Resting potential

Question 1

What term do we use to describe motor neurones?

Answer 1

• Myelinated motor neurone.

Question 2

Structure of myelinated motor neurone.

Role: cell body.

Answer 2

• Cell body: contains organelles found in typical animal cell, inc nucleus.
• Proteins/ neurotransmitters made here.

Question 3

Structure of myelinated motor neurone.

Role: Dendrites.

Answer 3

• Role: carry action potentials to surrounding cells.

Question 4

Structure of myelinated motor neurone.

Role: axon.

Answer 4

• Role: conductive, long fibre that carries nervous impulse along motor neurone.

Question 5

Structure of myelinated motor neurone.

Role: Schwann cells.

Answer 5

• Role: Schwann cells wrap around axon to form myelin sheath.

Question 6

Structure of myelinated motor neurone.

Role: myelin sheath.

Answer 6

• Lipid:
• Doesn’t allow charged ions to move through it (from inside to outside of axon.)
• Doesn’t allow impulse to pass through.

Question 7

Structure of myelinated motor neurone.

Nodes of Ranvier

Answer 7

• Gaps between the myelin sheath.
• At each Node of Ranvier, action potential can be generated.

Question 8

Def: resting potential.

Answer 8

• The difference in electrical charge between inside and outside of neurone when it is not conducting an electrical impulse.

Question 9

What is resting potential value? Why is it negative?

Answer 9

• Resting potential: -70mV.
• Why negative: More Na+ and K+ ions outside compared to inside neurone.
• Inside neurone: comparatively more negative than outside.

Question 10

How is a resting potential established?

MS answer.

Answer 10

1.) Active transport of Na+ and K+ ions using sodium-potassium pump.
2.) Pump moves 2K+ ions in and 3Na+ ions out of axon.
3.) Higher concentration of K+ ions inside and higher concentration of Na+ ions outside. Creates electrochemical gradient.
4.) K+ diffuses out/ Na+ diffuses into axon by facilitated diffusion through channel proteins.
5.) Membrane more permeable to K+ ions, more ions moved out –> resulting in -70mV inside the axon.

Question 11

Does establishing a resting potential require ATP? Why/ why not?

Answer 11

• Yes.
• Active transport of Na+ and K+ ions using sodium-potassium pump.

Question 12

What three proteins in axon cell-surface membrane help to establish resting potential?

Answer 12

• Sodium-potassium pump: carrier protein.
• K+ channel protein.
• Na+ channel protein.

Question 13

2K+ ions move inside …….. and 3Na+ ions move to ……… …. ………

Answer 13

1.) Axon.
2.) Outside the axon.

Question 14

2 reasons.

Why is axon membrane more permeable to K+ ions than Na+ ions?

Answer 14

1.) More K+ protein channels than Na+ channels.
2.) K+ channels mostly open, Na+ channels may only open when high enough voltage.

Question 15

Name of Na+ protein channels that would only open at high enough voltage.

Answer 15

• Na+ voltage-gated channels.

Question 16

Paper 2 2021

Scientist investigated effect of inhibitors on neurones. She added respiratory inhibitor to neurone. Resting potential of neurone changes from -70mV to 0mV.
Explain why.

Answer 16

• No/ less ATP produced.
• No/ less active transport.
• Electrochemical gradient not maintained.