GI pharmacology Flashcards
Functions the GI system performs
Takes food and fluid into the body
Absorbs nutrients and fluid
Excretes waste products
Ruminant Stomach chambers
Reticulum
Rumen
Omasum
Abomasum (the “true” stomach)
Horses, rabbits, and some rodents have developed … (part of GI system)
a very large colon, which helps them to digest plant material,
Two stomachs of birds
proventriculus (stomach)
ventriculus (gizzard)
Colon
*removes water from the material, *forms certain vitamins in hind-gut fermenters (a part of the colon in rabbits and horses),
*stores waste products
salivary glands
begin enzymatic digestion by producing enzymes that break down starch into simpler carbohydrates.
Pancreatic enzymes (general process)
Go to the duodenum to break down fats, carbohydrates, and proteins,
sodium bicarbonate from the pancreas
neutralizes hydrochloric acid from the stomach.
Bile salts,
Produced in the liver
delivered to the duodenum
aid in digestion by emulsifying fats.
Bile
Stored in the gallbladder
Gall bladder is absent in some animals (e.g., horses and rats).
Structures of GI tract
Dpends on the species
the mouth, teeth, tongue,
salivary glands,
esophagus and outpocketings of the esophagus (i.e., crop, reticulum, rumen, and omasum),
stomach,
liver,
pancreas,
duodenum,
jejunum,
ileum,
cecum,
colon,
rectum,
anus.
Three basic regulation systems of GI system:
The autonomic nervous system (ANS).
Gastrointestinal hormones
specialized cells of the GI tract
specialized cells of the GI tract
Gastric parietal cells use H2 receptors to attach histamines which increases the release of hydrochloric acid in the stomach.
Gastrointestinal hormones
Gastrin, secretin, and cholecystokinin
exert control over many functions such as gastric secretion, emptying of the gallbladder, and gastric emptying.
The autonomic nervous system regulation of GI system (big picture)
- Stimulation of the parasympathetic portion
- Stimulation of the sympathetic branch
- Stimulation of various intrinsic receptors in the GI tract, such as the myenteric plexus (stretch receptor), also may increase peristaltic activity.
Cool fact - Bonus -Some physiologists consider the intrinsic receptors (myenteric plexus and Meissner’s plexus) to be a third portion of the ANS called the enteric nervous system (Ganong, 2003).
Stimulation of the parasympathetic system in GI regulation (3)
Increases intestinal motility and tone,
increases intestinal secretions,
stimulates relaxation of sphincters.
Stimulation of the sympathetic branch in GI regulation
Decreases intestinal motility and tone,
decreases intestinal secretions,
inhibits sphincters.
The myenteric plexus (stretch receptor) may
increase peristaltic activity in the GI system
chemoreceptor trigger zone (CRTZ)
An area in the brain that activates the vomiting center when stimulated by toxic substances in the blood.
vomiting center
An area in the medulla that may be stimulated by the chemoreceptor trigger zone, the cerebrum, or peripheral receptors to induce vomiting.
Emetic contraindications
1) are comatose or are having a seizure,
(2) have depressed pharyngeal reflexes,
(3) are in shock or have dyspnea,
(4) bloat or esophageal damage,
(5) have ingested strong acid, alkali, or other caustic substances.
Emetic
Agents used to induce vomiting.
Animals that don’t usually vomit
rabbits, some rodents, and horses
Apomorphine (GI system)
A morphine derivative that stimulates dopamine receptors in the CRTZ and acts as an emetic.
this drug is poorly absorbed after oral administration and is therefore usually administered parenterally or topically in the conjunctival sac
Xylazine
Not classified as an emetic,
the label indicates that it induces vomiting within 3 to 5 minutes.
Some clinicians consider xylazine to be the agent of choice for inducing vomiting in cats.
Yohimbine or atipamezole can be used to reverse the emetic effects.
Hydrogen Peroxide for vomiting
can be used orally to induce vomiting.
Caused by irritant effect on the oropharynx and stomach lining
The dosage is 1 mL/lb (1 teaspoon (5 mL) per 5 pounds) of body weight.
Not to exceed 45 ml
Can be repeated once
Don’t need to remember all this but …
The oropharynx includes the following tissues:
The middle part of the throat behind the mouth.
The back one third of the tongue.
The soft palate (the back of the roof of the mouth), including the uvula.
The side and back walls of the throat.
The tonsils.