What reflex causes an infant to startle in response to a loud sound or sudden movement?

• A. Moro reflex
• B. Rooting reflex
• C. Grasp reflex
• D. Walking reflex

Answer: (A)

The reflex that causes an infant to startle in response to a loud sound or sudden movement is the Moro reflex. This reflex is an involuntary response that occurs when an infant perceives a sensation of falling or experiences a startling stimulus. When the Moro reflex is triggered, the infant will extend their arms and legs, arch their back, and then quickly bring everything back into their body, as if trying to hold onto something for safety. This reflex is considered a protective mechanism and is an important part of the newborn's development.

The Moro reflex typically appears around the time of birth and diminishes by about four to six months of age as the infant's nervous system matures. It is often assessed by pediatricians and is a key indicator of neurological function in newborns. The other listed reflexes, such as the rooting reflex, which helps the baby find the breast or bottle for feeding, the grasp reflex, which enables babies to hold onto objects, and the walking reflex, where infants appear to make walking movements when held upright, serve different purposes and do not involve the startle response.