Nerve Conduction

Question 1

Draw a diagram of a myelinated nerve and action potential

Answer 1

pg 3

Question 2

What are the two different types of nerve conduction?

Answer 2

electronic conduction

saltatory conduction

Question 3

Where are the nodes of ranvier

Answer 3

in b/w the myelin sheathes on a nerve cell

Question 4

electronic conduction is through a ______ neuron

Answer 4

non-myelinated

Question 5

saltatory conduction is through a ______ neuron

Answer 5

myelinated

Question 6

describe how action potential travels vis electronic vs saltatory conduction

Answer 6

much faster via saltatory b/c the myelin sheaths help it travel faster

Question 7

“conduction velocity” is another way of saying

Answer 7

propagation: a AP traveling down a cell

Question 8

what are the two passive properties of axonal membranes

Answer 8

time & space

Question 9

time and space constants are refelctions of what

Answer 9

the physical properties of the neuronal memrane

Question 10

describe what the time constant tells you

Answer 10

how rapidly a membrane will respond to a stimulus.

the time it takes for the membrane potential change to reach 63% of its final value.

Question 11

RmCm represents

Answer 11

time constant

Question 12

what variables represent time constant

Answer 12

RmCm

Question 13

the time constant represents the amount of time it will take for the membrane potential to reach what percent of its final value

Answer 13

63%

Question 14

the smaller the time constant, the greater

Answer 14

the propagation velocity

Question 15

what does Rm stand for

Answer 15

Resistive properties of the membrane

Question 16

Rm is inversely related to what

Answer 16

permeability

Question 17

if there is high membrane resistance, there will be

Answer 17

low permeability

increased time constant

Question 18

What does Cm stand for?

Answer 18

Membrane Capacitance

Question 19

really generally, membrane capacitance is a fancy way for saying

Answer 19

cell size

Question 20

the larger the membrane capacitance, the

Answer 20

the greater the amount of charge that must flow to depolarize the membrane, the longer the time constant will be.

Question 21

What is the equation for the length (space) constant?

Answer 21

√Rmd/Ri4

Question 22

define the length constant

Answer 22

the distance it takes for the depolarization to decay by 63%

Question 23

the greater the space constant, the

Answer 23

greater the propagation velocity

Question 24

What does 
Rm
d
Ri
stand for in the length constant equation

Answer 24

Rm = membrane resistance
d = diameter of axon
Ri = internal resistance

Question 25

Using the length constant, describe why humans have myelinated axons

Answer 25

In order to increase propagation velocity by a factor of 2, the axon diameter has to quadruple because of the square root relationship in the length constant formula. Not practical in humans. √Rmd/Ri4

Question 26

another name for length constant

Answer 26

space constant

Question 27

the propagation veloctiy is directly proportional to what? inversely proportional to what?

Answer 27

directly proportional to the space constant | inversely proportional to the time constant

Question 28

what has to be done in electronic conduction in order for AP to be propegated along the entire length of the axon?

Answer 28

each adj. region has to be depolarized

Question 29

what forms myelin

Answer 29

axon wrapped in sheath of schwann cells

Question 30

what cells surround the axon in the CNS

Answer 30

Oligodendroglial cells

Question 31

what cells surround the axon in the PNS

Answer 31

schwann cells

Question 32

where is AP generated in myelnated axon

Answer 32

nodes of ranvier

Question 33

myelin does what to the membrane resistance & the membrane capitance

Answer 33

increases membrane resistane | decreases membrane capitance

Question 34

what does myelin do to Cm and Rm

Answer 34

The myelin effectively reduces the Cm and increases Rm to decrease time constant and increase length constant

Question 35

myelinated axon has greater conduction velocity than an unmyelinated axon fiber that is how much larger in diameter

Answer 35

100x

Question 36

in unmyelinated axons, what determines the conduction velocity

Answer 36

the diameter of the axon | the larger the diameter of the axon, the greater the speed of propagation

Question 37

in myelinated axons, what determmines the conduction velociy

Answer 37

the distance b/w the nodes of ranvier | the greater the distance b/w the nodes of ranvier, the greater the velocity of the AP propagation

Question 38

the larger the membrane capacitance, what happens to time constant

Answer 38

increases time it takes to make depolarization change | longer time constant

Question 39

large diameter axon compared to small diameter, resistance to flow smaller in which one

Answer 39

the large diameter axon

Question 40

a lot of resistance what happens to time constant

Answer 40

increases time constant

Question 41

low resistance to membrane (no myelin) what happens to time constant what happens regarding capacitance

Answer 41

decrease in time constant high capacitance overall take more time for time constant

Question 42

the more cell membrane needed to charge up, the longer its going to take to

Answer 42

make depolarization change

Question 43

the shorter the time constant the

Answer 43

faster the velocity propagation

Question 44

if it has high resistance it likely is a

Answer 44

myelinated neuron

Question 45

why do you want resistance to be high

Answer 45

so the AP doesn't leave | think of it as insulation

Question 46

longer length constant means what

Answer 46

it will move farther before it decays

Question 47

when you get to node of ranvier you will always trigger a

Answer 47

action potential

Question 48

capacitance goes way what with myelination

Answer 48

down

Question 49

in MS what happens

Answer 49

start loosing myelin

Question 50

what happens to conduction velocity in MS and why

Answer 50

it decreases | b/c resistance of membrane has gone down but capacitance has gone up. so the neurons will act like un-myelinated neuron

Question 51

what happens to length constant in MS

Answer 51

goes down

Question 52

what happens to time constant in MS

Answer 52

goes up

Question 53

for unmyelinated nerve conduction velocity is proprotional to

Answer 53

diameter of axon

Question 54

myelinated nerve velocity of propagation is determed by

Answer 54

distance b/w nodes of ranvier