knowledge of how the brain controls language has come from studying people with speech problems called aphasias. Wernicke's area: At the junction of parietal, and temporal lobes, close to the occipital lobe; important for comprehension. Broca's area: In the posterior part of the frontal cortex, responsible for articulation of speech. Receptive Aphasia: Damage to Wernicke's area results in aphasias related to comprehension—individuals have difficulty understanding spoken or written language even though their hearing and vision are unimpaired. May have fluent speech, but scramble words; sentences make no sense. Expressive Aphasia: Due to damage to Broca's area. Individuals have difficulty making the coordinated respiratory and oral movements needed for language, even though they can move their lips and tongues. They understand simple language and know what they want to say, but have trouble forming words. doc speak about something seen, heard, wernicke: choice of words to be spoken, brocas: translate message into pattern -Highly evolved process Aphasia: speech problems See something, decoded by primary visual cortex, info sent to Wernicke's are and then broca's area Hear something, sent to wernickes area and then brocas area Wernicke: words processed Broca: sent words to larynx and produce the response Receptive aphasia: they don't understand that they don't understand, can make up words Expressive: understand language and know what they want to say, but can't say it

Control of Eye Movement

Movements of the eyes are produced by contractions of the extrinsic eye muscles, innervated by neurons from the brain. 1.Produced by contraction of 6 extrinsic eye muscles 2.Three types of movement a.Saccadic eye movement: high-velocity movements that keep the image focused on the fovea centralis (good for reading) -Saccadic eye movements are very high speed movements of both eyes that target an image in the fovea. b.Smooth pursuit movements: match the speed of a moving object -Smooth pursuit movements are slower, and match the speed of moving objects to keep their images in the fovea. c.Vergence movements: allow both eyes to converge so image is at the fovea of both eyes -Vergence movements cause the eyes to converge so that an image of an object is brought to the fovea of both eyes, allowing the object to be seen clearly 3-dimensionally.

Interneuron

Multipolar neuron located entirely within the CNS

Equilibrium Potentials

Nernst Equation for K+ and Na+ Equilibrium potential has to be +66 for sodium to be in equilibrium Equilibrium potential has to be -90mv for potassium to be in equilibrium

Autonomic motor nerve

Nerve that stimulates contraction (or inhibits contraction) of smooth muscle and cardiac muscle and that stimulates glandular secretion

Somatic motor nerve

Nerve that stimulates contraction of skeletal muscles

Peripheral nervous system (PNS)

Nerves, ganglia, and nerve plexuses (outside of the CNS)

Two neighboring neurons are at rest. Neuron A has a resting membrane potential of -80mV, Neuron B has a resting membrane potential of -70mV. Which is likely to be TRUE?

Neuron A has more K+ channels open than Neuron B.

Sensory neuron (afferent neuron)

Neuron that transmits impulses from a sensory receptor into the CNS

Motor neuron (efferent neuron)

Neuron that transmits impulses from the CNS to an effector organ; for example, a muscle

Neurotrophins

Neurotrophins promote neuronal growth in the fetal brain a.Nerve growth factor (NGF) b.Brain-derived neurotrophic factor (BDNF) c.Glial-derived neurotrophic factor (GDNF) d.Neurotrophin-3, neurotrophin-4/5 e. In adults, neurotrophins aid in the maintenance of sympathetic ganglia and the regeneration of sensory neurons.

Smell

Olfactory Apparatus a.Smell is also called olfaction. b.Olfactory receptors located in the olfactory epithelium of the nasal cavity. c.Basal stem cells replace receptors damaged by the environment. Olfactory receptors are bipolar neurons with ciliated dendrites projecting into the nasal cavity. Proteins in the cilia bind to odors. ~380 genes code for ~380 different olfactory receptors. a.One odorant molecule stimulates one protein doc The olfactory apparatus is made up of olfactory sensory neurons (bipolar neurons), supporting sustancular cells, and basal stem cells. Each bipolar sensory neuron has one dendrite that projects into the nasal cavity where it terminates in a knob containing cilia. The plasma membrane of the cilia contains the receptor proteins that bind to odorant molecules. Humans have about 400 different olfactory receptor proteins. Each olfactory sensory neuron expresses only one gene that produces one type of these receptor proteins. The olfactory receptor proteins are GPCR. The second messenger is cAMP which opens ion channels that allow inward flow of sodium and calcium ions. This results in graded depolarization, the receptor potential which can lead to action potentials.

Hypothalamus and Pituitary Gland

Regulation of the Pituitary Gland 1)ADH and oxytocin are transported along the hypothalamo-hypophyseal tract to the posterior pituitary gland, where they are stored until needed. 2)The hypothalamus also produces releasing hormones and inhibiting hormones that are transported along the hypothalamo-hypophyseal portal system to regulate the secretion of pituitary hormones. -ADH: vasopressin ADH and oxytocin produced in hypothalamus *Hypothalamus-hypophyseal tract is made up of neurons Hypothalamo-hypophyseal portal system is made up of blood vessels

action potential: At +30mV, Na+ channels close, and K+ channels open.

Results in repolarization of membrane potential

Effect of Light on the Rods

Rods and cones are activated when light produces a chemical change in pigment molecules in the membranous discs. Each rod contains 1000s of molecules of pigment, rhodopsin. Rhodopsin absorbs green lights best and is made up of the protein opsin and a vit 1.Rods allow black-and-white vision in low light 2.Contain the pigment rhodopsin, which absorbs green light best a.Absorption causes rhodopsin to dissociate into retinaldehyde and opsin. -A derived molecule Retinal also known as retinaldehyde or retinene. b.Retinaldehyde (also called retinal) is derived from vitamin A. c.Called the bleaching reaction 3.Visual Cycle of Retinal a. In rhodopsin, retinal exists in an 11-cis form. b. After bleaching, the retinal is in an all-trans form. To be reincorporated into retinal, it must be converted back into 11-cis. -Retinal can exist in 2 forms: an all trans form and an 11-cis form. It is the 11-cs retinal that is bound to opsin. When light energy is absorbed by retinal, it is converted to the all trans form causing it to dissociate from opsin. This is known as the bleaching reaction. This dissociation changes the ion permeability of the rod plasma membrane and ultimately produces a nerve impulse in the retinal ganglion cells that travels through the optic nerve to the visual cortex in the occipital lobe. c. This occurs in the pigment epithelial cells. 4.Dark Adaptation a.When a person enters a dark room after being in the light, there are fewer photopigments in the rods and cones. b.After about 20 minutes, more visual pigments are produced, and the person's eyes adapt to the dark. -Due to these reactions, rods provide black and white vision under low light intensity conditions. The process of visual cycle of retinal involves the recycling of retinal from the all trans form to the 11-cis form and is carried out by the cis-trans isomerase in the retinal pigment epithelium. -The bleaching reaction in the light lowers the amount of rhodopsin in the rods and visual pigments in the cones. When a person moves from the light into a darkened room, sensitivity to light is low and the vision is poor. -A slow increase in photoreceptor sensitivity, known as dark adaptation, occurs reaching maximal sensitivity in about 20 minutes due to incr. am. of pigments being produced.

The supporting cells that form myelin sheaths on neurons in the PNS are

Schwann cells

Ascending Tracts

Sensory cortex in left hemisphere Right body goes to left brain, decausation Decausation can happen in medulla oblongata or the spinal cord Foot: primary neuron and then sypanses with secondary neuron

Medications used to treat depression most commonly target which neurotransmitter?

Serotonin.

Which of these is NOT a characteristic of Action potentials? They are produced by voltage-gated ion channels. They are conducted without decrement. Sodium and potassium gates open at the same time. The membrane potential reverses polarity during depolarization

Sodium and potassium gates open at the same time

Parietal lobe

Somatesthetic interpretation (for example, cutaneous and muscular sensations); understanding speech and formulating words to express thoughts and emotions; interpretation of textures and shapes

Other Autonomic Neurotransmitters

Some postganglionic autonomic neurons do not release ACh or norepinephrine. a.Called "nonadrenergic, noncholinergic fibers" b.Proposed neurotransmitters include ATP, vasoactive intestinal peptide (VIP), and nitric oxide (NO).

Cerebral Lateralization

Some tasks seem to be performed better by one side of the brain than the other. a.Right hemisphere: visuospatial tasks, recognizing faces, composing music, arranging blocks, reading maps b.Left hemisphere: Language, speech, writing, calculations, understand music Somatesthetic sensation from each side of the body projects to contralateral sides of the postcentral gyrus. Communication between the sides occurs through the corpus callosum; this is severed in some forms of epilepsy. -Right and left hemisphere are identical and lots of communication using the corpus callosum Visual info and auditory info are integrated in different parts of brain and put together to give holistic interpretation and then analysis/comprehension Some processes may be carried out redundantly

Steps of Long-Term Potentiation

Steps of Long-term potentiation (LTP) in the hippocampus: 1)Synapses that are stimulated at a high frequency exhibit increased excitability. 2)In these synapses, glutamate is the NT. 3)The postsynaptic neuron has both AMPA and NMDA receptors for glutamate. 4)Glutamate binds to AMPA receptor, allowing Na+ in. 5)This depolarizes the cell and activates NMDA receptor channels (which were inactive due to a Mg+2 blocking the pore). 6)NMDA allows Ca2+ and Na+ in. 7)The Ca2+ binds to a protein called calmodulin, and together they activate an enzyme called CaMKII. 8)CaMKII causes more AMPA receptors to be inserted into the plasma membrane. This strengthens the synapse-it becomes more sensitive to glutamate release (EPSP). -Magnesium removal involves two things: 1.Binding of glutamine to the NMDA 2.depolarization of plasma membrane

Compare the role of G proteins in the senses of taste and sight. What is the advantage of having G-proteins mediate the effect of a stimulus on a receptor cell? [HInt: This phenomenon is very important in the endocrine system as well. ]

Sweet, umami, and bitter all involve interactions with GPCRs. G proteins are dissociatied which leads to depolarization of the receptor cells and activation of an associated sensory neuron. With the effect of light on the retina, each opsin is assoicated with over a 100 regulatory G proteins known as transducins. Dissociation of rhodopsin activates G-proteins when light hits photoreceptors. The advantage of having G protein mediate the effect of a stimulus on a receptor cell is because the dissociation of g protein complexes releases many g protein subunits leading to an amplification of the signal. Many G proteins may be associated with 1 receptor protein which gives great sensitivity through amplification

"A refractory period occurs following all types of potentials." Is this statement TRUE or FALSE? Explain why. What structures are responsisble for the refractory period?

The absolute refractory period is during the action potential. The relative refractory period is after the Na+ channels have inactivated, they need to reset to the closed position. The voltage-gated channel has 2 gates: activation gate and inactivation gate. At the end of the action potential, when the membrane potential is going back to -70 mV, the Na voltage-gated channels are resetting to the closed state. Some reset quickly while others may take a little longer. This time, before all the Na channels have reset is the relative refractory period. A suprathreshold (or above threshold) stimulus can result in an Action potential during the relative refractory period. It is the presence of refractory periods that prevent the summation of APs and are responsible for the unidirectional propagation of APs.

Which of the following is TRUE about one of the two gates in Na+ channels in axons?

The closing of the inactivation gate stops the depolarization during an action potential

Electrical Activity of theRetinal Cells

The only cells in the retina capable of firing action potentials are the retinal ganglion cells and amacrine cells. The rods and cones, and bipolar cells can only produce graded EPSPs and IPSPs. 1.Dark Current a.In the dark, rhodopsin is inactive; photoreceptors are depolarized at rest and inhibit (hyperpolarize) bipolar cells -In the dark, the photoreceptors are depolarized, and release an inhibitory neurotransmitter that hyperpolarizes the bipolar cells. The inhibited bipolar cells do not release excitatory NTs onto ganglion cells and there are no Aps. It is important to note that light falling on the photoreceptors inhibits the photoreceptors from releasing their inhibitory NT and thus stimulates the bipolar cells. The bipolar cells then secrete excitatory NT onto ganglion cells and Aps are sent to the brain. b.Na+ channels in rods and cones are open, depolarizing the photoreceptor. -A rod or cone has many sodium channels in the plasma membrane of the outer segment, and in the dark, many of these channels are open. As a result, sodium continues to diffuse into the outer segment and into the inner segment. This small flow of sodium in the absence of light is called the dark current. c.This allows the photoreceptor to release inhibiting neurotransmitter in the dark. -Dark current keeps the photoreceptors depolarized in the dark. Light causes the sodium channels to close thus reducing the dark current and causing the photoreceptors to hyperpolarize. 2.When Light Hits Photoreceptors a.Dissociation of rhodopsin activates a G-protein(transducins)/2nd messenger system. oActivation of the enzyme phosphodiesterase converts cGMP to GMP. oThis closes Na+ channels. b.Photoreceptors are hyperpolarized, and inhibition on bipolar cells is lifted. c.Bipolar cells activate ganglion cells that transmit APs to the brain. -Dark current: depolarizes the photoreceptor -Light stops the dark current hyperpolarizing the photoreceptor

Retina

The retina has a one-cell think retinal pigmented epithelium, photoreceptor rods and cones, and layers of other neurons. 1.The retina is a forward extension of the brain, so the neural layers face outward toward the incoming light -The photoreceptors are behind layers of neurons and so light needs to travel through several layers before striking the photoreceptors. -The outer layer of neurons are called retinal ganglion cells and receive synaptic input from bipolar cells, which in turn receive input from rods and cones. The synaptic activity therefore is flowing the opposite direction to the flow of light. 2.Neuron axons in the retina are gathered at a point called the optic disc (blind spot) and exit as the optic nerve -Neurons in the retina contribute fibers that are gathered together at the optic disc, where they exit the retina as the optic nerve along with blood vessels. This region lacks photoreceptors and is known as the blind spot. 3.Blood vessels also enter and leave here. 1. Photoreceptors (rods and cones) are in the inner layer (toward the vitreous body) 2. These synapse on a middle layer of bipolar cells, which synapse on the outer layer of ganglion cells. 3. There are also horizontal cells and amacrine cells within the layers 4. Light flows in towards the retina, while the synaptic activity flows outward. doc

five categories of taste

The specialized epithelial cells are known as taste cells. Different tastes are produced by different chemicals that contact the microvilli of these cells. Five categories of taste: All taste buds present in all areas of tongue; taste influenced by temperature and texture of food 1)Salty 2)Sour 3)Sweet 4)Umami (meaty) that is stimulated by glutamate 5)Bitter -Although it was believed that different regions of the tongue were specialized for different tastes, this is no longer believed to be true. All areas of the tongue are able to respond to all 5 tastes. Not only that, even a single taste bud, which can have taste cells sensitive to all tastes. However, a particular taste cell is sensitive to only one category of taste and activates a sensory neuron that transmits information regarding that specific taste to the brain. -There is a lot of individual variation in the density of taste receptors. However, for everyone, the flavor of food depends not only on the stimulation of taste buds but even more on its stimulation of olfactory receptors. The olfactory sense is stimulated by sniffing and by air pushed up behind the nose when we swallow. -Taste is also influenced by temperature and texture of the food. -The salty taste of food is due to the presence of sodium or some other cations, which activate specific receptor cells for the salty taste. Sodium ion entering the receptor through channels causes depolarization which results in the release of the neurotransmitter. -Sour taste is due to the entry of hydrogen ions. All acids taste sour. -In contrast, sweet, umami, and bitter all involve interactions with GPCRs. G proteins involved in taste are called gustducins. Dissociation of gustducin leads to depolarization of the receptor cell and activation of an associated sensory neuron.

Imagine yourself at the starting block of the 100 meter dash of the olympics. The gun is about to go off in the biggest race of your life. What is the autonomic nervous system doing at this point? How are your organs responding? Provide details.

The sympathetic part of the autonomic nervous system is activated because the excitment of the race activates my fight or flight response. My body prepares for the intense physical activity by increasing my heart rate and blood glucose levels and by diverting blood to skeletal muscles. My body also starts to release norepinphrine from postganglionic neurons and secrete epinephrine from the adrenal medulla. Digestive activites are decreased in order to divert more energy to the physical activity. Sweat glands are activated and start secreting and my blood vessels and lungs dilate so I can breath more. My pupils dilate so I can take in more light.

Which of these is NOT a characteristic of synaptic potentials?

They are all or none.

Sympathetic Neuron Pathways

Tonically active: up or down doc

Motor & Sensory Areas of the Cerebral Cortex

Two maps of the human body Upside down projections of body parts on the maps Body regions with the most density of sensory receptors take up larger areas on the cortex. Body regions with the _____ number of motor innervations represent larger areas in the cerebral cortex. Temporal lobe has auditory centers that are important for the interpretation of auditory and visual information. Occipital lobe is mostly involved with vision and coordination of eye movements. Primary motor cortex: decisions are taken and sent to various voluntary skeletal muscle Primary sensory cortex: info from parts of body are received More sensitive a part of the body is, the more area it has on the sensory cortex (sensitivity) More fine control of the skeletal muscle, the more the area it is devoted to on the motor cortex (control) doc

Frontal lobe

Voluntary motor control of skeletal muscles; personality; higher intellectual processes (for example, concentration, planning, and decision making); verbal communication

Sensory Receptors

We receive a lot of information from the world around us and from inside of us. We are only aware of some of that information. There are many stimuli we are completely unaware of, because we do not have receptors for them. 1.Sensory receptors transduce (change) different forms of energy into nerve impulses. 2.Different modalities of sensations (sound, light, pressure) are processed by differences in sensory receptors, neural pathways and synaptic connections. 3.Some stimuli pass on to the cerebral cortex, where they reach conscious perception but other are acted on subconsciously. 4.At each step along the way, the nervous system can modulate and shape the information. Our perceptions of the world around us - its textures, colors, sounds, warmth, smells and tastes- are created by the brain from electrochemical nerve impulses delivered to it from sensory receptors. All sensory pathways have some features in common. They begin with a stimulus in the form of physical energy that acts on a sensory receptor. The receptor or sensor is a transducer that converts the stimulus to an intracellular signal, which is usually a change in membrane potential. If the stimulus is above threshold, Aps pass along a sensory neuron to the Central nervous system, where they are integrated. Some stimuli pass on to the cerebral cortex, where they reach conscious perception but other are acted on subconsciously. At each step along the way, the nervous system can modulate and shape the information.

You have a patient who, following a stroke, has impaired comprehension of language. TheMRI is likely to reveal damage in which area?

Wernicke's area

Procedural memory (explicit or implicit; nondeclarative)

Words and numbers: prefrontal cortex, Broca's area, Wernicke'sarea Spatial: prefrontal cortex, visual association areas Seconds to minutes Words and numbers: keeping a new phone number in your head until you dial it Spatial: mentally following a route

Rise in Ca+2 Results in Permanent Change in Postsynaptic Neurons

a)Ca2+ enters the nucleus and binds to calmodulin b)Together activate a protein kinase that activates a transcription factor called CREB (cyclic AMP response element binding protein) c)Activate genes to produce mRNA and proteins, including dendritic spines with AMPA receptors inserted. d)A retrograde messenger (most likely NO) is released into the synapse, and the presynaptic axon is changed so that more glutamate can be released and increase LTP e)Endocannabinoids may lift inhibition from GABA-releasing neurons on the synapse, further strengthening it. doc

Pupil and Iris

a.The iris can increase or decrease the diameter of the pupil to increase of reduce the amount of light entering the lens oConstriction of pupil is produced by contraction of circular muscle of the iris in response to parasympathetic stimulation oDilation is produced by the contraction of radial muscles fibers of the dilator pupillae muscle in response sympathetic stimulation doc

Nernst Equation

a.Used to calculate equilibrium potentials b.Based on ion concentrations: Ex=(61/z)log [X0]/[Xi] Ex = equilibrium potential in mV for ion X Xo = concentration of ion outside the cell Xi = concentration of ion inside the cell z = valence of ion (+1 for sodium or potassium)

Olfactory Pathways

a. Olfactory neurons are unmyelinated and synapse on a glomerulus in the olfactory bulb. 1)Each type of olfactory receptor synapses on a particular glomerulus. 2)For example, a flower (complex array of odor molecules) may excite several types of odor receptors. 3)This is coded according to which glomeruli are stimulated. 4)Odor identification is improved by lateral inhibition b.The glomeruli in the olfactory bulb synapse on the primary olfactory cortex of the frontal and parietal lobes c.Interconnections are made with the amydgala, hippocampus, and limbic system through the piriform cortex d.Prefrontal cortex also receives taste which connects the two senses The processing of the olfactory information begins in the olfactory bulb, where the bipolar sensory neurons synapse with spherical glomeruli. Each glomerulus receives input from only one type of olfactory receptor. Identification of an odor is improved by inhibition by GABA released from periglomerular cells that surround the glomerulus. This is a type of lateral inhibition and sharpens odor perception. How can the human brain perceive almost 10,000 odors, if each sensory axon carries information relating to only one of about 400 olfactory receptor proteins? It is possible that the same odorant molecule binds to a specific receptor protein with high affinity but it may also bind less avidly to other receptor proteins. A particular odorant may be perceived by the pattern of activity in the glomeruli of the olfactory bulb. Different odors may have different patterns or 'fingerprints.' The primary olfactory cortex have interconnections with the amygdaloid body, hippocampus, and other parts of the limbic system. The prefrontal cortex receives taste and smell information. The interconnections between the olfactory and limbic system may explain the close relationship between the sense of smell and emotions, and how a particular smell can evoke a emotionally charged memories.

action potentials: coding for stimulus intensity

a.A stronger stimulus will make action potentials occur more frequently. (frequency modulated), resulting in more NT secretion. b.A stronger stimulus may also activate more neurons in a nerve. This is called recruitment. doc

action potential: refractory Periods

a.Action potentials can only increase in frequency to a certain point. There is a refractory period after an action potential when the neuron cannot become excited again. b.The absolute refractory period occurs during the action potential. Na+ channels are inactive (not just closed). c.The relative refractory period is when K+ channels are still open. Only a very strong (suprathreshold) stimulus can overcome this. d.Each action potential remains a separate (discrete), all-or-none event. doc -Always time gap between action potentials i.e. refractory period Pre to post -Action potential goes away cell body towards axon terminal -Absolute refractory period Inactivation of Na+ channels during action potentials

Aging is Associated with Increased Sympathetic Activity

a.Associated with increased levels of sympathetic activity b.Increased sympathetic tone c.Increased risk for hypertension and cardiovascular diseases

Changes in Membrane Potential (RMP 3)

a.At rest, a neuron is considered polarized when the inside is more negative than the outside. b.When the membrane potential inside the cell increases (becomes more positive), this is called depolarization. c.A return to resting potential is called repolarization. d.When the membrane potential inside the cell decreases (becomes more negative), this is called hyperpolarization. Changes can be measured by recording the voltage inside and outside the cell. -Inside is more negative so measures the difference between inside and outside doc

3.Conduction in an Unmyelinated Neuron

a.Axon potentials are produced down the entire length of the axon at every patch of membrane. b.The conduction rate is slow because so many action potentials are generated, each one, an individual event. c.The amplitude of each action potential is the same - conducted without decrement -Decrement: reduction or decrease

Postganglionic Axons Have Varicosities

a.Axons of postganglionic neurons have various swellings called varicosities that release neurotransmitter along the length of the axon. b.Sympathetic and parasympathetic neurons innervate the same tissues but release different neurotransmitters doc

3.Structural Classification of Neurons

a.Based on the number of processes that extend from the cell body. b.Pseudounipolar: single short process that branches like a T to form 2 longer processes; sensory neurons c.Bipolar neurons: have two processes, one on either end; found in retina of eye d.Multipolar neurons: several dendrites and one axon; most common type doc

Cholinesterase Inhibitors

a.Cholinesterase inhibitors are drugs that block the action of AChE, increasing the amount of ACh in the synaptic cleft and enhancing cholinergic synaptic transmission. b.Neostigmine, physostigmine, pyridostigmine, and others are used to treat myasthenia gravis and are important in the treatment of Alzheimer's disease. c.However, nerve gas and organophosphate pesticides can kill their intended victims by inhibiting AChE and overstimulating cholinergic synapses.

chronic pain

a.Chronic pain is also known as pathologic pain or neuropathic pain- most common is diabetic neuropathy (develops as consequence of chronically elevated glucose levels). High blood sugar damages nerves throughout the body. Depending on the affected nerves, diabetic neuropathy can range from pain and numbness in legs and feet to problems with digestive system, urinary tract, blood vessels, and heart. For some, diabetic neuropathy can be very painful and disabling. We do not fully understand what causes neuropathic pain, which makes its treatment difficult.

Lens

a.Composed of layers of living cells that are normally completely clear b.Avascular: lacks blood vessels c. Cell metabolism is very low and anaerobic lens is transparent, composed of clear cells that lack organelles and are connected by gap junctions A cataract is an area of cloudiness in the lens. doc

How an Odorant Molecule Depolarizes an Olfactory Receptor

a.GPCR b.Odor binding activates adenylate cyclase to make cAMP and PPi (pyrophosphate) c.cAMP opens Na+ and Ca2+ channels d.Produces a graded depolarization which stimulates the action potential e.Up to 50 G-proteins may be associated with 1 receptor protein - gives great sensitivity through amplification Dissociation of G protein complexes releases many G protein subunits leading to an amplification of the signal. This might explain the sensitivity of the human nose: we can small a billionth of an ounce of perfume in air. Even then, our sense of smell is vastly inferior to that of other mammals. Each bipolar olfactory neuron has one unmyelinated axon, which projects through the ethmoid bone into the olfactory bulb of the cerebral cortex, where is synapses with 2nd order neurons. Thus the sense of smell is directly transmitted to the cerebral cortex. doc

2.Myelin Sheath in CNS

a.In the CNS, the myelin sheath is produced by oligodendrocytes. b.One oligodendrocyte sends extensions to several axons and each wraps around a section of an axon c.Myelin gives these tissues (axons) a white color = white matter. d.Gray matter is cell bodies and dendrites which lack myelin sheaths doc

Light Enters the Eye Through the Pupil

a.Light passes through the cornea and into the anterior chamber of the eye. b.Next, it passes through the pupil (opening surrounded by a pigmented muscle, the iris), which can dilate or constrict (due to the pigmented iris muscle) to allow more or less light in. -light enters the lens c.Then it passes through the lens, which can change shape to focus the image. d.Then passes through the posterior chamber and the vitreous body e.Finally, it hits the retina, where photoreceptors are found and then absorbed by the pigmented choroid layer. -light from the lens enters the neural layer, which contains photoreceptors, at the back of the eye. This neural layer is the retina. Light that passes through the retina is absorbed by the darkly pigments choroid layer underneath. -While passing through the retina, some of this light stimulates photoreceptors, which in turn activate neurons. Axons of the retinal neurons gather together as the optic nerve and exit the retina through the optic disc also known as the blind spot as this region lacks photoreceptors. The optic disc is also the site of entry and exit of blood vessels. -The structure of the eye is shown here. The outermost layer of the eye is a tough coat of connective tissue called the sclera, seen as the white of the eyes. The sclera is continuous with the transparent cornea.

Sleep

a.May be genetically controlled, although sleep is affected by environmental factors b.Neurotransmitters involved 1)Histamine - wakefulness 2)Adenosine & GABA - sleep 3)Serotonin - induces REM sleep and stimulates non-REM sleep c.Two recognized categories: 1)REM: rapid eye movement; state when dreams occur. Theta waves are seen here. 2)Non-REM: also called resting sleep; divided into four stages, determined by EEG waves seen. Stages 3 and 4 are often called slow-wave sleep, characterized by delta waves. We will die if don't sleep for 2 or 3 nights Non-REM: 1,2,3,4. 4,3,2,1 is one cycle and lasts 90 minutes, then burst of REM for 20 minutes and then back to non-REM for one cycle, then burst of REM 5 or 6 of these cycles in one nights sleep

Alzheimer's Disease (AD)

a.Most common form of dementia b.Characteristics 1)Loss of cholinergic fibers in hippocampus and cerebral cortex 2)Accumulation of extracellular proteins called senile plaques 3)Accumulation of intracellular proteins forming neurofibrillary tangles c.Amyloid precursor protein (APP) is broken down into peptides called amyloid beta (Aβ) (form amyloids senile plaques) d.Tau protein: Normal Tau proteins stabilize microtubules but in AD, they aggregate and form neurofibrillary tangles. e.Toxic changes in Alzheimer's Disease 1)Loss of synapses and dendritic spines 2)Reduced LTP 3)Reduced excitotoxicity leading to neuron apoptosis 4)Mitochondrial release of ROS causing oxidative stress and apoptosis -Dendritic spines have role in memory LTP: learning

4.Conduction in a Myelinated Neuron

a.Myelin provides insulation, improving the speed of cable properties. b.Nodes of Ranvier allow Na+ and K+ to cross the membrane every 1 to 2 mm. c.Na+ ion channels are concentrated at the nodes d.Action potentials "jump" from node to node. e.This is called saltatory conduction.

4.Classification of Nerves

a.Nerves are bundles of axons located outside the CNS b.Most are composed of both sensory and motor neurons and are called mixed nerves. c.Some of the cranial nerves have sensory fibers only. d.A bundle of axons in the CNS is called a tract.

Altering Membrane Potential (RMP 2)

a.Neurons and muscle cells can change their membrane potentials. b.Called excitability or irritability c.Caused by changes in the permeability to certain ions d.Ions will follow their electrochemical gradient which equals a combination of concentration gradient and attraction to opposite charges. e.Flow of ions are called ion currents which occur in limited areas where ion channels are located

action potential: all-or-none law

a.Once threshold has been reached, an action potential will happen. b.The size of the stimulus will not affect the size of the action potential; it will always reach +30mV. c.The size of the stimulus will not affect action potential duration.

action potential: After-Hyperpolarization or Overshoot

a.Repolarization actually overshoots resting potential and gets down to −85mV. b.Na+/K+ pumps can reestablish resting potential after many depolarization- repolarization events. graphs and flowchart on doc

Long Term Potentiation

a.Short-term memory involves a recurrent circuit (reverberating circuit) where neurons synapse on each other in a circle. b.Long-term memory requires a relatively permanent change in neuron chemical structure and synapses. -How do we learn so we can learn better Short term: Continuous activation of synapse

2.Motor Neurons

a.Somatic motor neurons: responsible for reflexes and voluntary control of skeletal muscles b.Autonomic motor neurons: innervate involuntary targets such as smooth muscle, cardiac muscle, and glands i.Sympathetic-emergency situations; "fight or flight" ii.Parasympathetic-normal functions; "rest and digest" doc

referred pain

a.Sometimes somatic pain information can synapse on the same interneuron as a neuron carrying visceral pain information. The brain may interpret heart pain as arm pain, or gallbladder pain as back pain; called referred pain Pain in the heart and other internal organs is often poorly localized and may be felt in areas far removed from the site of the stimulus. For example, the pain of cardiac ischemia (reduction in blood flow to cardiac muscle) may be felt in the neck and down the left shoulder and arm. This referred pain apparently occurs when visceral ad somatic sensory pain inputs converge on a single ascending tract. When painful stimuli arise in visceral receptors, the brain is unable to distinguish visceral signals form the more common signal arising from the somatic receptors. As a result it interprets the pain as coming from the somatic regions rather then the viscera.

action potentials: cable properties of neurons

a.The ability of neurons to conduct charges through their cytoplasm b.Poor due to high internal resistance to the spread of charges and leaking of charges through the membrane c.Neurons could not depend on cable properties to move an impulse down the length of an axon.

Adrenal Glands

a.The adrenal medulla secretes epinephrine and norepinephrine when stimulated by the sympathetic nervous system as a part of mass activation b.Embryologically, the adrenal medulla is a modified ganglion and is innervated directly by preganglionic sympathetic neurons.

Examples of Adrenergic and Cholinergic Agonists and Antagonists receptor types, drug that stimulate, drugs that block

alpha1 receptor-adrenergic; phenylephrine (vasoconstrictor, nasal decongestant) stimulates; phentolamine (short-term control of hypertension) blocks alpha2-adrenergic; clonidine (control of hypertension) stimulates; yohimbine (raise blood pressure; improved male sex function) blocks beta1-adrenergic; dobutamine (increased cardiac contractility and cardiac output) stimulates; metoprolol, atenolol (treatment of hypertension) blocks beta2-adrenergic; terbutaline, albuterol (dilate bronchioles to treat asthma) stimulates muscarinic cholinergic; methacholine; pilocarpine (pilocarpine is used to constrict pupils) stimulates; atropine (reduces secretions of respiratory passages; treats overactive bladder; reduces intestinal contrctions; others) blocks nicotinic cholinergic; nicotine (no therapeutic uses; numberous toxic effects include first stimulation then depression of all autonomic ganglia and neuromuscular junctions stimulates; D-tubocurarine (neuromuscular blockage causing muscle relaxation during surgery and orthopedic procedures) blocks

Chemicals that Are or May Be NTs

amines: histamine, serotonin catecholamines: dopamine, (epinephrine-a hormone), norepinephrine choline derivative: acetylcholine, aspartic acid, GABA (gamma-aminobutyric acid), glutamic acid, glycine polypeptides: glucagon, insulin, somatostatin, substance P, ACTH (adrenocorticotropic hormone), Angiotensis II, endogenous opioids, LHRH, TRH, vasopressin, CCK lipids: endocannabinoids gases: nitric oxide, carbon monoxide purines: ATP

Action potential

amplitude: all-or-none stimulus for opening of ionic gates: depolarization initial effect of stimulus: Na+ channels open cause of repolarization: opening of K+ gates conduction distance: regenerated over length of the axon positive feedback bwtn depolarization and opening of Na+ gates: Yes maximum depolarization: +40 mV summation: no summation---all-or-none refractory period: yes effect of drugs: ACh effects inhibited by tetrodotoxin, not by curare

EPSP: excitatory postsynaptic potential

amplitude: graded stimulus for opening of ionic gates: acetylcholine (ACh) or other excitatory neurotransmitter initial effect of stimulus: common channels for Na+ and K+ open cause of repolarization: loss of intracellular positive charges with time and distance conduction distance: 1 to 2mm; a localized potential positive feedback bwtn depolarization and opening of Na+ gates: No maximum depolarization: close to zero summation: summation of EPSPs, producing graded depolarization effect of drugs: ACh effects inhibited by curare, not by tetrodotoxin

Depolarization of an axon is usually produced by

an inward diffusion of sodium ions

The blood-brain barrier results mostly from the action of ________, a type of neuroglia.

astrocytes

GABA Receptors Contain aChloride Channel

b. GABA 1)Gamma-aminobutyric acid is the most common neurotransmitter in the brain and is used by 1/3 of the brain's neurons. 2)It is inhibitory, opening Cl− channels when it binds to its receptor. 3)It is involved in motor control. Degeneration of GABA-secreting neurons in the cerebellum results in Huntington disease.

An electroencephalogram obtained from an adult who is thinking would probably display many

beta

two point threshold (mm) and body region

big toe-10 sole of foot-22 calf-48 thigh-46 back-42 forehead-18 palm-13 thumb-3 first finger-2

Cells in the retina which connect photoreceptors and ganglion cells are called

bipolar cells

Excessive alcohol intake can cause difficulty maintaining posture and coordinating body movements. This is likely due to alcohol's effect stimulatory effect on GABA-releasing neurons in the

cerebellum

Which is the largest part of the brain?

cerebrum

Sleep Cycles

d.Sleep pattern 1)Sleep cycle repeats every 90 minutes, and most people go through five per night. 2)If allowed to awaken naturally, people usually do so during REM sleep. 3)Slow-wave is prominent in the first part of sleep, while REM is prominent in the second half -As you progress through the night, REM part becomes longer and longer. Brain is very active during REM, beta waves seen (mentally focused) -skeletal muscles are paralyzed, so if you're running in dream you're not actually Non-REM: theta and delta, lower frequencies, slow sleep, restful sleep -tossing and turning is during non-REM -paradoxical sleep doc

Catecholamine Family of Molecules

doc

Hypothalamus, Pons, and Medulla Initiate Autonomic, Endocrine, and Behavioral Responses

doc

Saltatory Conduction in a Myelinated Neuron

doc

K+ is the Ion Primarily Responsible for RMP

doc hyperkalemia hypokalemia

Receptor Activity in Autonomic Regulation

doc*

REM and Non-REM Sleep

e.REM sleep 1)Some brain regions are more active during REM sleep than during the waking state. 2)The limbic system (involved in emotion) is very active during REM sleep. 3)Breathing and heart rate may be very irregular. 4)Benefits consolidation of nondeclarative memories f.Non-REM sleep 1)As you fall asleep, neurons decrease their firing rates, decreasing blood flow and energy metabolism. 2)Breathing and heart rate are very regular. 3)Non-REM sleep may allow repair of metabolic damage done to cells by free radicals and allows time for the neuroplasticity mechanisms needed to store memories. 4)Benefits consolidation of spatial and declarative memories

autonomic motor

effector organs: cardiac muscle, smooth muscle, and glands presence of ganglia: cell bodies of postganglionic autonomic fibers located in paravertebral, prevertebral (collateral), and terminal ganglia number of neurons from CNS to effector: two type of neuromuscular junction: no specialization of postsynaptic membrane; all areas of smooth muscle cells contain receptor proteins for neurotransmitters effect of nerve impulse of muscle: either excitatory or inhibitory type of nerve fibers: slow-conducting; preganglion fibers lightly myelinated but thin (3 um); postganglionic fibers unmyelinated and very thin (about 1.0 um) effect of denervation: muscle tone and function persist; target cells show denervation hypersensitivity

Adrenergic Effects of sympathoadrenal in Different Organs adrenergic receptor

eye; contraction of radical fibers of the iris dilates the pupils; alpha1 receptor heart; increase in heart rate and contraction strength; beta1 primarily receptor skin and visceral vessels; arterioles constrict due to smooth muscle contraction: alpha1 receptor; arterioles dilate due to hormone epinephrine; beta2 receptor lungs; bronchioles (airways) dilate due to smooth muscle relaxation; beta2 receptor stomach and intestine; contraction of sphincters in digestive tract slows passage of food; alpha1 receptor liver; glycogenolysis and secretion of glucose; alpha1 and beta 2 receptors

The optic nerves from each eye cross at the optic chiasm, so all visual information from the right eye is received by the left side of the brain.

false

cutaneous receptors receptor, structure, sensation, location

free nerve endings; unmyelinated dendrites of sensory neurons; light touch, hot, cold, nociception (pain); around hair follicles, throughout skin merkel's discs; expanded dendritic endings associated with 50 to 70 specialized cells; sustained touch and indented depth; base of epidermis (stratum basale) ruffini corpuscles (endings); enlarged dedritic endings with open, elongated capsule; skin stretch; deep in dermis and hypodermis meissner's corpuscles; dendrites encapsulated in connective tissue; changes in texture, slow vibrations; upper dermis (papillary layer) pacinian corpuscles; dendrites encapsulated by concentric lamellae of connective tissue structures; deep pressure, fast vibrations; deep in dermis

Mutation of the N-methyl-D-aspartate (NMDA) receptor would affect the ability of ________ to regulate neural function.

glutamate

The ________________ is best described as "an interconnected group of brain structures including parts of the frontal lobecortex, temporal lobe, thalamus, and hypothalamus, that is associated with learning, emotional experience, and behavior?"

limbic system

insula

memory; sensory (principally pain) and visceral integration

A drug that affects both divisions of the autonomic system is going to bind to, or block, which type of neurotransmitter receptor?

nicotinic acetylcholine receptor

Cholinergic Receptors and Responses to ACh receptor, tissue, response, mechanisms

nicotinic receptor; skeletal muscle; depolarization, producing action potentials and muscle contraction; ACh opens cation channel in receptor nicotinic receptor; autonomic ganglia; depolarization, causing activation of postganglionic neurons; ACh open cation channel in receptor muscarinic (M3, M5); smooth muscle, glands; depolarization and contraction of smooth muscle, secretions of glands; ACh activates G-Protein coupled receptor, opening Ca2+ channels and increasing cytosolic Ca2+ muscarinic (M2); heart; hyperpolarization, slowing rate of spontaneous depolarization; ACh activates G-portein coupled receptor, opening channels for K+

Categories of SensoryReceptors a.According to the type of signal they transduce:

oChemoreceptors: sense chemical stimuli in the environment (taste, smell) or blood - e.g taste buds, olfactory epithelium; oPhotoreceptors: sense light -the rods & cones in the retina; oThermoreceptors: respond to cold or heat oMechanoreceptors: stimulated by mechanical deformation of the receptor plasma membrane, e.g. touch and pressure receptors in the skin and hair cells within the inner ear. (touch, hearing) Sensory receptors can be classified structurally as dendritic endings of sensory neurons or whole cells.

Categories of Sensory Receptors d.Receptors can be classified by the origin of the information:

oExteroceptors: respond to stimuli from outside the body; includes cutaneous receptors and special senses oInteroceptors: respond to internal stimuli; found in organs; monitor blood pressure, pH, and oxygen concentrations. -Interoceptors include mechanoreceptors and chemoreceptors.

5.Action Potential Conduction Speed

oIncreased diameter of the neuron reduces resistance to the spread of charges via cable properties. oMyelination increases the speed because of saltatory conduction Thin, unmyelinated neuron speed 1.0m/sec Thick, myelinated neuron speed 100m/sec doc

categories of sensory receptors b.Nociceptors

oPain receptors that depolarize in response to stimuli i.e. when tissues are damaged oStimuli can include heat, cold, pressure, chemicals (nitric oxide), acid, and ATP oGlutamate and substance P are the main neurotransmitters. oPerception of pain can be enhanced or reduced by emotions, concepts, and expectations. oPain reduction (analgesia) depends mainly on endogenous opioids including beta endorphin but nonopioid mechanism also functions to reduce pain perception. Sensory neurons enter the spinal cord in the dorsal roots and relay the information to the brain.

Categories of Sensory Receptors c.Receptors can be classified by the type of information they deliver to the brain:

oProprioceptors: found in muscles, tendons, and joints. Provide a sense of body position and allows fine muscle control. -Proprioceptors include muscle spindles, Golgi tendon organs, and joint receptors. These provide a sense of body position and allow fine control of skeletal movements. oCutaneous (skin) receptors - touch and pressure receptors, heat and cold receptors, and pain receptors oSpecial senses - vision, hearing, taste, smell, equilibrium

Processes that Influence the Resting Membrane Potential

picture! fixed anions and unequal permeabilities of plasma membrane to diffusible ions Na+/K+ fixed anions: can't move if plasma membrane is more permeable to potassium ions than sodium ions that means it has more potassium leak channels asymmetrical dissolution: uneven distribution of ions across the plasma membrane

Cutaneous Receptors

several different types of receptors in the skin, each of which is specialized to be maximally sensitive to one modality of sensation. A receptor will be activated when a given area of the skin is stimulated; this area is the receptive field for that receptor. Receptive fields can overlap. The cutaneous sensations of touch, pressure, heat and cold, and pain are mediated by the dendritic nerve endings of different sensory neurons. 1.Pain, cold, and heat receptors are naked dendrites of sensory neurons. 2.Touch and pressure receptors have special structures around their dendrites. a.Merkel's disks b.Meissner's corpuscles c.Pacinian corpuscles d.Ruffini corpuscles

Identify sites in the figure where only graded potentials can occur.

sites 1 and 3

Muscarinic ACh Receptors (mAChR) Steps in the Activation and Deactivation of G-Proteins

step 1: When the membrane receptor protein is not bound to its regulatory molecule ligand, the alpha, beta, and gamma G-protein subunits are aggregated together and attached to the receptor; the alpha subunit binds GDP. Step 2: When the ligand (neurotransmitter or other regulatory molecule) binds to the receptor, the alpha subunit releases GDP and binds GTP; this allows the alpha subunit to dissociate from the beta-gamma subunits. Step 3: Either the alpha subunit or the beta-gamma complex moves through the membrane and binds to a membrane effector protein (either an ion channel or an enzyme). Step 4: Deactivation of the effector protein is caused by the alpha subunit hydrolyzing GTP to GDP. Step 5: This allows the subunits to again reaggregate and bind to the unstimulated receptor protein (which is no longer bound to its regulatory molecule ligand).

chemoreceptors

stimulus: dissolved chemicals mechanism: chemical interaction affects ionic permeability of sensory cells ex: smell and taste (exteroceptors) osmoreceptors and carotid body chemoreceptors (interoreceptors)

photoreceptors

stimulus: light mechanism: photochemical reaction affects ionic permeability of receptor cell ex: rods and cones in retina of eye

mechanoreceptors

stimulus: mechanical force mechanism: deforms plasma membranes of sensory dendrites or deforms hair cells that activate sensory nerve endings example: cutaneous touch and pressure receptors; vestibular apparatus and cochlea

nociceptors

stimulus: tissue damage mechanism: damaged tissues release chemicals that excite sensory endings ex: cutaneous pain receptors

The ability of the nervous system to change activity at synapses is called

synaptic plasticity

As the strength of a depolarizing stimulus to an axon is increased

the frequency with which the action potentials are produced increases

The region of the brain that is the most important control area for homeostatic regulation of the internal environment is:

the hypothalamus

The Nernst equation allows one to calculate

the membrane potential that would result from the intra- and extracellular concentrations of a single ion to which the membrane is permeable

The minimum depolarization needed to open Na + gates is called the

threshold

An inhibitory postsynaptic potential could be produced by a neurotransmitter that opens Cl - channels.

true

Both depolarization and repolarization are caused by the diffusion of ions down their concentration gradient.

true

Conduction without decrement means that action potentials transmitted down an axon will not decrease in amplitude.

true

The nicotinic ACh receptor is a ligand-gated channel.

true

Sensory Receptors: How good are they?

we see two different colors of gray but theres actually just one? -Propeception: awareness of body movement

Physical Support of the CNS

•Bone serves to support and to protect the structures of the CNS and PNS. •Cranium •Vertebrae •Meninges are the membranes that line the structures and add additional support and protection. •Dura mater •Arachnoid mater •Pia mater •Cerebrospinal fluid (CSF) protects and cushions the structures. -Brain weighs 1 and ½ kg, jelly like Cerebrospinal fluid surrounds brain, provides buoyancy -if injury to skull, fluid protects brain 3 meninges are layers that protect brain and spinal cord -Dura mater closest to brain, pia most outside and strongest -Skull protects brain