Final Exam GI Physiology Questions Flashcards
What hypothalamic neurotransmitters help control hunger and satiety centers?
CCK, CRH, Neuropeptide Y, and Leptin
What control mechanisms help to achieve INTRINSIC control of the GI Tract?
Enteric Nervous System
Endocrine Cells in the gut wall
Cells that secrete paracrine substances
Local tissue factors
Where would you find interneurons of the enteric nervous system and what are they commonly known as? What do they do?
Submucosa (Meissner’s) plexi
Myenteric (Auerbach’s) plexi
They synapse onto muscles, glands, and secretory and absorptive epithelium.
What do endocrine cells in the gut wall respond to?
Directly to GI tract luminal contents
NTs
Paracrine substances
Histamine, somatostatin, prostaglandins, and serotonin are examples of what kind of substance?
Paracrine substances
What are the MOST important sites of hormone production in the GI Tract?
Stomach and Small Intestine
What is a local tissue factor?
Simple products of metabolism whose concentrations affect neighboring blood vessels.
Increased concentration of tissue factors (CO2, H+, and K+) result in ____________ of neighboring blood vessels.
Vasodilation
What control mechanisms help to achieve EXTRINSIC control of the GI Tract?
Afferent neurons projecting from GI Tract to either extramural plexi or CNS
Afferent neurons that convey sensory info to the CNS
SNS and PSNS EFFerent neurons
Somatic nervous system EFFerent neurons
Endocrine cells outside the gut wall
What control mechanisms help to achieve DIRECT control of the GI Tract?
The direct interaction of NTs, hormones and paracrine substances with gut wall muscles, glandular tissue, and secretory or absorptive epithelium
How is INDIRECT control of the GI Tract achieved?
Through regulation of perfusion
The GI system can receive up to what percent of cardiac output when active?
30%
What is the overall effect of SNS stimulation?
Vasoconstriction and decreased blood flow
What do SNS postganglionic neurons secrete?
NE
What receptors predominate at GI vasculature?
alpha-1 adrenergic receptors
What do PSNS postganglionic neurons secrete?
VIP and ACh
What does VIP do?
Inhibits actin-myosin interaction in muscle
Promotes production of NO which leads to vasodilation
What does ACh do?
Promotes production of NO which leads to vasodilation
What does Epinephrine from the adrenal medulla do when stimulating alpha-1 adrenergic receptors?
Vasoconstriction
What does Epinephrine do when stimulating beta-2 adrenergic receptors?
Vasodilation
The effects of epinephrine stimulation prevail on which receptors?
alpha-1
What does gastrin and other peptide hormones of the GIT do?
Vasodilation
Which two substances have a powerful vasoconstrictive effect resulting from a decreased ECV (effective circulating volume)?
Angiotensin II and ADH
Histamine and Prostaglandins (paracrine secretions) are _______ in effect.
Histamine and prostaglandins are vasodilatory
Local tissue factors like CO2, H+ and K+ are __________.
CO2, H+, and K+ are vasodilatory
At rest, the kidneys require what percent of cardiac output?
22%
At rest, the GI tract and Liver together require what percent of cardiac output?
23%
Where in the GI Tract would you find VSM (visceral smooth muscle)?
From the esophagus to the internal anal sphincter.
The VSM (visceral smooth muscles) exhibit a spontaneous pattern of depolarization and repolarization called ____ ____.
Slow waves
Where are slow waves generated?
In the myenteric plexus by interstitial cells.
Slows waves give rise to what?
BER (basic electrical rhythm)
Where is the BER (basic electrical rhythm) greatest?
In the duodenum
What are the propagated motility patterns?
Peristalsis and Antiperistalsis are both propagated motility patterns.
Peristalsis is a classic example of a ______ reflex.
Peripheral reflex
PSNS innervation of of GI tract musculature are most pronounced where?
At the esophagus, stomach, and rectum.
T or F: Peristalsis occurs in the absence of CNS input.
True
What is the gastrocolic reflex initiated by? What is the effect?
Gastric distension initiates the gastrocolic reflex.
The effect is mass movements at the distal colon promoting the movement of feces into the rectum.
What is the ileogastric reflex initiated by? What is the effect?
Ileal distension initiates the ileogastric reflex.
The effect is DECREASED gastric motility.
Distension of the stomach is recognized by mechanoreceptors which stimulate vagal neurons in the medulla. This stimulates neurons in the gastric mucosa to secrete gastrin, histamine, and HCL. This process is an example of what?
A vagovagal reflex
What is the overall effect of SNS innervation on GI Tract function?
Inhibition- SNS
What is the overall effect of PSNS innervation on GI Tract function?
Excitatory- PSNS
What is an example of PSNS control of GI Tract function?
LES (lower esophageal sphincter)
As gastric motility increases, PSNS excitatory fibers (via ACh) promote contraction of the LES. What is the purpose of this?
To prevent backflux of acidic chyme into the esophagus
Relaxation of the LES is due to ________ firing of Vagal inhibitory fibers (VIF)
relaxation from increased firing of VIF
Contraction of the LES is due to ______ firing of vagal excitatory fibers (VEF)
contraction from increased firing of VEF
Which secretion protects and lubricates GIT mucosa?
Mucin
Which secretion creates the optimum pH for enzymatic activity in the GIT?
HCO3-
Which secretion destroys food-borne bacteria in the GIT?
HCl
Which secretion solubilizes ingesta?
H20
Which secretion hydrolyzes ingesta?
H20 and hydrolytic enzymes
Which secretion emulsifies lipids?
Bile
What drives the secretion of Na+, K+, and H+ (and water then follows)?
Cl-
What happens to the volume of plasma when the volume of secretions increases?
The volume of plasma decreases
Where would you find Cl- entering secretory cells by way of secondary active transport?
Basolateral membrane
What is a secretagogue?
A neurotransmitter, hormone, or paracrine molecule that promotes secretion.
Reception of secretagogues ________ the uptake of Cl- into the basolateral membrane
Increases the uptake of Cl-
What are the most important modifications made by ductular cells to primary secretions?
Reabsorption of Na+ and Cl-
Secretion of K+ and HCO3-
The secondary secretion, the secretion that actually enters the lumen of the tubular gut at the mouth or small intestine, is distinctly more _______ than the primary secretion.
Secondary secretion is distinctly more ALKALINE than primary secretion.
What are the 3 types of salivary glands?
Serous, Mucus-secreting, and Mixed
Which animals use saliva for evaporative cooling?
Dogs and cats
Which animals primarily use saliva for buffering?
Ruminants
What cells produce saliva?
Acinar cells
What are the components of saliva?
Water, Electrolytes, Amylase, Lipase, IgA, Mucin, I-
Ruminants also have: (PO4)-2 and urea in their saliva
What is the effect of PSNS and SNS on saliva?
Both act to immediately INCREASE the volume of saliva
Is salivary gland secretion subsequent to SNS stimulation long or short-lived?
Short-lived
Do salivary glands receive endocrine signals from the GI Tract?
NO!
