Receptors (Resting and action potentials)

Why are receptors specific?

They only detect one particular stimulus

What is a resting potential?

When a neurone is not transmitting an action potential

What does the Na/k+ pump transport out of the axon in the resting potential?

3 Na+

What does the Na/k+ pump transport into the axon in the resting potential?

2 K+

How are the Na and K transported?

Active transport

What does the membrane being differentially permeable mean?

Some K+ channels are open but there are no Na+ channels

What does the membrane being differentially permeable allow?

The facilitated diffusion of K+ out of the axon

What does the difference in charged ions either side of the membrane give?

A potential difference

What is the Potential difference at the resting potential?

-70mV

What activates an action potential?

A stimulus

What does the stimulus near the region of the membrane cause?

Some Na+ channels to open

What happens if there’s a bigger stimulus?

More Na+ channels open

What does Na+ channels opening allow?

Facilitated diffusion of Na+ back into the axon

What happens if the threshold is met?

Opens the voltage gated Na+ channels

What happens when the voltage gated Na+ channels are opened?

Allows Na+ to flood into the axon

What makes the membrane depolarised?

More positive ions inside than outside the membrane

When is the action potential achieved?

At 40mV

What happens when the action potential is reached?

Na+ channels close and k+ channels open

How do the K+ ions move out?

Facilitated diffusion

What happens to the membrane when K+ are moved out the axon?

Repolarised

What happens at the resting potential?

K+ channels are slow to close

What happens when the K+ channels are slow to close?

Hyperpolarisation of the membrane

Why is the membrane hyperpolarised?

Too many K+ leaving the axon

What is the refractory period?

Once the k+ channels close, the Na/k+ pump resets the resting potential