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I've got kidney disease > Lecture 30 > Flashcards

Lecture 30 Flashcards

1
Q

What is the main driver for gastric acid secretion?

A

histamine

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2
Q

Which system is part of the switch off gastric acid secretion part?

A

ENS

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3
Q

Why do we need a switch off system to turn of gastric acid secretion?

A

So that we don’t over acidify the stomach

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4
Q

What are the two sites of feedback inhibition? Why are these the sites? What does it involve?

A
  • body/corpus which is the site of acid secretion because here, they can sense if there is more input coming
  • antral region which is the site of gastrin secretion

This involves somatostatin

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5
Q

Explain the feedback inhibition of acid secretion by events in the antral region

A

The antral region detects the presence of H+ ions in the lumen (if it is too acidic, not enough HCl is being absorbed by the food so the H+ conc is too high), it stimulates the secretion of somatostatin from D cells

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6
Q

Where is somatostatin made and secreted from?

A

from D cells in the antrum or the body

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7
Q

What does somatostatin act as when released from the antrum? (as opposed to the body/fundus)

A

it can act as a paracrine hormone which inhibits the production of gastrin by the G cells and it can act as an endocrine hormone to inhibit parietal cells

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8
Q

What role do D cells do in switching off the gastric acid secretion?

A

They sense the acidity in the lumen and if it becomes too acidic then it releases somatostatin

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9
Q

Once somatostatin is released from D cells in the antrum, what happens? What mode of action is this?

A

It finds its receptor in the G cell which switches off the production of gastrin. This is a paracrine action

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10
Q

How can we switch off the “switch off system”? Why would we want to do this?

A

During a meal when there is food in your stomach you have distention of the stomach wall so the stomach expands. This produces a positive signal to release gastric acid but we also have to switch off the “switch off system” so it doesn’t switch off our gastric acid secretion. This negative input to the D cells stays there until the food is in the stomach.

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11
Q

When is the “switch off system” switched on? ie. when does it become important that we switch gastric acid secretion off?

A

If the distention in the stomach becomes less and less because we have passed on the food to the duodenum, the inhibition of the D cells is released so that the D cells produce more somatostatin to inhibit the gastric acid secretion.

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12
Q

What is the endocrine effect of somatostatin when released from the antral region?

A

It goes into the blood and finds the receptor on the parietal cell to switch off the parietal cell so it won’t produce any acid

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13
Q

What is the purpose of somatostatin being released from the D cells in the body/fundus?

A

This is the same as when it is released from D cells in the antrum: it is released to reduce gastric acid secretion

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14
Q

When somatostatin is released by D cells in the body/fundus, it acts as a __________ hormone. What are its effects?

A

paracrine

  • it inhibits acid secretion by parietal cells
  • it inhibits ECL cells so that histamine production is reduced
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15
Q

As long as there is food in the stomach, there is ______ input to the D cells from the ENS

A

negative

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16
Q

The feedback inhibition of gastric acid secretion
A. is mainly based on the enteric nerve system.
B. is mainly dependent on gastrin.
C. is entirely based on paracrine feedback.
D. is independent of the stomach body region.
E. is mainly facilitated by somatostatin.

A

E. is mainly facilitated by somatostatin.

17
Q

Explain the phases of gastric acid secretion

A

The phases are coordinated - when one is finished we need to turn secretion on then off.

18
Q

What is the basal rate (baseline rate) of gastric acid secretion?

A

15 - 30 mL/hr

19
Q

What are the 3 clear phases of control of gastric acid secretion?

A
  • cephalic
  • gastric
  • intestinal
20
Q

What is the purpose of the cephalic phase?

A

This prepares the stomach for the arrival of food

21
Q

What are the stimuli for the cephalic phase?

A
  • thought
  • sight
  • smell of food
  • act of chewing and presence of food in the mouth
22
Q

The cephalic phase stimulates secretion via the what?

A

parasympathetic nervous system

23
Q

During the cephalic phase the PNS stimulates the _____ which in turn does what?

A

ENS
- directly stimulates the parietal cells
- stimulates the release of gastrin from the antral region into the blood
(this stimulates the release of acid from parietal cells in the body of the stomach and stimulates the ECL cells to secrete histamine which stimulates the parietal cells)
- stimulates the release of histamine from the ECL cells (which has a paracrine stimulation of the parietal cells)

24
Q

What is the purpose of the gastric phase?

A

so that the stomach can control secretion

25
Q

During the cephalic phase, receptors in the stomach respond to what?

A
  • stretch (distention)

- products of digestion (antrum)

26
Q

During the gastric phase, the receptors in the stomach stimulate secretion via what two reflexes?

A

ENS - a local reflex

an external reflex involving the CNS (due to distention)

27
Q

What is the vagovagal reflex?

A

This is when there is distention from a local reflex which goes to the brain, then back to the ENS and then it can facilitate the activity of the ECL cells, the G cells and the parietal cells

28
Q

What is the purpose of the intestinal phase?

A

The main effect is to inhibit secretion. the intestinal controls secretion by the stomach

29
Q

What is the stimuli for the intestinal phase?

A

This is when there is distention or increase [H+] or increased osmolarity or increased nutrients in the intestine.

30
Q

What are the pathways involved in the intestinal phase?

A

Long and short neural reflexes, CCK, secretin and other duodenal hormones

30
Q

What are the pathways involved in the intestinal phase?

A

Long and short neural reflexes, CCK, secretin and other duodenal hormones

31
Q

Where does fat digestion happen?

A

In the small intestine

32
Q

Explain the role of pepsin secretion

A

This is the same factors that control acid secretion - there is parallel secretion of acid and pepsin

33
Q

What is the purpose of CCK and secretin released by the SI in the intestinal phase?

A

This is for negative regulation of the G cells and parietal cells to decrease acid secretion. They are also coordinators of the pancreas to secrete pancreatic fluid and enzymes to neutralise the acid from the stomach

34
Q

Gastric acid secretion
A. is increased in the intestinal phase.
B. is regulated by acid and digestion products in the duodenum.
C. is mainly driven by sight, smell and thought.
D. is independent of the cephalic phase.
E. is down-regulated by the enteric nerve system.

A

B. is regulated by acid and digestion products in the duodenum.

I've got kidney disease (43 decks)

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