Svarsviðbragðkerfi

Svarsviðbragðkerfi, often translated as 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. The brain does receive the sensory input, and a message is sent to the brain allowing it to command the action. However, the reflex action itself is mediated by the spinal cord.

A typical reflex arc involves five components: a receptor, a sensory neuron, an integration center, a motor neuron, and an effector. The receptor detects a stimulus. The sensory neuron transmits the signal from the receptor to the central nervous system (CNS). The integration center, usually in the spinal cord, processes the information and generates an appropriate response. The motor neuron carries the signal from the CNS to the effector. The effector, typically a muscle or gland, carries out the response.

There are two main types of reflex arcs: monosynaptic and polysynaptic. In a monosynaptic reflex arc, there is only one synapse between the sensory neuron and the motor neuron. An example is the stretch reflex. In a polysynaptic reflex arc, there are two or more synapses. The withdrawal reflex is an example of a polysynaptic reflex. Reflex arcs are essential for protecting the body from harm, maintaining posture and balance, and regulating internal organs.