Gastrointestinal Hormones

GASTROINTESTINAL HORMONES

Q. 1

Which of the following reduces gastric secretions?

 A Secretin
 B

Peptides

 C Vagal discharge
 D

Epinephrine

Q. 1

Which of the following reduces gastric secretions?

 A Secretin
 B

Peptides

 C Vagal discharge
 D

Epinephrine

Ans. A

Explanation:

Secretin

REF: Ganong’s 22nd ed chapter 26

Stimuli that affect gastrin secretion:

  • Stimuli that increase gastrin secretion

–                 Luminal

–                 Peptides and amino acids

–                 Distention

–                 Neural

–                 Increased vagal discharge via GRP

–                 Blood-born

–                 Calcium

–                 Epinephrine

  • Stimuli that inhibit gastrin secretion  

–          Luminal     

–          Acid 

–          Somatostatin

–          Blood-borne

–          Secretin, GIP, VIP, glucagon, calcitonin


Q. 2 Best stimulii for the secretion of secretin is
 A Protein
 B Food carbohydrate
 C Water
 D None of the above
Q. 2 Best stimulii for the secretion of secretin is
 A Protein
 B Food carbohydrate
 C Water
 D None of the above
Ans. A

Explanation:

Protein


Q. 3

Best stimuli for pancreatic secretion rich in electrolytes ?

 A

Ach

 B

CCK

 C

Secretin

 D

Gastrin

Q. 3

Best stimuli for pancreatic secretion rich in electrolytes ?

 A

Ach

 B

CCK

 C

Secretin

 D

Gastrin

Ans. C

Explanation:

Secretin increases the secretion of bicarbonate by the duct cells of the pancreas and biliary tract. It thus causes the secretion of a watery, alkaline pancreatic juice. Its action on pancreatic duct cells is mediated via cAMP. It also augments the action of CCK in producing pancreatic secretion of digestive enzymes. It decreases gastric acid secretion and may cause contraction of the pyloric sphincter.

Ref: Barrett K.E., Barman S.M., Boitano S., Brooks H.L. (2012). Chapter 25. Overview of Gastrointestinal Function & Regulation. In K.E. Barrett, S.M. Barman, S. Boitano, H.L. Brooks (Eds), Ganong’s Review of Medical Physiology, 24e.

Q. 4

The important function of the GI hormone secretin is:

 A

Stimulates pancreatic fluid and bicarbonate secretion

 B

Inhibits gastric acid secretion

 C

Inhibits intestinal motility

 D

Increases gastric acid secretion

Q. 4

The important function of the GI hormone secretin is:

 A

Stimulates pancreatic fluid and bicarbonate secretion

 B

Inhibits gastric acid secretion

 C

Inhibits intestinal motility

 D

Increases gastric acid secretion

Ans. A

Explanation:

SECRETIN:
 
It is the first hormone discovered in GIT.
It is a 27 amino acid peptide secreted from the S cells of the stomach.
 
Functions:
1. Stimulates pancreatic fluid and enzymatic secretion (Most important function)
2. Inhibits gastric acid secretion
3. Decreases intestinal motility
It also function as an enterogastrone – i,e released when is fat is present in the intestine.
 
Ref: Sleisenger and Fordtran’s, Edition-9, Page-7

 


Q. 5

Cholecystokinin is produced from:

 A

Hepatocyte

 B

Gastric mucosa

 C

Duodenal mucosa

 D

Epithelial cells of distal common bile duct

Q. 5

Cholecystokinin is produced from:

 A

Hepatocyte

 B

Gastric mucosa

 C

Duodenal mucosa

 D

Epithelial cells of distal common bile duct

Ans. C

Explanation:

The major factor controlling the contraction of the gallbladder is the  hormone cholecystokinin (CCK), which is released from the duodenal mucosa in response to the ingestion of fats and amino acids.


Reference:
Harrisons Principles of Internal Medicine, 18th Edition, Page 2616

 


Q. 6

Which of the following statements, regarding ‘secretin’ is least correct?

 A

Increases bicarbonate rich secretion

 B

Inhibit gastric acid secretion

 C

Causes contraction of pyloric sphincter

 D

Increases gastric acid secretion

Q. 6

Which of the following statements, regarding ‘secretin’ is least correct?

 A

Increases bicarbonate rich secretion

 B

Inhibit gastric acid secretion

 C

Causes contraction of pyloric sphincter

 D

Increases gastric acid secretion

Ans. D

Explanation:

Gastrin decreases gastric acid secretion.
 
Ref: Ganong’s Review of Medical Physiology, 22nd Edition, Pages 462, 486; Guyton and Hall – Textbook of Medical Physiology, 10th Edition, Pages 745, 747

Q. 7

Lower esophageal sphincter pressure is increased by all of the following substances, EXCEPT:

 A

Gastrin

 B

Vasopressin

 C

Glucagon

 D

Secretin

Q. 7

Lower esophageal sphincter pressure is increased by all of the following substances, EXCEPT:

 A

Gastrin

 B

Vasopressin

 C

Glucagon

 D

Secretin

Ans. D

Explanation:

The lower esophageal sphincter, a physiologic entity but not an anatomic structure, plays an important part in preventing gastroesophageal reflux. Neural, hormonal, myogenic, and mechanical factors influence the tone of the sphincter. Gastrin, vasopressin, glucagon, adrenergic agonists, and cholinergic agents increase the pressure. Secretin has the opposite effect.  


Q. 8

Release of which of the following peptides leads to an increase in the secretion of pancreatic enzymes into the small intestine?

 A

Cholecystokinin

 B

Gastrin

 C

Motilin

 D

Secretin

Q. 8

Release of which of the following peptides leads to an increase in the secretion of pancreatic enzymes into the small intestine?

 A

Cholecystokinin

 B

Gastrin

 C

Motilin

 D

Secretin

Ans. A

Explanation:

Release of cholecystokinin is stimulated by the presence of peptides, amino acids, or fatty acids in the small intestine. Cholecystokinin acts on the pancreas to stimulate secretion of pancreatic enzymes that aid in the digestion of these compounds.

Gastrin secretion is stimulated by the presence of peptides or amino acids in the lumen of the stomach, and produces an increase in gastric H+ secretion.

Motilin is a hormone that regulates the migrating myoelectric complex, a series of contractions that occur during fasting, clearing the stomach and small intestine of any residual food.

Secretin secretion is stimulated by the presence of H+ and fatty acids in the duodenum, and causes an increase in pancreatic and biliary HCO3; release and a decrease in gastric H+ release.

Ref: Barrett K.E., Barman S.M., Boitano S., Brooks H.L. (2012). Chapter 25. Overview of Gastrointestinal Function & Regulation. In K.E. Barrett, S.M. Barman, S. Boitano, H.L. Brooks (Eds), Ganong’s Review of Medical Physiology, 24e.


Q. 9

Trophic action on mucosa of large intestine is provided by the following hormone:

 A

Cholecystokinin

 B

Gastrin

 C

Secretin

 D

Bile acid

Q. 9

Trophic action on mucosa of large intestine is provided by the following hormone:

 A

Cholecystokinin

 B

Gastrin

 C

Secretin

 D

Bile acid

Ans. B

Explanation:

Gastrin has a variety of actions, but its principal physiologic actions are stimulation of gastric acid and pepsin secretion and stimulation of the growth of the mucosa of the stomach and small and large intestines (trophic action)
 
Ref: Barrett K.E., Barman S.M., Boitano S., Brooks H.L. (2012). Chapter 25. Overview of Gastrointestinal Function & Regulation. In K.E. Barrett, S.M. Barman, S. Boitano, H.L. Brooks (Eds), Ganong’s Review of Medical Physiology, 24e.

Q. 10

Which of these statements are correct regarding acid secretion in stomach:

 A

Gastrin increases acid secretion

 B

Secretin decreases acid secretion

 C

H2 blockers decrease acid secretion

 D

All

Q. 10

Which of these statements are correct regarding acid secretion in stomach:

 A

Gastrin increases acid secretion

 B

Secretin decreases acid secretion

 C

H2 blockers decrease acid secretion

 D

All

Ans. D

Explanation:

A i.e. Gastrin increases acid secretion; B i.e. Secretin decreases acid secretion; C i.e. H2 blocker decreases acid secretion


Q. 11

Which inhibits gastric secretion ?

 A

Secretin

 B

Insulin

 C

High gastric pH

 D

Calcium

Q. 11

Which inhibits gastric secretion ?

 A

Secretin

 B

Insulin

 C

High gastric pH

 D

Calcium

Ans. A

Explanation:

A i.e. Secretin

Gastrin is a hormone which is produced by G-cells in the lateral wall of glands in the antral portion of gastric mucose. It is also found in pancreatic islets in fetal life, gastrinomas of pancreas, and pituitary glandQ, hypothalamus, medulla oblongata and in vagus & sciatic nerves.


Q. 12

Which of the following is TRUE regarding gastric emptying:

 A

Decreased by CCK.

 B

Decreased by gastrin

 C

Increased by secretin

 D

Decreased by insulin.

Q. 12

Which of the following is TRUE regarding gastric emptying:

 A

Decreased by CCK.

 B

Decreased by gastrin

 C

Increased by secretin

 D

Decreased by insulin.

Ans. A

Explanation:

A i.e. Decreased by CCK


Q. 13

Stimulation for gastric emptying :

 A

Secretin

 B

CCK

 C

Gastrin

 D

All

Q. 13

Stimulation for gastric emptying :

 A

Secretin

 B

CCK

 C

Gastrin

 D

All

Ans. C

Explanation:

C i.e. Gastrin


Q. 14

True about secretin is:

 A

Increased gallbladder contraction and HCO3 rich pancreatic fluid

 B

Increased gastrin secretion

 C

Gastric hypermotility

 D

Increase enzyme rich pancreatic fluid

Q. 14

True about secretin is:

 A

Increased gallbladder contraction and HCO3 rich pancreatic fluid

 B

Increased gastrin secretion

 C

Gastric hypermotility

 D

Increase enzyme rich pancreatic fluid

Ans. A

Explanation:

A i.e. Increased gallbladder contraction and HCO3 rich pancreatic fluid


Q. 15

Actions of cholecystokinin include all of the following except :

 A

Contraction of gall bladder

 B

Secretion of pancreatic juice rich in enzymes

 C

Increases the secretion of enterokinase

 D

All

Q. 15

Actions of cholecystokinin include all of the following except :

 A

Contraction of gall bladder

 B

Secretion of pancreatic juice rich in enzymes

 C

Increases the secretion of enterokinase

 D

All

Ans. C

Explanation:

C i.e. Increases the secretion of enterokinase

Secretin hormone stimulates copious secretion of a very alkaline pancreatic jute that is rich in water & HCO 3and poor

in enzymes and Cl-Q. It also stimulates bile secretion (choleretics)Q but has no role in synthesis of bile salt and bile acids. It augments action of CCKPZ but inhibits gastrin secretion and gastric emptying & motalityQ.


Q. 16

Which of the following statements, regarding ‘secretin’ is least correct?

 A

Increases bicarbonate rich secretion

 B

Inhibit gastric acid secretion

 C

Increases gastric acid secretion

 D

Causes contraction of pyloric sphincter

Q. 16

Which of the following statements, regarding ‘secretin’ is least correct?

 A

Increases bicarbonate rich secretion

 B

Inhibit gastric acid secretion

 C

Increases gastric acid secretion

 D

Causes contraction of pyloric sphincter

Ans. C

Explanation:

C i.e. Increase gastric acid secretion


Q. 17

Most potent stimulus for secretin is –

 A

Dilatation of intestine

 B

Acid chime

 C

Protein

 D

Fat

Q. 17

Most potent stimulus for secretin is –

 A

Dilatation of intestine

 B

Acid chime

 C

Protein

 D

Fat

Ans. B

Explanation:

B i.e. Acid chyme


Q. 18

Pancreatic juice rich in water and electrolytes poor in enzymes is secreted in response to :

 A

Pancreatozymin

 B

Cholecystokinin

 C

Secretin

 D

Proteins

Q. 18

Pancreatic juice rich in water and electrolytes poor in enzymes is secreted in response to :

 A

Pancreatozymin

 B

Cholecystokinin

 C

Secretin

 D

Proteins

Ans. C

Explanation:

C i.e. Secretin


Q. 19

Secretin does not cause :

 A

Secretin does not cause :

 B

Auguments the action of CCK

 C

Contraction of pyloic sphincter

 D

Gastric secretion increase

Q. 19

Secretin does not cause :

 A

Secretin does not cause :

 B

Auguments the action of CCK

 C

Contraction of pyloic sphincter

 D

Gastric secretion increase

Ans. D

Explanation:

D i.e. Gastric secretion increases


Q. 20

Best stimuli for secretin is-

 A

Protein

 B

Acid

 C

Fat

 D

Bile

Q. 20

Best stimuli for secretin is-

 A

Protein

 B

Acid

 C

Fat

 D

Bile

Ans. B

Explanation:

B i.e. Acid


Q. 21

Maximum contraction of gall bladder is seen with:

 A

CCK

 B

Secretin

 C

Gastrin

 D

Enterogastrone

Q. 21

Maximum contraction of gall bladder is seen with:

 A

CCK

 B

Secretin

 C

Gastrin

 D

Enterogastrone

Ans. A

Explanation:

A i.e. CCK

Most potent stimulus for causing gall bladder contraction is CCK-PZQ.


Q. 22

Emptying of stomach is facilitated by:

September 2012

 A

Secretin

 B

CCK-PZ

 C

GIP

 D

Gastrin

Q. 22

Emptying of stomach is facilitated by:

September 2012

 A

Secretin

 B

CCK-PZ

 C

GIP

 D

Gastrin

Ans. D

Explanation:

Ans. D i.e. Gastrin

Gastrin

  • It is a peptide hormone that stimulates secretion of gastric acid (HC1) by the parietal cells of the stomach and aids in gastric motility.
  • It is released by G cells in the antrum of the stomach (the portion of the stomach adjacent the pyloric valve), duodenum, and the pancreas.
  • Its release is stimulated by peptides in the lumen of the stomach.

Q. 23

Which of the following decreases intestinal motility:

March 2011

 A

CCK

 B

Serotonin

 C

Gastrin

 D

Secretin

Q. 23

Which of the following decreases intestinal motility:

March 2011

 A

CCK

 B

Serotonin

 C

Gastrin

 D

Secretin

Ans. D

Explanation:

Ans. D: Secretin

The strength of the contractions of small intestine is proportional to the frequency of the spike generated by the slow waves

“Slow wave” amplitude is increased by GIT hormones released during digestion e.g. gastrin, CCK-PZ and motilin; whereas secretin and glucagons decrease the slow wave amplitude

Intestinal motility

  • Digestive hormones, cholecystokinin (CCK), gastrin and motilin increase intestinal motility
  • Secretin decreases the activity.
  • Serotonin and insulin can increase motility
  • Glucagon can decrease motility.

Secretin

  • Secretin is synthesized in cytoplasmic secretory granules of S-cells which are found mainly in mucosa of duodenum and smaller numbers in jejunum of small intestine
  • Secretin is released into circulation and/or intestinal lumen in response to low duodenal pH.
  • Also the secretion of secretin is increased by the products of protein digestion bathing the mucosa of the upper small intestine.
  • It is the active form of prosecretin.
  • This acidity is due to hydrochloric acid in the chyme that enters the duodenum from the stomach via the pyloric sphincter.
  • Secretin targets the pancreas, which causes the organ to secrete a bicarbonate-rich fluid that flows into the intestine.
  • Bicarbonate ion is a base that neutralizes the acid, thus establishing a pH favorable to the action of other digestive enzymes in the small intestine and preventing acid burns.
  • Other factors are also involved in the release of secretin such as bile salts and fatty acids, which result in additional bicarbonates being added to the small intestine.
  • Secretin release is inhibited by H2 receptor antagonists, which reduce gastric acid secretion.
  • As a result, if the pH in the duodenum increases above 4.5, secretin cannot be released
  • Secretin increases water and bicarbonate secretion from duodenal Brunner’s glands in order to buffer the incoming protons of the acidic chyme.
  • It also enhances the effects of cholecystokinin to induce the secretion of digestive enzymes and bile from pancreas and gallbladder, respectively.
  • It counteracts blood glucose concentration spikes by triggering increased insulin release from pancreas, following oral glucose intake.
  • Although secretin releases gastrin from gastrinomas, it inhibits gastrin release from the normal stomach.
  • It reduces acid secretion from the stomach by inhibiting gastrin release from G cells.
  • In addition, secretin stimulates pepsin secretion from chief cells

Q. 24

Effect of cholecystokinin on GIT ‑

 A

Increases gastric acid secretion

 B

Increases small intestinal peristlasis

 C

Increases gastric motility

 D

Relaxes gall bladder

Q. 24

Effect of cholecystokinin on GIT ‑

 A

Increases gastric acid secretion

 B

Increases small intestinal peristlasis

 C

Increases gastric motility

 D

Relaxes gall bladder

Ans. B

Explanation:

Ans. is ‘b’ i.e., Increases small intestinal peristalsis


Q. 25

The most important hormone that increases gallbladder contraction after a fatty meal is:

 A

Gastrin

 B

Secretin

 C

CCK

 D

GIP

Q. 25

The most important hormone that increases gallbladder contraction after a fatty meal is:

 A

Gastrin

 B

Secretin

 C

CCK

 D

GIP

Ans. C

Explanation:

Ans. c. CCK



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