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► Med - Anatomy & Physiology > Neurology 2 > Flashcards

Neurology 2 Flashcards

1
Q

what are action potentials caused by?

A

graded potentials

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2
Q

what causes ion differences?

A

the membrane

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3
Q

what does neuron and muscles cells use the ion differences to produce?

A

action potential

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4
Q

what do graded potentials go up and down from?

A

diffusion across the membrane

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5
Q

what will happen if certain molecules bind to ligand-gated sodium channels?

A

it will produce a depolarization (graded potential)

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6
Q

what happens if graded potentials summat to (or past) the threshold in the initial segment?

A

an action potential will occur in the initial segment (all-or-none principle)

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7
Q

what can graded potentials do before diffusing away?

A

persist for a while

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8
Q

what is the difference in length of action and graded potentials?

A

graded potentials are long, action potentials are only 1-2 milliseconds long and a graded potential can be added together

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9
Q

where do action potentials occur?

A

in the initial segment in the axon

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10
Q

where do graded potential occur?

A

cell bodies and dendrites but can diffuse far enough that they reach the initial segment (axon)

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11
Q

what is an action potential for the membrane?

A

a quick change

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12
Q

what is a depolarization phase followed by?

A

a repolarization phase and afterpotential

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13
Q

what is the depolarization phase?

A

when the membrane potential moves away from the resting state and becomes more positive

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14
Q

what is the afterpotential?

A

when the plasma membrane becomes hyperpolarized after repolarization

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15
Q

what is the repolarization phase?

A

when the membrane potential returns toward the resting state and becomes more negative

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16
Q

what encourages action potentials?

A

graded depolarizations

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17
Q

what discourages action potentials?

A

graded hyperpolarizations

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18
Q

what will a graded depolarization to or past the threshold do?

A

open voltage-regulated sodium channels producing the depolarization and action potential

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19
Q

what do voltage-regulated sodium channels have?

A

two gates operated independently

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20
Q

what are the three possibilities for the voltage-regulated sodium channels?

A

1) closed but CAN open (inactivation gate open and activation gate closed)
2) open- (both gates open)
3) closed and CANNOT open (inactivation gate closed and activation gate open)

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21
Q

what does a graded potential do to the membrane?

A

depolarizes it to the threshold

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22
Q

what are the gates when a graded potential is below the threshold?

A

sodium channels are closed but can open

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23
Q

what are the gates when a graded potential is at the threshold?

A

the sodium channels are open

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24
Q

what are the gates when a graded potential is at +30mV?

A

the sodium inactivation gates close and voltage-gated potassium channels open producing the repolarization

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25
Q

what are the gates when a graded potential is in repolarization?

A

the sodium-voltage gated channel activation gates close and then the inactivation gates open

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26
Q

what happens to the potassium voltage-regulated channels when at -70mV

A

they close

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27
Q

what dose the closing of the potassium regulated channels when at -70mV allow for?

A

the membrane polarization to exceed -70mV (afterpotential)

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28
Q

after the afterpotential of the potassium voltage regulated channel exceeding -70mV what occurs?

A

the membrane potential returns to -70mV

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29
Q

what happens to the small amount of sodium ions that came into the potassium voltage channel?

A

it is quickly pumped out

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30
Q

where does the all-or-none principle occur?

A

in the initial segment

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31
Q

what needs to occur in order for an action potential to occur?

A

needs to reach the threshold

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32
Q

between the time that the sodium channels open until the sodium channels are returned to configuration before a depolarization what occurs?

A

the initial segment will NOT respond to any graded potential to generate another action potential (absolute refractory period)

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33
Q

between the return of the sodium channels to the configuration before depolarization until the return to the resting membrane potential what occurs?

A

another action potential can be generated by a larger stimulus than the original one (relative refractory period)

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34
Q

what will a larger stimulus past the threshold generate?

A

a series of action potential (up to a limit) and higher frequency of action potentials is interpreted as a stronger signal

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35
Q

what do action potentials propagate from?

A

the initial segment to the axon terminals

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36
Q

`what will happen with an unmyelinated axon?

A

the depolarization of one section during the depolarization phase will depolarize the next section to the threshold.

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37
Q

what will happen with a myelinated axon?

A

the depolarization of one node depolarizes the next node to the threshold, propagating the action potential down the axon in saltatory conduction

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38
Q

what influences the propagation speed of action potentials? (3) (PTD)

A

1) the presence of myelin
2) the thickness of myelin
3) the diameter of the axon

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39
Q

what are the characteristics of type A fibers? (3) (TLF)

A

1) thick myelin
2) large axon
3) fastest

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40
Q

what are the characteristics of type B fibers? (3) (TMS)

A

1) thin myelin
2) medium axon)
3) slower than Type A but faster than Type C

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41
Q

what are the characteristics of type C fibers? (3) (NTS)

A

1) no myelin
2) thin axon
3) slowest

42
Q

what happens at the synapse?

A

information from one neuron (the presynaptic cell) is transmitted to another neuron or an effector cell (postsynaptic cell)

43
Q

how many synapses does the average neuron have?

A

about 5000

44
Q

how many synapses do certain neurons have in the cerebellum?

A

up to 200,000

45
Q

are electrical synapses rare or common?

A

rare

46
Q

how are cells connected in electrical synapses?

A

by gap junction

47
Q

in electrical synapses what is an action potential in the presynaptic cell aways generate ?

A

an action potential in the postsynaptic cell (2 cells behave as one making it fast)

48
Q

what are the most common synapses between neurons?

A

chemical synapses

49
Q

in chemical synapses what occurs to the action potential in the presynaptic cell?

A

it MAY generate an action potential in the postsynaptic cell (allows information processing) (slower)

50
Q

in chemical synapses what is the presynaptic termainal separated from?

A

the postsynaptic membrane

51
Q

what is the presynaptic terminal separated from the post synaptic membrane by in chemical synapses?

A

a synaptic cleft

52
Q

what are synaptic clefts usually filled with?

A

synaptic vesicles containing a neurotransmitter

53
Q

in chemical synapses when an action potential in the presynaptic axon opens what happens?

A

voltage-gated calcium channels and the calcium causes synaptic vesicles to fuse with the presynaptic axon membrane

54
Q

what happens when synaptic vesicles fuse with the presynaptic axon membrane in chemical synapses?

A

the neurotransmitter is dumped into the synaptic cleft

55
Q

after the neurotransmitter is dumped into the synaptic cleft in chemical synapses what does the neurotransmitter usually do?

A

bind to a ligand-gated ion channel that produces a graded depolarization or hyperpolarization

56
Q

when neurotransmitters bind to ligand-gated channels in chemical synapses and produce a grade depolarization or hyperpolarization, what does that depend on?

A

the ion that crosses the membrane and receptor

57
Q

what happens to neurotransmitter in chemical synapses?

A

either enzymatically degraded, taken up by the presynaptic terminal or diffuses out of the synapse

58
Q

what are the neurotransmitters in chemical synapses usually?

A

ligand-gated channels to which only specific molecules can bind

59
Q

what does the effect of a neurotransmitter in chemical synapses on a postynaptic membrane depend on?

A

the nature of the neurotransmimtter receptor and what ion crosses the membrane

60
Q

what is an example that the neurotransmitter AcH would be used for?

A

myasthenia gravis

61
Q

what is an example that the neurotransmitter serotonin would be used for?

A

antidepressant therapy and hallucinogens

62
Q

what are some transitters that fall into the category of biogenic amines?

A

1) serotonin
2) dopamine
3) norepinephrine

63
Q

what is an example that the neurotransmitter dopamine would be used for?

A

drug addiction and parkinson disease

64
Q

what is an example that the neurotransmitter norepinephrine would be used for

A

ADHD and amphetamines

65
Q

what neurotransmitters fall into the category of amino acids? (3) (GGG)

A

1) gamma-amino butyric acid (GABA)
2) Glycine
3) glutamate

66
Q

what is an example that the neurotransmitter GABA would be used for? (3) (BBA)

A

1) barbiturates
2) benzodiazepines (anti-anxiety drugs)
3) alcohol dependence

67
Q

what is an example that the neurotransmitter glycine would be used for?

A

strychnine poisoning

68
Q

what is an example that the neurotransmitter glutamate would be used for?

A

stroke and excitotoxicity

69
Q

what have many substances been identified as?

A

neurotransmittesr

70
Q

what do some neurons release?

A

more than one neurotransmitter

71
Q

what are neuromodulators?

A

neurotransmitters released by neurons that affect synaptic activity at distant synapses

72
Q

what do some drugs affect?

A

synaptic activity

73
Q

what do axoaxonic synapses do?

A

either reduce or increase the amount of neurotransmitters released

74
Q

what is it called when axoaxonic synapses reduce the amount of neurotransmitters released?

A

presynaptic inhibition

75
Q

what is it called when axoaxonic synapses increase the amount of neurotransmitters released?

A

presynaptic facilitation

76
Q

what is a graded depolarization in a postsynaptic neuron called?

A

excitatory postsynaptic potential (EPSP)

77
Q

what is true of EPSP?

A

the neuron is close to firing

78
Q

what neurotransmitter falls into the category of purines?

A

adenosine

79
Q

what is an example that the neurotransmit adenosine is used for?

A

neuroprotective agent and caffeine

80
Q

what is a neurotransmitter that falls under the category neuropeptides?

A

endorphins

81
Q

what is an example of what the neurotransmitter neuropeptides (endorphins) are used for?

A

pain therapy and opiates

82
Q

what is a neurotransmitter that falls into the category of gases?

A

nitric oxide

83
Q

what is an example that the neurotransmitter nitric oxide is used for?

A

stroke damage and treatment for erectile dysfunction

84
Q

what is a graded hyperpolarization in a postsynaptic neuron called?

A

an inhibitory postsynaptic potential (IPSP)

85
Q

what is true of IPSP?

A

the neurons is further from firing

86
Q

is a single EPSP large enough to depolarize the initial segment to or past the threshold?

A

no

87
Q

even though a single EPSP isn’t large to depolarize the initial segment to or past the threshold what does it do?

A

persist for a period of time

88
Q

what has to happen to ESPS and IPSP in order for an action potential to be produced?

A

the EPSP and IPSP are added together in time and the neuron does nothing until the membrane at the initial segment is depolarized to or past the theshold

89
Q

what are two ways that EPSPs can be added together?

A

1) spatial summation

2) temporal summation

90
Q

where do EPSPs and IPSPs ocur?

A

on the dendrite

91
Q

how does spatial summation occur?

A

by 2 or more neurons

92
Q

how does temporal summation occur?

A

by one neuron

93
Q

with thousands of neuron synapses on a neuron what are neural pathways?

A

complex

94
Q

what type of pathways exist?

A

serial and parallel

95
Q

what are some of the circuits that there are evidence of? (4) (CDRP)

A

1) convergent pathways
2) diverging pathways
3) reverberating circuits
4) parallel after-discharge circuits

96
Q

what does convergent pathways allow?

A

IPSPs and EPSPs to affect an output. multiple neurons converge upon and synapse with a smaller number of neurons

97
Q

what does diverging pathways do?

A

enlarge the effect of a signal

98
Q

what does reverberating circuits do?

A

produce a series of action potentials

99
Q

what does parallel after-discharge circuits have?

A

complex functions

100
Q

what type of pathway does divergent pathways create?

A

parallel pathways

101
Q

what does the reverberating circuit cause?

A

complete tetanus

102
Q

what type of circuit is parellel-discharge circuit?

A

serial

► Med - Anatomy & Physiology (130 decks)

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