PHYSIOLOGY EXAM 2

Describe the functions of the medulla oblongata.

-Autonomic nervous center functions: cardio and respiratory -All ascending and descending tracts between the brain and spinal cord pass through the medulla -lower half of brainstem -regulate autonomic involuntary functions

Describe the dopaminergic neurons of the midbrain.

-Dopaminergic neurons project to basal nuclei and limbic system -Those neurons leading to areas of the limbic system, hippocampus, amygdala and areas linking to the reward system are key areas for drug addiction studies. -Dopamine (a neurotransmitter and hormones associated with 'good feelings') is released in the nucleus accumbens (collection of neurons) after consumption of certain addictive drugs.

axon hillock/initial segment

beginning of axon, where axon emerges from cell body

axon terminals

branches at the end of the axon that release neurotransmitters

depolarizing potential in post synaptic neuron; response to excitatory synapse activation

EPSP

Compare EPSPs and IPSPs and explain how action potentials can be stimulated by EPSPs.

EPSP: Opening Na+ or Ca2+ channels results in a graded depolarization called an excitatory postsynaptic potential (EPSP) •Brings postsynaptic membrane closer to threshold (Depolarizing). IPSP: Opening K+ or Cl− channels results in a graded hyperpolarization called inhibitory postsynaptic potential (IPSP) •Brings postsynaptic membrane further from threshold (Hyperpolarizing) •Decreasing the likelihood of an action potential EPSP brings the neuron's potential closer to its firing threshold (about -50mV).

most complex integrating areas of the nervous system; aids in processing information into perceptual images

cerebral cortex

Choose the answer that correctly lists, in chronological order, the events involved in synaptic transmission from pre to post-synaptic cells. a: A nerve impulse reaches the axon terminal. b: Neurotransmitter molecules diffuse across the synaptic cleft. c: An action potential begins in the postsynaptic cell. d: Neurotransmitter molecules bind to receptors in the postsynaptic cell. e: A voltage change occurs in the postsynaptic cell.

a,b,d,e,c

postganglionic parasympathetic neurotransmitter

acetylcholine

Epinephrine

adrenal medulla

List the major sensory receptors.

chemoreceptor: interprets chemical stimuli photoreceptor:rods & cones, stimulated by light energy thermoreceptor: temperature perception mechanoreceptor: respond to pressure, mechanical deformation nociceptor: pain stimuli, interprets presence of chemicals from tissue damage

sensory neuron

conduct impulses from sensory receptors to the CNS, unipolar, dorsal ganglia of the spinal cord

motor neuron

conduct impulses from the CNS to target organs (muscles or glands), multipolar, motorcortex (brainstem+spinal cord)

sympathetic and parasympathetic in what division

autonomic

innervates cardiac muscle, smooth muscle, glands

autonomic nervous system

function of sensory neurons

have an end to receive sensory stimuli and produce the nerve impulse and the other delivers impulse to synapse in the CNS. The cell body is located in the middle

Postsynaptic inhibition is produced by

hyperpolarization of the postsynaptic membrane

Antidiuretic hormone (ADH) and oxytocin are synthesized in the

hypothalamus

insulating material covering axons

myelin

Where are nicotinic ACh receptors located in the body? What is an example of drugs that stimulate this receptor? (Select the two correct answers)

nicotine skeletal muscles cells

postganglionic sympathetic neurotransmitter

norepinephrine

One of the brains' reward systems is the dopaminergic neurons that project from the VTA to the ___________.

nucleus accumbens (basal nuclei)

preganglionic fibers leave CNS from brainstem and sacral portions of spinal cord

parasympathetic

Antidiuretic hormone (ADH)

posterior pituitary

Insulin

promotes cellular uptake of glucose

repolarization

reestablishment of resting membrane potential after depolarization, move from +30 to -70 because K+ leaves the cell losing the positive

Describe the neural pathways and structures involved in a reflex arc

reflex arc: path taken by nerve impulses in reflex •Reflex responses to stimuli is a multi-step process. •A stimulus occurs at the receptor of a sensory neuron. This is sent along the afferent neuron as a nervous impulse and is received by the central nervous system •The interneuron makes connections to the motor neuron. The motor neuron transmits the impulse to the effector organ.

A rapid decrease in sodium permeability and simultaneous increase in potassium permeability is responsible for _____.

repolarization

relative refractory periods

second action potential can happen only if stimulus strength is greater than usual Why can it occur here? •Some K+ channels still open •Magnitude of the potential will be reduced

• Describe the purpose of the thyroid gland and its hormones

secrete metabolic hormones Stimulate protein synthesis, promote maturate of nervous system, increase rate of cell respiration, Hyperthyroid (over producing thyroid hormones) vs. Hypothyroid (not enough thyroid hormone) •Produces two iodine-containing molecules T4 (thyroxine) and T3 (triiodothyronine - T4 is generally converted to T3) •In order to produce adequate amounts of T3 and T4, we need iodine in our diet - as in iodinized salt (some NaCl is NaI) •Insufficient iodine amounts can lead to growth of a goiter

innervates skeletal muscle

somatic nervous system

Compare and contrast the somatic and autonomic divisions of the PNS.

somatic: involuntary effects; skeletal muscles; no ganglia; 1 neuron; excitatory only; fast-conducting autonomic: cardiac, smooth muscle, glands, cell bodies of postganglionic in paravertebral, prevertebral, and terminal ganglia, 2 neurons, either excitatory or inhibitory, slow-conducting -The somatic nervous system is associated with voluntary responses (though many can happen without conscious awareness, like breathing) -autonomic nervous system is associated with involuntary responses, such as those related to homeostasis.

Identify the hormones of the adrenal medulla and describe the hormone effects, especially under stress

•Mineralocorticoids from the zona glomerulosa regulate Na+ and K+ balance. •Example: aldosterone •Glucocorticoids from the zona fasciculata regulate glucose metabolism. Example: cortisol •Stress increases secretion of ACTH, which results in increased glucocorticoid release. •The stress hormones are glucocorticoids, epinephrine, and CRH Functions •Maintain blood pressure - vascular effects •Shutdown nonessential functions like reproduction •Inhibits inflammation and certain immune responses Complete absence of cortisol always fatal! •Stimulated by sympathetic axons •Release Epinephrine & Norepinephrine: ◦Increase cardiac output, respiratory rate, and mental alertness; dilate coronary blood vessels; elevate metabolic rates

• Distinguish between the anterior and posterior pituitary, and identify the hormones secreted by each part.

tract: posterior portal: anterior anterior: controlled via releasing and inhibiting hormones transported through the hypothalamo-hypophyseal portal system. posterior: oxytocin and ADH (storage, synthesized in hypothalamus) posterior: The posterior pituitary gland does not produce hormones, but rather stores and secretes hormones produced by the hypothalamus. anterior: does manufacture hormones, secretion of hormones regulated by two classes of hormones. These hormones—secreted by the hypothalamus—are the releasing hormones that stimulate the secretion of hormones from the anterior pituitary and the inhibiting hormones that inhibit secretion.

oligodendrocytes

which is the glial cell type that insulates axons in the CNS, form myelin sheaths in cns

Suppose that a net summation of EPSPs and IPSPs brings the membrane potential of the postsynaptic neuron to -51mV. Will an action potential occur in the postsynaptic neuron?

yes

Identify the hormones of the pancreas.

•Homeostasis of blood glucose critical as it is primary energy source for brain •Glucagon and insulin •Regulate blood glucose levels, Causes an antagonistic effect (blocking)-insulin lowers blood glucose levels by enhancing transport of glucose, it counters any activity that would increase levels of glucose. Glucagon promotes raising the glucose concentrations

Explain how ligand-gated channels produce synaptic potentials, using the nicotinic ACh receptor as an example.

•Ligand gated: opening in response to binding of a chemical ligand to its receptors in post synaptic plasma membrane nicotinic receptor: for acetylcholine in autonomic ganglia/neuromuscular junctions, stimulated by nicotine, postsynaptic cell •Ach binds at post synaptic cell, o ex: skeletal muscle cells (how muscles contract) -Agonist: nicotine -Antagonist: curare •Binding of 2 acetylcholine molecules opens a channel •Due to electrochemical gradient, more Na+ flows in than K+ out, EPSP is begun

Describe the structure of the sympathetic nervous system, locating the ganglia and the preganglionic and postganglionic neurons.

-Sympathetic on either side of the spinal cord first ganglia, second also close -The majority of ganglia of the sympathetic system belong to a network of sympathetic chain ganglia that runs alongside the vertebral column. -fight/flight -preganglionic fibers exit spinal cord in ventral roots of spinal nerves -cause divergent effects -thoracolumbar -postganglionic neuron neurotransmitter is Norepinephrine(adrenergic synapse) -•Divergence of impulses to ganglia of the sympathetic system and convergence of impulse within ganglia can result in mass activation-increasing activity in response to fight or flight situations, prepare body for intense physical activity •Release of norepinephrine from postganglionic neurons and the secretion of epinephrine from the adrenal medulla.

how action potential is conducted down the axon

-The depolarization of the first AP is the stimulus for the new action potential in the region just ahead of it and so on... •Each AP is its own separate event and is said to be regenerated •However: Positive feedback of Na+ allows the action potential to travel without decrement (decrease) thus reaching the end with the same amplitude, continuous conduction slow SALTATORY CONDUCTION -Myelinated Neurons: Myelin prevents Na+ and K+ from moving through the membrane. -AP move faster due to 'leaping from node to node' compared to ion channels located ALL along the axon

List the functions of the hypothalamus and indicate the other brain regions that cooperate with the hypothalamus in the performance of these functions.

-regulating homeostasis. executive region in charge of the autonomic nervous system and the endocrine system through its regulation of the anterior pituitary gland -Other parts of the hypothalamus are involved in memory and emotion as part of the limbic system. -Influenced by higher brain centers -Master command center for neural and endocrine coordination, regulates pituitary gland -Why? Controls what you need to survive: eating, drinking, regulation of body temp, etc. -Produce two hormones: ADH & oxytocin -Transported for release by posterior pituitary -Produce releasing and inhibiting hormones transported and released by anterior pituitary

Define the main functions of the central nervous system

1.Receives input from sensory neurons and directs activity of motor neurons 2.Association neurons integrate sensory information and help direct the appropriate response to maintain homeostasis and respond to the environment. 3.Humans are capable of learning and memory adding a layer of modification to our behaviors

Explain the sequence of hypothalamo-hypophyseal portal hormones

1.Regulatory hormone controls secretion of anterior pituitary hormone 2.Anterior pituitary hormone then controls the secretion of a hormone from another endocrine gland 3.The last hormone does the action on its target cell

absolute refractory periods

A second stimulus will not produce an action potential Why? •Na+ channels are inactivated •As soon as inactivation is removed (channel back to resting) and Na+ are closed, the channel can reopen to second stimulus

effect of increased stimulus strength on action potentials

A stronger stimulus, which might depolarize the membrane well past threshold, will not make a "bigger" action potential. Action potentials are "all or none." Either the membrane reaches the threshold and everything occurs as described above, or the membrane does not reach the threshold and nothing else happens. All action potentials peak at the same voltage (+30 mV), so one action potential is not bigger than another. Stronger stimuli will initiate multiple action potentials more quickly, but the individual signals are not bigger, Strength of stimulus affects frequency of AP and may recruit more neurons to have AP

how chemically regulated channels differ from voltage-regulated channels

A voltage-gated channel is a channel that responds to changes in the electrical properties of the membrane in which it is embedded, open when the transmembrane voltage changes around them, open in response to a specific chemical stimulus (E.g: neurotransmitter, such as acetylcholine, or a hormone); these are specifically important at synapses chemically regulated channels open on postsynaptic membranes, these open in response to a change in the membrane potential; these are important in conducting action potentials along axons

how action potentials are produced in the eye, and the neural pathways

AP: Photoreceptor and bipolar cells only undergo graded responses, they lack the voltage-gated channels that mediate action potentials, Ganglion cells are the first cells in the pathway where action potentials can be initiated ,Glutamate is neurotransmitter released neural pathway: -Optic nerve (cranial 2) from each eye meet at the optic chiasm, project to many areas mainly the thalamus -Other inputs come in from brainstem & visual cortex -Some visual pathway neurons project to areas other than visual cortex, like hypothalamus -Information is coded in spatial and temporal electrical activity-we perceive it all as a visual image consisting of lines, colors, contrast and movement

how the perception of pain differs from that of the other somatic senses

After initial AP: Changes can occur that may increase or decrease sensitivity to pain Pain can last after original stimulus is gone Pain can be altered by past experiences, emotions and simultaneous activation of other senses Ex. Phantom limb Pain reduction depends mainly on endogenous opioids.

dendrites

Branchlike parts of a neuron that are specialized to receive information.

Identify the five lobes of the brain and their major functions.

Frontal: cognitive functions and control of voluntary movement or activity. Parietal: integrates sensory information with numerous modalities, including spatial sense and proprioception (where body is in space) Occipital: vision processing Temporal: Decoding sensory input (visual and auditory) into derived meanings for retention of visual memory and language comprehension Insula: Processing and integration of taste sensation, visceral and pain sensation and vestibular functions

Explain how G-protein-coupled channels produce synaptic potentials, using the muscarinic ACh receptor as an example.

G-proetin: alpha beta gamma membrane protein, activate other proteins, associate is response to membrane signal Muscarinic Ach receptors •Ach binds at post synaptic cell oEx: digestive cells or cardio cells -Agonist: muscarine -Antagonist: atropine •Binding at the receptor opens ion channels indirectly by using a G-protein. -Dopamine and norepinephrine receptors do this too! ACh binds to receptor which causes beta-gamma subunits to dissociate from alpha subunit (G-protein subunit dissociates) - beta-gamma binds to K channel causing it to open resulting in outward diffusion of K (slowing heart rate)

Apply examples of dual innervation of the sympathetic and parasympathetic divisions of the autonomic system

Homeostasis is the balance between the two systems. At each target effector, dual innervation determines activity. For example, the heart receives connections from both the sympathetic and parasympathetic divisions. One causes heart rate to increase, whereas the other causes heart rate to decrease.

myelin sheath

Myelin is a lipid-rich sheath that surrounds the axon and by doing so creates a myelin sheath that facilitates the transmission of electrical signals along the axon. increase rate

how action potentials are produced in the ear, and their neural pathways

Neural pathways: -Cochlear nerve fibers synapse with interneurons in the brainstem. -Different arrival times from each ear and intensity help determine sound source also the shape of the outer ear and head movements -Vestibulocochlear nerve, brainstem (medulla obloganta), thalamus ,auditory cortex AP: -Receptor cells called Hair cells(mechanoreceptors) -The hairs on the cell called Stereocilia are bent back and forth as sound waves vibrate -K+ channels open, Ca2+ open -Bursts of neurotransmitters are then released onto afferent neurons -glutimate (neurotransmitter) binds and causes action potentials in neurons making up the vestibulocochlear nerve

how the myelin sheath is formed in CNS and PNS

Oligodendrocytes (CNS) and Schwann cells (PNS)

Describe negative feedback inhibition in the regulation of hypothalamic and anterior pituitary hormones.

The relationship between the hypothalamus, anterior pituitary, and the target tissue is sometimes called an axis. Hypothalmus-pituitary-adrenal thyroid axis 1. imbalance 2. hormone release 3. correction 4. negative feedback =homeostasis Negative feedback is characterized by the inhibition of further secretion of a hormone in response to adequate levels of that hormone. As glucocorticoid concentrations in the blood rise, the hypothalamus and pituitary gland reduce their signaling to the adrenal glands to prevent additional glucocorticoid secretion.

how is an action potential is produced.

This starts with a channel opening for Na+ in the membrane. Because the concentration of Na+ is higher outside the cell than inside the cell , ions will rush into the cell. Because sodium is a positively charged ion, it will change the relative voltage immediately inside the cell relative to immediately outside. The resting potential is the state of the membrane at a voltage of -70 mV, so the sodium cation entering the cell will cause it to become less negative. This is known as depolarization, meaning the membrane potential moves toward zero. The concentration gradient for Na+ is so strong that it will continue to enter the cell even after the membrane potential has become zero, so that the voltage immediately begins to become positive. The electrical gradient also plays a role, as negative proteins in the cell attract the sodium ion. The membrane potential will reach +30 mV by the time sodium has entered the cell. As the membrane potential reaches +30 mV, other voltage-gated channels are opening in the membrane. These channels are specific for the potassium ion. A concentration gradient acts on K+, as well. As K+ starts to leave the cell, taking a positive charge with it, the membrane potential begins to move back toward its resting voltage. This is called repolarization, meaning that the membrane voltage moves back toward the -70 mV value of the resting membrane potential. Repolarization returns the membrane potential to the -70 mV value that indicates the resting potential, but it actually overshoots that value. Potassium ions reach equilibrium when the membrane voltage is below -70 mV, so a period of hyperpolarization occurs while the K+ channels are open. Those K+ channels are slightly delayed in closing, accounting for this short overshoot.

Describe the sequence of events by which action potentials stimulate the release of neurotransmitters from presynaptic axons.

Upon arrival of an action potential at the pre-synaptic axon neurotransmitters are released into the synaptic cleft via the action of voltage-gated calcium channels. 1) Action potential conducted by axon reaches axon terminal 2) Voltage-gated Ca2+ channels open 3) Ca2+ binds to sensor protein in cytoplasm 4) Ca2+-protein complex stimulates fusion and exocytosis of neurotransmitter

What type of channel opens in response to an action potential arriving at the axon terminal and functions to allow synaptic vesicles to release neurotransmitters?

Voltage gated Ca2+ channels

How do voltage-gated channels differ from leak channels in the membrane of a cell?

Voltage gated Sodium channels open in response to a stimuli across the membrane. Leak channels are open during resting potential for Potassium.

adrenal medulla

epinephrine through blood as a hormone norepinephrine as neurotransmitter

Antidiuretic hormone is released by the anterior pituitary in response to decreased plasma osmolality.

false

Clusters of neuron cell bodies where the two neurons of your autonomic system meet is termed:

ganglia

node of ranvier

gaps in the myelin covering of an axon, important to the way that electrical signals travel down the axon, facilitate the rapid conduction of nerve impulses.

This hormone raises plasma concentration of blood sugar by decreasing the storage of sugar and releasing stored glucose.

glucagon

Describe how insulin and glucagon secretion are affected by eating and by fasting and explain the actions of these two hormones.

glucagon: increase blood glucose levels insulin: decrease blood glucose levels The body derives glucose from the breakdown of the carbohydrate-containing foods and drinks we consume. Receptors in the pancreas can sense the decline in blood glucose levels, such as during periods of fasting or during prolonged labor or exercise. In response, the alpha cells of the pancreas secrete the hormone glucagon, which has several effects:

adrenal cortex hormone

glucocorticoids (cortisol) and mineralocorticoids

Cortisol

inhibits inflammation & immune response, maintain blood pressure

depolarization

inside of membrane becomes less negative "+" because sodium cation enter, loss of polarity, membrane potential towards zero

Pancreas hormones

insulin and glucagon

association neuron/interneuron

located completely within the CNS and integrate functions of the nervous system, multipolar, impulses between neurons, not sensory or motor

controls functions such as breathing and heart rate

medulla oblongata

pineal gland hormone

melatonin

hyperpolarization

membrane potential becomes more negative, further from zero, IPSP

preganglionic fibers leave CNS at thoracic and lumbar portions of spinal cord

sympathetic

Identify the neurotransmitters of the sympathetic and parasympathetic divisions, and the hormone released by the adrenal medulla. (Review receptors for neurotransmitters)

sympathetic: norepinephrine parasympathetic: acetylcholine hormone released by medulla: ephinephrine

In the autonomic nervous system, two divisions have antagonistic effects on one another. ___________ will increase the rate of depolarization of the pacemaker cells. ____________ will decrease the rate of depolarization of pacemaker cells.

sympathetic; parasympathetic

synapse

the junction between the axon terminal of the sending neuron and the dendrite of the receiving neuron

cell body

the main part of a neuron is the cell body, which is also known as the soma The cell body contains the nucleus and most of the major organelles.

axon

the neuron extension that passes messages through its branches to other neurons or to muscles or glands, a fiber that emerges from the cell body and projects to target cells.

monoamines and depression.

•Monoamines: synthesized from amino acids •Examples: dopamine, norepinephrine, epinephrine(not common), all three called catecholamines. All use a second messenger system. •After activating their receptors they are transported back into axon terminal or broken down by enzymes •Neurons releasing catecholamines located in the CNS: regulate mood, attention, hormone release, states of consciousness and more •To treat depression among other diseases or disorders, a monoamine oxidase (enzyme breaking down monoamines) inhibitors may be used. It inhibits the process of breaking down the catecholamine by enzymes therefore increasing the concentration of dopamine and norepinephrine at a synapse

• Discuss how hormones can up-regulate and down-regulate receptors.

•The number and affinity of receptors themselves can be regulated. ◦Can be up-regulated (increase in #) or down-regulated. ◦Done to receptors of hormone or by hormone for other receptors ◦Prolonged exposure to high concentrations of hormone may result in a decreased number of receptors for that hormone. down-regulation: the presence of a significant level of a hormone circulating in the bloodstream can cause its target cells to decrease their number of receptors for that hormone, allows cells to become less reactive to the excessive hormone levels. up-regulation: When the level of a hormone is chronically reduced, increase their number of receptors, allows cells to be more sensitive to the hormone that is present.

Describe the structure and innervation pathways of the parasympathetic division of the autonomic system.

•The parasympathetic division is antagonistic to the sympathetic division. •Releases ACh from postganglionic neurons •Slows heart rate (decreases rate of pacemaker cells), and increases digestive activities •As a note: the parasympathetic division is not normally activated as a whole. In other words there is no mass activation of this division -craniosacral -preganglionic neurons located in nuclei of brainstem and lateral horn of sacral spinal cord