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Phgy 210 > Digestive system lecture 6 > Flashcards

Digestive system lecture 6 Flashcards

1
Q

What are the 3 stages of vomiting?
What siganls it?
What are the SI functions?

A

-3 stages:
ANS discharge and Nausea
Retching
Emesis
-Vomiting Centre vs. CTZ
-signaled by afferents throughout the body
-Small Intestine Functions – mixing, slow propulsion

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2
Q

What are the colon functions?
What are the long reflexes?

A

Colon Functions – mixing, very slow propulsion, storage
Long Reflexes – Gastroileal, Ileocolic, Gastrocolic reflexes stimulated by entrance of new meal into the stomach to empty
small intestine and colon

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3
Q

What happens in absence of vomiting center?
What about in absence of CTZ (chemoreceptor target zone)

A

in absence of vomiting center you cant vomit even with CTZ
-without CTZ you cant vomit in response to circulating emetic agents but youd still have normal afferent inputs that cant trigger this process

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4
Q

What happens in phase 1,II, and III in the MMC (migrating myoelectric (motor) complex)?
How long is each phase/

A

-Phase I (60 min): no spike potentials, no contractions
-Phase II (20 min) irregular spike potentials and contractions
-Phase III (10 min): regular spike potentials and contractions

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5
Q

What happens when there is no meal in the stomach?
What happens when there is a meal?

A

-no meal, means there is strong MMC acitivty
-with a meal the pattern is interrupted

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6
Q

What is the propagation rate from stomach to distal ileum

A

-5cm/min

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7
Q

What is the MMC restricted to?
What initiates the MMC?

A

MMC - restricted to Distal Stomach and Small Intestine
-ENS (enteric nervous system) – periodic activation of
pattern-generating circuitry

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8
Q

How does MMC propgate?
When does it get interrupeted?

A

PROPAGATION:
-via * ENS with modulation via ANS and Gut Peptides
-INTERRUPTION: Intake of a new meal

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9
Q

What is the MMC function?

A

“Housekeeping”
Gastric emptying of large, nondigestible part

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10
Q

What is an example of the gastric emptying of MMC function?

A

-allows penny to force through spincter, alos fiber which cant be digested by stomach

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11
Q

What are the 3 functions of git/

A
  1. MOTILITY (muscular activity)–>Propulsion & Physical Breakdown
  2. SECRETION (glandular activity)–>Chemical Breakdown
  3. ABSORPTION Transfer to Circulation
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12
Q

What does exocrine and endocrine secretion do?
Where does each go during gland excretion?

A

exocrine=secreted by glandular cells into GIT lumen
-lumen is external environment since it is continuous with it
secreted into GIT external environment
-endocrine=into bloodstream (internal environment

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13
Q

What are the 4 processes of digestion?

A

-Sequence of interdependent steps
* Duplication of Enzyme Activity
* Medium requirements – pH, ions
* Enzymes are proteins (body wants to recycle them)

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14
Q

What is the defintion of digestion?
What does it result from?
Where are the secretions released?

A

-Chemical breakdown of food to progressively smaller molecules
-Results from the secretory activity of a large number of exocrine glands found within and in association with the GIT
-The secretions are released into the lumen of the digestive tract

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15
Q

WHat type of activity is secretion, what does it depend on?
What does secretion result in?

A

-Secretion is an active, energy dependent and blood flow dependent process,
-resulting in the release of a fluid containing ions and a variety of enzymes

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16
Q

What are the 3 types of enzymes and what they breakdown?

A

-amylases=breakdown starches
-proteases=breakdown of protein
-lipases=breakdown of fats

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17
Q

What are the 2 patterns of regulation?
Where are they most present?

A
  1. Nervous (ANS) (mainly at the mouth/stomach)
  2. Hormonal (gut peptides) (most important for distal part of GIT)
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18
Q

What are the 3 salivary gland, what do they secrete?
What protects and lubricates?

A
  • Parotid (serous fluid)
  • Submandibular (mucin+serous)
  • Sublingual (mucin rich fluid)
    mucin-mucous
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19
Q

What 2 secretions allow for chemical digestion?

A

Secretion of salivary amylase
* Begins carbohydrate digestion
-Tongue produces lingual lipase (for lipid digestion)

20
Q

What is the volume of saliva per day?
What are the ions in it, what type of solution is it?
What is the pH?

A

-VOLUME: 0.5 – 1.5 liters/day
IONS: Na+, K+, Cl-HCO3-, HYPOTONIC
-6.5-7.0 (neutral solution)

21
Q

What converts starch (polysaccharaides) to maltose (Disaccharides)
What only operates at neutral pH?
What are the other kinds of secretions?
Which ones are present in largest quantity?

A

amylase and ptylin
-ptylin
-mucin, lipase and lyzosyme (breaks down bacterial cell walls
-ptylin and mucous

22
Q

How are glands regulated by the ANS?

A

-parasympathetic is blocked by atropine, but when Ach releasd it increases secretion causing vasodilation (increase blood flow)
-sympathetic leads to vasoconstriction

23
Q

How does the eyes/nose regulate salivary secretion?
How do the sensory receptors in the mouth regulate it?
How is salivary gland activated

A

eyes/nose are higher centers which lead to salivary centers in medulla
-sensory receptor in mouth are afferent signals which also lead to salivary center
-from the salivary center there is efferent signal (via parasym.) that activate salivary gland

24
Q

What are the 2 main phases of secretion?
What type of secretion activates the first phase?

A

cephalic phase-psychic (conditioned reflex, like thinking of food)
and gustatory (taste, food in mouth-
2.gastric/intestinal (occurs when food is warm/spicy)

25
Q

How much Mixed gastric juice is produced per day?
What type of fluid is it, what type of ions compose it?
What is the pH?

A

1.5 – 2 liters/day
Isotonic Fluid: Na+, K+, Cl- , H
pH 1 – 2

26
Q

What does H+ ion produce in mixed gastric juice
what are the 4 things in mixed gastric juice

A

-H+ most importat since it produces acidic pH of stomach
-HCl
-pepsinogen
-intrinsic factor
-mucin

27
Q

What are the enzymes involved in protein digestion?

A

-initally pepsin, trypsin, chymotrypsin an elastase
then aminopeptidase and carboxypeptidase break them down into individual amino acid

28
Q

What do surface epithelial cells secrete?
What do cardiac and pyloric tubular glands secrete?

A

Surface epithelial cells throughout the GIT secrete a mucous, alkaline fluid
-CARDIAC and PYLORIC tubular glands secrete an alkaline, mucin-rich fluid

29
Q

What does the body and fundus tubular glands secrete?
What do tubular glands do?

A

-FUNDUS and BODY tubular glands
secrete acid, enzymes and Intrinsic Factor
-tubular glands increase SA of inner GIT for secretion

30
Q

What do the parietal cell, chief cell and the mucous neck cells secrete in the fundus and corpus?

A

-parietal (oxyntic) cell)=Hcl
-chief cell=pepsinogen
-mucous neck cell=mucin

31
Q

Where is HCl secreted?
Why is it filled with mitochondria?

A

-HCl is produced and secreted into canaliculis which contrains channels that connect with lumen
-filled with mitochondria so that it has enough energy to produce HCl

32
Q

What is the basal side of the tubular gland in contact with?
What is the ratio of bicarbonate to H+ ion, where is each secreted to/from?
What does bicarbonate do?

A

-contact with blood
-for every H+ ion pumped out of lumen, 1 bicarbonat ion is pumped back into blood ot diffused back into blood (1;1)
-bicarbonate in blood alkanizes it at the level of the stomach

33
Q

What does carbonic anhydrase do?
Where is the H+/K+ ATPase, what does it do, what do you need for the function?
Where can ATPase H+/K+ be found?

A

-takes CO2 in blood and produces H+ and HCO3-
-H+/K+ ATPase is at the apical part of the cell and moves H+ ions into lumen, need ATP for function
-only in this part of body which makes it a good target for ulcer medication

34
Q

Where is the Na+/K+ ATPase?
What does it do?

A

-basolateral portion of cell and it is important for maintaing ionic gradient

35
Q

How much secretion do we get from the postprandial (urinary) alkaline tide?

A

-we get 2L of secretion bc when moving HCl we are also putting water into lumen of stomach

36
Q

What is parietal cell secretion?
What is the pH?
What is secretion dependent on?

A

-pure HCl fluid
-constant composition of pH-0.8
secretion is independent of stimulus type or magnitude

37
Q

What is pH of mixed gastric juice?
What is it modified by?
What does it pH depend on?

A

-pH=1-2
modified by non parital alkaline gastric secretions
-depends on number of parieal cells that are active (which lowers pH)

38
Q

What are the 4 functions of HCl?

A

-precipitaes soluble proteins (allwos the proteins to remain longer in the stomach)
-denatures proteins (more readily digested)
-activates pepsin
-provides optimal pH for pepsin activity (need low pH for pepsin)

39
Q

What is pepsinogen?
When is it active?

A

-secreted by chief cells and it is a zymogen which means it is not active at when it is secreted from these cells
-only active when in contact with HCl in the stomach

40
Q

What can pepsin do when formed?
What can pepsin do, at what pH?

A
  • it can do autocatalysis, can cleave off pepsinogen into pepsin on its own (HCl pH<6)
    -convert protein into polypeptides pH2-3
41
Q

What is special about intrinsic factor, what is it?
What is it required for?
What does it protect?

A

-only secretion of the stomach essential to life
-it is a glycoprotein which is secreted by parietal cells
-required for absorption of vitamin B12 in the distal small intestine (ileum)
-protects vitamin b12 as it moves through GIT

42
Q

What happens when there is intrinsic factor defiency?
Why does it form?
What does it lead to

A

-pernicous anemia bc RBC are not able to form properly due to lack of vit B12, which is neccessary for producing DNA
leads to macrocytic RBC

43
Q

What happens when vit B12 is coupled with intrinsic factor?
What happens without ileum?

A

-it is absorbed at the level of the distal ileum
-cant absorb vit B12 without ileum

44
Q

What are the locations of mucin secretion?

A

-all surface epithelial cells
-cardiac and pyloric tubular glands
-mucous neck cells (fundus and corpus)

45
Q

What happens when CL- enters the cell?
After this what is H+ available for?

A

-Cl- entering the cell is actively transported across the canalicular membrane
-H+ available from the dissociation of intracellular water, is also actively pumped into the canaliculi in exchange for K+

46
Q

What does the secretion of H+ leave in the cell?
What does result in and cause/produce?

A

-excess OH-
-resulting in an increase in intracellular pH.
-This causes more CO2 to diffuse in from the plasma (together with cellular
metabolic CO2 ) combines with water in the presence of Carbonic Anhydrase to produce H2CO3

47
Q

what does H2CO3 react with in the scheme for HCl secretion, what does it restore, and give rise to?
how does water move into canaliculi

A

H2CO3 reacts with the excess OH- to yield H2O and HCO3-
-the latter diffuses into the circulation, restoring the intracellular status quo, and
giving rise to an increased alkalinity in the venous blood
-it moves into canaliculi passively

Phgy 210 (24 decks)

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