College of Massage Therapists of British Columbia (CMTBC) Practice Exam

What type of reflex is initiated in response to a painful stimulus?

1. Flexor Withdrawal Reflex

2. Monosynaptic Reflex

3. Crossed-Extensor Reflex

4. Tendon Reflex

The correct answer is: Flexor Withdrawal Reflex

The flexor withdrawal reflex is a protective mechanism crucial for survival, triggered by painful stimuli. When a body part, such as a hand or foot, encounters a painful stimulus—like touching a hot surface—the sensory neurons transmit a signal to the spinal cord. In response, the spinal cord facilitates an immediate activation of the motor neurons that cause the flexor muscles to contract, leading to the withdrawal of the affected limb away from the source of pain. This reflex occurs rapidly and automatically, allowing for a quick response without the need for conscious thought. In comparison, the monosynaptic reflex involves a simple pathway where a sensory neuron directly communicates with a motor neuron, for example, in the patellar reflex. The crossed-extensor reflex involves a more complex interaction where one limb withdraws while the opposite limb extends to maintain balance, usually also in reaction to a painful stimulus. The tendon reflex is more about regulating muscle tension and protecting muscles from excessive force rather than responding directly to pain. Therefore, the flexor withdrawal reflex is the most relevant answer for a reflex initiated specifically due to a painful stimulus.