Lecture 29 Unit 4 Flashcards
what are the three phases in regulation of digestion
- cephalic phase
- gastric phase
- intestinal phase
what happens in the cephalic phase
- anticipation
- prepares the mouth and stomach for food
what is stimulated in the cephalic phase
the cerebral cortex
what happens in the cerebral cortex in the cephalic phase
sight, smell, taste, and thoughts of food stimulate the parasympathetic nervous system to stimulation salivation and gastric glands to secrete gastric juices
what nerves increase salivation
facial and glossopharyngeal nerves
what nerve stimulates gastric gland to secrete gastric juice
vagus nerve
what happens in the gastric phase
breakdown of material
in the gastric phase what are the neural influences over stomach activity
- stretch receptors and chemoreceptors signal bolus entry
- vigorous peristalsis and gastric gland secretions
- chyme periodically released into the duodenum
in the gastric phase what are the endocrine influences over stomach activity
-distension and presence of food in stomach cause G cells to secrete gastrin into bloodstream; gastrin increases gastric gland secretions and motility and causes pyloric sphincter relaxation
what happens in neural and hormonal regulation in gastric emptying
- distention of the stomach and presence of undigested contents increase the secretion of gastrin hormone and vagal nerve impulses
- stimulates contraction of the lower esophageal sphincter and the stomach as well as relaxation of the pyloric sphincter for emptying
what happens in the intestinal phase
controlled release of chyme
what happens when chyme enters duodenum
slows gastric activity and increases intestinal activity
what are the neural influences in the intestinal phase
distension of the duodenum and chemical contents of the chyme activate sympathetic nerves which slow gastric activity (enterogastric reflex)
what are the endocrine influences in the intestinal phase
distention of duodenum and contents of chyme trigger hormonal release from enteroendorcrine cells in the duodenum
what are the hormones secreted in the intestinal phase and what do they do
- secretin-hormone decreases stomach secretions
- cholecystokinin (CCK)- decreases stomach emptying
what does the enterogastric reflex do
regulates the amount of chyme released into the duodenum
what is the entrogastric reflex initiated by
distension of duodenum and contents of the chyme
how does the enterogastric reflex work
sensory impulses sent to the medulla inhibit parasympathetic stimulation of the stomach
what are the hormones released by the enterogastric reflex and what do they do
cholecystokinin and secretin stimulate sympathetic impulses both inhibiting gastric emptying
what does secretin do
acidity in intestine causes increased sodium bicarbonate release
what does CCK do
fats and proteins cause increased digestive enzyme releasee
what are the steps in regulation of pancreatic secretions by enteroendocrine cells
- parasympathetic impulses along vagus nerves stimulate secretion of pancreatic enzymes
- acidic chyme containing partially digested fats and proteins
- CCK and secretin are released
- stimulates secretion of pancreatic juices rich in bicarbonate ions and digestive enzymes
what are the steps in the regulation of bile secretion by enteroendocrine cells
- parasympathetic impulses along vagus nerves stimulate bile production in the liver
- fatty acids and amino acids in chyme entering the duodenum stimulate secretion of CCK and secretin into blood
- CCK causes contraction of gallbladder
- secretin enhances flow of bile rile HCO3- from liver
