Control Of The Digestive System Flashcards
(38 cards)
Where is the cephalic phase?
The head
Where is the Gastric phase?
Stomach
Where is the intestinal phase?
The intestine
The cephalic phase:
- triggered by sight, smell, taste, thought, chewing or swallowing food
- saliva is secreted
- stomach, pancreatic and liver secretions happen
- gastric contractions
The gastric phase:
- triggered by presence of food in the stomach
- distension
- peptide fragments, caffeine & alcohol present
- increased gastric motility
- gastric juice is produced
The intestinal phase:
- triggered by presence of food in the duodenum
- distension
- chemical composition of food
- pancreas secretes bicarbonate into the duodenum
- pancreas secretes digestive enzymes into the duodenum
- gallbladder releases bile into the duodenum
- segmentation contractions of the small intestine happen
External stimuli that activate regulatory factors:
- cephalic factors
- emotion
Local stimuli within the gastrointestinal tract that activate regulatory factors:
- stretch or distension of the gastrointestinal tract wall
- chemical components of the lumen
- osmolarity of the contents in the lumen
What does stretching / distension of the gastrointestinal tract wall do?
- stimulates mechanoreceptors
What do chemical components in the lumen do?
Stimulate chemoreceptors
What does the osmolarity of the contents in the lumen do?
- stimulates osmoreceptors
Regulatory factors activated to regulate motility and secretion:
- intrinsic nerve plexuse
- extrinsic nerves
- gastrointestinal hormones
- Intrinsic nerve plexuses
- submucosal plexus & Myenteric plexus = are in the gastrointestinal tract wall and run its entire length
Responsible for short reflexes = influence motility or secretion in response to specific local stimuli
- stimulation of a receptor in one area of the tract, neurally influences activity of another region in the tract
- this provides a mechanism for self regulation of the tract & helps to coordinate activity of organs within
Small volume for =
Weaker contractions
Larger volumes for =
Stronger contractions
Do lipid rich meals have a longer or shorter digestion time?
Longer
Do carbohydrate rich meals have a longer or shorter digestion time?
Shorter
- Extrinsic nerves, what are they?
- nerve fibres from both branches of the autonomic nervous system
- sympathetic & parasympathetic nerves
Why do extrinsic nerves have long reflexes?
- involves long pathways between the central nervous system and the digestive system
Where do the extrinsic nerves start and what do they respond to?
Originate = outside the digestive system
Respond to = cephalic factors & emotion
How to extrinsic nerves influence gastrointestinal tract motility and secretion?
- modifies ongoing activity in the intrinsic plexus
- alters the level of gastrointestinal hormones secretion
- acts directly on the smooth muscle and glands
What do parasympathetic nerves increase?
- gastrointestinal tract motility
- secretion of digestive enzymes
- secretions of gastrointestinal hormones
What do sympathetic nerves do to these factors?
- decrease them
