5.3.7 Factors that Affect the Speed of Conduction

Question 1

What is the speed of conduction?

Answer 1

How quickly an impulse is transmitted along a neurone

Question 2

What factors affect speed of conduction?

Answer 2

• Myelination
• Diameter of axon
• Temperature

Question 3

How does temperature affect speed of conduction?

Answer 3

• Mammals less so, because they maintain a relatively steady body temperature
• However in cold blooded animals, cooler conditions mean less kinetic energy available so rate of facilitated diffusion of potassium and sodium ions during action potential is slowed

Question 4

How does diameter of axon affect speed of conduction?

Answer 4

• Thicker axons, higher speed of conduction
• Thicker axons have a greater surface area so higher rate of diffusion of potassium and sodium ions through protein channels
• Increased rate of depolarisation so action potentials can occur

Question 5

How does myelination affect speed of conduction?

Answer 5

• More myelination, higher speed of conduction
• Depolarisation occurs only between nodes at Ranvier
• So skip out sections where Schwann cells are present
• Schwann cells allow action potentials to jump from one node to the next, called Saltatory Conduction
• So impulse travels much faster than unmyelinated neurones