refleks

Refleks (often spelled reflex in English) refers to an involuntary, nearly instantaneous response to a stimulus. These responses occur without conscious intent and are typically stereotyped, meaning the same stimulus produces the same response in a given organism.

A reflex arc underlies most reflexes. It typically includes a receptor that detects the stimulus, a sensory (afferent) neuron that transmits the signal to the central nervous system, one or more interneurons, and a motor (efferent) neuron that triggers an effector, usually a muscle or gland. Many reflexes are somatic and involve skeletal muscles, but there are also autonomic reflexes that affect smooth muscle or glands. Reflexes can be monosynaptic, with a single synapse between sensory and motor neurons (as in the stretch reflex), or polysynaptic, involving one or more interneurons.

Common categories include:

- Somatic reflexes such as the knee-jerk (patellar) reflex, withdrawal reflex, and crossed extensor reflex.

- Cranial nerve reflexes such as the pupillary light reflex and corneal reflex.

- Autonomic reflexes such as the baroreceptor reflex, pupillary accommodation, and digestive reflexes.

Conditioned reflexes are learned associations that extend the concept of reflex beyond automatic responses, as shown in Pavlovian experiments where a neutral stimulus becomes linked to a reflex response through repetition.

Clinical relevance: Reflex testing is a standard part of neurological examination. Reflexes are graded in a scale (e.g., 0 to 4+) to assess nerve pathway integrity. Hyperreflexia can indicate upper motor neuron lesions, while hyporeflexia or areflexia can point to lower motor neuron damage or peripheral neuropathies. Reflexes provide a rapid, noninvasive measure of nervous system function.

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