QS Study

Conditioned reflex involved in the secretion of gastric juice:

Gastric Juice is the mixture of secretions from all the glands present in the stomach. It is most helpful in digestion of food. It helps in absorbing the food in the body very easily. The gastric juice is made of 99.45% of water and 0 .55% of solids. The solids include 0.15% of inorganic and 0.4% of organic substances. Gastric secretion occurs in three phases out of this conditioned reflex occurs in cephalic phase.

Fig: Secretion of Gastric Juice

Cephalic phase: This phase occurs even before food enters the stomach, especially while it is being eaten. It results from the sight, smell, thought or taste of food, and the greater the appetite the more intense is the stimulation. Conditioned reflexes like sight, smell, thought of food causes secretion of the gastric juice. Presence of food in the mouth also causes secretion in the stomach. Neurogenic signals that cause the cephalic phase of gastric secretion can originate in the cerebral cortex or in the appetite centers of the amygdala or hypothalamus. They are transmitted through the dorsal motor nuclei of the vagi and thence through the vagus nerves to the stomach. The cephalic phase of gastric secretion is mediated entirely through the vagus nerve. A variety of sensory stimuli including the sight, smell, and taste of food elicits acid secretion in the stomach.

This phase of secretion normally accounts for about 20 percent of the gastric secretion associated with eating a meal.