Achillesrefleksien

Achillesrefleksien, also known as the ankle jerk reflex, is a stretch reflex mediated by the tibial nerve. It is elicited by tapping the Achilles tendon, which is the tendon connecting the calf muscles to the heel bone. This tap stretches the gastrocnemius and soleus muscles, stimulating muscle spindles. These sensory receptors send signals via afferent nerve fibers to the spinal cord. Within the spinal cord, the sensory neurons directly synapse with motor neurons. These motor neurons then transmit efferent signals back to the calf muscles, causing them to contract and the foot to plantarflex, or point downwards. This action is involuntary and occurs too quickly for conscious thought to influence.

The Achilles reflex is a common neurological examination technique used to assess the integrity of the S1 and S2 nerve roots, as well as the tibial nerve and the muscles they innervate. A normal reflex involves a brisk plantarflexion of the foot. An absent or diminished reflex can indicate damage to the nerves, spinal cord, or muscles, or conditions such as peripheral neuropathy or a herniated disc. Conversely, an exaggerated or hyperactive reflex, known as hyperreflexia, can suggest an upper motor neuron lesion, such as stroke or spinal cord injury, or conditions like hyperthyroidism. The reflex is typically tested with the patient either lying on their stomach with their feet hanging off the edge of the examination table, or kneeling on a chair.