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dmd 5248 > Nervous System Physiology > Flashcards

Nervous System Physiology Flashcards

1
Q

What is resting potential

A

the transmembrane potential or a resting cell

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2
Q

how is resting potential established

A

with Na/K pumps, they pump sodium in and potassium out against their concentration gradient

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3
Q

what is equilibrium potential

A

the transmembrane potential when there is no net movement of a particular ion across the cell membrane

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4
Q

the equilibrium potential of K = -90mv, Na = 66mv. what is the resting potential of a neuron and why

A

it is -70 mv. its much closer to the potential of K because the membrane is much more permeable to K than Na

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5
Q

What are the characteristics of the sodium potassium pump

A

it is powered by ATP
it carries 3 Na+ out, and 2 K+ in
it balances passive forces of diffusion
it maintains the resting potential of -70 mv

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6
Q

what causes membrane potential to change

A

temporary changes in membrane permeability caused by the opening or closing of specific membrane channels

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7
Q

What are the two types of channels that affect transmembrane potential

A 
passive (leak) channels
- always open
- permeability changes with conditions
active (gated) channels. 
- open and close due to stimuli
- at resting potential most are closed
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8
Q

What are the three types of gated channels

A

chemically gated
voltage gated
mechanically gated

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9
Q

what are chemically gated channels

A

channels found on the cell body and dendrites that open with chemicals (ACh)

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10
Q

what are voltage gated channels

A

channels found in axons, skeletal muscle, sarcolemma, and cardiac muscle that are characteristic of an excitable membrane. they open and close due to changes of the transmembrane potential

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11
Q

what are mechanically gated channels

A

channels found in sensory receptors of touch, pressure, and vibration that respond to distortion of the membrane

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12
Q

what is a graded potential

A

a temporary and local change in resting potential caused by a stimulus. the larger the stimulus, the larger the change in resting potential

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13
Q

what is depolarization

A

a shift in transmembrane potential toward 0 mv, caused by a stimuli that causes movement of Na+ through a channel. it depolarizes the nearby plasma membrane

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14
Q

what is repolarization

A

when the depolarizing stimuli is removed, the resting potential of the membrane moves back to -70 mv

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15
Q

what is hyperpolarization

A

when the resting potential moves away (lower) from -70 mv (example = -80 mv)

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16
Q

What is an action potential

A

an electrical impulse produced by graded potentials that propogates along surface of axons to the synapse

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17
Q

what initiates an action potential

A

graded potentials that are large enought (10-15 mv) at the axon hillock to depolarize it to threshold (-60 to -55 mv) (this is the potential at which sodium voltage gated channels open)

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18
Q

what is the all or none principle of action potentials

A

action potentials don’t vary in strength, if threshold is reached the action potential is the same no matter the strength of the graded potential. if threshold isn’t reached there is no action potential

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19
Q

what are the four steps of an action potential

A
  1. depolarization to threshold
  2. activation of Na+ voltage gated channels
  3. inactivation of Na+ voltage gated channels and activation of K+ voltage gated channels
  4. return to normal permeability
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20
Q

what happens at -60 mv

A

voltage gated Na+ channels open, sodium rushes into the cytoplasm, inner membrane changes from - to +, causing rapid depolarization

21
Q

What happens at +30 mv

A

voltage gated Na+ channels close (inactivation gate)
voltage gated K+ channels open
repolarization begins

22
Q

when do voltage gated K+ channels begin, and finish closing

A

they begin to close at -70 mv, and finish closing at -90 mv. at this point the membrane is hyperpolarized, but it returns to normal and the action potential is over

23
Q

what is needed for the Na/K pump to work

A

ATP

24
Q

what is the refractory period

A

the time period that starts at the beginning of an action potential and ends when it returns to resting potential during which the membrane will not respond normally to additional stimuli

25
Q

what are the two refractory periods

A 
absolute = sodium channels are open or inactivated and no action potential can occur
relative = membrane potential is close to normal, and a very large stimulus can cause an action potential
26
Q

what is propagation of an action potential

A

the movement of an action potential generated in the axon hillock along the entire length of the axon

27
Q

what are the two types of action potential propagation, and what determines which kind will occur

A 
continuous propagation (unmyelinated)
saltatory propagation (myelinated)
28
Q

which is faster and why saltatory or continuous propagation

A

saltatory, because it essentially skips over the myelinated segements and occurs in the nodes of ranvier

29
Q

what happens to the propagation speed if you have a large diameter axon

A

the larger the diameter, the faster the propagation due to less resistance

30
Q

what are the three different groups of axons

A

Type A, Type B, Type C

31
Q

what are type A axon fibers

A

large, myelinated, high speed axons that carry rapid information to/from the CNS (touch, balance, position, motor impulses)

32
Q

what are type B axon fibers

A

medium, myelinated, medium speed axons that carry intermediate signals like sensory information and peripheral effectors

33
Q

what are type C fibers

A

small, unmyelinated slow speed axons that carry slower information like involuntary muscle and gland controls

34
Q

What are the three parts of a synapse

A

presynaptic neuron
synaptic cleft
postsynaptic neuron

35
Q

what are the two types of synapses

A

electrical (direct physical contact between cells)

chemical (signal transmitted across a gap by neurotransmitters)

36
Q

what are the two types of neurotransmitters

A

excitatory (cause depolarization and promote action potentials)
inhibitory (cause hyperpolarization and inhibit action potentials)

37
Q

is ACh an excitatory or inhibitory neurotransmitter

A

it can be both, which one it is is determined by the receptor, not the neurotransmitter (usually excitatory, but inhibitory at cadiac neuromuscular junctions)

38
Q

what does AChE do

A

breaks down the ACh in the synaptic cleft, in order to stop the ACh from activating postsynaptic receptors

39
Q

what is the synaptic delay

A

the signals stops at a synapse for .3 mseconds, so fewer synapses = quicker response (reflexes sometimes only have 1)

40
Q

what is synaptic fatigue

A

when the neurotransmitter can’t be recycled fast enough to meet the demands of intense stimuli

41
Q

what are some important neurotransmitters

A

Norepinephrine
dopamine
seratonin
GABA

42
Q

what are neuromodulators

A

chemicals similar to neurotransmitters, but have slow, long lasting effects.

43
Q

What are the three ways that neurotransmitters and neuromodulators actually affect postsynaptic cells

A

direct effects on membrane channels
via G proteins (work through second messengers - adenylate cyclase and cAMP, cAMP opens channels)
via intracellular enzymes
(some other enzyme opens channels)

44
Q

What are EPSPs and IPSPs

A

they are postsynaptic potentials
EPSP = excitatory (depolarization)
IPSP = inhibitory (hyperpolarization)

45
Q

what is summation

A

when multiple EPSPs are added together so that threshold can be reached

46
Q

what is temporal and spatial summation

A

temporal summation is when one presynaptic neuron sends multiple, quick EPSPs that are added together until they reach threshold
spatial summation is when multiple presynaptic neurons send EPSPs at the same time, then they are added together and they reach threshold

47
Q

what is the effect of hormones and neruromodulators on the activity of neurotransmitters

A

they can affect the sensitivity to neurotransmitters and thus shift the balance of EPSPs and IPSPs

48
Q

what is presynaptic facilitation

A

when there is a synapse that sends EPSPs and causes Na gates to open more on another neuron just before that neurons synapse so that it sends more neurotransmittors

49
Q

what is presynaptic inhibition

A

when there is a synapse that sends IPSPs and causes Na gates to close on another neuron just before the synapse of that neuron so that less Na comes in, and less neurotransmitters are sent

dmd 5248 (12 decks)

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