Membranes of pre-synaptic and post-synaptic neurons play an important role in transmission of nerve impulses. Explain the principles of synaptic transmission. (8marks)

Synapse is the gap between two adjacent neurons in which neurotransmitters are released. Arriving action potential depolarises pre-synaptic membrane. This causes voltage gated calcium channels in membrane to open and leads to an influx of calcium ions. This then causes vesicles containing neurotransmitters to move towards and fuse with pre-synaptic membrane. Contents are then released via exocytosis into synapse. Neurotransmitters move towards the post synaptic membrane due to diffusion and bind to receptors. Any excess neurotransmitter is broken down and removed. Neurotransmitters binding to receptors causes opening of channels which allows sodium/potassium ions to diffuse. Leading to depolarisation and initiation of the the action potential in post synaptic membrane. Remember: You can get marks for annotated and clear diagrams in examTwo marks are awarded for SPAG