What is the primary function of neurotransmitters?

• A. To regulate body temperature
• B. To transmit signals across synapses
• C. To defend against infections
• D. To synthesize hormones

Answer: (B)

The primary function of neurotransmitters is to transmit signals across synapses. Neurotransmitters are chemical messengers released by neurons that cross the synaptic cleft—the small gap between neurons—allowing for communication between them. When an electrical signal, or action potential, reaches the end of a neuron, neurotransmitters are released into the synapse and bind to receptors on the adjacent neuron. This binding can either excite or inhibit the receiving neuron, depending on the type of neurotransmitter and receptor involved, ultimately influencing various physiological and behavioral responses.

In the context of the other options, regulating body temperature is primarily handled by the hypothalamus and other mechanisms, not neurotransmitters directly. Defense against infections is the role of the immune system, involving various cells and proteins, rather than neurotransmitters. The synthesis of hormones is a function of endocrine glands and does not directly pertain to neurotransmitters, which are specific to neuronal communication. Thus, the action of neurotransmitters in facilitating communication between neurons is fundamental to the functioning of the nervous system.