Kroppsreflexes

Kroppsreflexes, or body reflexes, are involuntary, rapid, and stereotyped motor responses to specific stimuli. They are mediated by the nervous system and occur without conscious thought. Broadly, reflexes are classified as somatic, involving skeletal muscles, or autonomic (visceral), involving glands or smooth muscle.

A reflex arc consists of a receptor, a primary sensory neuron, an integration center in the spinal cord or brainstem, a motor neuron, and an effector. Many somatic reflexes are monosynaptic, such as the myotatic (stretch) reflex, whereas others are polysynaptic and involve interneurons. Sensory input from muscle spindles, Golgi tendon organs, or cutaneous receptors is translated into motor output via alpha motor neurons, with gamma motor neurons modulating spindle sensitivity.

Common examples include the patellar reflex (knee jerk), Achilles reflex, withdrawal (flexor) reflex, and cross‑ed extension reflex. Cranial reflexes such as the pupillary light reflex and corneal reflex are mediated by brainstem circuits. Autonomic reflexes regulate activities such as pupil size, salivation, and cardiovascular responses.

Clinically, assessment of reflexes helps localize neurological damage. Diminished or absent reflexes can indicate lower motor neuron disease or peripheral nerve injury, while exaggerated reflexes and spasticity may signal upper motor neuron lesions. Abnormal reflexes such as the Babinski sign provide additional diagnostic information.

Reflexes are modulated by higher brain centers and descending pathways; factors such as fatigue, attention, and pharmacologic agents can alter reflex strength. Understanding kroppsreflexes provides insight into nervous system function, development, and clinical neurology.