Graph of 15.2

Question 1

What happens at 1?

Answer 1

Na+ ions/K+ ion pump active maintaining resting potential

Question 2

What happens at 2?

Answer 2

Stimulus causes some Na+ ions channels to open allowing some Na+ ions into the axon

Question 3

What happening at 3?

Answer 3

Resting potential of -70mV When no impulse

Question 4

What happening at 4?

Answer 4

Membrane potential is less negative as Na+ ions diffuse through the axon

(-55mV threshold reached)

Question 5

What happening at 5?

Answer 5

All Na+ ion channels open - rapid influex (IN) of Na+ ions

Question 6

What is happening at 6?

Answer 6

All Na+ ion channels close at +40mV

Question 7

What happening at 7?

Answer 7

All K+ ion channels open

Question 8

What is happening at 8?

Answer 8

Rapid eff;ux (OUT) of K+ ions = electricla charge inside axon falls as K+ ions move out so axon membrane starts to be repolarised back to the original -70mV

Question 9

What is happening at 9?

Answer 9

K+ ion channels remai open = hyper polarisation

Question 10

What is happening at 10?

Answer 10

K+ ion channels clse at -80mV/90mV

Question 11

What is happening at 11?

Answer 11

Na/K ion pump now allow membrane potential to go from hyper-polarised back to resting potential of -70mV

Question 12

What is happening at 12?

Answer 12

Resting potential is re-estbalished at -70mV

Question 13

Explain the shape of the curve for sodium ions between 0.5 ms and 0.7 ms

Answer 13

Sodium channel protein close

Sodium ions move into the axon membrane by faciliated diffusion (depolarisation)

More sodium channels are open

Makes inside of axon less negative

Question 14

During an action potential, the membrane potnetial rises to + 40mV and then falls

Use this information to explain the fall in membrane potential

Answer 14

Potassium channels open

Sodium channel protein close

Potassium ions move out of axon membrane by facilitated diffusion (repolarising)

Making axon membrane change from +ve to -ve

Question 15

After exercise,

some ATP is used to re-estbalish the resting potential in axons

Explain how the resting potential is re-established

Answer 15

Resting potential is re-established

Active transport is used to pump 3Na+ out of the axon membrane and pump 2K+ in the axon membrane using sodium-potassium pump

Question 16

Protein C requires ATP to function

Describe the function of C

Answer 16

C is the sodium-potassiium pump

It requires ATP for active transpirt to move 3Na+ ions out of the membrane and 2k+ in the membrane

This helps to restore resting potential

Restores ion balance after an action potential

Transport sodium and potassium ions

Question 17

The plasma membrane of the neurone is more permeable to the potassium ions than the sodium ions

Give the evidence from diagram that supports this

Answer 17

Fewer protein B molecules to transport sodium ions

Question 18

Describe how the resting potential is re-established in an axon by the movement of ions across the membrane

Answer 18

Pump 3Na+ ions out of the axon membrane while 2K+ pump in using sodium-potassium pump by active transpirt

Some diffusion of K+ out of thr axon (more channel proteins of K+ than Na+)

Question 19

Sodium and potassium ions can only cross the axon membrane through porteins

Explain why

Answer 19

Can not pass through the phospholipid bilayer

Because water soluble and not lipid soluble

Charged

Hydrophillic

Question 20

Protein A and B differ from each other

Explain why different proteins are required for the diffusion of ions through membrane

Answer 20

Different proteins have different specific tetirary structure

Ions have different sizes/shapes