Crossed extensor reflex

Crossed extensor reflex is a reflex action that occurs in response to a painful stimulus. It is a type of withdrawal reflex that involves the coordination of both sides of the body to maintain balance and posture. This reflex is an important component of the nervous system and plays a crucial role in locomotion and protective reflexes.

Mechanism

The crossed extensor reflex is initiated when a painful stimulus, such as stepping on a sharp object, activates nociceptors in the skin. The sensory neurons transmit the pain signal to the spinal cord, where it synapses with interneurons. These interneurons then activate motor neurons on both sides of the body.

On the side of the body that received the painful stimulus (the ipsilateral side), the reflex causes the flexor muscles to contract and the extensor muscles to relax, resulting in the withdrawal of the limb from the painful stimulus. Simultaneously, on the opposite side of the body (the contralateral side), the reflex causes the extensor muscles to contract and the flexor muscles to relax, which helps to support the body's weight and maintain balance.

Components

The crossed extensor reflex involves several key components:

• Nociceptors: Sensory receptors that detect painful stimuli.
• Sensory neurons: Transmit the pain signal to the spinal cord.
• Interneurons: Relay the signal within the spinal cord and coordinate the response.
• Motor neurons: Activate the muscles to produce the reflex action.
• Flexor muscles: Muscles that contract to withdraw the limb.
• Extensor muscles: Muscles that contract to support the body.

Clinical Significance

The crossed extensor reflex is an important diagnostic tool in neurology. It can be used to assess the integrity of the spinal cord and the functioning of the nervous system. Abnormalities in this reflex may indicate damage to the spinal cord or other neurological disorders.

Related Reflexes

• Withdrawal reflex
• Stretch reflex
• Golgi tendon reflex

See Also

• Nervous system
• Reflex arc
• Spinal cord
• Motor neuron
• Interneuron