Bráðarviðbrögðum

Bráðarviðbrögðum, often translated as "reflexes" or "reflex actions," refers to involuntary, rapid, and stereotyped responses to stimuli. These actions are mediated by the nervous system, specifically through reflex arcs. A reflex arc is a neural pathway that controls a reflex. In vertebrates, most sensory neurons do not pass directly into the brain, but synapse in the spinal cord. This characteristic allows for faster reflex actions to occur by activating spinal motor neurons without the delay of routing signals through the brain.

There are several types of reflexes. Sensory receptors detect a stimulus, such as heat or a sharp object. This information is transmitted by sensory neurons to the spinal cord or brainstem. In the spinal cord, the sensory neuron may synapse directly with a motor neuron (monosynaptic reflex) or with one or more interneurons, which then synapse with motor neurons (polysynaptic reflex). Motor neurons then carry the signal to an effector, typically a muscle or gland, which produces the response.

Common examples of bráðarviðbrögðum include the withdrawal reflex, where you quickly pull your hand away from a hot object, and the patellar reflex (knee-jerk reflex), where a tap on the knee causes the leg to extend. These reflexes are crucial for protecting the body from injury and maintaining posture and balance. While involuntary, some reflexes can be modified or consciously controlled to a limited extent. Their study provides valuable insights into the functioning of the nervous system.