reflexcentrum

A reflexcentrum is a neural pathway that controls a reflex. It is the basic functional unit of the nervous system that produces a reflex action. Reflexes are involuntary and nearly instantaneous movements in response to a stimulus. The reflex arc typically involves a sensory receptor, a sensory neuron, one or more interneurons (in polysynaptic reflexes), a motor neuron, and an effector.

When a stimulus is detected by a sensory receptor, it generates a nerve impulse. This impulse travels along the sensory neuron to the spinal cord or brainstem, which acts as the central processing unit for the reflex. In the central nervous system, the sensory neuron synapses with one or more interneurons, or directly with a motor neuron. These interneurons may modulate the signal or transmit it to other parts of the nervous system. The motor neuron then carries the impulse away from the central nervous system to an effector, which is usually a muscle or gland. The effector responds to the impulse by contracting or secreting, resulting in the reflex action.

The simplest reflex arc, known as a monosynaptic reflex, involves only a sensory neuron and a motor neuron with a direct synapse between them. An example is the stretch reflex, such as the patellar reflex (knee-jerk). More complex reflexes, called polysynaptic reflexes, involve one or more interneurons, increasing the time it takes for the reflex to occur and allowing for more intricate responses. The withdrawal reflex from a painful stimulus is a common example of a polysynaptic reflex. Reflex centers are found in various levels of the central nervous system, including the spinal cord, brainstem, and even higher brain centers for certain complex reflexes.