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Physiology > Lecture 4 > Flashcards

Lecture 4 Flashcards

1
Q

T or F? Conduction is faster if the time constant is shorter.

A

T

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2
Q

T or F? Conduction is faster if the time length constant is shorter.

A

F. longer

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3
Q

How do the neurons of vertebrates and invertebrates differ?

A

invertebrates have a few very large neurons - escape response

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4
Q

The human body has about ___ neurons.

A

100 million

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5
Q

What is MS:

A

loss of myelin, debilitating loss of conduction in the NS

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6
Q

T or F? Graded synaptic potential decay exponentially with distance.

A

T, due to leakage of positive charge

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7
Q

Will a graded potential decay faster in a cell with a high or low membrane resistance?

A

low

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8
Q

What does the decline of the voltage of the graded synaptic potential depend on?

A

is the resistance of the membrane high or is the resistance of the internal cytoplasm high?

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9
Q

T or F? High membrane resistance reduces the decline of a graded synaptic potential?

A

T

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10
Q

T or F? High internal resistance reduces the decline of a graded synaptic potential.

A

F. Low internal…

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11
Q

Do GPs increase or decrease slowly with time?

A

increase

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12
Q

Do GP’s amplitude decrease or increase with distance?

A

decrease

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13
Q

How much time it takes for a graded potential to reach 63% of its maximum value:

A

time constant

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14
Q

How far a graded potential travels before it has decreased in amplitude to 37% of its initial value:

A

Space constant

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15
Q

What will happen to the voltage signals within an axon if the gated channels are blocked?

A

the signals decay with distance in an exponential manner

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16
Q

When is delta Vm measured?

A

after Vm reaches a steady state

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17
Q

math symbol for space constant

A

lambda

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18
Q

The space constant is AKA:

A

length constant

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19
Q

the distance along the nerve fiber where the voltage falls to 37% of the original voltage:

A

space constant (or length constant)

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20
Q

The likelihood of AP going down vs out is related to:

A

space constant

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21
Q

The space/length constant is related to:

A

membrane and internal resistance

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22
Q

How is the membrane resistance determined?

A

by the # of open channels

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23
Q

What is one space/length constant?

A

When a signals voltage has decreased to 37% of what it started out to be, how far how it traveled - that distance is one space/length constant

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24
Q

Internal res is determined by:

A

diameter of the fiber

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25
Q

Will a small diameter fiber have a high or low internal resistance?

A

high

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26
Q

T or F? The smaller the membrane resistance the further the charge will travel.

A

F. The BIGGER the..

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27
Q

T or F? Shorter space constants result in faster conduction.

A

F. Longer space…

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28
Q

What changes with the axon radius?

A

the internal resistance

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29
Q

Length constant is related to:

A

the radius of the cell

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30
Q

The larger the radius, the (bigger/smaller) the length constant.

A

bigger

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31
Q

PM resistance is inversely proportional to:

A

the radius of the nerve fiber

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32
Q

internal resistance is inversely proportional to:

A

(radius)^2 of the nerve fiber

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33
Q

As the nerve fiber radius increases, the space constant _______

A

increases

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34
Q

As the nerve fiber radius increases, electrical signals travel ______.

A

faster

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35
Q

If more channels open on the membrane, the space constant will _______.

A

decrease (check)

36
Q

What does the time constant describe?

A

how fast membrane voltage changes at one location

37
Q

What is capacitance?

A

A measure of how many charges are needed to change cell voltage

38
Q

Explain time constant

A

look at one spot and ask how quickly that one spot changes its voltage

39
Q

Why is a slow depolarization less likely to produce an AP?

A

bc Na channels are closing

40
Q

Will a cell depolarize slowly or quickly at a short time constant?

A

quickly

41
Q

What 2 factors influence the time constant?

A

membrane resistance and membrane capacitance

42
Q

To get a fast response you want a ___ length constant and a ___ time constant.

A

long, short

43
Q

What affect would open channels have on the length constant?

A

slow down the length constant

44
Q

What is the time constant related to?

A

capacitance and resistance

45
Q

What determines the speed of a response?

A

membrane time constant

46
Q

T or F? A fast time constant reaches threshold much sooner

A

T

47
Q

The time required for the voltage to increase or decrease to 63% of the peak:

A

time constant

48
Q

Do neurons with high me capacitance have long or short time constants?

A

long

49
Q

T or F? Myelin increases the capacitance and shortens the time constant.

A

F. lowers capacitance and shortens the time constant

50
Q

Which curve will be higher on the graph, short time constant or long time constant?

A

short

51
Q

What type of circuit is the membrane?

A

RC circuit

52
Q

What is capacitance determined by?

A

thickness of lipid membrane

53
Q

T or F? C for cells varies greatly.

A

F. bc the thickness of most cell membranes is about the same

54
Q

What does a capacitor do?

A

absorbs charges

55
Q

Will the voltage of a cell change slowly or quickly if you only have a resistor?

A

quickly

56
Q

How does adding a capacitor to a cell effect the voltage change?

A

voltage will change slowly

57
Q

This influences graded potential amplitude and speed of response:

A

resistance

58
Q

This controls the speed of electrical response:

A

capacitance

59
Q

Would you need to decrease or increase the capacitance to get a faster response?

A

decrease

60
Q

How can you decrease capacitance of a cell?

A

add myelin, separates opposite charges, not as hard to keep them apart

61
Q

T or F? Myelin increase capacitance.

A

F. Decreases

62
Q

This separated charges across a membrane:

A

capacitor

63
Q

Would you make a membrane thicker or thinner to lower capacitance?

A

thicker

64
Q

Myelin is wrappings of:

A

glial cell membranes

65
Q

Where are the channels concentrated on a nerve fiber?

A

bw myelin

66
Q

T or F? Negative charge travels underneath the myelin until it gets to the next node.

A

F. Positive

67
Q

Space immediately adjacent to the Node of Ranvier:

A

paranode (myelin attachment)

68
Q

This is the myelin attachment:

A

paranode

69
Q

Space adjacent to the paranode:

A

juxtaparanode

70
Q

T or F? K+ channels are located at the Nodes of Ranvier.

A

F. in internodal regions

71
Q

What is the internodal conduction time?

A

less than 0.1 msec

72
Q

When does conduction through an internal region slow?

A

when you are producing another AP at the node

73
Q

Through how many nodes can an AP travel through an unmyelinated axon before it can not produce another?

A

a couple

74
Q

Why does the AP decay w/out myelin?

A

Current leaks out through PM (Na+ leaks out)

75
Q

Which has higher conduction speeds, small diameter non0myelinated axon or large myelinated axon?

A

large myelinated

76
Q

Local circuit current in myelinated axons is sufficient to depolarize how many downstream nodes beyond a block node?

A

1 or more

77
Q

How is resistance affected if the diameter is increased?

A

resistance is lowered

78
Q

Do squids have myelinated or unmyelinated axons?

A

un

79
Q

What does conduction velocity depend upon?

A

Axon diameter and myelination

80
Q

Synchronized activity by a large number of neurons:

A

field potential

81
Q

How must neurons be oriented in field potentials?

A

same direction

82
Q

the measure of voltage of many neurons:

A

field potential

83
Q

Why do the neurons have to be oriented in the same direction for a field potential?

A

to generate a magnetic field

84
Q

T or F? The extracellular potentials produced by field potentials can summate.

A

T

85
Q

What is an ERG?

A

Electroretinogram

86
Q

T or F? The field potential remains the same for the retina no matter how intense of dim light a light flash is.

A

F.

87
Q

How can you determine if photo receptors are functional in the eye?

A

Electrode on retina, flash a light, get various wave forms similar to an EKG

Physiology (55 decks)

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