FACTORS THAT AFFECT SPEED OF ACTION POTENTIAL

Question 1

1. axonal diameter

Answer 1

1. the longer the diameter of the axon, the faster it conducts impulses

Question 2

axon type

Answer 2

1. A-alpha
2. A- beta
3. c

Question 3

the explanation for axonal diameter

Answer 3

larger diameter means there is less friction and more pathway for impulses to move faster before they collide with other particles in the axon.

Question 4

2. temperature

Answer 4

A. high/warm temperature= faster impulse conduction

B. low/cold temperatures= slower conduction because it slows down the opening of sodium ion channels

Question 5

3. degree of myelination

Answer 5

1. myelinated axon conducts impulses faster
   - Shawn cells produce the myelin sheath
   - nodes of the receiver has a lot of sodium gated ion channel thus depolarization occurs there

Question 6

saltatory conduction

Answer 6

1. only occurs in myelinated axons.
2. is the propagation of action potentials along myelinated axons from one node of Ranvier to the next node, increasing the conduction velocity of action potentials.

Question 7

unmyelinated axon

Answer 7

1. there is continuous conduction/ depolarization

2. slower conduction of impulses since there is no saltatory conduction

Question 8

multiple sclerosis

Answer 8

• Autoimmune disease: Immune system attacks the myelin sheath

• Scar – “sclerosis” – forms at the site of damage and blocks action
potential propagation

• Leads to decreased conduction velocity
• Symptoms vary according to location and severity of attacks

Question 9

Action potentials
a) increase in magnitude if the strength of the stimulus
increases.

Answer 9

false

Question 10

action potential result from graded potentials reaching subthreshold
values.

Answer 10

false

Question 11

action potentials are generated during the absolute refractory period

Answer 11

false

Question 12

action potentials are variable in amplitude

Answer 12

false

Question 13

an action potential occurs at nodes of Ranvier

Answer 13

true

Question 14

A decrease in body temperature increases neuronal action

potential velocity.

Answer 14

false

Question 15

Saltatory conduction occurs in myelinated fibers

Answer 15

true

Question 16

The conduction velocity increases with increasing neuronal fiber
diameter.

Answer 16

true

Question 17

Demyelination results in an increase in conduction velocity

Answer 17

false

Question 18

Conduction velocity is slower in neuronal C-fibres than Aalpha fibers.

Answer 18

true, A-fibers are myelinated while C fibers are unmyelinated