Synaptic transmissionAQA A-Level Biology: Mind map

Exam questions on Synaptic transmission

1. A neurophysiologist is studying a cholinergic synapse between a presynaptic neurone and a postsynaptic neurone in an autonomic ganglion removed from a mammal. She stimulates the presynaptic neurone so that action potentials arrive at its synaptic knob, and records the response of the postsynaptic neurone.
   Explain why transmission across the synapse can only occur in one direction.2 marks
2. A postsynaptic neurone in a spinal cord preparation has a resting potential of −70 mV and a threshold potential of −55 mV. Each time an excitatory presynaptic neurone releases neurotransmitter, it depolarises the postsynaptic membrane by about 5 mV; this depolarisation fades within a few milliseconds.
   A different presynaptic neurone is inhibitory. Explain how it would reduce the chance of an action potential in the postsynaptic neurone.2 marks
3. A student prepares a frog nerve–muscle preparation in which a motor neurone is still attached to a skeletal muscle fibre. The motor neurone ends at a neuromuscular junction, which uses the same neurotransmitter as the cholinergic synapse in an autonomic ganglion.
   Compare transmission across a cholinergic synapse between two neurones with transmission across a neuromuscular junction.3 marks