Action Potentials

Question 1

What is a delayed rectifier?

Answer 1

K+ ion channels slow to open after depolarisation

Reset membrane potential

Question 2

What is the refractory period?

Answer 2

The time in which an excitable cell is unable to generate a subsequent action potential
Absolute- all sodium channels open so no more to open
Relative- cell is repolarising (hyperpolarisation) so reduced probability of depolarisation

Question 3

What influences action potential conduction velocity?

Answer 3

Axon diameter- resistance to cytoplasm
Resistance of plasma membrane
Na+ ion channel density along axon
Myelination

Question 4

What does the action potential initiate along the myelinated axon?

Answer 4

Axon hillock/ axon initial segment

Node to node communication- passive depolarisation to next node

Question 5

What is the different in conduction velocity between unmyelinated and myelinated axons?

Answer 5

Not- 1/10 m/s

Myelinated- 60/120 m/s

Question 6

What are mechanoreceptors?

Answer 6

Stretch, bend or pressure sensitive unmyelinated fibres

Mechanosensitive ion channels- gating depends on stretch of surrounding membrane

Question 7

What information is encoded by the action potential?

Answer 7

Stimulus strength- firing frequency

Stimulus onset/ offset- first and last action potential