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PR MCAT Biology/Biochem > nervous system > Flashcards

nervous system Flashcards

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1
Q

distinguish between a bipolar and multipolar neuron

A

bipolar has on dendrite (and one axon)
multipolar has many dendrites (and one axon)

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2
Q

distinguish between a neuron and a nerve

A

a neuron is a single cell while a nerve is a large bundle of many different axons from different neurons

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3
Q

what is the cell’s resting membrane potential (RMP)

A

-70mV

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4
Q

what are the 2 primary protein structures that are required to establish the RMP?

A

Na+/K+ ATPase and K+ leak channels

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5
Q

what establishes the K+ concentration gradient in a cell (where K+ flows down its concentration gradient out of a cell via its K+ leak channels)?

A

Na+/K+ ATPase pump

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6
Q

is the inside of the cell membrane at RMP slightly negative or positive?

A

negative

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7
Q

distinguish between depolarization and hyperpolarization

A

depolarization is where the inside of the cell membrane becomes less negative (or becomes positive); caused by influx of Na+ and/or Ca++
hyperpolarization is where the inside of the cell membrane becomes more negative compared to the RMP; caused by influx of K+ out of the cell (leaving it’s bound proteins, which carry a slight - charge inside the cell) and Cl- inside the cell

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8
Q

what is the threshold potential of voltage-gated Na+ channels to open? to close?

A

-50mV causes them to open
+35mV causes them to close

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9
Q

what is the threshold potential of voltage-gated K+ channels to open? to close?

A

+35mV to open
-90mV to close

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10
Q

could the Na+/K+ ATPase pump bring the cell back to RMP w/o K+ leak channels?

A

yes, but reaching RMP would take longer

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11
Q

If a toxin prevents voltage-gated Na+ channels from closing, how will this affect the voltage-gated K+ channels and Na+/K+ ATPase pump?

A

It would cause the voltage-gated K+ channels to open and remain open; and the Na+/K+ ATPase pump to always run, as both are attempting to reach repolarization

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12
Q

what cells produce myelin in the CNS and PNS?

A

CNS myelin is produced by oligodendrocytes
PNS myelin is produced by Schwann cells

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13
Q

Name the basic functions of astrocytes, microglia, and ependymal cells?

A

all reside in CNS
astrocytes (glial cells of CNS): they are the “workhorses” of the CNS because they have many supportive functions: guide neuronal development; responsible for reuptake of neurotransmitters in synaptic clefts, which helps to regulate synaptic communication; form blood brain barrier; have glycogen residues, which indirectly increases the ATP production of neurons
microglia: remove dead cells and debris
ependymal cells: produce and circulate CSF

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14
Q

what are satellite cells?

A

they are the astrocytes of the PNS

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15
Q

what is an equillibrium potential? what is the equillibrium potential of Na+ and K+?

A

equillibrium potential is the potential at which there is no gradient or driving force for that ion & therefore will be no net movement of that ion

Na+ = +50mV

(note that voltage-gated Na+ channels will close prior to reaching their equillibrium potential)

K+ = -90mV

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16
Q

distingiuish between absolute and relative refractory period for an action potential

A

absolute refractory period: a neuron will not fire another action potential under any circumstance because during this time the voltage-gated Na+ channels are inactivated and unable to open

relative refractory period: a neuron could potentially fire another action potential, but the inside of the membrane is still more negative than it’s RMP (-70mV) because the voltage-gated K+ channels are still open, which means more of a stimulus is needed to activate another action potential.

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17
Q

Distingiush between an electrical synapse and a chemical synapse

A

electrical synpase: occur when the cytoplasm of 2 cells are joined by gap junctions; the action potential spreads directly from one cell to the next. these synapses are not common in the nervous system, but are seen in smooth and cardiac muscle

chemical synapse: found at the end of axons where htye meet their target cell; this is where an electrical signal becomes a chemical signal i.e. neuromuscular junction where neuron synpases with muscle cell

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18
Q

what are the steps of chemical synapse in the nervous system, starting when the action potential reaches the synnpatic knob

A

1) action potential reaches synaptic knob
2) depolarization of presynaptic membrane causes voltage-gated Ca2+ channels to open and influx of Ca2+ into cell
3) Exocytosis of neurotransmitters, where they diffuse accross the synaptic cleft
4) neurotransmitter binds to ligand-gated ion channels on the postsynaptic membrane, causing those channels to open and ions (i.e. Na+ and Cl-) flow into the cell
5) if depolarization of the postsynaptic cell reaches threshold, it’ll generate an action potential
6) Neurotransmitters are degraded (bind to reuptake proteins that deliver them to astrocytes, which then recycle and redeliver them for reuse)

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19
Q

where is acetylcholine found and what is it degraded by?

A

found between neurons in autonomic nevous system and between neuromuscular junctions (junctions of skeletal, smooth, and cardiac muscle)

degraded by acetylcholinesterase (AChE)

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20
Q

compare how acetylcholine is used to how norepinephrine/epinephrine is used in the nervous system

A

ACh is used in between presynaptic and postsynaptic neurons, and is also used by the postsynaptic neuron in the autonomic nervous system. all somatic nervous system neurons use ACh on their target cell (muscle cell)

norepi/epi is used at the postsynpatic neuron in the autonomic nervouse system (used in fight or flight)

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21
Q

excitatory neurotransmitters and inhibitory neurotransmitters. whaich one causes depolarization and which hyperpolarization? what event occurs that causes this depolarization and hyperpolarization?

A

excitatory cause depolarization: channels open and Na+ and Ca2+ flow into cell, causing the membrane to become less negative and therefore depolarizing. therefore, excitatory neurotransmitters increase action potentials

inhibitory cause hyperpolarization: channels open and cause K+ flow out of cell and Cl- flow into cell, causing the membrane to become more negative, thus hyperpolarizing the membrane, making it less susceptible to depolarization. therefore, inhibitory neurotransmitters decrease action potentialsd

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22
Q

a neurotransmitter can be excitatory in some cases but inhibitory in others. Why?

A

because the neurotransmitter itself doesn’t determine if the postsynaptic neuron depolarizes. it’s the neurotransmitter’s receptor and it’s associated ion channel that determines whether or not the postsynaptic neuron gets depolarized.

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23
Q

If an inhibitor of AChE is added to a neuromuscular junction, then the postsynnpatic membrane will be depolarized longer with each action potential. Why?

A

because ACh will remain longer in the synaptic cleft and therefore, the ligand-gated Na+ channels will remain open longer, making depolarization last longer.

*Note that this will quicken the refractory period, so the postsynaptic neuron will not be depolarized more frequently, just the length of the depolarization peroid will be longer.

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24
Q

distinguish between temporal summation and spatial summation

A

temporal summation: one presynaptic neuron fires action potentials so rapidly that EPSPs or IPSPs pile up on top of each other, the additive effect of which would hopefully reach the threshold required for depolarization/hyperpolarization

spatial summation: EPSPs or IPSPs from all the synapses on the postsynaptic neuron are summed at a given moment in time (therefore, multiple neurons have an additive effect on one postsynaptic neuron)

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25
Q

1) for the muscle stretch reflex: a sensory neuron detects the stretch of muscle and sends the signal to an ____ in the spinal cord, which is directly attached to an ____ neuron that sends a signal to contract the quadricep muscle.
2) Concurrently, the inhibitory interneuron is also stimulated and send a signal via another efferent neuron to the hamstring, causing the hamstring to relax. This is referred to as ______ inhibition

A

1) interneuron, efferent
2) reciprocal

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26
Q

distinguish between the somatic and autonomic nervous system

A

somatic: responsible for sensation and voluntary muscle control
autonomic: responsible for involuntary processes (i.e. heart rate, digestion, smooth muscle contraction, etc.)

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27
Q

myelinated axons are aka ____ matter, while unmyelinated axons are aka ____ matter

A

white, grey

28
Q

what are the main functions of the medulla oblongata, pons, and cerebellum

A

medulla oblongata: autonomic/involuntary functions

pons: some autonomic functions, works with cerebellum to coordinate movement and balance
cerebellum: coordinates complex movements; balance, spatial equillibrium

29
Q

main function of midbrain (mesencephalon)

A

visual and auditory reflexes, eye movement

contains RAS (reticular activating system): responsible for arousal and wakefulness

30
Q

what is the brainstem comprised of?

A

the medulla, pons, and midbrain

31
Q

The forebrain (prosencephalon) includes the diencephalon and telencephalon. what brain structures are included in each?

A

diencephalon = thalamus and hypothalamus

telencephalon = the 2 cerebral hemispheres

32
Q

distinguish between the functions of the thalamus and hypothalamus

A

thalamus: relay station; processes sensory info except olfactory
hypothalamus: homeostasis (i.e. temp regulation and other hormones that help regulate homeostasis), emotion, behavior

33
Q

Distinguish between the main functions of the frontal, parietal, temporal, and occipital lobes

A

frontal: initiates all voluntary movement; complex reasoning skills and problem solving
parietal: general sensations (i.e. touch, temp, pressure, etc.) and gustation
temporal: process auditory and olfactory sensation; short term memory, language comprehension, emotion

occipital lobes: process visual sensation

34
Q

function of the basal nuclei/basal ganglia?

A

voluntary muscle control and coordinates movement; procedural learning and habits; overall inhibitory (whereas cerebrum is excitatory)

35
Q

function of limbic system. what are the 3 main structures of the limbic system?

A

emotion, memory (storage and retrieval), learning

amygdala, cingulate gyrus, and hippocampus

36
Q

the vagus nerve is a cranial nerve that is part of the ____ nervous system; it’s ganglia end on the surface of the heart, stomach, and otehr visceral organs, and ____(increases or decreases) HR and ______(increases or decreases) GI activity

A

parasympathetic

decreases HR

increases GI activity

37
Q

All somatic nerves innervate skeletal muscle and use ___ as their neurotransmitter

A

ACh

38
Q

does the somatic or the autonomic nervous system have pre and postsynaptic neurons?

A

autonomic

39
Q

all autonomic preganglionic neurons release ___ neurotransmitter

A

ACh

40
Q

All parasympathetic postganglionic neurons release _____, whereas all sympathetic postganglionic neurons release ______

A

ACh, epinephrine

41
Q

what do the adrenal cortex and adrenal medulla release?

A

cortex: sex steroids, glucocorticoids (cortisol) and mineral corticoids (aldosterone)
medulla: epinephrine

42
Q

What type of receptor is a Pacinian corpuscle and what do they detect?

A

a mechanoreceptor

they are pressure sensors deep in skin

43
Q

what do mechanoreceptors detect?

A

stetching, pressure in skin, and vibrations in ear (cochlea and semicircular canals)

44
Q

what type of receptor is an olfactory and gustatory receptor?

A

chemoreceptors

45
Q

what are nociceptors

A

pain receptors

46
Q

what are the only electromagnetic receptors found in humans?

A

rods and cones in the eye

47
Q

distinguish between phasic receptors and tonic receptors

A

phasic receptors fire action potentials only when the stimulus begins

tonic receptors fire when the stimulus begins, but also continue firing as long as the stimulus continous, but they are prone to adaptation

48
Q

what is adaptation regarding adaptation of a stimulus?

A

refers to a decrease in firing frequency when the intensity of a stimulus remains constant

49
Q

what type of receptor does not undergo adaptation?

A

nociceptors

50
Q

what is proprioception?

A

awareness of self/position of body

aka kinesthetic sense

51
Q

olfactory receptors in the roof of the nasopharynx are connected to the olfactory nerves, which project to the olfactory bulbs in the ____ lobe

A

temporal

52
Q

which structures of the ear are involved in equalizing pressure on both sides of the eardrum

A

round window and eustachian tube

53
Q

the mechanism of hearing is performed by what structure of the ear?

A

the cochlea: contains peilymph, endolymph, and the organ of Corti (which is comprised of the basilar membrane, hair cells, and tectorial membrane)

discplacement of the hair cells cause ion channels to open and neurotransmitters to be released. this is how sound vibrations are converted to nerve impulses. the dendrites of the afferent neurons are stimulated by the neurotransmitter release.

54
Q

how are pitch and loudness distinguished in the ear?

A

pitch is distinguished by which regions of neurons are stimulated

loudness is distinguished by the amplitutde of vibration (larger vibrations cause more frequent action potentials)

55
Q

what are the 3 semicircular canals of the vestibular complex?

A

utricle, saccule, and ampullae

56
Q

in the eye, rods and cones connect to ___ cells, which connect to ___ cells, whose axons comprise the optic nerve

A

bipolar, ganglion

57
Q

what is the fovea

A

the part of the eye that only contains cones and is responsible for visual acuity

58
Q

1) In the ____(light or dark), rods and cones are resting, and retinal has several trans bonds and one cis bond. This keeps the Na+ channel on opsin ______(hyperpolarized or depolarized).
2) In the ____(light or dark), the retinal is converted to the all-trans forms, triggering Na+ channel to close, ______(hyperpolarizing or depolarizing) the cell

A

1) dark, depolarized
2) light, hyperpolarizing

59
Q

what neurotransmitter is released by photoreceptors? what is the postsynaptic cell in which this neurotransmitter binds?

A

glutamate, bipolar neuron

60
Q

what are the 3 types of cones

A

blue, green, red

61
Q

distinguish between myopia, hyperopia, and presbyopia

A

myopia: nearsightedness
hyperopia: farsightedness
presbyopia: inability to focus/accommodate (results from loss of flexibility in the lens)

62
Q

distinguish between absolute threshold and difference threshold

A

absolute threshold: the minimum stimilus required to activate a sensory receptor by 50% and therefore detect a sensation

difference threshold: aka the just noticeable difference (JND), the minimum noticeable difference between any 2 stimuli

63
Q

what is weber’s law?

A

states that any 2 stimuli must differ by a constant proportion in order for their differen e to be perceptible. the exact proportion varies by stimulus. i.e. in humans, 2 objects must differ in weight by 2% in order for a human to tell the difference.

64
Q

what is signal detection theory?

A

attempts to predict how and when someone will detect a stimulus. involves a hit, miss, false alarm (signal not present but person thought it was), and correct rejection

65
Q
A

PR MCAT Biology/Biochem (13 decks)

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