nevronene

Neurons, or nerve cells, are the basic units of the nervous system. They are specialized for the rapid transmission of information through electrical and chemical signals. A typical neuron consists of a cell body (soma) that houses the nucleus; dendrites that receive input; and a long axon that conducts impulses away from the cell body. Many axons are insulated by a myelin sheath formed by glial cells, which increases the speed of signal transmission. Gaps in the myelin, called nodes of Ranvier, enable rapid conduction through saltatory transmission. At synapses—the junctions with other neurons or effectors—the axon terminal releases neurotransmitters into the synaptic cleft, influencing the activity of the postsynaptic cell.

Electrical signaling begins with a resting membrane potential. A stimulus can depolarize the membrane to a threshold, triggering an action potential that travels along the axon. Ion channels and ion gradients control the rise and fall of voltage, converting electrical signals into chemical signals at the synapse.

Neurons are functionally categorized as sensory (afferent), motor (efferent), and interneurons, which form local circuits within the nervous system. They form intricate networks supported by glial cells that provide metabolic support, insulation, and homeostasis. Neuronal circuits develop through guided growth, synaptic pruning, and experience-driven plasticity. Long-lasting changes in synaptic strength, such as long-term potentiation, underlie learning and memory. In adults, neurogenesis occurs in a limited number of regions, most notably in parts of the hippocampus.

Understanding neurons is central to neuroscience, as they underpin perception, movement, and cognition, and their dysfunction contributes to many neurological disorders.