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Flashcards in Lecture 4 Deck (87):
1

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

T

2

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

F. longer

3

How do the neurons of vertebrates and invertebrates differ?

invertebrates have a few very large neurons - escape response

4

The human body has about ___ neurons.

100 million

5

What is MS:

loss of myelin, debilitating loss of conduction in the NS

6

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

T, due to leakage of positive charge

7

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

low

8

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

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

9

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

T

10

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

F. Low internal...

11

Do GPs increase or decrease slowly with time?

increase

12

Do GP's amplitude decrease or increase with distance?

decrease

13

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

time constant

14

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

Space constant

15

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

the signals decay with distance in an exponential manner

16

When is delta Vm measured?

after Vm reaches a steady state

17

math symbol for space constant

lambda

18

The space constant is AKA:

length constant

19

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

space constant (or length constant)

20

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

space constant

21

The space/length constant is related to:

membrane and internal resistance

22

How is the membrane resistance determined?

by the # of open channels

23

What is one space/length constant?

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

24

Internal res is determined by:

diameter of the fiber

25

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

high

26

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

F. The BIGGER the..

27

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

F. Longer space...

28

What changes with the axon radius?

the internal resistance

29

Length constant is related to:

the radius of the cell

30

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

bigger

31

PM resistance is inversely proportional to:

the radius of the nerve fiber

32

internal resistance is inversely proportional to:

(radius)^2 of the nerve fiber

33

As the nerve fiber radius increases, the space constant _______

increases

34

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

faster

35

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

decrease (check)

36

What does the time constant describe?

how fast membrane voltage changes at one location

37

What is capacitance?

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

38

Explain time constant

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

39

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

bc Na channels are closing

40

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

quickly

41

What 2 factors influence the time constant?

membrane resistance and membrane capacitance

42

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

long, short

43

What affect would open channels have on the length constant?

slow down the length constant

44

What is the time constant related to?

capacitance and resistance

45

What determines the speed of a response?

membrane time constant

46

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

T

47

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

time constant

48

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

long

49

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

F. lowers capacitance and shortens the time constant

50

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

short

51

What type of circuit is the membrane?

RC circuit

52

What is capacitance determined by?

thickness of lipid membrane

53

T or F? C for cells varies greatly.

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

54

What does a capacitor do?

absorbs charges

55

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

quickly

56

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

voltage will change slowly

57

This influences graded potential amplitude and speed of response:

resistance

58

This controls the speed of electrical response:

capacitance

59

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

decrease

60

How can you decrease capacitance of a cell?

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

61

T or F? Myelin increase capacitance.

F. Decreases

62

This separated charges across a membrane:

capacitor

63

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

thicker

64

Myelin is wrappings of:

glial cell membranes

65

Where are the channels concentrated on a nerve fiber?

bw myelin

66

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

F. Positive

67

Space immediately adjacent to the Node of Ranvier:

paranode (myelin attachment)

68

This is the myelin attachment:

paranode

69

Space adjacent to the paranode:

juxtaparanode

70

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

F. in internodal regions

71

What is the internodal conduction time?

less than 0.1 msec

72

When does conduction through an internal region slow?

when you are producing another AP at the node

73

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

a couple

74

Why does the AP decay w/out myelin?

Current leaks out through PM (Na+ leaks out)

75

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

large myelinated

76

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

1 or more

77

How is resistance affected if the diameter is increased?

resistance is lowered

78

Do squids have myelinated or unmyelinated axons?

un

79

What does conduction velocity depend upon?

Axon diameter and myelination

80

Synchronized activity by a large number of neurons:

field potential

81

How must neurons be oriented in field potentials?

same direction

82

the measure of voltage of many neurons:

field potential

83

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

to generate a magnetic field

84

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

T

85

What is an ERG?

Electroretinogram

86

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

F.

87

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

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