1.5.7 speed of transmission

Question 1

myelination

Answer 1

chwann cells wrap around the axon of neurones to create a myelin sheath.
The myelin sheath acts as an electrical insulator because it is impermeable to ions (Na+ and K+).
Depolarisation and action potentials cannot occur at the myelinated parts of the axon and can only occur in the gaps between (the nodes of Ranvier).
The nervous impulse jumps from one node to the next. This is called saltatory conduction.

Question 2

temperature

Answer 2

An increase in temperature increases kinetic energy.

Ions move across the membrane more rapidly when they have more kinetic energy.

Question 3

axon diameter

Answer 3

Giant axons are found in the giant squid and allow it to have a rapid escape response.
Greater axon diameter means there is a greater surface area for the movement of ions across the cell membrane.