1.4d Nerve impulse better one

Question 1

How a neurotransmitter triggers a nerve impulse?

Answer 1

1. Neurotransmitter binds to receptor protein (ligand-gated channel) at synapse.
2. Ligand gated channel opens, so Na+ ions diffuse into neuron.
3. Na+ ion movement causes depolarisation of the plasma membrane.
4. Depolarisation reaches critical threshold level.
5. Voltage gated channel opens, so Na+ ions diffuse into neurons down electrochemical gradient.

Question 2

How the resting potential is reset?

Answer 2

1. Voltage-gated channel opens, so Na+ ions diffuse into neuron.
2. Voltage builds up so Na+ channels is inactivated and K+ channel opens.
3. K+ ions diffuse out of the neuron to reverse depolarisation.
4. Resting potential is restored so K+ channels close again and Na+ channels ready again.
5. Sodium-potassium pumps resets the electrochemical gradient.