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GI Physiology II
Solomon 3/22/11 lecture 1 hr Guyton ch 64
75
Physiology
Undergraduate 4
03/21/2011

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Term
hunger
Definition
a response to peripheral signals of energy levels
Term
hypothalamic feeding center
Definition
consolidates hunger signals and regulates outflow and response
Term
apetite
Definition
which is cultural: apetite or hunger?
Term
brainstem and hypothalmus
Definition
satiety signals act on what parts of the brain?
Term
leptin, insulin, CCK
Definition
what are some of the possible peripheral signals for satiety?
Term
satiety
Definition
sense of being fed or gratified to capacity
Term
leptin
Definition
hormone synthesized and released by fat cells that inhibits apetite, the more fat cells you have, the more of this you have
Term
leptin and insulin
Definition
critical signaling factors to the brain (hypothalmus) to stimulate food intake (or not) and increase metabolic rate (or not)
Term
chewing
Definition
both voluntary and sterotypic
stimulates salivary secretion
has a net nutritional function
Term
beta-carotene

the point is that you get more nutrients by chewing your food
Definition
particle size reduction leading to cell wall rupture is more important for the _____ bioaccessibility of raw compared to thermally processed carrots

(straight off the slide)
Term
lack of teeth
Definition
one of the major causes of malnutrition in the elderly
Term
membrane spanning, g-protein coupled receptors
Definition
what kind of receptors are taste receptors?
Term
salt, sweet, bitter, umami (what happened to sour?)
Definition
what are the 4 tastes?
Term
swallowing (like chewing it is both involuntary and stereotypic)
Definition
______ is a complex process involving multiple neural inputs, inhibition of respiration, closure of glottis, relaxation of the upper esophageal sphincter, and receptive relaxation of the stomach
Term
1) close soft palate of nasopharynx
2) close glottis with muscles
Definition
what is closed off in the process of swallowing
Term
yes, because the glottis contracts well enough to allow swallowing
Definition
can you survive if the EPIglottis is removed?
Term
1)transport of solids and liquids
2) prevention of air intake
3) prevention of reflux (stomach to esophagus)
Definition
what are the 3 functions of the esophagus?
Term
the lower esophageal sphincter
Definition
what prevents stomach contents from being sucked into the esophagus, since the esophagus has negative pressure inside the thoracic cavity?
Term
upper 1/3 (striated muscle)
Definition
what part of the esophagus is affected by myasthenia gravis? polymoysitis?
Term
lower 1/3 (smooth muscle)
Definition
what part of the esophagus is affected by scleroderma? achalasia?
Term
neuronal mechanisms (no hormones etc) just excitatory or inhibitory signals
Definition
what controls esophageal peristalsis?
Term
no, different CNS centers control the two regions
Definition
Is the upper striated part of the esophagus controlled by the same brain centers as the lower smooth muscle part?
Term
dorsal motor nuclei
Definition
what pare of the brain controls the esophageal motor functions?
Term
stimulatory: acetyl CoA
inhibitory: NO/DIP
Definition
what is a stimulatory neurotransmitter to esophageal smooth muscle contractions? what is inhibitory?
Term
esoophageal sphincters
Definition
a few centimeters in length, smooth muscle adapted for tonic contraction. what is it?
Term
neither, both are closed BETWEEN swallows
Definition
which esophageal sphincter is open between swallowing?
Term
upper relaxes during swallowing
lower relaxes as a peristaltic wave approaches
Definition
when does the upper esophageal sphincter relax? the lower?
Term
2 upper(aka phayngeoesophageal) and lower(aka cardiac, or gastroesophageal)
Definition
how many esophageal sphincters are there?
Term
gastroesophageal Reflux disease
Definition
what does GERD stand for?
Term
pregnant women and elderly
Definition
who is GERD common in?
Term
inhibit gastric acid secretion
Definition
how is GERD treated?
Term
1) temporary food storage
2) digestive motility
3) secretion of acid, pepsinogen, intrinsic factor
4) emptying
5) pyloric sphincter
6) pathophysiology
Definition
list the functions of the stomach
Term
Center for Ulcer Research and Education
Definition
what does CURE stand for?
Term
cardia, fundus, body, pylorus
Definition
list the functional divisions of the stomach from proximal to distal
Term
distal- pylorus
Definition
which part of the stomach controls gastric acid secretion?
Term
1) mucus to protect the stomach lining
2) bicarb
Definition
what do mucus neck cells secrete?
Term
1) gastric acid (HCl)
2) intrinsic factor (Ca++ absorbtion)
Definition
what do parietal(oxyntic) cells secrete?
Term
histamine (stimulate acid)
Definition
what do enterochromaffin-like cells secrete?
Term
1) pepsin(ogen)
2) gastric lipase
Definition
what do chief cells secrete?
Term
Somatostatin (inhibits acid)
Definition
what do D cells secrete?
Term
Gastrin (stimulates acid)
Definition
what do G cells secrete?
Term
arrival of the esophageal peristaltic wave
this accommodates for an increased volume of food (allows the stomach to stretch)
Definition
what initiates gastric receptive relaxation? what does this do?
Term
BER (basic electrical rhythm)
Definition
what controls gastric peristalsis/trituration?
Term
3 cycles/min so it takes 20 seconds to depolarize
Definition
what is the rate of the BER?
Term
trituration
Definition
the name of the process for reducing the particle size of a substance by grinding, as by grinding of powders in a mortar with a pestle
Term
pyloric sphincter relaxes (so there is lower pressure in the intestines causing the stomach contents to move in)
Definition
emptying of the stomach does not occur until when?
Term
neural factors
Definition
what decreases pyloric sphincter pressure?
Term
in squirts, it causes CCK release which activates the pyloric sphincter and slows the emptying of the stomach
Definition
how is chyme released from the stomach?
Term
1) helps break down proteins
2) protects against some pathogens
3) increases absorbtion of B12, iron, and calcium
4) it maintains the pH for other enzymes to function well
5) helps release nutrients from food
Definition
why does the stomach secrete acid?
Term
Ferrous: Fe2+
Definition
what state is iron best absorbed in?
Term
Ferrous: Fe2+
Definition
what state is iron best absorbed in?
Term
150 mM (pH 1)
Definition
what concentration do cells secrete HCl at?
Term
gastrin, histamine, acetylcholine
Definition
what activates oxyntic cells?
Term
they have a structural trasnformation that increases apical surface area, where the proton pump is inserted
Definition
how do oxyntic cells change when they are ready to secrete?
Term
a H+/K+ ATPase pump
Definition
what pumps H+ out of oxyntic cells?
Term
K+
Definition
what does the stomach REQUIRE to produce acid?
Term
CO2(diffusion?), Cl-(diffusion), H2O(osmosis), and K+ enter the cell from the extra cellular fluid
(K+ pumped in with Na+/K+ active transport)

inside the cell CO2 + H20 make HCO3 and H+

HCO3- is pumped into the extracellular fluid by using the Cl- ion going down its gradient

H+ is pumped out into the lumen with K+ flowing in from the lumen(this pump is present elsewhere in the body but only active in the stomach)


things that go into the lumen: H+(K+ pump), Na+(diffusion), Cl-(diffusion), H2O (diffusion)
Definition
describe transport of H+ out of an oxyntic cell?
Term
local(low pH) and vagal reflexes that release Ach
Definition
how are chief cells activated?
Term
the ER, cheif cells make a lot of proteins (pepsinogen & gastric lipase)
Definition
what organelle is particularly large in a chief cell? why?
Term
1) cephalic -vagal (smell/taste/anticipate food, also parasympathetics excite pepsin and acid production)
2) gastric (local nervous secretory reflexes-when food hits the stomach, vagal reflexes, gastrin-histamine stimulation)
3) intestinal (nervous and hormonal mechanisms)
Definition
list the phases of GI activation, what stimulates each?
Term
1) central activation(cephalic) of vagal efferents that release ACh
2) short and long reflexes cause release of ACh
3) protein digestion products cause release of gastrin
4) gastrin stimulates enterochromaffin (ECL) cells that release histamin
Definition
describe the 3 ways to stimulate gastric secretion
Term
Ca++, cAMP
Definition
what are the secondary messengers (intracellular) of the oxyntic cell?
Term
esophageal peristalsis won't let the food/liquid go in reverse, even if you are upside down
Definition
why can you do a keg stand?
Term
1) food -> distension of the stomach -> neural reflex -> Ach release -> parietal stimulation(HCl release)

2) food in stomach-> buffer the acid -> pH increase -> block of somatostatin secretion [somatostatin inhibits G cells, ECL cells, and parietal cells]

3) food in stomach -> presence of aa, and peptides -> G cell stimulation(gastrin release) -> ECL stimulation(histamine release) -> parietal cell stimulation(Hcl release)


in summary: food, distension, or acid affect gastric secretion
Definition
how are parietal cells stimulated (go into detail)
Term
increased distension
increased osmolarity
increased acid
increased fats and peptides

all of these cause neural reflexes-> decreased Ach release-> decreased parietal cell stimulation

these also cause enterogastrone release (CCK, secretin) which inhibit histamine release by ECL cells (inhibiting parietal cells)
Definition
what does chyme in the duodenum cause?
Term
inhibitory: histamine release is inhibited, and neural input is inhibited
Definition
is the intestinal phase mostly excitatory or inhibitory?
Term
1) mucus + 2)bicarb (note: bicarb sticks to the mucus, keeping it close to the cells, but mucus doesn't really do much)

2) tight intercellular junctions: prevent acid from slipping between cells
Definition
what 3 things prevent the stomach from digesting itself?
Term
CNS
Definition
what mediates nausea?
Term
1) esophageal sphincters open
2) pyloric sphincter closes
3) abdominal muscles contract
Definition
list the vomiting sequence
Term
parietal cells
Definition
what secretes intrinsic factor?
Term
B12/cobalamine
Definition
what does intrinsic factor bind?
Term
adults: aid RBC development
kids: aids neuronal development
Definition
what does B12 do in adults? in kids?
Term
megaloblastic anemia
Definition
what does B12 deficiency cause?
Term
loss of parietal cells with gastritis (no intrinsic factor secretion)

GERD treated by a proton pump inhibitor prevents intrinsic factor secretion
Definition
why does gastritis cause B12 deficiency? why does GERD cause it?
Term
amylase does not break down cellulose, so the only way to break it down is chewing
Definition
why is chewing fibrous foods important?
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