Insulin – Receptors And Regulation Of Secretion

INSULIN – RECEPTORS AND REGULATION OF SECRETION

Q. 1

Which is/are the GI hormones stimulating insulin secretion?

 A

GIP

 B

Gastrin

 C

Secretin 

 D

All of the above

Q. 1

Which is/are the GI hormones stimulating insulin secretion?

 A

GIP

 B

Gastrin

 C

Secretin 

 D

All of the above

Ans. D

Explanation:

GIP, Gastrin, Secretin & CCK.

Stimulating factor for insulin secretion:

  • Glucose – Relationship between glucose concentration & insulin secretion is “SIGMOIDAL
  • Mannose
  • Amino acids (arginine, leucine)
  • Intestinal hormones –GLP -1.
    • GIP.
    • Gastrin.
    • Secretin.
    • CCK
  • β-keto acids
  • Parasympathetic stimulation – 
    • Acetylcholine
    • cAMP
    • β-adrenergic stimulation.
  • Drugs:Endocrine hormones like Growth hormone, Glucagon & Glucocorticoids.
    • Theophylline.
    • Sulfonylureas

Q. 2

How many polypepide chains does insulin compose of ?

 A

4 chains

 B

3 chains 

 C

2 chains 

 D

5 chains 

Q. 2

How many polypepide chains does insulin compose of ?

 A

4 chains

 B

3 chains 

 C

2 chains 

 D

5 chains 

Ans. C

Explanation:

  • Insulin is two-chain polypeptide hormone, with 51 amino acids.
  • Structure: 
    • 2 chains – A & B chain.
    • A – chain – 21 amino acids; B – chain – 30 amino acids.
  • Half-life-: About 5 mins

Q. 3

Which drug inhibits insulin secretion?

 A

Phenytoin

 B

amoxicillin

 C

Insulin itself 

 D

Both A & C

Q. 3

Which drug inhibits insulin secretion?

 A

Phenytoin

 B

amoxicillin

 C

Insulin itself 

 D

Both A & C

Ans. D

Explanation:

Phenytoin & insulin itself.

Insulin secretion inhibiting factors:

  • Somatostatin
  • 2-deoxyglucose
  • Mannoheptulose
  • α-adrenergic stimulation
  • β-adrenergic inhibitors
  • Galanin
  • Alloxan
  • Electrolyte – K+ depletion
  • Drugs:
    • Diazoxide.
    • Thiazide diuretics.
    • Phenytoin.
    • Microtubule inhibitors.
  • Note: Insulin itself is an inhibitor.

Q. 4

Which is the singke most important factor that stimulates insulin secretion?

 A

Decreased plasma glucose concentration inhibits insulin release. 

 B

Decreased plasma glucose concentration stimulate insulin release. 

 C

Increased plasma glucose concentration stimulate insulin release. 

 D

Increased plasma glucose concentration inhibits insulin release. 

Q. 4

Which is the singke most important factor that stimulates insulin secretion?

 A

Decreased plasma glucose concentration inhibits insulin release. 

 B

Decreased plasma glucose concentration stimulate insulin release. 

 C

Increased plasma glucose concentration stimulate insulin release. 

 D

Increased plasma glucose concentration inhibits insulin release. 

Ans. C

Explanation:

Plasma glucose concentration:

  • Increased plasma glucose concentration stimulate insulin release
  • Glucose entry is “Insulin-independent” via GLUT-2.
  • Glucose metabolized to pyruvate.
  • Ca2+ influx causes insulin efflux from secretory granules (secretion).

FACTORS INFLUENCING:

1. Stimulating factor:

  • Glucose – Relationship between glucose concentration & insulin secretion is “SIGMOIDAL
  • Intestinal hormones –GLP -1.
    • GIP.
    • Gastrin.
    • Secretin.
    • CCK
  • Parasympathetic stimulation – via acetylcholine.
  • Endocrine hormones – Growth hormone, Glucagon & Glucocorticoids.
 


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