Reflexen

Reflexes, or reflexen in Dutch, are involuntary, nearly instantaneous motor responses to a specific stimulus. They arise from reflex arcs, simple neural circuits that link sensory receptors to effectors. A typical arc includes a sensory receptor, an afferent neuron, processing in the spinal cord or brainstem, an efferent neuron, and an effector such as a muscle or gland. Because the response is fast and usually does not require conscious input, reflexes help protect the body and regulate physiology.

Reflexes are broadly categorized as somatic versus visceral (autonomic). Somatic reflexes control skeletal muscles; visceral reflexes regulate glands, smooth muscle, and cardiac function. They can be monosynaptic, as in the stretch (myotatic) reflex, where a single synapse between sensory and motor neurons yields a direct muscle contraction; or polysynaptic, with one or more interneurons in the spinal cord. Examples include the patellar reflex, the Achilles reflex, the withdrawal reflex, and cranial reflexes such as the pupillary light reflex and the corneal reflex.

Development and clinical relevance: Reflexes are present early in life and can be modified by development and experience. They can be tested clinically to assess nervous system integrity; abnormal reflexes (hyporeflexia, hyperreflexia, or areflexia) can indicate neuropathy or central nervous system disorders. Neuromodulation, fatigue, age, and disease can alter reflex magnitude and latency.