(S1W1) Neurophysiology part 5

Question 1

What is the refractory period?

Answer 1

• Whilst repolarising, the sodium channels are insensitive so they cannot be activated
• this ensures that when we have just had an action potential, we cannot have another action potential in the same place for a certain period of time
• a second sitmulus within this period of time will not stimulate an action potential

Question 2

What is the purpose of the refractory period?

Answer 2

to ensure the action potential only travels in one direction along the membrane

Question 3

What happens after depolarisation?

Answer 3

• After depolarisation, the sodium potassium pump uses energy (ATP) (active transport) to repolarise and return to baseline
• Active transport - splits an ATP into ADP and Phosphate, releasing energy which is used to actively transfer 3 sodium ions out for every 2 potassium ions pumped in

Question 4

When does it mean if hyperpolarisation occurs after depolarisation?

Answer 4

an over shoot has occured during repolarisation

Question 5

What is meant by summation in terms of membrane potentials?

Answer 5

summation of multiple signals that might not be strong enough individually to reach the threshold but can sum together to reach the threshold

Question 6

What are the two type of summation?

Answer 6

• temporal = timing
• spatial = location

Question 7

Explain temporal summation

Answer 7

• if the same dendrite was receiving different signals one after another, that would be temporal summation
• For example, if it takes about 15 ms to return to baseline from a signal that didn’t reach the threshold, if another signal is received at the same location within 15 ,s it can sum together with the previous signal to reach the threshold.

Question 8

What is spatial summation?

Answer 8

different signals received at the same/similar times but from different locations and can add up to reach the threshold