Lecture 23: Bioelectricity

Question 1

What is the threshold potential?

Answer 1

-59mV is the the minimum local depolarisation that triggers an action potential

Question 2

What occurs when +30mV is reached?

Answer 2

• depolarisation propagates along the axon - Action potential

Question 3

What must occur for an action potential to happen?

- steps involved

Answer 3

1. Stimulis gated Na+ channels open
2. at -59mV voltage-gated Na+ channels open
3. at +30mV voltage-gated Na+ channels close
4. Voltage-gated K+ channels open
5. K+ channels close at hyper-polarisation
   - RMP restored by sodium/potassium pump

Question 4

What is a refractory period?

Answer 4

• period where axon resists restimulation

Question 5

What is the absolute refractory period?

Answer 5

• the axon will not respond to any stimulus

- AP CANNOT happen

Question 6

What is the relative refractory period?

Answer 6

-only STRONG stimulis will initiate an AP

Question 7

How do action potentials propagated down axons?

Answer 7

by depolarisation in one part of the axon which causes adjacent voltage-gated Na+ channels to open
——> triggers depolarisation of adjacent parts of axon

Question 8

What factors increase the speed of conduction?

Answer 8

• Myelin sheath = prevent ions from leaking through membrane

- Nodes of Ranvier = SALATORY CONDUCTION - AP jumps btw nodes of ranvier