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PHGY 210 > digestion - lecture 6 > Flashcards

digestion - lecture 6 Flashcards

1
Q

what is mcc

A

migrating myoelectric (motor) complex

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2
Q

describe phase 1 of mcc

A

60 mins
no spike potentials on ber
no contractions

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3
Q

describe phase 2 of mcc

A

20 mins irregular spike potentials and contractions

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4
Q

describe phase 3 of mcc

A

10 mins
regular spike potentials and contractions
at its max force

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5
Q

describe myogenic properties of distal stomach - gen

A

each activates after the first - as go down more distally
interrupted by meal
phase 3 earlier and then later

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6
Q

where is mcc

A

distal stomach
si

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7
Q

describe initiation of mcc

A

not cns or ans
sometimes gut peptides can effect
needs ens - periodic activation of pattern generating circuitry

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8
Q

describe propagation of mcc

A

via ens with modulation via ans and gut peptides

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9
Q

describe interruption of mcc

A

intake of new meal

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10
Q

what is mcc function

A

housekeeping
gastric emptying of large nondigestible particles
mmc moves tings fowards - even in absence of meal = large turnover of cells in mucosa

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11
Q

describe secretion = exo vs endo

A

exo = into git, external lumen environment
endo = hormones into blood stream - intneral environment

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12
Q

what is process of digestion

A

sequence of interdependent steps
Enzymes = proteins = need to recycle eventually
duplication of enzyme activity
medium requirements = ph and ions for enzymes to function

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13
Q

what is digestion - secretion

A

chemical breakdown of food to progressively smaller molecules
results from secretory activity of large number of exocrine glands found in/with association with git
secretions released into lumen of digestive tract

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14
Q

describe secretion

A

active
depends on energy and blood flow
results in release of fluids containing ions and many enzymes
secretory cells near capillaries since need raw materials

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15
Q

name and describe 3 types of enzyme

A

amylases = breakdown starches/carbs
proteases = proteins
lipases = fats

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16
Q

describe pattern of regulation of secretion

A

nervous - ans = max control at mouth and lessens as go down git
Hormonal - gut peptides = important at bottom of git and not at top at alls

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17
Q

name mouth salivary glands

A

parotid
submandibular
sublingual

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18
Q

what do secretions in mouth do

A

protect and lubricate
Chemical digestion

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19
Q

describe a secretion that protects and lubricates

A

mucin - mucous

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20
Q

describe secretions that allow for chemical digestion

A

salivary amylase = can work at neutral ph, begins carb digestion
lingual lipase = only active at acidic ph = starts working in stomach only - produce by tongue for lipid digestion

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21
Q

describe the salivary glands

A

parotid = cheek, serous fluid
sublingual = mucin rich fluid to lubricate
submandibular gland = mixed fluid

22
Q

descrive saliva - components

A

0.5-1.5 liters/dat
Na+, K+, Cl-, HCO3-
hypotonic
ph 6.5-7.0

23
Q

descrive saliva - enzymes

A

amylase = ptylin ph ~7 breaksdown starch polysacch to maltose dissach
mucin
lipase
Lysozyme = break down bacteria cell walls

24
Q

describe gland regulation

A

ans =
parasymp mostly = mainly excitatory, blocked by atropine, ach on muscarinic = secretion and vasodilation
sympathetic = not much, vasoconstriction

25
describe regulation of salivary secretion
simple conditioned reflexes happens at cephalic phase = related to level of head eyes nose --> higher centers in cortex sensory receptors in mouth --> afferents both act on salivary centers in medulla efferents sent via parasymp = to salivary glands
26
describe phases of secretion
psychic - conditioned reflex, thinking/seeing food and gustatory - taste = CEPHALIC GASTRIC INTESTINAL
27
describe mixed gastric juice - components
15-2 liters/day isotonic fluid = Na+, K+, Cl- ****H+ ph 1-2 = v low
28
describe mixed gastric juice - enzymes and stuff
hcl pepsinogen (zymogen, inactive precursor) intrinsic factor (need for vit b12 at illeum) mucin (alkaline secretions)
29
name and describe enzymes involved in protein digestion
proteins to smaller peptides = pepsin, trypsin, chymotrypsin, elastase smaller peptides to aas = aminopeptidase and carboxypeptidase
30
describe surface epithelial cells throughout git
secrete mucous alkaline fluid = protect and lubricate
31
describe secretions of upper stomach
cardiac and pyloric tubular glands secrete akaline mucin rich fluid
32
describe secretions of lower stomach
fundus and body tubular glands secrete acid, enzymes and intrinsic factor
33
describe gastric glands in fundus and corpus
tubular gland = invagination, increases sa of secretion at level of stomach
34
Explain what gastric glands in fundus and corpus secrete
mucous neck cell = goblet cell, secretes mucin parietal cell secrets hcl into lumen of gland and enters stomach chief cells secrete pepsinogen = broken down to pepsin in presence of acid, secretes zymogen granules
35
describe structure of parietal cell
apical part intracellualr canaliculi= invaginations increase sa for cells to release hcl capillary at basolateral side =need lots of raw materials lots of mito since need lots of energy
36
describe parietal cell - carbonic anhydrase
alkalinzation of blood takes co2 from blood and produces bicard for every hcl molecular moving into lumen = 1 molecule bicarb moves into capillary
37
describe parietal cell - h+/k+ atpase
Important pump acidify lumen only on apical side in parietal cells ONLY usually h+ = 4x1o^-5 in cap = v small, huge gradient, pumping against = much energy needed hclm isotonic, 150meq h+ and 150 meq cl- proton pump = when inhibit = treatment for ulcers/lower stomach acids
38
describe parietal cell - na+/k+ atpase
keeps ionic balance not specific for parietal cells
39
describe postprandial urinary alkaline tide
can measure in urine sample water moves into lumen passively
40
describe cl- and h+
cl- entering cell =actively transported across canalicular membrane h+ = available from dissociation of intracellular water, actively pumped into canaliculi in exchange for k+
41
describe secretion of h+
leaves excess of oh- in cell results in increase of intracellular ph Causes more co2 to diffuse in from plasma (together with metabolic co2) combines with water in presence of carbonic anhydrase = produces h2co3 h2co3 reacts with excess oh- to give h20 and hc03- hco3 - diffuses into circ restoring intracellular status quo and gives rise to INCREASED ALKALINITY IN THE VENOUS BLOOD
42
where does water move
into canaliculi pasively
43
describe parietal cell secretion
pure hcl fluid constant composition, ph ~0.8 secretion independent of type, magnitude of stimulus mixed gastric juice, ph1-2 = modified by non parietal alkaline gastric secretions = depends on number of parietal cells active
44
and and describe the 3 functions of hcl
1 - precipitates soluble proteins = allows proteins to remain longer in stomach, curds = bigger so more time to breakdown 2 - denatures proteins more readily digested = easier for peptidases to work 3 - activates pepsin and provides optimal ph for pepsin to work (acidic)
45
what does hcl do
converts pepsinogen to pepsin pepsin = can cleave pepsinogn to pepsin = autocatalysis
46
what does pepsin do
converts proteins to polypeptides
47
what is intrinsic factor and explain
secretion of stomach essential to life glycoprotein secreted by parietal cells required for absorption of vit b12 in distal si = ileum
48
what happens if deficient in vit b12
pernicious anemia intrinsic factor-B12, must form complex
49
where is mucin secreted from - 3
1 - all surface epithelial cells 2 - cardiac and pyloric tubular glands - lots here 3 - mucous neck cells (fundus and corpus)
50
what is point of mcc ex
like with cherry pit can force through with these contractions - pyloric sphincter - objects big so takes time

PHGY 210 (36 decks)

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