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

Which reflex arc helps maintain balance during body movements?

1. Monosynaptic Reflex

2. Flexor Withdrawal Reflex

3. Crossed-Extensor Reflex

4. Stretch Reflex

The correct answer is: Crossed-Extensor Reflex

The correct answer is the crossed-extensor reflex. This reflex is vital for maintaining balance during body movements, particularly when one limb is withdrawn in response to a stimulus, such as stepping on a sharp object. The crossed-extensor reflex allows for the extension of the opposite limb to support the body’s weight, thus maintaining balance and stability. It involves a complex pathway that includes both excitatory and inhibitory signals to facilitate coordinated action. When a withdrawal reflex is triggered in one limb, the crossed-extensor reflex ensures that the opposite limb becomes activated, allowing the body to remain upright and balanced. This coordination is especially important in situations where rapid adjustments are necessary to maintain stability. In contrast, the monosynaptic reflex, like the patellar reflex, primarily facilitates immediate muscle contraction in response to a muscle stretch but does not provide the necessary support for balance during unexpected movements. The flexor withdrawal reflex is primarily focused on pulling a limb away from harmful stimuli and does not address balance. The stretch reflex helps maintain muscle tone and readiness but does not involve cross-limb coordination necessary for stability. Thus, the crossed-extensor reflex is crucial for effective balance maintenance in dynamic situations.