Describe what happens at a synapse in the human body. (6 marks)

Synapses are the junctions between neurons. An electrical impulse travels down the first neuron and arrives at the presynaptic membrane. The presence of an electrical impulse causes chemicals called neurotransmitters to be released into the synaptic cleft, where they then diffuse across the gap and toward the postsynaptic membrane of a second neuron. The neurotransmitter molecules then bind to receptors on the second neuron, an accumulation of bound neurotransmitters generating an electrical impulse in the neuron and allows the electrical signal to continue through the body. After the electrical signal has been generated, the neurotransmitter molecules are released from the receptors and reabsorbed back into the first neuron via the reuptake channels to avoid more impulses being generated unnecessarily.