Control Of The Digestive System Flashcards
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
