Rapid and involuntary response of the body to a stimulus.
Unlike voluntary movements, which require a conscious decision, reflexes are triggered automatically to protect the organism or maintain its balance. Removing your hand after touching a hot surface is a protective reflex.
Neuronal mechanisms
The reflex rests on a simple nerve circuit called the reflex arc. When a stimulus is detected by a sensory receptor, the information is transmitted from a sensory neuron to the spinal cord. There, it directly activates a motor neuron that controls the affected muscle, producing the response in a matter of milliseconds. In some cases, interneurons intervene to modulate the response and coordinate several muscles.
This function allows the body to react faster than the brain could decide, which is crucial for avoiding injury or maintaining posture and balance.
Types and roles of reflexes
Reflexes can be simple, such as the patellar reflex observed during a medical examination, or complex, such as the postural reflexes that permanently adjust the body’s position. They are vital to survival, providing immediate responses to potentially dangerous situations, and also participating in daily motor coordination.
- Motor neuron :
- Motor neurons involved in the transmission of motor information from the brain to the spinal cord and peripheral organs.
- Neuron :
- Basic cell of the nervous tissue, capable of receiving, analysing, reproducing and transmitting information in the form of an electrical or chemical signal.