Nerve Impulses - Synapse Steps

Resting State

This means they have a small electrical charge, with more positive ions (sodium) outside the cell and more negative ions (potassium) inside the cell.

Stimulation

This causes tiny gates in the neuron’s membrane to open and let in positive ions (sodium).

Action Potential

“All or none law” - If enough positive ions enter, it creates a big electrical signal - this signal travels down the neuron like a wave, passing from one part of the cell to the next (ie a nerve impulse).

Moving the Signal

It doesn't move backward because after each section of the neuron fires, it needs a short time to reset before it can fire again.

Synapse

When the nerve signal reaches the end of the neuron, it hits a small gap called a synapse. The signal can’t jump this gap directly, so the neuron releases chemicals called neurotransmitters into the gap.

Next Neuron

These neurotransmitters attach to the next neuron, and if the signal is strong enough, it triggers the next neuron to send the signal on or makes the muscle contract.

What happens at a synapse?

6 stages - Electrical -> chemical -> electrical.

Stage 1

Nerve impulse arrives at the synapse/presynaptic membrane

Stage 2

Vesicles release neurotransmitter molecules

Stage 3

Neurotransmitter is called acetylcholine

Stage 4

The neurotransmitter diffuses across the synapse

Stage 5

The neurotransmitter attaches to receptors/receiving neurons

Stage 6

Nerve impulse restarts in the receiving neuron