transmission speed of nerve impulses

Question 1

what are the three main factors that affect the speed at which nerve impulses travel along neurones?

Answer 1

temperature, axon diameter and myelination

Question 2

how does temperature affect the speed at which nerve impulses travel along neurone?

Answer 2

an increase in temperature will increase the speed of transmission up to a particular temperature. this is due to an increase in the diffusion of ions and in enzyme activity particularly in respiration which provides ATP for active transport by the sodium-potassium pump.

above a particular temperature denaturation of enzymes (affecting respiration) and of the proteins in the plasma membrane would stop impulses being transmitted.

Question 3

how does axon diameter affect the speed at which nerve impulses travel along neurone?

Answer 3

the greater the diameter of an axon, the faster the speed of conductance.

Question 4

how does myelination affect the speed at which nerve impulses travel along neurone?

Answer 4

in myelinated neurones (containing an insulating myelin sheath), speed of transmission of impulses is increased as the action potential ‘jumps’ from one gap (node of Ranvier) to the next. depolarisation only occurs at these nodes. this is known as saltatory conduction.

in non-myelinated neurones depolarisation occurs along the whole membrane of the axon which will slow down the speed of transmission.