- 1 What happens in the cephalic phase of digestion?
- 2 When does the cephalic phase occur?
- 3 What is the cephalic phase response?
- 4 What nerve stimulates gastric secretion?
- 5 What triggers the cephalic phase?
- 6 What stimulates the gastric phase?
- 7 Which nutrients remain in the stomach for the longest time?
- 8 What is the first phase of digestion?
- 9 Which phase controls how fast the stomach empties?
- 10 What are the phases of gastric juice?
- 11 Does smelling food increase insulin?
- 12 Can smelling food spike insulin?
- 13 What can eliminate the cephalic phase of gastric secretion?
- 14 What inhibits gastric function?
- 15 In which region of GI villi are most developed?
What happens in the cephalic phase of digestion?
The cephalic phase of digestion is the stage in which the stomach responds to the mere sight, smell, taste, or thought of food. About 20% of total acid secretion occurs before food enters the stomach.
When does the cephalic phase occur?
The cephalic phase of gastric secretion occurs in response to stimuli received by the senses —that is, taste, smell, sight, and sound. This phase of gastric secretion is entirely reflex in origin and is mediated by the vagus (10th cranial) nerve.
What is the cephalic phase response?
Cephalic phase responses (CPRs) are innate and learned physiological responses to sensory signals that prepare the gastrointestinal tract for the optimal processing of ingested foods. CPRs could be affected by inconsistencies in the associations between sensory signals and subsequent post-ingestive consequences.
What nerve stimulates gastric secretion?
The vagus nerve plays a central role in the regulation of gastric acid secretion and gastrin release.
What triggers the cephalic phase?
The cephalic phase of gastric secretion is initiated by the sight, smell, thought or taste of food. Neurological signals originate from the cerebral cortex and in the appetite centers of the amygdala and hypothalamus. This enhanced secretory activity is a conditioned reflex.
What stimulates the gastric phase?
Gastric secretion is stimulated chiefly by three chemicals: acetylcholine (ACh), histamine, and gastrin. Below pH of 2, stomach acid inhibits the parietal cells and G cells; this is a negative feedback loop that winds down the gastric phase as the need for pepsin and HCl declines.
Which nutrients remain in the stomach for the longest time?
Fats take the longest to digest—not only are they the last of the macronutrients to leave the stomach, but they also don’t go through the majority of the digestive process until they hit the small intestine.
What is the first phase of digestion?
The first is the cephalic phase. During this phase, chewing and swallowing stimulate the vagus nerve, which in turn signals cells in the stomach to release acid.
Which phase controls how fast the stomach empties?
The intestinal phase begins when chyme enters the small intestine, triggering digestive secretions. This phase controls the rate of gastric emptying.
What are the phases of gastric juice?
Gastric secretion occurs in three phases: cephalic, gastric, and intestinal. During each phase, the secretion of gastric juice can be stimulated or inhibited.
Does smelling food increase insulin?
When we anticipate or smell a meal, the parasympathetic nervous system triggers salivation and increases insulin production in response to the expectation that glucose will be entering the blood stream.
Can smelling food spike insulin?
Food odors stimulate appetite and innate food-seeking behavior in hungry animals. The smell of food also induces salivation and release of gastric acid and insulin.
What can eliminate the cephalic phase of gastric secretion?
Vagotomy (section of the vagus nerve, see Cases 4.1 and 4.2: 1) reduces the secretion of gastric juice mainly because its effect during the cephalic phase is abolished.
What inhibits gastric function?
Cholecystokinin (CCK) is known to inhibit gastric acid secretion and gastric emptying but its physiological role in the inhibition of gastric functions is not settled.
In which region of GI villi are most developed?
The villi number about 10 to 40 per square millimetre (6,000 to 25,000 per square inch) of tissue. They are most prevalent at the beginning of the small intestine and diminish in number toward the end of the tract.