Answer:
A) Synapses (although B. neurotransmitters and C. receptors are included in this neurotransmission system).
Explanation:
For neurons to send messages throughout the body, they need to communicate with each other to transmit signals. However, neurons are not simply connected to each other. At the end of each neuron is a small space called a synapse, and to communicate with the next cell, the signal must be able to traverse that small space. This occurs through a process known as neurotransmission.
When an electrical signal reaches the end of a neuron, it triggers the release of small sacs called vesicles that contain neurotransmitters. These sacs spill their contents into the synapse, where neurotransmitters move through space toward neighboring cells. These cells contain receptors where neurotransmitters can bind and trigger changes in cells.
Upon release, the neurotransmitter crosses the synaptic gap and binds to the receptor site on the other neuron, stimulating or inhibiting the receptor neuron depending on what the neurotransmitter is. Neurotransmitters act as a key and the receptor site acts as a block. It takes the right key to open specific locks. If the neurotransmitter is able to function at the receptor site, it will cause changes in the recipient cell.
