Deglutition or swallowing is probably a reflex phenomenon. Higher centres facilitate this reflex. Once aroused, the swallowing centre in the medulla evokes the complete act of swallowing by discharge through six nuclei and the motor neurones. This reflex act occurs in three stages: (1) First or oral, (2) Second or pharyngeal, and (3) Third or oesophageal (Fig. 9.46). (1) First [...]
In this article we will discuss about the interactions and metabolic effects of gastro-intestinal hormones. Interactions of Gastro-Intestinal Hormones: As gastrin stimulates acid secretion, it probably combines with specific receptor sites on the effector cells. When the concentration of gastrin is high, many receptor sites are occupied and when this concentration is low, few receptor sites are occupied. This relationship [...]
The various humoral (chemical) factors controlling the different secretions in the gastro-intestinal tract may be summarised as follows: 1. For Gastric Secretion: i. Gastrin- Responsible for gastric phase. ii. A chemical substance may be a hormone or secretagogue - Responsible for intestinal phase. iii. Enterogastrone- Inhibits gastric secretion. 2. For Pancreatic Secretion: i. Secretin- Main chemical stimulus. ii. Pancreozymin. iii. [...]