Action Potentials

Question 1

What is the function of action potentials?

Answer 1

1. Neurons send nerve impulses called action potentials. These involve changes to the concentration of sodium (Na+) and potassium (k+) ions across a membrane

Question 2

What are the stages of action potentials?

Answer 2

1. Depolarisation
2. Hyperpolarisation
3. Refractory period

Question 3

What happens within depolarisation?

Answer 3

1. If the threshold is reached, an action potential is triggered
2. Na+ ions continue to enter the neuron
3. The neuron becomes positively charged

Question 4

What happens within repolarisation?

Answer 4

1. Peak voltage occurs at +40MV (millivoltage)
2. Na+ channels close and k+ channels open
3. K+ ions leave the neuron
4. The neuron becomes negatively charged inside

Question 5

What happens within hyperpolarisation?

Answer 5

1. The charge of the neuron goes below normal resting potential
2. More k+ are outside the cell than Na+ are inside

Question 6

What happens within the refractory period?

Answer 6

1. Sodium/potassium pumps more k+ ions in and Na+ ions out
2. The neuron returns to its resting potential

Question 7

What happens within salutatory conduction?

Answer 7

1. The myelin sheath and nodes of ranvier allow the action potential to jump down the axon quicker as charges only occur at nodes of ranvier