What is a synapse?

A synapse is the junction or connection between two neurons, or between a neuron and another type of cell, where communication occurs. When an electrical impulse, or action potential, travels down a neuron and reaches the synapse, it triggers the release of neurotransmitters. These chemical messengers then cross the synaptic cleft, the small gap between the neurons, to bind to receptors on the receiving neuron, thereby continuing the transmission of the signal. This process is crucial for the functioning of the nervous system, enabling everything from reflexes to complex behaviors.

The other choices do not accurately define a synapse. A type of neurotransmitter refers to the chemicals that facilitate communication across synapses, but it is not the structure itself. The outer layer of the brain is known as the cerebral cortex, which plays a role in numerous higher-level brain functions but is distinct from synaptic connections. Lastly, a part of the spinal cord refers to the bundle of nerves that transmits signals to and from the brain but does not encompass the specific concept of a synapse.