BIOL 003 Lecture Notes - Lecture 12: Vagus Nerve, Monosaccharide, Sucrase
Document Summary
Digestion must be controlled by body regulated by 3 phases: cephalic (nervous) phase. Sight, smell, taste, thought of food stimulates medulla. Vagus nerves in medulla signals stomach to initiate secretion: Hcl, pepsinogen, mucous, intrinsic factor, gastrin (hormone that stimulates further gastric secretion: gastric (stretching) phase. Polypeptides produced from initial digestion stimulate release of more gastrin. Chyme moves into duodenum: intestinal (hormonal) phase. Chemoreceptors in duodenum detect acidic (ph 2) chyme signals gastric glands to reduce secretion. Secretin: stimulates release of bicarbonate from pancreas neutralise chyme (ph 2 since mixed with hcl) Cholecystokinin: stimulates release of enzymes from pancreas & release of bile from gall bladder. Exchange of fluids between gut cavity and blood system. Chyme: absorbed in small intestine villi capillaries/lymphatic vessels blood. Water, more minerals & vitamins absorbed in large intestine. Peptidases (e. g. carboxypeptidase): peptides amino acids. Energy released used to drive anabolic processes (e. g. food breaking down)
