reflekser

Reflekser (reflexes) are involuntary, stereotyped responses to specific stimuli, produced without conscious intention. They serve to protect the body, maintain posture, and regulate various physiological processes. The term covers a wide spectrum of neural circuits that operate through the peripheral and central nervous systems.

Mechanism and organization: Most reflexes are organized as reflex arcs that include a receptor, a sensory neuron, an integration center, a motor neuron, and an effector. The integration center is in the spinal cord or brainstem; many somatic reflexes are monosynaptic, with a direct connection between sensory and motor neurons, enabling rapid responses. Others are polysynaptic, involving interneurons and producing more complex movements or actions. Autonomic reflexes regulate smooth muscle, cardiac tissue, and glands and are controlled by the autonomic nervous system.

Types and examples: Somatic spinal reflexes include the stretch (myotatic) reflex, such as the knee-jerk, which contracts the muscle when a tendon is tapped. The withdrawal reflex is a polysynaptic response to painful stimuli, causing rapid limb withdrawal. The Golgi tendon reflex modulates muscle tension through inhibitory pathways. Autonomic reflexes include the pupillary light reflex, which adjusts pupil size, and various cardiovascular or digestive reflexes that respond to changes in the internal environment.

Clinical relevance: Reflex testing is a standard component of neurological examinations. Abnormal reflexes—hypo- or hyperreflexia, clonus, or asymmetry—can indicate peripheral nerve injury, spinal cord or brainstem pathology, or systemic conditions. Reflexes may be influenced by age, temperature, fatigue, and medications.

Development: Some reflexes are present at birth (primitive reflexes) and fade as the nervous system matures, while others emerge or refine with growth and learning.