Communication and homeostasis - action potentials

Question 1

Stimulus

Answer 1

Excites cell membrane, increasing permeability (sodium ion channels open).
Sodium ions diffuse into neurone down concentration gradient.
Inside of neurone less negative.

Question 2

Depolarisation

Answer 2

Potential different reaches threshold (-55mV).
Voltage-gated sodium ion channels open.
More sodium diffuses in - positive feedback

Question 3

Repolarisation

Answer 3

+30mV - sodium ion channels close and voltage-gated potassium ion channels open.
Membrane more permeable to potassium.
Potassium diffuses out down concentration gradient.
Starts getting membrane to resting potential - negative feedback.

Question 4

Hyperpolarisation

Answer 4

Potassium ion channels slow to close - too many potassium ions diffuse out = overshoot.
Potential difference more negative than resting potential.

Question 5

Resting potential

Answer 5

Ion channels at rest.
Sodium-potassium pump returns membrane to resting potential.
Refractory period - period of recovery.