What initiates receptive relaxation of gastric motility?

Receptive relaxation of gastric motility is primarily initiated by the vagovagal reflex triggered by the distention of the stomach. When food enters the stomach, the walls of the stomach stretch, which activates mechanoreceptors. This sensory information is transmitted through afferent fibers to the brainstem, which then sends back efferent signals via the vagus nerve to the stomach, facilitating relaxation of the smooth muscle. This reflex allows the stomach to accommodate a larger volume of food without a significant increase in internal pressure, making space for more ingested material and enabling effective digestion.

The correct choice highlights the role of the neural pathways involved in the regulation of gastric motility in response to physical changes within the stomach. Other options, such as increased gastric acid production, the presence of food in the small intestine, or contraction of the pyloric sphincter, do not directly initiate the receptive relaxation process. Instead, these factors may play roles in different aspects of gastrointestinal function and digestion, but they are not the primary triggers for receptive relaxation in the stomach.