WEEK 9: Gastrointestinal Health Flashcards
T or F
Most of the GI tract can function independently of the CNS
T
T or F
The cavities of the GI tract are internal
F
They are external (E.g. rectum and oral cavities)
What is the nervous system of the GI tract called?
The enteric nervous system (ENS)
T or F
The enteric nervous system cannot communicate with the central nervous system
F
It can but it largely acts independently
T or F
The enteric nervous system has as many nerves as are present in the spinal cord.
T
In a fasting state high lvls of … and low lvls of … and … are sensed in areas of the hypothalamus responsible for feeding behavior. This causes a hunger sensation.
Ghrelin
Leptin and Insulin
When a hungry body is presented with food, signals from the … and … are transmitted via the hypothalamus to the gastrointestinal tract to prepare for the meal.
eyes and nose aka. visual and olfactory cues
How does the gastrointestinal tract prepare for an incoming meal
By initiating involuntary salivation and increasing the secretions of the stomach.
As food is chewed it is formed into a lubricated bolus to facilitate what?
passage through the esophagus
Name the three types of salivary glands
Parotid, sublingual and submaxillary
memory tool: a paranoid linguist named max sub
The salivary glands produce what two distinct secretions?
A mucus secretion containing musin (a type of sugar-modified protein) and a serous secretion that contains the enzyme alpha-amylase.
memory tool: serous mucous
What purpose does the mucus secretion of saliva have?
The mucus secretion is important for lubricating the bolus of food that will be swallowed.
What purpose does the serous secretion of saliva have?
The alpha-amylase that makes up serous secretion begins the process of digestion of complex carbohydrates.
On average the salivary glands produce about … litre of secretions per day.
1 litre
How does the esophagus transport food to the stomach?
By peristalsis
T or F
The only role of the esophagus is to transport food from the mouth to the stomach
T
What is peristalsis?
The coordinated contraction and relaxation of muscle layers to propel the food bolus into the stomach.
What three main things does the stomach do?
The stomach has very muscular walls that churn food to process it
The stomach chemically processes food through hydrolysis
The stomach stores the food until it can be delivered as chyme to the duodenum
The rate of release of chyme from the stomach is partly regulated by…
the stomach but mostly regulated by the duodenum.
What does the pyloric sphincter of the stomach do?
The pyloric sphincter regulates the output of chyme into the duodenum.
The lining of the stomach contains many complex folds that contain a variety of cells responsible for … into the stomach as well as secretion of … hormones
secretion into the stomach as well as secretion of endocrine hormones
The entire surface of the stomach is lined by …-producing cells which also line the openings of the glands producing other secretions.
mucus-
Within the folds of the stomach are oxidic/parietal cells which produce … acid.
hydrochloric acid.
Hydrochloric acid secreted by parietal cells requires approx. … kilojules of energy per litre to produce.
6
What is the role of hydrochloric acid?
The role of hydrochloric acid is to hydrolyse a protein and carbohydrate, kill bacteria and activate protease (pepsinogen which is secreted by the peptic or cheif cells).
Parietal cells also secrete … factor (a glycoprotein that is required for absorption of vitamin B12.)
intrinsic factor
What is intrinsic factor?
a glycoprotein that is required for absorption of vitamin B12.
What is a zymogen?
an inactive substance which is converted into an enzyme when activated by another enzyme.
The pepcinogen secreted by the chief cells is a zymogen and is activated to … by …. at low pH.
pepsin
autocatyolic cleavage
T or F
Pepsin is a short spectrum peptidase that cleaves proteins at shorter peptide chains in the acidic environment of the stomach.
F
Broad spectrum
In total about … litres of gastric juice is produced per day depending on diet.
1.5 litres
Past the initial phase of secretion that occurs prior to the meal ingestion, the remaining …% of secretion occurs in response to the presence of food in the stomach.
70%
What is the vagovagal reflex?
Vagovagal reflex refers to gastrointestinal tract reflex circuits where afferent and efferent fibers of the vagus nerve coordinate responses to gut stimuli via the dorsal vagal complex in the brain.
Stimulation of secretion through the presence of food in the stomach is quite complex with a … component via the hypothalamus, local signaling of the …., and local … … signaling.
vagovagal
enteric nervous system
paracrine hormone
Parasympathetic release of … , enteric … signaling, and local release of … from endocrine cells all contribute to gastric secretion.
acetocholine
histamine
gastrin
… cells in the stomach monitor contents and secrete the hormone … which assists with digestion and … in response to the absence of nutrients in the stomach.
endocrine
gastrin
ghrelin
T or F
Most contractions in the stomach are weak and are involved in the mixing of food.
T
While most contractions in the stomach are weak and are involved in the mixing of food, a proportion are strong and …
peristaltic
Peristaltic contractions force the stomach contents (chyme) toward the ….
pyloric sphincter
Does the pyloric sphincter have a relatively high or low resting tone?
high
The high resting tone of the pyloric sphincter resists the passage of … through it.
chyme
When there are enough strong peristaltic contractions of the stomach this can force the chyme through the pyloric sphincter into the …
duodenum
T or F
Usually, chyme forced into the duodenum only a few millilitres per contraction
T
T or F
Most of the regulations of the stomach emptying arises from signals from the duodenum.
T
What are the types of signals that regulate stomach emptying?
signals from the duodenum
some regulation also occurs through signals arrising from the stomach.
T or F
The pressure of food in the stomach provides a signal that triggers the emptying the stomach
F
The stretching of the stomach does.
What sensors in what nervous sytem detect the stretching of the stomach which then promotes stomach emptying?
mechanosensors in the enteric nervous system
What 5 signals arise from the duodenum?
- Distension of the duodenum
- Acidity of the duodenal chyme
- Nutrients (the presence of)
- Irritation of the duodenum mucosa
- Osmolarity of the chyme
Some signals from the duodenum to the stomach are sent via the … nervous system
enteric nervous system
T or F
All signals from the duodenum regulate the rate at which stomach emptying occurs.
T
Some signals from the duodenum to the stomach are sent through … nerves via …. and back through … sympathetic nerves
intrinsic nerves via prevertebral sympathetic ganglia and back through inhibitory sympathetic nerves.
Some signals from the duodenum to the stomach are sent through the … nerves that stem to the …. and back.
vagus
brain stem
The small intestine is divided into what three sections?
The duodenum
The jejunum
The ileum
The duodenum is approx. …cm long and shapes like the letter …
30
c
The jejunum and the ileum are collectively about … metres in length
2.5 metres
How are the jejunum and ileum differentiated?
Through their anatomical appearance and blood supplies
T or F
All of the small intestine is involved in the further digestion and absorption of food
T
T or F
From a mechanical standpoint, the three sections of the small intestine operate differently
F
T or F
All of the small intestine is involved in the further digestion and absorption of food.
T
Peristalsis occurs throughout the … segmentation occurs predominantly in the …
gastrointestinal tract
small intestine
T or F
The pyloric sphincter only allows liquids to enter the intestine
T
The regulation of gastric function can be divided into what three phases
Cephalic phase
Gastric phase
Intestinal phase
The cephalic phase results from … stimuli
sensory
(Regarding the cephalic phase of gastric function)
Sensory stimuli stimulate efferent signaling via the … to promote secretion of … and … release from chief cells in the stomach (via GRP).
vagus nerve
histamine
pepsinogen
The vagus nerve is part of the … nervous system
parasympathetic
How does the vagus nerve secrete histamine?
via pituitary adenylate cyclase-activating peptide (PACAP) release onto enterochromaffin-like cells (ECL).
The vagus promotes gastric acid secretion by direct simulation of … cells and by stimulating … to secrete histamine
parietal
enterochromaffin-like cells (ECLs)
What neurotransmitter does the vagus nerve use to directly simulate parietal cells?
acetocholine
Which neurotransmitter promotes the release of HCl from parietal cells in the stomach?
histamine
Cephalic phase vagal signalling stimulates secretion from …. cells, resulting in delivery of as much as 25% of the total pancreatic enzyme secretion into the gastrointestinal tract.
exocrine pancreatic acinar
The gastric phase of the regulation of gastric function begins when …
Food enters the stomach, causing distension
Distension during the gastric phase of the regulation of gastric function, is a stimulus for the … nerve to promote … secretion
vagus
acid
As well as acid secretion distension also results in local ….
enteric reflexes
Once the food is broken down, the …. and … in the stomach also stimulate acid secretion either by stimulating the release of the hormone …, or to a lesser extent, by directly stimulating … cells.
amino acids
peptides
gastrin
parietal
(During the gastric phase of the regulation of gastric function)
Once the pH of the stomach falls below …, a … feedback loop inhibits the release of … to stop the cycle.
2.5
negative
gastrin