Action Potential II: Conduction

Question 1

What is a region of the nerve membrane without myelin called?

Answer 1

a node of Ranvier

Question 1

With myelination, _____ the nerve diameter ______ the conduction velocity.

Answer 1

doubling; doubles

Question 2

_____ are mediated by large, and therefore fast conducting, axons.

Answer 2

Reflexes

Question 2

With myelination, doubling the ______ doubles the ______.

Answer 2

nerve diameter; conduction velocity

Question 5

The _____ and ____ are carried principally by K+ ions.

Answer 5

axoplasmic; outward membrane currents

Question 5

The axoplasmic and outward membrane currents are carried principally by ____.

Answer 5

K+ ions

Question 6

What happens when anesthetic is applied to a long enough length of axon?

Answer 6

APs fire but cannot get past the anesthetic block bc the anesthetic blocks the Na+ channels

Question 6

The action potential “jumps” from node to node; this is called ______.

Answer 6

salutatory conduction

Question 7

______ is limited by the velocity of action potential propagation along sensory and motor axons.

Answer 7

Reaction time

Question 8

The effective resistance between the _____ and the ______ is increased by myelin.

Answer 8

axoplasm; extracellular fluid

Question 8

What is a node of Ranvier?

Answer 8

a region of the nerve membrane without myelin

Question 9

_____ depends only on axon diameter.

Answer 9

Conduction velocity

Question 10

When a node of Ranvier is depolarized to threshold, ____ in the nodal membrane ____ and the node becomes an active locus.

Answer 10

Na+ channels; open

Question 11

An active locus in a _____ axon will depolarize a _____ length of membrane ahead of the active locus than a large diameter axon.

Answer 11

small diameter; shorter

Question 12

The inward membrane current at the active locus is carried by _____.

Answer 12

Na+ ions

Question 13

The _____ “jumps” from node to node; this is called salutatory conduction.

Answer 13

action potential

Question 13

With ______, doubling the nerve diameter doubles the conduction velocity.

Answer 13

myelination

Question 14

The effective resistance between the axoplasm and the extracellular fluid is increased by _____.

Answer 14

myelin

Question 15

What is the safety factor of transmission?

Answer 15

axons have 5-10x excess # of Na+ channels

Question 17

The action potential will propagate more slowly in a ____.

Answer 17

small axon

Question 18

Conduction velocity depends only on _____.

Answer 18

axon diameter

Question 19

______ greatly increases conduction velocity.

Answer 19

Myelination

Question 21

Reflexes are mediated by _____, and therefore ____ conducting, axons.

Answer 21

large; fast

Question 22

The action potential will propagate more _____ in a small axon.

Answer 22

slowly

Question 24

Reaction time is limited by______ along sensory and motor axons.

Answer 24

the velocity of action potential propagation

Question 26

The ______ at the active locus is carried by Na+ ions.

Answer 26

inward membrane current

Question 27

When a ______ is depolarized to threshold, Na+ channels in the nodal membrane open and the node becomes ______.

Answer 27

node of Ranvier; an active locus

Question 29

The ______ between the axoplasm and the extracellular fluid is increased by myelin.

Answer 29

effective resistance

Question 30

Reaction time is limited by the velocity of action potential propagation along ______.

Answer 30

sensory and motor axons

Question 30

The action potential “jumps” from ______; this is called salutatory conduction.

Answer 30

node to node

Question 31

Myelination greatly increases _____.

Answer 31

conduction velocity

Question 32

The effective resistance between the axoplasm and the extracellular fluid is _______ by myelin.

Answer 32

increased

Question 33

Why is there a safety factor of transmission?

Answer 33

1) insures that action potentials will spread down all branches of the axon 2) it allows a shorter absolute refractory period 3) frequency and velocity of APs are increased

Question 34

What is the purpose of myelin?

Answer 34

to insulate the nerve fiber