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Physiology > Lecture 5- Nervous System > Flashcards

Lecture 5- Nervous System Flashcards

1
Q

what is membrane potential?

A

the difference in electrical voltage/charges across a cell membrane. it is a disequilibrium between the ECF & ICF.

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2
Q

what is membrane potential due to? aka why do we have this electrical disequilibrium?

A

due to 2 things:
1. due to ion movement through the transmembrane proteins (through leaky channel ions).
2. and because the interior of the cell is more negative than the exterior of the cell

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3
Q

what is the resting membrane potential?

A

when there is an absence of stimulation; there is no change in the membrane potential; when the cell is at rest and at a steady state

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4
Q

what is the number of the resting membrane potential? (what is the resting membrane potential of a neuron?)

A

-70 mV (millivolts)

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5
Q

what is the number of the resting membrane potential due to?

A

it is due to K+ (potassium)

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6
Q

what is graded potential?

A

*

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7
Q

what is action potential?

A

*

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8
Q

what is a synapse?

A

it is the communication between neurons and other cells through a neurotransmitter

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9
Q

what are the 2 divisions of the nervous system?

A

CNS = central nervous system (brain and spinal cord) and PNS = peripheral nervous system (peripheral nerves, ganglia, and nerve plexuses; everything else).

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10
Q

after an incoming signal is detected by sensory receptors, what happens?

A

the signal is sent to the CNS by the sensory neurons. we have the integration and decision making.

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11
Q

after the decision is made and comes out of the CNS, where does it go?

A

it goes to the PNS, where the efferent neurons (motor neurons) are divided into the somatic nerurons (controls our skeletal muscle; voluntary control) and the autonomic neurons (involuntary).

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12
Q

what is under the autonomic neurons?

A

sympathetic and parasympathetic nervous systems.

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13
Q

draw the nervous system diagram and study it

A
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14
Q

what are two ways neurons are classified by?

A

by functional and structural classification

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15
Q

what are the 3 functional categories of neurons?

A
  1. sensory neurons: they have the dendrites, cell body, and axon. there are 2: a) somatic senses which have myelination and b) neurons for smell and vision without the myelination.
  2. interneurons of CNS
  3. efferent neurons (with multiple dendrites)
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16
Q

what are the 4 structural categories of neurons?

A
  1. unipolar (dendrites merge onto axon)
  2. bipolar
  3. anaxonic
  4. multipolar
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17
Q

what is an association neuron/interneuron?

A

multipolar neuron located entirely within the CNS

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18
Q

what is the sensory neuron/ afferent neuron?

A

a neuron that transmits impulses from a sensory receptor into the CNS

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19
Q

what is a motor neuron / efferent neuron?

A

a neuron that transmits impulses from the CNS to an effector organ like a muscle

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20
Q

what is a nerve?

A

bundles of axons in PNS

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21
Q

what is a tract?

A

bundles of axons in the CNS

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22
Q

what is a somatic motor nerve?

A

a nerve that stimulates contraction of skeletal muscles

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23
Q

what is an automatic motor nerve?

A

a nerve that stimulates contraction of smooth and cardiac muscle

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24
Q

what is a ganglion?

A

a collection of neuron cell bodies in the PNS

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25
Q

what is a nucleus in the nervous system?

A

a collection of neuron cell bodies in the CNS

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26
Q

what is electrophysiology?

A

dealing with electricity

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27
Q

what is membrane potential change due to?

A

it is due to ion movement

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28
Q

what are 3 types of changes in membrane potential?

A
  1. depolarization
  2. repolarization
  3. hyperpolarization
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29
Q

what is depolarization?

A

when the membrane potential becomes more positive (+) than the resting membrane potential. it creates an electrical signal. this is because the cell is being stimulated.

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30
Q

what is repolarization?

A

when the depolarized membrane returns to the resting membrane potential

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31
Q

what is hyperpolarization?

A

it is when the membrane potential is less (more negative -) than the resting membrane potential.

32
Q

is the number -40 depolarized or hyperpolarized?

A

depolarized

33
Q

is the number -100 depolarized or hyperpolarized?

A

hyperpolarized?

34
Q

what do ion channels allow for?

A

they allow ions to move across a membrane.

35
Q

what is a mechanically-gated ion channel?

A

it deforms due to pressure and the channel changes shape. this is an example of facilitated diffusion. (we find this a lot in our skin).

36
Q

what are chemically-gated ion channels?

A

when the substrate has to bind in order for the channel to open. a particular chemical molecule needs to be present, its binds to the ECF part of the membrane, opens it, changes the membranes shape, and then is sent to the other side (the ICF side).

37
Q

what is voltage-gated ion channels?

A

It responds to a change in membrane potential. The channel has to open at a certain threshold voltage (some channels can be already open, and at certain voltages, they will close). The channel open or closes at a certain MAGIC number, which is the threshold.

38
Q

at resting potential, are the voltage-gated ion channels open or closed?

A

they are closed

39
Q

what happens to the voltage-gated ion channel when the membrane is depolarized?

A

the shape changes and it opens the voltage-gated channel

40
Q

what is graded potential?

A

a form of electrical signal because of a change in membrane potential. it is created because the cell is being stimulated by something.

41
Q

why is graded potential created?

A

because it:
1. responds to stimuli (receptors detect these stimulations. these receptors are located at the DENDRITES of the neuron). we generate graded potential at the sensors (receptors).

42
Q

where is graded potential produced?

A

It is produced at receptors and cell bodies. (Graded potential can be created at receptors or cell bodies, because both sites can receive stimulation).

43
Q

look at the different types of sensory receptors on slide 8 top right AND the neuron on the bottom

A
44
Q

when receptors get stimulated, what do they produce?

A

graded potential

45
Q

T/F: Graded potential can have weak or strong electrical strength

A

True

46
Q

what does it mean when graded potential has variable strength?

A

it means the stimulation can vary. It depends on the strength of the original stimuli.

47
Q

what is the travel distance like for graded potential?

A

it travels short distances and loses strength; the graded potential looses strength while traveling

48
Q

complete the sentence:
“as the strength of the stimulus increases, so does the strength of the ____ ____”

A

as the strength of the stimulus increases, so does the strength of the graded potential.

49
Q

what, generally, does action potential respond to?

A

action potential responds to graded potential

50
Q

what exactly does action potential respond to regarding graded potential?

A

Action potential responds to the levels at threshold OR SUPRAthreshold (above) from graded potentials. ALL OR NOTHING PHENOMENON.

51
Q

what number does the mebrane potential have to hit in order to generate action potential?

A

-55 mV. if graded potential doesn’t hit -55 mV, nothing happens and no action potential is generated

52
Q

where is action potential generated?

A

in the axon hillock rather than the dendrites/cell bodies

53
Q

T/F: Action potential maintains constant strength

A

True. the opposite of graded potential

54
Q

when the membrane potential is at SUBthreshold, what does that mean?

A

that means there isn’t enough graded potential, so no action potential is generated

55
Q

use charts on slides 10-13 to study action potential. draw it out, teach it, use a whiteboard, etc.

A
56
Q

what are the 9 steps of action potential?

A
  1. Resting membrane potential.
  2. Depolarizing stimulus (from arrival of graded potential).
  3. The membrane depolarizes to the threshold. The voltage-gated Na+ and K+ channels begin to open. This is at -55 mV, which is the threshold that opens the votage-gated channels. (The membrane depolarizes, so it becomes more positive, because Na+ is releases, and makes the membrane more positive by doing so).
  4. Rapid Na+ entry depolarizes the cell.
  5. Na+ channels close and slower K+ channels open. This is at +30 mV, so it closes.
  6. K+ moves from the cell to extracellular fluid. So since its going outside to the more positive area, the inside of the cell will become more negative, and therefore causing it to repolarize.
  7. K+ channels remain open and additional K+ leaves the cell, hyperpolarizing it.
  8. Votlage-gated K+ channels close, less K+ leaks out of the cell.
  9. Cell returns to the resting ion permeability and resting membrane potential. Action potential happens again.

at PEAK step (step 5): Votage gates for Na+ close, and gates for K+ fully open at -55 mV.

57
Q

since the K+ channels slowly open and close, and the K+ can still move, what happens?

A

the cell hyperpolarizes, its also called the undershoot (so under resting). Once we go past this point, the K+ channels fully close.

58
Q

what channels are used in action potential for Na+ and K+?

A

Leaky channel and ATPase

59
Q

about how long does action potential take?

A

about 3 milliseconds

60
Q

what serves as the stimulus for action potential?

A

the threshold that graded potential brings

61
Q

what are two types of voltage-gates under Na+ channels?

A

activation and inactivation gates

62
Q

at rest, what is the position of the activation and inactivation gate?

A

at -70 mV, the activation gate is closed and the inactivation gate is opened.

63
Q

when does the activation gate open?

A

at -55 mV, then Na+ comes in and the cell membrane depolarizes.

64
Q

does the inactivation gate close?

A

at +30 mV

65
Q

what does depolarization trigger for Na+?

A

the Na+ channel activation gates open rapidly, Na+ enters cell, more depolarization happens, and this cycle happens over and over again. It is a positive feedback mechanism and is ended by the inactivation gate closes and the opening of K+ channels.

66
Q

what does depolarization trigger for K+?

A

Slow K+ channels open, K+ leaves the cell, repolarization happens

67
Q

what is the only ion channel with 2 gates?

A

Na+; inactivation and activation gates

68
Q

what are two periods of action potential?

A

absolute refractory and relative refractory period

69
Q

what is absolute refractory period?

A

a time period that starts from the opening of activation gates to the time while inactivation gates remain closed (refers to Na+ voltage-gate). During this time, it cannot induce a 2nd action potential. It ensures one-way travel of action potential.

70
Q

what is relative refractory period?

A

a time period that is when Na+ inactivation gate is being restores, and K+ channels are slowly closing. A strong stimulus may induce a 2nd action potential.

71
Q

study relative and absolute refractory period table on pages 17-20

A
72
Q

what is saltatory conduction?

A

action potential transmits from node of ranvier to node of ranvier with myelinated axons.

73
Q

will every single node have the same strength?

A

Every single node will have the same strength and every action potential at a node is a new action potential but the same strength.

74
Q

what is the purpose of myelination?

A

to prevent the charge from escaping the neuron

75
Q

study graphs on page 22-25

A
76
Q

what is the difference between unmyelinated and myelinated axons?

A

unmeylinated axons take much longer and action potential has to be regenerated a lot. myelinated axons are quicker and more efficient

Physiology (9 decks)

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