Patellarirefleksi

Patellarirefleksi, also known as the knee-jerk reflex, is a simple reflex arc that involves the spinal cord and the quadriceps muscles. It is a monosynaptic reflex, meaning it involves only one synapse between the sensory neuron and the motor neuron. When the patellar tendon, located just below the kneecap, is tapped with a reflex hammer, the quadriceps femoris muscle is stretched. This stretching is detected by muscle spindles within the muscle, which are sensory receptors.

These muscle spindles send an electrical signal along a sensory neuron to the spinal cord. In the spinal cord, the sensory neuron directly synapses with a motor neuron. This motor neuron then sends a signal back to the quadriceps femoris muscle, causing it to contract. This contraction results in the sudden extension of the lower leg, which is the observable reflex.

The patellarirefleksi is a common test performed by healthcare professionals to assess the integrity of the nervous system, particularly the spinal cord and the peripheral nerves that control leg movement. An exaggerated, diminished, or absent reflex can indicate various neurological conditions, such as nerve damage, spinal cord injury, or diseases affecting the motor pathways. The reflex is a fundamental example used in understanding how reflexes function and their importance in maintaining posture and balance.