MYELINATION AND SALTATORY CONDUCTION

Question 1

what are nodes of ranvier and how are they adapted for depolarisation?

Answer 1

• gaps in the myelin sheath

- they have lots of Na+ and K+ channels so depolarisation ONLY happens there

Question 2

what is myelin sheath?

Answer 2

• Myelin is an electrical insulator produced by Schwann cells
• it prevents the movement of ions in/ out of the neurone (can’t be depolarised)

Question 3

what is saltatory conduction?

Answer 3

when an action potential jumps between nodes of ranvier, maintaining the transmission of nerve impulses

Question 4

how does temperature affect the speed of an action potential?

Answer 4

• higher temp = higher Ek

- so molecules diffuse faster (up to the optimum temperature)

Question 5

how does the diameter of the axon affect the speed of action potentials?

Answer 5

• greater dimeter = less friction so faster action potential
• less resistance
• more surface area for ion movement

Question 6

MS is a disease in which parts of the myelin sheath is surrounding neurones is damaged. Explain how this results in slower responses to stimuli.

Answer 6

• less saltatory conduction

- depolarisation has to spread over a greater length