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Physiology > 11 B > Flashcards

11 B Flashcards

1
Q

How do neurons respond to being excited?

A

Generating an action potential (nerve potential)

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2
Q

What is always the same no matter the stimuli in action potential?

A

Impulse

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3
Q

What are the two main types of ion channels?

A 
Leakage (nongated channels)
Gated channels (protein changes shape to open and close channel)
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4
Q

What are the three main types of ion gated channels?

A 
Chemically gated (ligand gated) channels
Voltage-gated channels
Mechanically gate channels
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5
Q

What opens a chemically gated channel?

A

Binding of a specific neurotransmitter

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6
Q

What opens and closes a voltage gated channel?

A

A response to changes in membrane potential

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7
Q

What opens and closes mechanically gated channels?

A

In response to physical deformation of receptors (sensory receptors)

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8
Q

What happens when gated channels are open?

A

Ions diffuse quickly across membrane along electrochemical gradients

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9
Q

What does ion flow across the membrane create in open gated channels?

A

electrical current and voltage changes across the membrane

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10
Q

How do solutes move in response to concentration gradients?

A

from higher concentration to lower concentration

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11
Q

How do solutes move in response to electrical gradients?

A

Toward the opposite charge

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12
Q

What is the resting membrane potential?

A

Potential difference across membrane of resting cell

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13
Q

What is the approximate resting membrane potential of the neurons?

A

-70 mV

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14
Q

What is the term for a resting membrane?

A

Polarized

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15
Q

What is the resting membrane potential generated by?

A

Differences in ionic makeup of intracellular fluid and extracellular fluid
Differential permeability of the plasma membrane

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16
Q

What solute/ion plays the most important role in membrane potential?

A

K+ (the membrane is more leaky to potassium ions)

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17
Q

What is the Na+ concentration of the ECF balanced by?

A

Chloride ions

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18
Q

What balances the positive charge created by the K+ ions in the ICF?

A

Negatively charged proteins

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19
Q

What is the membrane impermeable to?

A

Large anionic proteins

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20
Q

What is the membrane slightly permeable to?

A

sodium ions through leaky channels

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21
Q

What is the membrane quite permeable to?

A

Chloride ions

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22
Q

Why is the cell more negative on the inside of the cell?

A

More potassium diffuses out than sodium diffuses in

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23
Q

What protein stabilizes resting membrane potential?

A

The sodium-potassium pump

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24
Q

How many sodium ions are pumped in by the sodium potassium pump and how many potassium out of the cell?

A

3 sodium in to 2 potassium out

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25
Q

What are changes in the membrane potential used for?

A 
Communication signals
(signals to receive, integrate and send information
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26
Q

When does the membrane potential change?

A

Concentrations of ions across the membrane change

Membrane permeability to ions change

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27
Q

What two types of signals are produced when membrane potential changes?

A

Graded potentials

Action potentials

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28
Q

Where do graded potentials occur?

A

At the dendrite region

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29
Q

What happens during graded potentials?

A

Incoming signals operate over short distances

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30
Q

What happens during action potentials?

A

Long distance signals across the axon

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31
Q

What happens in depolarization?

A

A decrease in membrane potential (to zero and above)

The inside of the membrane becomes less negative than the resting membrane potential

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32
Q

What increases the probability of producing a nerve impulse?

A

Depolarization

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33
Q

What happens during hyperpolarization?

A

An increase in membrane potential (away from zero and below)

Inside of the cell is more negative than Resting membrane potential

34
Q

What reduces the probability of producing a nerve impulse?

A

Hyperpolarization

35
Q

What are graded potentials and what do they vary in?

A

They are short-lived localized changes in membrane potential that vary in magnitude with various strengths of stimulus

36
Q

What are graded potentials stimulated by?

A

Stimulus that opens gated ion channels

37
Q

What happens to the current over distance with graded potentials?

A

It dissipates quickly and decays

38
Q

Where in a neuron does an action potential pass through?

A

The axon

39
Q

What is the principle way neurons send signals?

A

Action potentials

40
Q

What is the principal means of long distance neural communication?

A

Action Potentials

41
Q

Where do action potentials occur in the body?

A

Muscle cells and axons of neurons

42
Q

What is an action potential?

A

A brief reversal of membrane potential with a change in voltage of around 100 mV

43
Q

What are the two voltage sensitive gates for Na+ channels?

A

Activation gates

Inactivation gates

44
Q

What gate of an Na+ channel is closed at rest?

A

Activation gates (when open they allow Na+ to enter the cell)

45
Q

What gates of the Na+ channels are open at rest?

A

Inactivation gates (Block the channel when open to prevent more Na+ from entering the cell)

46
Q

Is the voltage sensitive gate of K+ channels closed or open at rest?

A

Closed

47
Q

What gates are open and which ones are closed during the resting state?

A

The leakage channels are open to maintain RMP

THe Na+ and K+ channels are closed

48
Q

What happens to the gated channels during depolarization?

A

The local currents open voltage-gated Na+ channels to allow Na+ into the cell and this makes the ICF less negative

49
Q

What happens at threshold to the Na+ channels?

A

At threshold, positive feedback causes opening of all Na+ channels
Spike of action potential

50
Q

What happens to the channels during repolarizing phase?

A

Na+ channels slow inactivation gates close
Membrane permeability to Na+ declines to resting state
Slow voltage-gated K+ channels open so that K+ can exit the cell so negativity of the inside is restored

51
Q

What happens during hyperpolarization to gates?

A

Some K+ channels remain open and allows excessive K+ efflux

Na+ channels begin to reset

52
Q

What is the role of the sodium potassium pump?

A

After repolarization this pump restores the ionic conditions

53
Q

What must happen for an axon to fire?

A

Depolarization must reach threshold

54
Q

What is threshold?

A

Voltage at which AP is triggered

55
Q

What happens at threshold?

A

Membrane has been depolarized 15-20 mV
Na+ permeability increases
Na+ influx exceeds K+ efflux
Positive feedback cycle begins

56
Q

What is the all or none phenomenon?

A

An action potential either happens completely or not at all

57
Q

What does progagation allow for?

A

Action potential to serve as a signaling device

58
Q

What is propagation?

A

When the local currents cause depolarization of adjacent membrane areas in direction away from the origin (the depolarization spreads across the membrane)

59
Q

TF: Once initiated, an AP is self propagating?

A

True

60
Q

What happens to membrane depolarization in nonmyelinated axons?

A

Each successive segment of membrane depolarizes then repolarizes

61
Q

What does a stronger simuli cause for action potentials?

A

It causes action potentials to occur more frequently

62
Q

How does the central nervous system determine the stimulus intensity of action potentials?

A

The frequency of impulses (higher frequency means a stronger stimuli)

63
Q

What is the absolute refractory period?

A

When voltage-gated Na+ channels open and the neuron cannot respond to another stimuli

(time from opening Na+ channels until resetting of the channels)

64
Q

What does the absolute refractory period ensure?

A

That each ap is all or none

65
Q

What does the absolute refractory period enforce?

A

One way transmission of nerve impulses

66
Q

What happens during the relative refractory period?

A

Some K+ channels are still open
Most Na+ channels are resting state
Repolarization occurs

67
Q

What kind of stimuli could stimulate an Action potential in the relative refractory period?

A

Only exceptionally strong stimuli to reach threshold (remember hyperpolarization is occurring so that means the inside of the membrane is more negative than in resting state)

68
Q

What does the rate of action potential propagation depend on?

A 
Axon diameter (larger diameter = less resistance to local current flow so faster)
Degree of myelination (more myelination = faster)
69
Q

Where does continuous conduction occur?

A

In nonmyelinated axons

70
Q

Where does saltatory conduction occur?

A

In myelinated axons (faster)

71
Q

Where are action potentials generated in saltatory conduction?

A

Only in the gaps (no channels in the myelin)

72
Q

What kind of disease is multiple sclerosis?

A

An autoimmune disease where the myelin sheath in the CNS is destroyed

73
Q

What helps prevent MS?

A

High blood levels of vitamin D

74
Q

What are the treatments for MS?

A

Drugs that modify immune system’s activity

75
Q

What happens in MS?

A

The immune system attacks the myelin sheath in the CNS
Causes the myelin to create lesions called scleroses
Impulse conduction slows and eventually ceases

76
Q

What are the symptoms of MS?

A 
Visual disturbances
Weakness
Loss of muscular control
Speech disturbances
Urinary incontinence
77
Q

How can nerve fibers be classified?

A

Diameter
Degree of myelination
Speed of conduction

78
Q

What are the three groups of fibers?

A

A B C

79
Q

What group of fibers have a large diameter, myelination and are found in the joints and skeletal muscle?

A

Group A fibers

80
Q

What group of nerve fibers has the slowest impulse conduction?

A

Group C fibers
Smallest diameters
Unmyelinated ANS fibers

Physiology (17 decks)

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