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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
Q

describe regulation of salivary secretion

A

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
Q

describe phases of secretion

A

psychic - conditioned reflex, thinking/seeing food and gustatory - taste = CEPHALIC
GASTRIC
INTESTINAL

27
Q

describe mixed gastric juice - components

A

15-2 liters/day
isotonic fluid = Na+, K+, Cl- **H+
ph 1-2 = v low

28
Q

describe mixed gastric juice - enzymes and stuff

A

hcl
pepsinogen (zymogen, inactive precursor)
intrinsic factor (need for vit b12 at illeum)
mucin (alkaline secretions)

29
Q

name and describe enzymes involved in protein digestion

A

proteins to smaller peptides = pepsin, trypsin, chymotrypsin, elastase
smaller peptides to aas = aminopeptidase and carboxypeptidase

30
Q

describe surface epithelial cells throughout git

A

secrete mucous alkaline fluid = protect and lubricate

31
Q

describe secretions of upper stomach

A

cardiac and pyloric tubular glands secrete akaline mucin rich fluid

32
Q

describe secretions of lower stomach

A

fundus and body tubular glands secrete acid, enzymes and intrinsic factor

33
Q

describe gastric glands in fundus and corpus

A

tubular gland = invagination, increases sa of secretion at level of stomach

34
Q

Explain what gastric glands in fundus and corpus secrete

A

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
Q

describe structure of parietal cell

A

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
Q

describe parietal cell - carbonic anhydrase

A

alkalinzation of blood
takes co2 from blood and produces bicard
for every hcl molecular moving into lumen = 1 molecule bicarb moves into capillary

37
Q

describe parietal cell - h+/k+ atpase

A

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
Q

describe parietal cell - na+/k+ atpase

A

keeps ionic balance
not specific for parietal cells

39
Q

describe postprandial urinary alkaline tide

A

can measure in urine sample
water moves into lumen passively

40
Q

describe cl- and h+

A

cl- entering cell =actively transported across canalicular membrane
h+ = available from dissociation of intracellular water, actively pumped into canaliculi in exchange for k+

41
Q

describe secretion of h+

A

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
Q

where does water move

A

into canaliculi pasively

43
Q

describe parietal cell secretion

A

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
Q

and and describe the 3 functions of hcl

A

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
Q

what does hcl do

A

converts pepsinogen to pepsin
pepsin = can cleave pepsinogn to pepsin = autocatalysis

46
Q

what does pepsin do

A

converts proteins to polypeptides

47
Q

what is intrinsic factor and explain

A

secretion of stomach essential to life
glycoprotein
secreted by parietal cells
required for absorption of vit b12
in distal si = ileum

48
Q

what happens if deficient in vit b12

A

pernicious anemia
intrinsic factor-B12, must form complex

49
Q

where is mucin secreted from - 3

A

1 - all surface epithelial cells
2 - cardiac and pyloric tubular glands - lots here
3 - mucous neck cells (fundus and corpus)

50
Q

what is point of mcc ex

A

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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