Physical Therapy Assistant Practice Exam

Which reflex facilitates a change in muscle tone of an infant's extremities in response to head rotation?

1. Symmetrical tonic neck reflex

2. Asymmetrical tonic neck reflex

3. Rooting reflex

4. Palmar grasp reflex

The correct answer is: Asymmetrical tonic neck reflex

The Asymmetrical Tonic Neck Reflex (ATNR) is the reflex that facilitates a change in muscle tone of an infant's extremities in response to head rotation. This reflex typically emerges around two months of age and is characterized by the position of the infant's arms and legs in relation to the direction their head is turned. When an infant turns their head to one side, the arm and leg on that same side extend while the opposite arm and leg flex. This response helps the infant to develop hand-eye coordination and promotes the ability to reach for objects in their environment, as well as contributing to overall motor control. The ATNR is crucial for developing lateral movements and balance, laying the groundwork for future motor skills and coordination. Understanding this reflex is essential for physical therapy assistants, as it relates directly to the assessment of an infant's reflexes and overall neurological development. The other reflexes listed—such as the rooting reflex and palmar grasp reflex—serve different purposes in an infant's development but do not specifically relate to changes in extremity muscle tone in response to head movements like the ATNR does.