Neuronal conduction and myelin

Question 1

Which 2 constants affect the speed of action potential propagation?

Answer 1

• Space constant (aka line constant)

- Time constant

Question 2

What does the space constant mean?

Answer 2

Number describing how far current can spread passively down the axon before decaying

Question 3

Which symbol is used for the space constant?

Answer 3

λ

Question 4

Which kind of axons have a longer space constant?

Answer 4

Wider

Question 5

What does the time constant mean?

Answer 5

How long it takes for charge to build up across a membrane

Question 6

What is the effect of myelin on membrane resistance?

Answer 6

Myelin increases membrane resistance

Question 7

What is the effect of myelin on membrane capacitance?

Answer 7

Myelin decreases membrane capacitance

Question 8

What is membrane capacitance?

Answer 8

How stretchy the membrane is

Question 9

What is the effect of myelin on the speed of propagation of action potentials?

Answer 9

Speeds up AP conductance

Question 10

What happens in multiple sclerosis?

Answer 10

• Immune system attacks myelin causing diverse neurological symptoms
• CNS myelin can’t regenerate

Question 11

What happens in Guillain-Barre syndrome?

Answer 11

• Immune system attacks PNS myelin

- PNS myelin can regenerate so patients usually recover