Q.Digestive secretions are secreted only when needed. Discuss.

Step 1. Recall the neural trigger: the smell, sight and taste of food, along with its mechanical presence in the mouth, set off a reflex that starts salivary secretion, and gastric-juice secretion likewise begins even while food is still in the mouth, showing the nervous system anticipates and matches secretion to incoming food.

Step 2. Recall the hormonal trigger: local hormones produced by the gastric and intestinal mucosa, such as gastrin (stimulating HCl and pepsinogen secretion in the stomach) and cholecystokinin and secretin (stimulating pancreatic juice, bicarbonate and bile release once chyme reaches the duodenum), are released specifically when food or partly digested food is actually present in that region. …

Separate the two control mechanisms described in the chapter — neural reflexes and hormonal signals — and explain how …

• Describing only one control mechanism (neural or hormonal) and missing that both work together across different stages of digestion. …