Nervous

Nervous is an adjective with two principal senses. It can describe things relating to nerves or the nervous system, such as nervous tissue or nervous conduction, and it can describe a person who feels anxious, tense, or easily agitated. The word derives from Latin nervus, meaning "nerve" or "sinew," and entered English through Old French and early modern usage.

In biology, the nervous system coordinates sensation, thought, movement, and homeostatic regulation. It is divided into the central nervous system, which comprises the brain and spinal cord, and the peripheral nervous system, consisting of nerves outside the CNS. Neurons generate and transmit electrical signals, while glial cells provide support, insulation, and metabolic assistance. Communication occurs at synapses, where neurotransmitters bridge gaps between neurons or reach target cells.

When used to describe a person, nervous typically denotes temporary emotional states such as worry or anticipation of an event. Stress responses involve the autonomic nervous system and the release of catecholamines like norepinephrine and the hormone cortisol, leading to symptoms such as increased heart rate, sweating, and heightened alertness.

Disorders of the nervous system range from anxiety disorders and mood disorders to neuropathies, migraines, epilepsy, and degenerative diseases such as multiple sclerosis. Diagnosis is based on history, examination, and often imaging or electrophysiological tests, while treatment may include psychotherapy, medications, lifestyle changes, or rehabilitation depending on the condition.

In everyday use, nervous is a common descriptor for transient emotional states or for things involving the nervous system, while more precise terms (for example, anxiety, neurology) are used in medical or scientific contexts.