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BIPN 105 > Sciatic Nerve > Flashcards

Sciatic Nerve Flashcards

1
Q

What are the 5 parts that make up a neuron (nerve cell)?

A
  1. Dendrites
  2. Cell body
  3. Hillock
  4. Axon
  5. Terminals
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2
Q

What is the dendrites for?

A

-main input; where most neurons come into contact and where it synapses

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3
Q

What does the cell body have?

A

has nucleus

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4
Q

Where do APs start?

A

Hillock

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5
Q

What carries APs towards other cells?

A

Axon

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6
Q

What are the terminals for?

A

axon branches to contact multiple cells

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7
Q

What is the chemical potential of the inside of the cell membrane?

A 
[K+]= 150 mM
[Na+]= 15 mM
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8
Q

What is the chemical potential of the outside of the cell?

A 
[K+]= 5.5 mM
[Na+]= 150 mM
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9
Q

How do ions move for chemical potential?

A

pushing ions toward the lower [ ]

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10
Q

How do ions move for electrical potential?

A

pulling the ion back

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11
Q

What does the Nernst Equation calculate?

A

The equilibrium potential of an ion (Eion)

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12
Q

What is the Nernst equation?

A

Eion = (61/z) log ( [ion]outside / [ion]inside )

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13
Q

What is z?

A

z= ion’s charge

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14
Q

What is the equilibrium potential for potassium?

A 
Ek= (61/1) log (5.5/150)=
Ek= -90mV
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15
Q

What is the equilibrium potential for sodium?

A 
Ena= (61/1) log ( 150/15 )
Ena= +61 mV
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16
Q

What is the equilibrium potential of chloride?

A

Ecl= -70 mV

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17
Q

What does the Goldman equation calculate?

A

the membrane potential (Vm)

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18
Q

What is the Goldman equation?

A

Vm= (61/ |z|) log ( (Pk [K+]outside + PNa [Na+]outside + PCl [Cl-] inside) / (Pk [K+}inside + PNa [Na+]inside + PCl [Cl-] outside) )

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19
Q

What is P?

A

P= permeability

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20
Q

At rest which is greater between Pk and Pna? Why?

A

Pk&raquo_space; Pna

Because there are more K+ leak channels

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21
Q

What is the membrane potential at rest?

A

Vm= -70mV (closer to Ek because there is more K+ inside the cell)

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22
Q

What does it mean to depolarize?

A

Raise the membrane potential toward 0

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23
Q

What does repolarize mean?

A

return the membrane potential back to 0

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24
Q

What is hyperpolarize?

A

When the membrane potential is taken below rest

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25
Q

What type of recording is used to measure the membrane potential?

A

Intracellular recording

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26
Q

What is Threshold potential?

A

V(T); The membrane potential (Vm) at which an action potential is initiated

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27
Q

APs are considered to be…?

A

“All or Nothing”

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28
Q

What does subthreshold mean?

A

no AP

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29
Q

Suprathreshold?

A

complete AP

30
Q

What does V(T) serve as?

A

As a noise filter

31
Q

What do neurons use to code information?

A

frequency modulation

32
Q

What type of ion channels generate AP phases?

A

By voltage-gated ion channels

33
Q

What does the activity of voltage-gated ion channels depend on?

A

Activity is dependent on the Vm (membrane potential)

34
Q

What does depolarization trigger?

A

Na+ channel activation (opens)

35
Q

Why is there a large flux of Na+ into the cell when depolarization occurs?

A

Because the resting Vm is very far from Ena

36
Q

What are the 3 steps in Repolarization?

A
  1. Na+ channel inactivation
  2. K+ channel activation
  3. K+ flows out-> rapid repolarization
37
Q

What triggers Na+ channel inactivation for repolarization?

A
  • Time dependent (occurs as soon as Na+ channel open)

- Very fast

38
Q

What is the difference between inactivation and deactivation?

A
  • Inactivation: the channel is activated (open) but something is blocking the pore
  • Deactivation: the pore closes, stopping the ion from going through the channel
39
Q

What happens when hyperpolarization occurs?

A

Excess Ik (current of K+) leaving the cell

40
Q

What does excess K+ leaving the cell drive?

A

Drives Vm below resting Vm

41
Q

What are the 3 steps of Return to Vrest?

A
  1. K+ channel deactivation
  2. Na+ channel deactivation
  3. Vm -> Vrest
42
Q

What is K+ channel deactivation dependent and not dependent on?

A
  • Voltage-dependent (triggered by repolarization)

- NOT time dependent

43
Q

What is Na+ deactivation dependent on? What does it remove?

A
  • Voltage-dependent

- Required to remove inactivation of Na+ channels

44
Q

Which channels are the only ones activated at Vrest?

A

K+ leak channels are the only activated channels

45
Q

What are Refractory Periods?

A

how long a neuron must wait before it can fire a second AP

46
Q

What is Absolute Refractory Period (ARP)?

A

When a 2nd stimulus is fired-> no 2d AP

- Na+ channels are still inactivated

47
Q

What is Relative Refractory Period (RRP)?

A

When a big 2nd stimulus is fired -> 2nd AP generated

48
Q

Why does a 2nd AP generate during RRP?

A

Still have high Pk (some K+ channels haven’t deactivated yet)

49
Q

For conduction velocity, what size diameter causes velocity to be greater?

A

A bigger diameter

50
Q

What is Myelination?

A

lipid bilayer wrapped around an axon- acts as insulation so passively spreading depolarization does not drop below V(T)

51
Q

What is Saltatory conduction?

A
  • AP “jumps” node to node (depolarization passively spreads under the myelin)
  • APs regenerated at the nodes (so APs don’t get smaller as they spread)
  • APs spread much faster
52
Q

What are the types of neurons?

A

Type A, B, and C

53
Q

What are the type A subgroups?

A

alpha, beta, gamma, and delta fibers

54
Q

Which is the fastest to slowest of the fibers? Why?

A

Type A> B > C

  • Type A are large and myelinated (20-100 m/sec)
  • Type B are also myelinated but have a smaller diameter
  • Type C are small and not myelinated
55
Q

Which of the subgroups of type A are fastest to slowest?

A

alpha> beta> gamma> delta

56
Q

What type of fibers does the Sciatic Nerve mostly made of?

A

Type A fibers

57
Q

What are Compound nerves?

A

bundles of different types of axons

58
Q

What is Compound Action Potential (CAP)?

A

summation of individual APs

59
Q

What does max CAP mean?

A

all neurons types have been recruited

60
Q

Is a CAP an “All or Nothing” AP?

A

No, it is the summation of the individual “All or Nothing” APs of multiple neurons

61
Q

Why can’t you do an intracellular recording of the sciatic nerve?

A

Because the sciatic nerve is made up of thousands of axons, must do extracellular recording

62
Q

What is subtracted in a bipolar recording?

A

The voltage at the “-“ electrode from the voltage at the “+” electrode

63
Q

Which recording electrode records the “+” deflection?

A

negative recording electrode

64
Q

Which electrode records the “=” deflection?

A

positive recording electrode

65
Q

What phase of the AP are these electrodes recording?

A

Depolarization

66
Q

Which Type A fiber has the lowest threshold?

A

alpha, then beta, gamma, and delta

67
Q

What is Latency?

A

The time between the onset of the stimulus and the recording of the CAP

68
Q

Changing the polarity of the stimulus can affect what two things?

A

Can affect both the latency and CAP amplitude

69
Q

How do you calculate conduction velocity?

A

CV (m/sec or mm/msec) = distance traveled (mm) / time to travel this distance(msec)

70
Q

What is measured for conduction velocity?

A

The time at CAP amplitude between two consecutive CAPS and the distance traveled (from electrode to electrode)

71
Q

What is the “normal” range for conduction velocity?

A

20-100 msec

BIPN 105 (6 decks)

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