Question

The following is the scheme showing the path of reflex arc. Identify the different labeling A, B, C, D, E, F in the reflex arc.

• A. A- Stimulus, B- Effector, C- Motor nerve, D- Sensory nerve, E- Receptor, F- Response
• B. A- Stimulus, B- Receptor, C- Motor nerve, D- Sensory nerve, E- Effector, F- Response
• C. A- Stimulus, B- Effector, C- Sensory nerve, D- Motor nerve, E- Receptor, F- Response
• D. A- Stimulus, B- Receptor, C- Sensory nerve, D- Motor nerve, E- Effector, F- Response

Answer 1

The correct option is D A- Stimulus, B- Receptor, C- Sensory nerve, D- Motor nerve, E- Effector, F- Response

The patellar reflex or knee-jerk is a deep tendon reflex and is a monosynaptic reflex.

When the patellar tendon is tapped just below the knee, the patellar reflex is initiated and the lower leg kicks forward (via contraction of the quadriceps).

The tap initiates an action potential in a specialized structure known as a muscle spindle located within the quadriceps. This action potential travels to the spinal cord, via a sensory axon, which chemically communicates by releasing glutamate onto a motor nerve.

The result of this motor nerve activity is a contraction of the quadriceps muscle, leading to an extension of the lower leg at the knee.