Final answer:
The impedance to gastric flow, or regurgitation, is controlled by regulatory mechanisms like the enterogastric reflex which closes the pyloric sphincter, and by the gastric phase where stomach distension and pH changes prompt hormonal and neural responses.
Step-by-step explanation:
Impedance to gastric flow, often referred to as regurgitation, is determined by several factors involving the gastrointestinal system's regulatory mechanisms. Key elements include the activity of the duodenum in the intestinal phase of gastric secretion, hormonal signals such as intestinal gastrin, and neural responses like the enterogastric reflex. This reflex plays a crucial role as it can inhibit gastric emptying by triggering the pyloric sphincter to close, thus preventing additional chyme from entering the duodenum.
Gastric emptying is also tightly regulated by the gastric phase, which responds to the distension of the stomach and changes in pH levels within the gastric contents through a combination of hormonal and neural responses. Moreover, the mucosal barrier protects the stomach lining from self-digestion, ensuring that the digestive process does not damage the stomach's own cells.