Spread of the nerve impulse

Question 1

What does the speed at which a nerve impulse travels along the axon depend on?

Answer 1

• the diameter of the axon
• if the axon is myelinated or not
• resistance
• capacitance (surface area)

Question 2

What is the action potential threshold?

Answer 2

the depolarisation at which a neuron will fire an action potential

Question 3

What is the absolute refractory period?

Answer 3

the cells cannot be stimulated to its threshold - all Na channels closed

Question 4

What is the relative refractory period?

Answer 4

a stronger stimulus than normal could induce the action potential - some Na and more K channels open that normal

Question 5

Which axons transmit the fastest?

Answer 5

large diameter axons with fewer channels

Question 6

What is myelin?

Answer 6

a fatty sheath used to insulate the axon

Question 7

What produces myelin in the peripheral nervous system?

Answer 7

Schwann cells

Question 8

What produces myelin in the central nervous system?

Answer 8

Oligodendrocytes

Question 9

What is saltatory conduction?

Answer 9

the propagation of action potentials along myelinated axons from one node to the next

Question 10

What is the relationship between axon diameter and conduction velocity?

Answer 10

• for diameters above 1um myelinated axons are more efficient
• for diameters lower than that unmyelinated axons are more efficient

Question 11

What is the cytoplasm of a nerve axon called?

Answer 11

axoplasm