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PHYSIOLOGY GIS > lec 6 > Flashcards

lec 6 Flashcards

1
Q

Hydrochloric acid (HCl) function

A
  1. Activates the enzyme precursor pepsinogen
  2. Aids in the breakdown of connective tissue and muscle fibers
  3. Denatures protein بفك الflods
  4. Along with salivary lysozyme, kills most of the microorganisms ingested with food
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2
Q

Aids in the breakdown of connective tissue and muscle fibers how

A

reducing large food particles into smaller particles

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3
Q

Parietal cells secrete

A

HCL + IF

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4
Q

The pH of HCL

A

is about 0.8,

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5
Q

hydrogen ion concentration at 0.8 PH

A

about 3 million times that of the arterial blood

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6
Q

the pH of the cytoplasm of the parietal cell is

A

7.2 to 7.4

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7
Q

the parietal cells secrete an acid solution that contains

A

0.17 N HCl,

160 mmol/L) of HCl

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8
Q

HCL in other cells

A

4 X 10-5meq/L

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9
Q

that gastric venous blood has a higher pH than arterial blood when the stomach is secreting acid

A

To concentrate the hydrogen ions this tremendous amount requires more than 1500 calories of energy per liter of
gastric juice. While hydrogen ions are secreted, bicarbonate ions diffuse into the blood

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10
Q

alkaline tide”

A

HCO3-

is added to the venous blood, the pH of the blood increases

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11
Q

fate of HCO3-

A

will be secreted in pancreatic secretions to neutralize H+ in the small intestine.)

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12
Q

If vomiting occurs

A

gastric H+ never arrives in the small intestine, there is
▼
no stimulus for pancreatic HCO3
-secretion, and
▼
the arterial blood becomes alkaline (metabolic alkalosis).

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13
Q

The agents that stimulate H+ secretion

A
  1. Acetylcholine
  2. Gastrin
  3. Histamine
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14
Q

Acetylcholine and Gastrin will stimulate H+ secretion

A

Gq and the second messenger is IP3 and

increased intracellular [Ca+)

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15
Q

Acetylcholine and Gastrin will stimulate H+ secretion

A

Gq and the second messenger is IP3 and

increased intracellular [Ca+)

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16
Q

Histamine will stimulate H+ secretion

A

H2 receptor is coupled to adenylyl cyclase via a Gs protein. The second messenger for histamine is cAMP.

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17
Q

The second messenger for

histamine is

A

cAMP.

18
Q

the second messenger for Acetylcholine and Gastrin

A

IP3 and

increased intracellular [Ca+].

19
Q

Vagal stimulation (In the direct path)

A

vagus nerve →Acetylcholine → M3 r on parietal cell → HCL

20
Q

Vagal stimulation in the indirect path

A
  1. vagus n → Gastrin Releasing Peptide (GRP) →M3 r on G cells → Gastrin (carried from antrum to body by blood to stimulate H+ secretion
  2. vagus n→ Gastrin Releasing Peptide (GRP → M1 →entero-chromaffin-like(ECL) cells → Histamine →H2 receptor on P.C > H+
21
Q

The direct pathway is blocked by

A

Atropine

22
Q

atropine does not block HCl secretion completely

A

because it does not inhibit the indirect pathway, which uses GRP as a neurotransmitter.

23
Q

Vagotomy

A

eliminates both direct and indirect

pathways.

24
Q

Gastrin secretion increased by

A
  1. Stomach contents

2. Vagal stimulation

25
Q

Gastrin secretion increased by Stomach contents ?

A

Small peptides and stomach distension→ vago-vagal reflex →stimulate G cell → gastrin

26
Q

gastrin stimulate H+ secretion by Directly effect on parietal cell

A

Gastrin will bind Chole-cysto-kinin type B
(CCK-B) receptor in parietal cell
Gastrin will stimulate parietal cells to secretHCl

27
Q

gastrin stimulate H+ secretion Indirectly effect on ECL cell

A

Gastrin will bind Chole-cysto-kinin type B
(CCK-B) receptor in entro-chromaffin cell
(ECL); which stimulates Histamine secretion

28
Q

Histamine will diffuse from Enterochromaffin-like (ECL) cells to the nearby parietal cells

A

in paracrine Fashion

29
Q

H2 receptor-blocking drugs

A

cimetidine (the direct action of histamine

b. the histamine-potentiated effect of both acetylcholine and gastrin)

30
Q

The rate of hydrochloric is regulated

A

by independent actions of histamine, acetylcholine, and gastrin
by interactions among the three agents
(potentiation)

31
Q

result

A

ow concentration of stimulus given together can produce maximal effects

32
Q

explanation of potentiation in parietal cell

A

1.Each agent stimulates HCl secretion via a different receptor
2.both acetylcholine and gastrin stimulate
histamine release from enterochromaffin like cell

33
Q

Mechanism decrease release of

Hydrochloric acid by parietal cell

A
  1. Low pH (< 3.0) in the stomach
  2. Somatostatine
  3. prostaglandin
34
Q

Low pH (< 3.0) in the stomach

A
  1. Negative feedback

2. inhibits gastrin

35
Q

When the pH of the stomach contents is

< 3.0

A
  1. .(After a meal is ingested

2. When the stomach emptied

36
Q

Somatostatin is a

A

14-amino-acid peptide

37
Q

the gastrointestinal tract D cells located

A

the antrum and enteric nerves

38
Q

Somatostatin in

A

the gastrointestinal tract D cells (located in the antrum), and enteric nerves and
 pancreas from D cell in island of Langerhans
 the hypothalamus

39
Q

Somatostatin physiologic effects

A
  1. inhibits the secretion of numerous hormones and transmitters (GI hormones
    Pancreases and hypothalamus
    2.reduces intestinal fluid and pancreatic secretion
    3.slows GIT motility and inhibits gallbladder contraction
    4.direct contraction of vascular smooth muscle→ Lading to a reduction of portal and splanchnic blood flow
    5.inhibits secretion of some anterior pituitary hormones.
40
Q

Prostaglandins and Somatostatine inhibit gastric H+ secretion by

A

activating a Gi protein,
inhibiting adenylyl cyclase and
decreasing cAMP levels

41
Q

D cell in the antrum is stimulated by directly by

A

vagaus → calcitonin gene releasing peptide (CGRP) on M2
2.H+ is sensed by the D cells in the antrum Somatostatin transfer from D cell to parital cell by blood to inhibit HCl through Somatostatin type 2 (SST2)
receptor

PHYSIOLOGY GIS (17 decks)

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