Final answer:
The reflex being assessed when a newborn's cheek is stroked and the baby responds by turning the head and opening the lips is called the rooting reflex. This reflex, crucial for feeding, is part of a neurological exam to check for normal infant development and motor neuron function.
Step-by-step explanation:
The reflex that the PN (Pediatric Nurse) is assessing when the right side of a newborn's cheek is stroked, prompting the baby to turn the head towards the stimulated side and open the lips, is known as the rooting reflex. This reflex is crucial for a baby's survival as it helps the newborn locate the nipple to feed. The rooting reflex, alongside the sucking reflex and the grasp reflex, belongs to a set of instinctive behaviors that are present from birth and are indicators of proper neurological function, assessed during a neurological exam of reflexes to determine lower motor neuron (LMN) integrity.