Monosynaptic reflex means:

Monosynaptic reflex means:

• A. Two synapses
• B. One synapse
• C. Three synapses
• D. No synapses

Answer: (B)

A monosynaptic reflex has a direct, single communication between the sensory input and the motor output. When a muscle is stretched, the sensory neuron from the muscle spindle sends a signal straight to the motor neuron in the spinal cord, which then causes the same muscle to contract. That one synapse in the spinal cord makes the response very fast and requires no interneuron. This is why the stretch (knee-jerk) reflex is the classic example. If there were two or more synapses, an interneuron would be involved (disynaptic or polysynaptic), and the reflex would be slower. So the best description is one synapse.

A monosynaptic reflex has a direct, single communication between the sensory input and the motor output. When a muscle is stretched, the sensory neuron from the muscle spindle sends a signal straight to the motor neuron in the spinal cord, which then causes the same muscle to contract. That one synapse in the spinal cord makes the response very fast and requires no interneuron. This is why the stretch (knee-jerk) reflex is the classic example. If there were two or more synapses, an interneuron would be involved (disynaptic or polysynaptic), and the reflex would be slower. So the best description is one synapse.