Answer:
When a doctor strikes the child's kneecap:
- The sensory receptors located in the tendon receive the stimulus.
- Information travels by afferent pathway through the sensory component of motor nerve
- The integration center, in the spinal cord, receives the information and sends a motor response by efferent pathway.
- The quadriceps contracts and extends the leg.
Explanation:
The patellar reflex —by hitting the kneecap tendon—is an example of a reflex arc, which produces the extension of the leg over the knee as an involuntary response to the stimulus to strike the patellar tendon.
This reflex has five main components:
- Receptor.
- Sensitive fibers of a motor nerve (afferent pathway)
- Spinal cord integration center.
- Motor nerve fibers (efferent pathway).
- Effector.
The reflex arc occurs because the stimulus received does not travel to the brain, but to the spinal cord, which causes the reflex response to be faster.
When the doctor strikes sensory neurons below the boy's kneecap, the following sequence of events occurs:
- The sensory receptors located in the tendon receive the stimulus.
- Information travels by afferent pathway through the sensory component of the femoral nerve.
- The integration center, in the spinal cord, receives theinformation and sends a motor response by efferent pathway.
- The quadriceps contracts and extends the leg.
The patellar reflex evaluates the integrality of the reflex arc at that level, whose synapse occurs between the lumbar segments of the spinal nerve L₂ and L₄.
