When an individual has allergies it causes excess mucus to be produced in the nasal passages and sinus cavities. This excess of mucus cannot drain correctly and effectively out the nasal passages at times and as a result, the mucus containing foreign particles flows down the back of the throat, causing post nasal drip.
They transmit signals across a chemical synapse, such as in a neuromuscular junction, from one neuron (nerve cell) to another target neuron, muscle cell, or gland cell. Neurotransmitters are released from synaptic vesicles in synapses into the synaptic cleft, where they are received by receptors on other synapses.
The neurotransmitter then crosses the synaptic gap to reach the receptor site of the other cell or neuron. Then, in a process known as reuptake, the neurotransmitter attaches to the receptor site and is reabsorbed by the neuron. This all happens very quickly and efficiently. Neurotransmitters play a major role in everyday life and functioning.