CLINICAL MEDICINE

Detailed explanation-1: -Extracellular Signal Molecules Bind to Specific Receptors These include proteins, small peptides, amino acids, nucleotides, steroids, retinoids, fatty acid derivatives, and even dissolved gases such as nitric oxide and carbon monoxide.

Detailed explanation-2: -The neurotransmitters carry signals between neurons or from neurons to other types of target cells (such as muscle cells).

Detailed explanation-3: -Synaptic signaling. Neurotransmitter is released from vesicles at the end of the axon of the sending cell. It diffuses across the small gap between sending and target neurons and binds to receptors on the target neuron.