ABSTRACT

Reflexes are neuronal pathways that produce rapid, automatic and predictable responses to a stimulus. The basic components of the reflex arc include a receptor, afferent sensory neurone, synapse, efferent motor neurone and effector organ. The Bell–Magendie law states that the anterior spinal nerve roots contain only motor fibres and the posterior nerve roots contain only sensory fibres. The stretch reflex is a monosynaptic reflex that results in the contraction of a muscle in response to its being stretched. Stretch reflexes help maintain muscle tone, aid posture and prevent injury by opposing overstretching of muscles. The withdrawal reflex is an important reflex governing the response to a painful stimulus and is an example of a polysynaptic reflex. In order to maintain balance during a sudden flexor withdrawal of a lower limb, the pain stimulus activates a crossextensor reflex, which results in the automatic extension of the contralateral limb.