Structure and function of neurones (3)

Question 1

What’s the structure and function of a motor neurone?

Answer 1

• a long axon
• cell body which has many dendrites
• carries impulses from CNS to effectors

Question 2

What’s the structure and function of a sensory neurone?

Answer 2

• one long dendron which carries and impulse from receptor cells to the cell body
• one short axon carries nerve impulses from the cell body to the CNS

Question 3

What’s the structure and function of relay neurones?

Answer 3

• many short dendrites carry nerve impulses from sensory neurones to the cell body
• axon carries nerve impulses from the cell body to motor neurones

Question 4

What is myelination?

Answer 4

• axons become myelinated as Schwann cells wrap around it and create a fatty layer called a myelin sheath
• the myelin sheath acts as an electrical insulator and helps to protect the nerves from damage and speeds up the transmission of impulses

Question 5

What are the gaps between schwann cells called?

Answer 5

nodes of Ranvier

Question 6

How does myelination speed up nerve impulses?

Answer 6

• depolarisation only happens at the nodes of Ranvier as sodium ion channels are concentrated at the nodes
• the neurone’s cytoplasm conducts enough electical charge to depolarise thr next node so the impulse jumps
• this is called saltatory conduction and its very fast
• this increses the conduction velocity (the speed at which an impulse travels along a neurone) and means that myelinated axons have a higher conduction velocity than un-myelinated neurones.