Nervous impulses

Resting potential

• maintenance of -70mV across membrane.

• No impulse is being transmitted.

Action potential

• difference is reversed and signal is transmitted.

Threshold

a threshold must be reached in order for signal to be sent. (-55mV).

Positive feedback

If enough Na+ move into membrane, triggers more Na+ channels to open.

What happens to Na+ channels when a Stimulus is detected?

FACILITATED DIFFUSION.

• Na+ channels open and Na+ diffuses into membrane causing depolarisation.(less negative)

• Increases permeability.

Generator potential

small changes in membrane potential due to stimuli.

What happens when a large stimulus is detected?

• More Na+ channels open and more Na+ diffuse in. LARGE DEPOLARISATION.

• reaches threshold and reaches +40mv

repolarisation/refractory period

• Na+ channels close and cell is trying to return to resting potential.

• becomes less positive.

• K+ channels open.

Hyperpolarisation

Due to K+ channels opening and moving out so goes slightly under -60mV.

All or nothing response

• Nothing: small stimulus, threshold isnt reached, no action potential.

• large stimulus: action potential definitely reached.

• Frequency of AP shows size of stimulus. More = large.