Nervous System

Which of the following pairs of cells and structures possess myelin sheaths?

• I and II

• II and III

• III and IV

• IV and I

A delay of 0.5ms occurs in transmission across a synapse because

• calcium ions diffuse into the synaptic knob

• ion channels in the postsynaptic membrane respond slowly to the presence of acetylcholine which diffuses across the cleft

• the synaptic knob releases acetylcholine which diffuses across the cleft

• the presynaptic membrane is in a refractory period

Which combination below shows how positive feedback affects a change in output and the directional flow of an impulse? Output : Directional flow

• Large : same direction

• Small : opposite direction

• Large : no direction

• Small : same direction

Which of the following explains why respiratory poison would affect the transmission of nerve impulses?

• Na+ gates require energy to open

• Energy is required to restore the resting potential

• Energy is required to change the voltage potential from -70mV to +40mV

• They act as inhibitors of transmitter substances

• A

• B

• C

• D

The speed of transmission of a nerve impulse is affected by the

• strength of the impulse

• concentration of acetyl choline

• presence of the myelin sheath

• amount of Na+ that enters the neurone

The diagram shows the gap between two neurones. The protein receptors for the neurotransmitter are located at

• 1

• 2

• 3

• 4

Which region assists in speeding up the conduction of nerve impulses?

• I

• II

• III

• IV

Diffusion of sodium ions into the axon occurs at

• I

• II

• III

• IV

• A

• B

• C

• D