Q.Chemicals which are released at the synaptic junction are called

Imagine a relay race where one runner has to hand a baton to the next before the message can keep moving. A single neuron is like one runner: it can carry an impulse along its own length, but it cannot by itself reach every part of the body. To pass information onward, it must hand the signal over to the next neuron. The place where this handover happens is called a synapse, and the way the signal crosses it is the synaptic transmission mechanism.

A synapse is formed where the membrane of one neuron meets the membrane of the next. The neuron that brings the impulse up to the junction is called the pre-synaptic neuron, and the one that receives it on the far side is the post-synaptic neuron. There are two kinds of synapse, and they hand the signal over in very different ways.

• At an electrical synapse the two membranes lie extremely close together, almost touching. Electric current can therefore flow straight from one neuron into the next, much as an impulse moves along a single continuous axon. This makes transmission very fast, but such synapses are rare in the human body.
• At a chemical synapse the two neurons are not in direct contact. A narrow, fluid-filled gap called the synaptic cleft separates them. Since electricity cannot leap this gap, the signal is carried across by chemical messengers called neurotransmitters, which are stored in tiny sacs (synaptic vesicles) in the pre-synaptic terminal.

Understanding synaptic transmission matters because it is the point where the nervous system does more than just carry a message — it decides what to do with it. A chemical synapse can make the next neuron either more likely or less likely to fire, and it is by combining countless such decisions that the brain processes and controls everything the body does.