Chapter 11, 12 and 13 Nervous System
bipolar disorder
is a group of disorders characterized by episodes of abnormally elevated mood (called mania) followed by episodes of depression. Many treatments for bipolar disorder involve decreasing the ease with which axons generate action potentials, generally by blocking sodium ion channels in the axolemma.
An elevated ridge on the surface of the cerebrum is known as a
gyrus
The neural tube in embryonic state becomes the Central Nervous System: True or False
True
What is the hyperpolarization value in an axon?
-90mV
absolute refractory period
- A stimulus during this time will not cause second action potential The minimum length of time after an action potential during which another action potential cannot begin.
vestibular cortex
- Conscious awareness of balance and position of the head, located in the insula (not shown on the diagram)
The CNS is comprised of the Brain and Spinal Cord Evolutionary Development is termed Cephalization
- Increased number of neurons in the head, especially the anterior portion (site of complex thinking)
primary visual cortex
- Receives visual information from the retinas Visual association area - Processes (integrates) the incoming information and uses past visual experiences to interpret visual stimuli (e.g., color, form, and movement)
What is the threshold potential value?
-55mV
Depolarization Phase
-Some of the gated Na+ channels are opened (chemically-gated channels open with a neurotransmitter) allowing more Na+ in and a local change in polarity (graded potential) -If enough Na+ enters (threshold is about -50 mV), then voltage-gated channels open up and the membrane polarity reverses to +30mV, that's an action potential
Bipolar
1 axon and 1 dendrite Rare, located in special senses (retina and olfactory epithelium, auditory and gustatory areas)
Adult brain regions
1. Cerebral hemispheres 2. Diencephalon 3. Brain stem (midbrain, pons, and medulla) 4. Cerebellum
What affects conduction velocity?
1. affect of axon diameter • Larger diameter fibers have less resistance to local current flow and have faster impulse conduction 2. Effect of myelination • Continuous conduction in unmyelinated axons is 30x slower than saltatory conduction in myelinated axons • Myelin sheaths insulate and prevent leakage of charge • Voltage-gated Na+ channels are located only at the nodes • Action potentials jump rapidly from node to node
cranial nerves
12 pairs of nerves that carry messages to and from the brain
12 cranial nerves in order
1. olfactory: Function: Purely sensory - carries afferent impulses of sense of smell. Testing: Person is asked to stiff aromatic smells such as cloves or vanilla and indentify. 11. optic, Function: Purely sensory carries afferent impulses from retina to visual occipital cortex for visual interpretation. associated with vision. Testing: eye exams opthamoloscope to detect papilledema Swelling of optic disc. 111, oculomotor, Function: Nerve that supply four out of six extrinsic muscle that move the eyeball. Primary motor- somatic motor fibers to inferior oblique and superior, inferior and medial rectus muscle, which direct eyeball, and levator palpebrae muscles of the superior eye lid; parasympathetic fibers to smooth muscle controlling lens shape and pupil size. Testing: Pupils are examined for size, shape and equality. 1V. trochlear, Function: Nerve that supplies on extrinsic eye muscle works with Nerve 111 Oculomotor. Primary Motor- provides somatic motor fibers to superior oblique muscles that moves the eyeball. Testing: with cranial nerve 111. V. trigeminal, Function: Nerve that supplies sensory fibers to face and motor fibers for chewing. V1. abducens, Function: Nerve that supplies one eye muscle that turns eye lateral. V11. facial, Function: Nerve that supplies all muscle for facial expression. Include Temporal, zygomatic, buccal, mandibular, and cervical nerves. V111. vestibulocochlear, function: Auditory nerves, hearing and balance IX. glossopharyngeal, function: Nerve supplies tongue and pharynx, Stimulates motor movement during swallowing and conducts taste and general sensory impulses. X. vagus, Function: Nerve that supplied heart, lung, and abdominal organs, involved in breathing, heart rate, and digestion. Mixed fibers carry somatic motor impulses to pharynx and larynx and sensory fibers from same structure, very large portion are parasympathetic motor fibers which supply the heart and smooth muscles of the abdominal transmits impulses from viscera. Testing: Cranial nerve 1X and X are tested together, since both effect the throat. X1. accessory, Function: Mixed but mostly motor - provides somatic motor fibers to sternocleidomastoid and trapezius muscles. Testing: both muscles are checked for strength by asking person to rotate head and shrug shoulders. X11.hypoglossal Function: Chewing swallowing and speech. Mixed: but primarily motor in function. Carries somatic motor fibers to muscles of the tongue. Testing: Person is asked to protrude and retract tongue.
Proteins serve as membrane ion channels True or False
True
What are local potentials/graded potentials?
A local / Graded potential is a small, local change in the membrane potential of a neuron. A local potential may either depolarize the neuron, making it less negative, or can hyperpolarize the neuron, making it more negative. Local potentials are graded, reversible, decremental with distance, and useful for short-distance signaling only. Local/ Graded potentials (in the Dendrites)
Action potentials are non-decremental. What does that mean?
Action potentials are non decremental meaning they do not lose strength. Non-decremental means that the action potential doesn't lose strength, or diminish as it travels. Its a wave of many action potentials as it travels down the axon. This action of the Action potential is called self-propagating, meaning that each action potential triggers another one in a neighboring section of the axon. Like a domino effect.
Central Nervous System (CNS)
Brain and spinal cord • Integration and command center
Dendrites
Branchlike parts of a neuron that are specialized to receive information. • Input region receives incoming signals • Pass this information to the cell body • Use graded potentials short term potential
The ability to produce language is a function of _________, whereas the ability to understand language is a function of
Broca's area; Wernicki's area
Axons
Carry impulses away from the cell body • One axon per cell, arises from the axon hillock • Occasional branches (axon collaterals) • Numerous terminal branches • Knoblike axon terminals secrete neurotransmitters • Conducting region of a neuron • Use Action Potentials (long distance signals)
Structures of basal nuclei
Caudate nucleus.) are C-shaped rings of gray matter that sit lateral to the lateral ventricles in each hemisphere. The caudate nucleus is named for its long, slender "tail" that curls around and points anteriorly. Putamen. The putamen (poo-TAY-men; "pod") lies posterior and inferior to the caudate nucleus and is connected to it via small bridges of gray matter. The caudate nucleus and putamen are similar structurally and functionally, and are thus sometimes referred to as a single structure called the corpus striatum. Globus pallidus. The globus pallidus ("pale globe"), which sits medial to the putamen, is named for the fact that it contains more myelinated fibers than the other basal nuclei and is thus paler.
Two types of Gated Channels are:
Chemically gated channels—open with binding of a specific neurotransmitter Voltage-gated channels—open and close in response to changes in membrane potential
brain stem function
Connects brain and spinal cord, controls involuntary muscles Brain Stem • Controls automatic behaviors for survival • Midbrain has visual reflex centers that coordinate head and eye movements to visually follow an object and auditory relay centers that cause a reflexive response to sound • Pons maintains normal rhythm of breathing and provides bladder control and urination reflexes with the Pontine Storage and Pontine Micturition centers • Medulla Oblongata joins the spinal cord at foramen magnum and is the site of the Autonomic Reflex Centers • Cardiovascular - heart rate, blood vessel diameter (blood pressure) • Respiratory - breathing rhythm, rate and depth • AND Others - Vomiting, Hiccupping, Swallowing, Coughing, Sneezing
Microglial cells (CNS)
DEFENSIVE CELLS: Protects from disease, clear dead neurons
What is it called when the inside of a neuron becomes less negative/more positive?
Depolarization: is when the inside of the cell becomes less negative / More positive. Increasing the probability of producing a nerve impulse
Neurons (nerve cells)
Electrically excitable cells that initiate, transmit, and receive nerve impulses Highly specialized, conduct nerve impulses from one part of the body to another Special characteristics: Long-lived (→ 100 years or more) Amitotic—with few exceptions High metabolic rate—need a continuous supply of oxygen and glucose
The cerebral hemispheres are divided into five lobes
Frontal lobes. The anterior most lobe is the frontal lobe. ts posterior boundary is called the central sulcus. Just anterior to the central sulcus is the precentral gyrus. Parietal lobes. Posterior to the frontal lobes are the paired parietal lobes (pah-RY-eh-tal). The major gyrus of each of these lobes is the postcentral gyrus, which sits just posterior to the central sulcus. Temporal lobes. The paired temporal lobes are on the lateral surfaces of the hemisphere, separated from the frontal and parietal lobes by the lateral fissure. Occipital lobes. The posterior lobe of each cerebral hemisphere is the occipital lobe. It is separated from the parietal lobe by the parieto-occipital sulcus (look ahead to Figure 12.12). Insulas. As you can see in Figure 12.4c, the paired insulas (IN-syoo-lahz) are visible only when you pry the frontal, parietal, and temporal lobes apart at the lateral fissure (remember this with the mnemonic "the insula is insulated by the other lobes"). Gray Matter: Cerebral Cortex
Two types of signals
Graded potentials (in the Dendrites) • Incoming short-distance signals • Can change in magnitude and decrease in strength. Action potentials (used by Axons, generated by the Axon Hillock) • Long-distance signals of axons and muscle cells • Membrane potential has an amplitude of ~100 mV, in other words membrane potential was -70 mV and jumps up to +30mV
serial processing
Input travels along one pathway to a specific destination • Works in an all-or-none manner to produce a specific response • Example: reflexes—rapid, automatic responses to stimuli that always cause the same response • Reflex arcs (pathways) have five essential components: receptor, sensory neuron, CNS integration center, motor neuron, and effector
_____________________________________encompass a wide variety of processes, including maintenance of homeostasis; higher mental functions such as use of language and learning; interpretation of sensory stimuli; and planning and monitoring movement.
Integrative functions
function of myelin
It functions to: • Protect the axon • Electrically insulate to increase the speed of nerve impulses
Where is the vestibular cortex found? and What is its function?
It is found in the posterior part of the insula and adjacent to parietal cortext It is responsible for conscious awareness of balance (position of head in space)
During an action potential, repolarization is caused by:
K+ exiting the axoplasm. When voltage-gated K+ channels open, K+ exit the cell, driven by their electrochemical gradient.
What are the Two main types of ion channels ?
Leakage (non-gated) channels—always open. Look like a tunnel and follow the concentration gradient from high to low. • Gated channels: • Chemically gated channels—open with binding of a specific neurotransmitter • Voltage-gated channels—open and close in response to changes in membrane potential
Specialization in Cortical Function
Left hemisphere: Controls Language, Math, and logic Right hemisphere: Insight, visual-spatial skills, intuition, and artistic skills • Left and right hemispheres communicate via fiber tracts in the cerebral white matter—Corpus Callosum
ependymal cells
Line cerebrospinal fluid filled cavities produce cerebrospinal fluid
Local potentials are decremental. What does that mean?
Local potentials are also decremental in nature. This means the changes in membrane potential they produce are small, and the current generated is lost across the membrane over very short distances, no more than a few millimeters
Local potentials cannot be used for
Long distance signaling, they are only useful for short distances.
resting membrane potential
Membrane Potential of an inactive neuron is -70 mV Membrane Permeability: Impermeable to negatively charged proteins, permeable to other ions due to leakage channels Sodium-potassium pump maintains the proper ion distribution
Depolarization
Membrane potential approaches zero, Inside the membrane becomes less negative Increasing the probability of producing a nerve impulse
segmented protein lipid sheath around axons functions to: • Protect the axon • Electrically insulate to increase the speed of nerve impulses
Myelin Sheaths are:
What is neural integration?
Neural Integration is where all incoming stimuli are combined. If enough of the stimuli are depolarizing their accumulative effect will reach the trigger zone.
What is repolarization?
Once the membrane potential peaks at its full depolarized potential; the Inactivation gates closes plugging the channel at +30mV. Then the voltage gated sodium channels inactivate and Sodium ions stop. At this point voltage gated potassium ions slowly open and potassium ions exit the neuron by an electrochemical gradient causing the cell to stop gaining positive charges to lose positive charges which begins repolarization. A negative membrane potential is repolarization.
What happens inside the axon when the trigger zone reaches this value?
Once the threshold has been met -55mV. Voltage Gated Sodium Ion Channels open and sodium rush quickly into the neuron driven by their electro chemical gradient and cause a rapid depolarization to +30mV
relative refractory period
Only a very strong stimulus will open the sodium channels to generate another action potential during this time
resting state
Only leakage channels for Na+ and K+ are open -All gated Na+ and K+ channels are closed
Synaptic transmission allows voluntary movement, cognition, sensation, and emotion, as well as countless other processes. True or False
True
Somatosensory cortex (parietal lobe)
Receives sensory information from the skin, skeletal muscles, and joints and identifies what body part is being stimulated Somatosensory Association Area - Integrates (processes) sensory input from primary somatosensory cortex to determine size, texture, and relationship of parts of objects being felt
What is it called when the inside of a neuron becomes less positive/more negative?
Repolarization, is when the neuron becomes more negative. Restoring the resting electrical conditions of the neuron. In resting it is Negative inside, and Positive on the outside of the Neuron
The AP is caused by permeability changes in the plasma membrane
Resting Potential: only K is open Depolarized: Voltage Gated channels Na+ opens. Hyperpolarized: chemically Gated K+ channel open
Reticular Formation
Reticular activating system (RAS), maintains homeostasis with the hypothalamus • Sends impulses to cerebral cortex to keep it conscious/alert • Filters out 99% of stimuli (repetitive or weak) • Coma: prolonged unconsciousness, person is completely unresponsive, even to painful stimuli, can be caused by severe injury to the RAS
Satellite Cells and Schwann Cells (PNS)
Satellite cells Surround neuron cell bodies. Satellites, and astrocytes do the same job The Schwann cells Form myelin sheaths - Do the same job as oligodendrocytes in the CNS
Myelin Sheaths in the (PNS)
Schwann cells wraps many times around the axon • Myelin sheath—concentric layers of Schwann cell membrane
Ependymal cells (CNS)
Secrete cerebrospinal fluid (CSF) have cilia to help circulate the CSF Blood-Cerebrospinal fluid barrier--separates the central nervous system tissue fluid from the cerebrospinal fluid in the cavities CSF cushions the brain and spinal cord, supplies nutrients, and removes metabolic waste
Functional Classification of Neurons Sensory
Sensory: (afferent) Incoming information from sensory receptors toward the CNS Motor (efferent) Carry impulses (often commands) from the CNS to effectors. The ventral roots of the spinal cord are motor nerves. Interneurons (association neurons) Conduct signals through pathways within the CNS
anxiety disorders
The hallmark of anxiety disorders is an exaggerated and inappropriate fear response, believed to stem from abnormalities in norepinephrine, serotonin, and GABA transmission. Drugs used to treat anxiety disorders may include the antidepressants already discussed, drugs that enhance GABA activity, and other drugs that modulate norepinephrine transmission.
propagation of the action potential
Sodium comes into cell - Na+ influx causes depolarization of the cell Local currents affect adjacent areas in the forward direction Depolarization opens voltage-gated channels and triggers an action potential Repolarization wave follows the depolarization wave
Motor Division of the Peripheral Nervous System
Somatic Voluntary Nervous System ( SNS) conscious control of skeletal muscles Autonomic ( Involuntary ) Nervous System ( ANS) Nerve fibers in organs • Regulates smooth muscle, cardiac muscle, and glands • Two functional subdivisions • Sympathetic--speeds up action • Parasympathetic--slows down action
What are the two main features of an electrical synapse?
Synaptic transmission is bidirectional. In an electrical synapse, transmission is usually bidirectional, which means that either neuron may act as the presynaptic or the postsynaptic neuron and that current may flow in either direction between the two cells. Synaptic transmission is nearly instantaneous. The delay between depolarization of the presynaptic neuron and change in potential of the postsynaptic neuron is less than 0.1 ms (millisecond), which is extraordinarily fast (we will see that transmission at most chemical synapses requires from one to a few milliseconds).
What are the two receptive regions of a neuron?
The Dendrite Region, and the Cell body
limbic system
The Limbic System provides emotional impact for experiences (butterflies in your stomach when you are nervous, skunks smell bad) • Communicates with the prefrontal lobes, emotional reaction to events, conscious awareness of emotional richness in our lives
Where does action potential propagation start and stop?
The action potentials starts at the Trigger zone which is the Axon Hillock and stops at the Axon Terminal.
What two factors determine the strength of a local potential?
The degree of change in the membrane potential during a Local / Graded potential depends on several factors: 1. The length of stimulation, 2. The number of ion channels that open and what type of ion channels that open.
What is the visceral sensory area?
The insular cortex (deep to sylvian fissure) is a ________________________ of the neocortex that receives input from the thalamus (ventral posterior nuclei). ... The amygdala, a limbic basal nucleus of the rhinencephalon, is involved in generating visceral activity, particularly fearful emotional behavior.
pre-motor cortex
The motor area that is involved in repetitive and patterned action such as playing a musical instrument
primary motor cortex
The motor area that provides conscious control of precise movement of skeletal muscles
The nervous system when developing in an Embryo
The nervous system originates from the neural tube and neural crest formed from ectoderm • The neural tube becomes the CNS • Neuroepithelial cells of the neural tube undergo differentiation to form cells needed for development • Cells (neuroblasts) become amitotic and migrate • Neuroblasts sprout axons to connect with targets and become neurons.
presynaptic neuron
The neuron that is sending the signal towards the synapse in the nervous system
What determines if an action potential is generated from a local potential?
The strength of the potential. If the strength can depolarize the Trigger zone and meet the threshold then an action potential will come. Its all or none. Once the threshold of about -50 mV), then voltage-gated channels open up and the membrane polarity reverses to +30mV, that's is an action potential.
Broca's area
This area is active during speaking. Stimulates muscles involved in speech production
primary somatosensory cortex
This area receives the sensory information from the skin, skeletal muscles and joints
In the CNS, bundles of axons are called_________________________. In the PNS bundles of axons area called _________________________________.
Tracts, nerves
Two areas of the cortex are directly involved in language: Broca's area, a premotor area for speech sounds, located in the anterolateral frontal lobe, and Wernicke's area, or the integrative speech area, located in the temporal and parietal lobes. True or False
True
Voltage-gated Sodium - Na+ channels are located only at the node of Ranvier. True or False
True
Generating an Action potential is an all-or-none phenomenon (no such thing as a weak AP), a strong stimulus causes impulses to be generated more often. True or false
True - all or none
Neurotransmitter effects may be excitatory (depolarizing) and/or inhibitory (hyperpolarizing) True or False
True effects can be either way
Functionally, the most complex part of the brain is the region of gray matter known as the Cerebral cortex . True Or False
True regarding gray matter
hyperpolarizing local potentials can be caused by:
When the cell gains negative charges due to Cl- entering the cytosol, the result is a local hyperpolarization.
An ____________________________ is a large uniform depolarization followed by a rapid repolarization.
action potential
Neurilemma
additional external myelin sheath that is formed by Schwann cells and found only on axons in the peripheral nervous system bulge of Schwann cell cytoplasm
Sensory, or _______________, neurons carry signals toward the central nervous system (CNS)
afferent
Satellite cells (PNS)
are flat cells that surround the cell bodies of neurons in the peripheral nervous system (PNS).
Type B fibers
are intermediate in diameter (2-3 μm) and most are myelinated. They typically have a maximum conduction speed of about 15 m/sec (about 32 mi/h), and include certain efferent fibers of the autonomic nervous system and certain sensory axons coming from organs.
depressive disorders
are marked by disturbances in mood and are thought to be caused by a deficiency in synaptic transmission of serotonin, norepinephrine, and/or dopamine. Pharmacological treatment makes use of drugs that prolong the lifespan of these neurotransmitters, particularly serotonin, in the synaptic cleft. The most widely used antidepressants are selective serotonin reuptake inhibitors (SSRIs), which block only the serotonin transporter, preventing the reuptake of serotonin by the presynaptic neuron.
Type A fibers
are the largest-diameter axons (5-20 μm), all of which are myelinated. These characteristics give them the fastest conduction speed, with a maximum speed of about 120 m/sec (about 250 mi/h). Type A fibers are found in parts of the body with which the CNS must communicate extremely rapidly, such as certain sensory axons from joints and muscle fibers, as well as motor axons to skeletal muscles.
Type C fibers
are the smallest fibers (0.5-1.5 μm) and are unmyelinated. Their conduction speed is the slowest, conducting action potentials only at about 0.5-2 m/sec (about 1-5 mi/h). Type C fibers include other efferent fibers of the autonomic nervous system and certain sensory axons that transmit pain, temperature, and certain pressure sensations.
gustatory cortex
area of the brain that receives and interprets tastes from the tongue
What are three locations where presynaptic axons connect with a postsynaptic neuron?
axodendritic, axosomatic, and axoaxonic synapses,
axoaxonic synapse
axon to axon
axosomatic synapse
axon to cell body or (soma) soma another name for the cell body
Axodentric
axon to dendrite
In an electrical synapse, transmission is usually ________________________________, which means that either neuron may act as the presynaptic or the postsynaptic neuron and that current may flow in either direction between the two cells..
bidirectional
Electrical synapses are found primarily in areas of the __________________that are responsible for programmed, automatic behaviors such as breathing. They are also present in developing nervous tissue in the embryo and fetus
brain
Hypothalamus
brain region controlling the pituitary gland Some of these include regulating much of the autonomic nervous system, the sleep/wake cycle, thirst and hunger, and body temperature.
The ________________________is perhaps the most important part of the brain in terms of our immediate survival because its nuclei control many basic homeostatic functions, including maintenance of heart rate and breathing rhythm
brainstem
Finish this sentence: In reality, a nerve impulse is not one action potential but
but a wave of consecutive action potentials
electrical synapse
ccurs between cells that are electrically coupled via gap junctions. In these synapses, the axolemmas of the two neurons are nearly touching (they are separated by only about 3.5 nm) and the gap junctions contain precisely aligned channels that form pores through which ions and other small substances may travel. This allows the electric current to flow directly from the axoplasm of one neuron to that of the next
The most metabolically active part of a neuron is its large ______________, or _______________. The cell body is the most conspicuous part of the neuron because it is responsible for maintaining the sometimes huge cytoplasmic volume of the neuron and also for manufacturing all the proteins the neuron needs.
cell body, or soma.
The integrative functions of the nervous system are carried out exclusively by the ____________________________________.
central nervous system (CNS)
visceral cortex
conscious awareness of visceral sensations. Ex) (upset stomach, full bladder), located in the insula (not shown on the diagram)
the thalamus regulates ________________________activity.
cortical
The____________ and ________increase the surface area of the brain and make it a much more compact structure; if our brains were smooth, we would require much larger skulls to hold them.
gyri and sulci
Fissures
deep grooves in the brain tissue
Multiple sclerosis is an autoimmune disease that results in the destruction of myelin, a process called ____________________________. To simulate the effect of multiple sclerosis, the first half of this axon is myelinated and the second half is demyelinated. Where in this axon would a high speed of propagation occur, and where would a low speed occur? Drag the arrows to the appropriate segments of the axon
demylenation
membrane potential
difference between the voltage measured on each side of a membrane
the ____________and _____________increase the surface area of the brain and make it a much more compact structure; if our brains were smooth, we would require much larger skulls to hold them.
gyri, sulci
Gyri
elevated ridges of brain tissue
within a nerve, each axon is surrounded by a delicate connective sheath called ____________________________. which insulates it from the neuron processes next to it. This is an additional layer to the Myelin Sheath
endoneurium
all fascicles of axons are bound together by a white, fibrous connective tissue called:
epineurium
Current:
flow of electrical charge (ions) between two points
Oligodendrocytes (CNS)
form the myelin sheath in the brain and the spinal cord around CNS nerve fibers Branched cells Wraps CNS nerve fibers, forming myelin sheaths, Insulation that improves conduction of signals All motor neurons are myelinated Some nervous tissue is myelinated All myelination is white
The central sulcus separates which lobes?
frontal from parietal
basal nuclei
has a motor Function, similar to the cerebellum • Influences movements executed by the primary motor cortex so they are carried out appropriately • Regulate intensity of slow or habitual movements • Inhibits unnecessary movements
The diencephalon is found at the physical center of the brain. Structurally and functionally the diencephalon has four components:
he large, central thalamus (THAL-ah-muss; "inner chamber"); the posterior and superior epithalamus (epi- = "above"); the inferior hypothalamus; and the subthalamus
primary auditory cortex
hearing, temporal lobe, Receives incoming signals (pitch, loudness, and location) Auditory association area - Processes sounds, matches up what you hear to stored sound memories
Insulator
high electrical resistance (myelin)
Neurons
highly excitable/irritable cells that transmit electrical signals
Resistance
hindrance to charge flow (the plasma membrane)
The ____________________________ provides a link between the nervous system and the endocrine system.
hypothalamus
Schizophrenia. The disease schizophrenia (skit′-zoh-FREEN-ee-ah)
is characterized by repetitive psychotic episodes—periods during which a person is unable to appropriately test his or her beliefs and perceptions against reality. Schizophrenia is thought to result from excessive release of dopamine, so pharmacological management of the disorder primarily involves blocking postsynaptic dopamine receptors.
Cerebrum
is that part of the brain responsible for our higher mental functions, which is why deep thinkers are sometimes called "cerebral."
The parietal and temporal lobes are separated by the __________________________
lateral fissure
The functional brain system that participates in memory, learning, emotion, and behavior is the ___________________________________.
limbic system
conductor
low electrical resistance (open ion channels)
Multipolar
many dendrites, one axon, most common in the body 99% of all neurons (all multipolar are motor neurons)
Voltage (mV)
measure of potential energy
The axon depolarizes to what maximum value?
membrane polarity of about +30mV
Hyperpolarization
membrane potential moves away from zero), Inside the membrane becomes more negative, Reducing the probability of producing a nerve impulse. Th inside of cell becomes even more negative
Cerebral Cortex: Functional Areas
motor areas: control voluntary movement, commands muscles sensory areas: conscious awareness of sensation, receives incoming information association areas: integrate (process) diverse information to put it all together and make sense out of it, they can handle many incoming messages at once, also help store it as memory and decide what action to take
In a myelinated axon
myelin keeps current in axons (voltage doesn't decay much). APs are generated only in the nodes of Ranvier and appear to jump rapidly from node to node.
white matter
myelinated axons
The primary visual cortex lies at the posterior end of the ________________________________ and is the first area to receive visual input. It feeds this information into surrounding visual association areas, which process color, object movement, and depth.
occipital lobe
voltage gated channels
open and close in response to changes in membrane potential. A change in the Voltage
chemically gated channels
open with binding of a specific neurotransmitter
The parietal and occipital lobes are separated by the ___________________________________
parieto-occipital sulcus.
Gray matter
part of CNS unmyelinated fibers
groups of axons are bound by a coarser connective tissue called_____________________________________________________.
perineurium ( to form bundles of fibers called fascicles
Postsynaptic neuron
receives signal from presynaptic and conducts its signal away from the synapse
pineal gland
secretes melatonin
Functions of the nervous system
sensory input, integration, motor output
trigeminal nerve function
sensory: face, teeth, tongue motor: muscles of mastication
Sulci
shallow grooves in the brain tissue
Unipolar
single, short process that has two branches off the cell body • Most of the sensory neurons, peripheral nerves
Tetrodotoxin blocks voltage-gated_______________________________ and therefore prevents the rapid depolarization phase of the action potential. Ingestion of tetrodotoxin can lead to paralysis and death due to failure of neurons to fire action potentials and muscles to respond to them.
sodium ion channels
The transfer of chemical or electrical signals between neurons at a synapse is called _______________________________
synaptic transmission,
The______________________________ is literally the "main entrance" into the cerebral cortex—nearly all stimuli destined for the cerebral cortex must first pass through the thalamus. This allows the thalamus to control which information reaches the cerebral cortex and where the information is sent, which means that ultimately the thalamus regulates cortical activity.
thalamus
axon hillock
the cone-shaped area on the cell body from which the axon originates action potentials start at the axon hillock
The cerebellum functions in
the planning and coordination of movement
parallel processing
the processing of many aspects of a problem simultaneously • Input travels along several pathways • One stimulus promotes numerous responses • Important for higher-level mental functioning • Example: a smell may remind one of the odor and associated experiences
In an unmyelinated axon
voltage-gated Na+ and K+ channels regenerate the action potential at each point along the axon, so voltage does not decay. Conduction is slow because movements of ions and of the gates of channel proteins take time and must occur before voltage regeneration occurs.
The channels that open at the threshold potential of -55 mV to cause depolarization are:
voltage-gated Na+ channels. When the axolemma reaches threshold, voltage-gated Na+ channels open.
bare plasma membrane
without voltage-gated channels, as on a dendrite, voltage decays because current leaks across the membrane
Neuroglia (glial cells)
—supporting cells: They outnumber neurons 10 to 1 and make up half of the brain's mass
Synapse
• A junction that mediates information transfer from one neuron to another neuron, or to an effector cell. • Presynaptic neuron—conducts impulses toward the synapse • Postsynaptic neuron—transmits impulses away from the synapse • Most synapses are chemical, fewer are electrical
information transfer
• AP arrives at axon terminal of the presynaptic neuron and opens voltage-gated Ca2+ channels • A calcium sensing protein binds Ca2+ and promotes fusion of synaptic vesicles with axon membrane • Exocytosis of neurotransmitter occurs • Neurotransmitter diffuses and binds to receptors (chemically-gated ion channels) on the postsynaptic neuron • Ion channels are opened, causing an excitatory or inhibitory event (graded potential
cell death
• About 2/3 of neurons die before birth • Death results in cells that fail to make functional synaptic contacts • Many cells also die due to apoptosis (programmed cell death) during development • Normal, healthy brain has about 200 Billion neurons
cell body of neuron
• Biosynthetic center of a neuron • Well-developed Rough ER and Golgi apparatus • Axon hillock—cone-shaped area leads to axon • Clusters of cell bodies are called nuclei in the CNS, ganglia in the PNS
synaptic cleft
• Fluid-filled space separating the presynaptic and postsynaptic neurons • Prevents nerve impulses from directly passing from one neuron to the next • Transmission across the synaptic cleft: Is a chemical event (as opposed to an electrical one) Involves release, diffusion, and binding of neurotransmitters Ensures unidirectional ( meaning one direction) communication between neurons
Myelin Sheaths in the CNS
• Formed by processes of oligodendrocytes, not whole cells • White matter—Parts of CNS containing myelinated fibers • Gray matter—Parts of CNS containing cell bodies and unmyelinated fibers
Patterns of Neural Processing: Serial Processing
• Input travels along one pathway to a specific destination • System works in all-or-none manner to produce specific, anticipated response • Example - spinal reflexes - Rapid, automatic responses to stimuli - Particular stimulus always causes same response - Occur over pathways called reflex arcs • Five components: receptor, sensory neuron, CNS integration center, motor neuron, effector
Role of the Sodium-Potassium Pump
• Ionic redistribution gets reset back to resting conditions by thousands of sodium-potassium pumps
When gated channels are open:
• Ions diffuse along their electrochemical gradients • Chemical concentration gradients (from higher to lower) or and • Electrical gradients (opposite charges attract) • Ion flow causes voltage changes across the membrane (membrane potential), creating the electrical current
Signal Types in a Neuron
• Membrane potential changes when: • Membrane permeability changes • Concentrations of ions change • Changes in membrane potential are signals used to receive, integrate and send information
Astrocytes (CNS)
• Most abundant Neuralgia - glial cells • Support and brace neurons • Maintain the blood-brain barrier= Keeps the CNS isolated from chemicals and hormones in the bloodstream • Control the chemical environment by "mopping up" leaked potassium ions and neurotransmitters so they can be used again • Help process information
Neurotransmitters
• Most neurons make two or more neurotransmitters, which are released at different stimulation frequencies • 50 or more neurotransmitters have been identified • Classified by chemical structure and by function • Neurotransmitter effects may be excitatory (depolarizing) and/or inhibitory (hyperpolarizing)
myelin sheath
• Myelin Sheaths in the PNS • Schwann cells wraps many times around the axon • Myelin sheath—concentric layers of Schwann cell membrane • Neurilemma—bulge of Schwann cell cytoplasm • Nodes of Ranvier • Myelin sheath gaps between adjacent Schwann cells • Sites where axon branches can emerge
Nodes of Ranvier
• Myelin sheath gaps between adjacent Schwann cells • Sites where axon branches can emerge
Peripheal Nervous System (PNS)
• Nerves carry messages to and from the central nervous system • Two divisions of PNS • Sensory (afferent) division • Receptors detect conditions of the skin, skeletal muscles, joints, and organs • Motor (efferent) division • Transmits impulses from the CNS to muscles or glands (effectors)
what are the Principles of Electricity?
• Opposite charges attract each other • Energy is required to separate opposite charges across a membrane • Energy is liberated when the charges move toward one another • If opposite charges are separated, the system has potential energy
Microglia (CNS)
• Smallest glial cells • Monitor health of neurons • Migrate toward injured or infected neurons • Turn into special types of macrophages that phagocytize microorganisms and neuronal debris • White blood cells are not allowed in the central nervous system
Chemical Synapses
• Specialized for the release and reception of neurotransmitters • Typically composed of two parts • Axon terminal of the presynaptic neuron, which contains synaptic vesicles • Receptor region on the postsynaptic neuron
Developmental Aspects of Neurons
• The nervous system originates from the neural tube and neural crest formed from ectoderm • The neural tube becomes the CNS • Neuroepithelial cells of the neural tube undergo differentiation to form cells needed for development • Cells (neuroblasts) become amitotic and migrate • Neuroblasts sprout axons to connect with targets and become neurons
Events at a chemical synapse
❶❶ An action potential in the presynaptic neuron triggers calcium ion channels in the axon terminal to open. An action potential reaches the axon terminal of the presynaptic neuron, which triggers the opening of voltage-gated calcium ion channels in its axolemma. ❷❷ Influx of calcium ions causes synaptic vesicles to release neurotransmitters into the synaptic cleft. Calcium ions enter the axon terminal, causing synaptic vesicles in the area to fuse with the presynaptic membrane. This releases neurotransmitters into the synaptic cleft via exocytosis. ❸❸ Neurotransmitters bind to receptors on the postsynaptic neuron. The neurotransmitters diffuse across the synaptic cleft, where they bind to neurotransmitter receptors on the membrane of the postsynaptic neuron. ❹❹ Ion channels open, leading to a local potential and possibly an action potential. The binding of neurotransmitters to receptors generally either opens or closes ligand-gated ion channels in the postsynaptic membrane, resulting in a local potential. Such local potentials may or may not lead to an action potential in the postsynaptic neuron.
