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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
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

Physiology (55 decks)

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