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3 fundamental processes
- motility
- secretion
- absorption
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priming factors
depolarize smooth muscle -> GI motility
-
Priming factors include (3)
- distenton
- parasympathetic stimulation
- GI hormons
-
hyperpolarizing factors lead to
decreased GI motility
-
hyperpolarizing factors include (2)
- sympathetic stimulation
- GI hormons
-
What reflex control peristalsis
andaptive reflexes
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release mode in paracrine vs endocrine
- paracrine: diffusion
- endocrine: circ
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Brain of the gut:
Enteric NS (myenteric and submucosal)
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2 most common neurotransmitters in Enteric Sys
- acetylcholine (excitatory)
- norepinephrine (inhibitory)
-
Myenteric plexus:
monitors...
motor neurons connect to...
influences GI...
- monitors mechanoreceptors
- motor neurons connect to muscle cells
- influences motility
-
Submucosal plexus:
monitors...
motor neurons connect to...
influences GI...
- monitors chemicals
- motor neurons connect tosecretory, endocrine and mucous cells
- influences GI secretions
-
Parasympathetic vs Sympathetic on GI tract ->
- Parasympathetic:
- decrease motility
- decrease secretion
- increase sphincter tone
-
primary neurotransmitter of sympathetic NS
norepinephrine
-
Primary neurotransmitter of sympathetic NS
acetylcholine
-
Primary stimulus of GI tract
distention
-
Peristalic Rush
intense mucosal inflammation -> powerful/rapid peristalsis -> diarrhea
-
Reflexes that stimulate Salivation:
- parasympathetic reflex (CrN 7 & 9)
- conditioned reflex (CNS-> salivary senter)
-
Warming up phase:
- CrN 10 activated ->
- Vagal reflex ->
- stimulation of stomach, SI, pancreas and bile
-
Ruminent saliva must be ____ d/t
alkaline d/t microorganisms in rumen
-
Chewing is controled by (2)
- Chewing Relfex
- involving CrN 5
-
Phases of swallowing
- Voluntary
- Reflex
- Esophogeal
-
Voluntary phase involves...
tongue moving bolus to pharynx
-
Reflex phase involves
- touch receptors->
- CrN 9/ ->
- swallowing center (medulla oblangata) ->
- soft palat lifts ->
- larynx closed ->
- parastalic waves
-
Esophogeal Phase involves:
- Bolus -> stomach
- esophogeal sphincter relaxes
-
achalasia:
Megaesophogus caused by failure of lower sphincter to relax (genetic malfunction of myenteric plexus)
-
myathenia gravis-
acetylcholine receptor deficit/damage leading to megaesophagous
-
megaesophagous is caused by (3)
- Achlasia
- PRAA
- Myasthenia Gravis
-
functions of the stomach (4)
- Temp storage
- Mixing of food w/ gatric secretions and liquification of ingesta into chyme
- Chemical/enzymatic digestion (especially proteins)
- Controlled release of chyme into SI
-
Accomodation Reflex-
Vagal relax leads to a reduction in muscle tone of proximal stomach to allow temporary storage of food
-
Satiety is caused by
- Suppression of Vagus
- or
- Stimulation of sympathetic system
-
Mixing occurs in the ____ stomach and utilizes ______
in the Distal stomach and utilizes retropulsion
-
Migratiing Motility Complex:
When fasting occurs, peristalic waves occur between the stomach and ileum and the pylorus is relaxed => to clear stomach and SI
-
Two types of mucosa in stomach
- Non-Glandular = cuntaneous
- Glandular
-
Glandular mucosa of stomach contains which cell types (6):
- Mucus Cells
- Parietal Cells
- Enterochromaffin Cells
- Chief Cells
- G cells (Gastrin)
- Stem Cells
-
Mucosal layer of stomach protects against (3)
- mechanical stress
- acids
- digestive enzymes
-
What controls secretion of mucous and bicarbonates in the stomach?
Prostaglandins, which is controlled by Local (Enteric) & Central (Vagal) Reflexes
-
-
Enterochromaffin-like cells secrete
Histamine
-
Chief Cells secrete
Pepsinogen/Prochymosin
-
-
What stimulates parietal cells
- (-> HCl)
- AcetylcholineGastrin
- Histamine (in response to Gastrin)
-
Instead of pepsinogin, nursing animals secrete
Procymosin (rennin in calves)
-
Pepsinogen release in activated by
Low pH
-
How can antihistamine cause anemia?
- to HCl/Intrensic Factor release ->
- No intestinal absorption of B12 ->
- No erythropoiesis
-
Empting of Chyme must be matched with
the digestive and absorptive capacity of the SI
-
Consequences of vomiting are:
- Loss of Fluid (low BP and Shock)
- Loss of K+ (weakness/hyporeflexia)
- Loss of H+ (hypoventilation)
-
Importance of gastrointestinal mucosa
- barrier btw guy lumen and body
- allows transfer of nutrients, but no chemials or bacteria
-
What can interrupt the GI Barrier (4)?
- Stress
- NSAIDS
- Ischemia
- Infections
-
Tx for disruptions to GI barrier
- Reduce Stress
- Histamine (H2) blockers
- Proton Pump Blockers
- Antibiotics
-
Components of the GI Barrier (4)
- Mucous/bincarbonate
- Prostaglandins E2
- Epithelial and Stem Cells
- Bactericidal Peptides/Immunoglobins A
-
Why is vomiting immposible in horses
- acute angle btw esophogus and stomach
- clamp-like structure of diaphram
-
Vomiting is a reflex under the control of the....
vomiting center in the brain stem
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