Neurotransmitters enable neurons to communicate through synaptic transmission. Neurotransmitters are released from nerve endings into synaptic cleft. They bind to receptors on target tissues, affecting excitatory or inhibitory responses. Neurotransmitters act for short periods, then are destroyed or reabsorbed
Serotonin is produced in brain stem from tryptophan, affecting mood and digestion. Dopamine is made in brain base through two-step process from tyrosine. Both neurotransmitters impact mood, digestion, and sleep
MAOA gene provides instructions for monoamine oxidase A enzyme. Enzyme breaks down neurotransmitters serotonin, epinephrine, norepinephrine, and dopamine. Helps break down excess tyramine in diet. Plays role in normal brain development before birth
AChR is an integral membrane protein responding to acetylcholine. Nicotinic receptors (nAChR) respond to nicotine and are ion channels. Muscarinic receptors (mAChR) respond to muscarine and are G-protein-coupled. nAChRs consist of five subunits arranged like staves around barrel
Chemical synapses enable neuron-to-neuron and neuron-to-non-neuronal cell communication. Synaptic cleft is 20 nm wide, allowing rapid neurotransmitter concentration changes. Adult human brain contains 100-500 trillion synapses. Synapses can be symmetric (inhibitory) or asymmetric (excitatory)
Amacrine cells are inhibitory interneurons in retina's inner plexiform layer. Named from Greek for their short neuronal processes. Project dendritic arbors onto inner plexiform layer. Work laterally, affecting bipolar cell output