Speed of the nerve impulse

Question 1

Name + explain the factors that affect the speed action potential travels.

Answer 1

Myelin sheath - saltatory conduction is faster than unmyelinated axon conduction
Axon diameter - Greater diameter, less leaker, faster conduction
Temperature - optimal temp for respiration, produce ATP, ATP used for active transport

Question 2

What is the all or nothing principle?

Answer 2

The stimulus must exceed the threshold value in order to trigger an action potential. If it does not, no action potential occurs.

Question 3

what 2 ways can an organism perceive the size of a stimulus?

Answer 3

By the number of impulses passing in a given time. Bigger stimulus -> more impulses

By having different neurones with different threshold values

Question 4

What is the purpose of the all or nothing principle?

Answer 4

The brain would be overloaded if aware of every stimulus. Therefore, minor or irrelevant stimuli is filtered out.

Question 5

What is the refractory period and why does it occur?

Answer 5

The time period between separate action potentials being generated in an axon.

This occurs as inward movement of Na+ ions is prevented as voltage gated channels are still closed.

Question 6

Purpose of the refractory period.

Answer 6

Ensures action potential is propagated in only one direction

Produces discrete impulses - action potentials are distinct and separate

Limits number of action potentials - limits strength of stimulus