15.4 speed of nerve impulse

Question 1

what is the refractory period?

Answer 1

prevention of inward movement of Na+ ions because Na+ voltage-gated channels are closed
-> impossible for further action potential to be generated

Question 2

what is meant by the all-or-nothing principle?

Answer 2

• threshold value must be reached or no action potential & impulse is formed
• only stimulus > threshold value will generate action potential & impulse

Question 3

in which 3 ways is the refractory period important?

Answer 3

1- ensure action potentials are propagated in 1 direction only
2- produce discrete impulses - new action potential can’t be produced immediately
3- limits the number of action potentials in an axon in a given time