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