Neurophysiology part 1 stack 3

Question 1

Repolarization in generating an AP resets ____, not ionic conditions?

Answer 1

electrical conditions

Question 2

What occurs after repolarization in generating an action potential?

Answer 2

Na+/k+ pumps restore ionic conditions

Question 3

How are the concentrations of Na+ and K+ different on each side of the membrane after repolarization?

Answer 3

Na+ concentration is higher outside cell, K+ concentration is higher inside cell

Question 4

True or false: not all depolarization events produce APS

Answer 4

True

Question 5

What must occur for an axon to “fire”?

Answer 5

depolarization must reach threshold voltage to trigger AP

Question 6

What 4 conditions are involved at threshold that must be reached for axon to fire?

Answer 6

• Membrane is depolarized by 15 to 20 mV
• Na+ permeability increases
  -Na+ influx exceeds K+ efflux
• The + feedback cycle begins

Question 7

What is the definition of All-or-None?

Answer 7

When an AP either happens completely or does not happen at all

Question 8

What does propagation allow an AP to do?

Answer 8

to be transmitted from origin down entire axon length toward terminals

Question 9

Na+ influx through voltage gates in one membrane area cause___?

Answer 9

local currents that cause opening of Na+ voltage gates in adjacent membrane areas, leading to depolarization of area and to next as a result

Question 10

an AP is self propagating ___?

Answer 10

once propagation is initiated

Question 11

What happens in nonmyelinated axons in propagation?

Answer 11

each successive segment of membrane depolarizes then repolarizes

Question 12

What differs in myelinated axons?

Answer 12

Propagation

Question 13

Why is no new AP generated in AP origin?

Answer 13

due to Na+ channels closer to AP origin being inactivated

Question 14

What direction do APs occur?

Answer 14

only in a forward direction

Question 15

All APs are __ and are independent of what ?

Answer 15

alike, stimulus intensity

Question 16

How can CNS tell difference between a weak stimulus and a strong one?

Answer 16

by the frequency of impulses

Question 17

What is frequency regarding APs?

Answer 17

the number of impulses received per second (impulse/second)

Question 18

Higher frequency in AP mean ?

Answer 18

stronger stimulus

Question 19

Time in which neuron cannot trigger another AP is know as?

Answer 19

refractory period where voltage gated Na+ channels ar open, preventing neuron from responding to another stimulus

Question 20

What are the two types of refractory period?

Answer 20

absolute refractory period and relative refractory period

Question 21

Absolute refractory period is the time from what to what?

Answer 21

opening of Na+ channels until resetting of the channels

Question 22

What does absolute refractory period ensure?

Answer 22

that each AP is an all-or-none event

Question 23

Absolute refractory period enforce ___?

Answer 23

one way transmission of nerve impulses

Question 24

What are Na+ channels and K+ channels like in relative refractory period?

Answer 24

Most Na+ channels have returned to their resting state and some K+ channels still reopen

Question 25

Relative refractory period follow refractory period, true or false?

Answer 25

True

Question 26

Repolarization is occurring in relative refractory period, true or false?

Answer 26

True

Question 27

What state is the threshold in relative refractory period?

Answer 27

threshold for AP generation is elevated

Question 28

What could stimulate an AP in relative refractory periods?

Answer 28

only exceptionally strong stimulus

Question 30

Review: where do APs occur in?

Answer 30

only in axons

Question 31

AP conduction velocities in axons vary widely, true or false?

Answer 31

true

Question 32

What two factors doe rate of AP propagation depend on?

Answer 32

axon diameter; large diameter fibers have less resistance to local current flow so have faster impulse condition and degree of myelination

Question 33

What are the two types of conduction depending on presence of absence of myelin in conducting velocity?

Answer 33

continuous velocity and saltatory conduction

Question 34

What are continuous conduction like?

Answer 34

slow and occurs in nonmyelinated axons

Question 35

What are saltatory conduction like?

Answer 35

are about 30 times faster than continuous conduction and occurs in myelinated axons

Question 36

What is the role of myelin sheaths in saltatory conduction?

Answer 36

insulate and prevent leakage of charge

Question 37

___ channels are located at myelin sheath gaps in saltatory conduction?

Answer 37

voltage-gated Na+

Question 38

APs are generated in what location is saltatory conduction?

Answer 38

sheath gaps and electrical signals jump rapidly from gap to gap

Question 39

What factors are never fibers classified on?

Answer 39

diameter, degree of myelination, and speed of conduction

Question 40

What are group A nerve fibers ?

Answer 40

are the largest diameter and include myelinated somatic sensory and motor fibers of skin, skeletal muscles, and joints

Question 41

What nerve fibers are intermediate in diameter and involve lightly myelinated fibers?

Answer 41

Group B

Question 42

Group C fiber are ___ diameter and ___?

Answer 42

smallest, unmyelinated

Question 43

What two group of nerve fibers include ANS visceral motor and sensory fibers that serve visceral organs?

Answer 43

group B and C nerve fibers