The patellar reflex tests which nerve root and how is it performed?

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Multiple Choice

The patellar reflex tests which nerve root and how is it performed?

The patellar reflex mainly tests the L4 nerve root through the femoral nerve. When the patellar tendon is tapped with the knee slightly flexed, the quadriceps muscle is stretched. This triggers a monosynaptic reflex arc: sensory signals from muscle spindles travel to the spinal cord via the femoral nerve, then motor signals return to the quadriceps, causing a brisk knee extension. The slight knee flexion optimizes the stretch and prevents guarding or passive resistance from surrounding muscles, giving a clear reflex. This is why the best answer is the one describing L4 and tapping the patellar tendon with the knee in slight flexion. Other choices involve different nerve roots or nonstandard knee positions for eliciting the reflex.

The patellar reflex mainly tests the L4 nerve root through the femoral nerve. When the patellar tendon is tapped with the knee slightly flexed, the quadriceps muscle is stretched. This triggers a monosynaptic reflex arc: sensory signals from muscle spindles travel to the spinal cord via the femoral nerve, then motor signals return to the quadriceps, causing a brisk knee extension. The slight knee flexion optimizes the stretch and prevents guarding or passive resistance from surrounding muscles, giving a clear reflex.

This is why the best answer is the one describing L4 and tapping the patellar tendon with the knee in slight flexion. Other choices involve different nerve roots or nonstandard knee positions for eliciting the reflex.

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