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MD4001 Week 9 > The Endocrine Pancreas: Alpha and Beta Cell Function > Flashcards

The Endocrine Pancreas: Alpha and Beta Cell Function Flashcards

1
Q

Where does the pancreas grow?

A

Develops as an outgrowth of the gut tube

Closely associated with the development of the gallbladder

Ducts joint before emptying into the duodenum

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2
Q

What does the exocrine pancreas produce?

A

Pancreatic acini produce pancreatic amylase

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3
Q

What does the endocrine pancreas produce?

A

Islets of langerhans produce hormones

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4
Q

How much of the pancreas is endocrine?

A

2%

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5
Q

What are the various cell types in the Islets of Langerhans?

A

Alpha and alpha 2 produce glucagon

Beta cells produce insulin

Alpha 1, gamma and delta cells produce somatostatin

F cells- pancreatic polypeptide

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6
Q

What are the main endocrine functions?

A

Control of blood glucose in absorptive and postabsorptive states (insulin and glucagon)

Stimulate/ inhibit digestive enzyme and HCO3- secretion in GI tract (pancreatic peptide and somatostatin

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7
Q

Describe the anatomy of the islet of Langerhans?

A

Alpha cells exteriorly

Delta more interiorly with Beta cells

Blood flows from the centre to the periphery

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8
Q

How does the body synthesize and process insulin?

A

mRNA encoding preproinsulin is processed by ribosome

This then forms insulin

Moved to golgi where cleavage occurs

Then passed to secretory granule

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9
Q

How does absorption of food in the GI tract effect the beta cell for insulin release?

A

Presence of free fatty acids

Presence of GI tract hormones, incretins, GIP, GLP, CCK

Presence of certain amino acid

Increased blood glucose

PSNS stimulation

Beta adrenergic stimulation

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10
Q

How does alpha cell affect the beta cells?

A

Glucagon increases insulin production

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11
Q

How does the delta cell affect beta cells?

A

Releases somatostatin which inhibits insulin release

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12
Q

What affect does alpha adrenergic stimulation on beta cells?

A

Decrease release of insulin

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13
Q

What are the mechanisms of insulin release from the pancreatic Beta cell?

A

Glucose enters the cell vai GLUT2 transporter which mediates facilitated diffusion of glucose into the cell

The increased glucose influx stimulates glucose metabolism leading to an increase in ATP

The increased ATP inhibits an ATP sensitive potassium channel

Inhibition of this potassium channel causes depolarization in the beta cell

The depolarization activates a voltage gated calcium channel in the plasma membrane

This activation promotes calcium influx and therefor provokes calcium induced calcium release

The elevated calcium leads to exocytosis and release into the blood of insulin contained within the secretory granules

Other modulators of secretion act via the adenylyl cyclase-cAMP- protein kinase A pathways and the phospholipase C- phosphoinositide pathway

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14
Q

What are the physiological actions of insulin?

A

Increased protein synthesis

Increased glycogenesis to increased glucose transport into cells (muscle and adipose tissue) to decreased blood glucose

Increased lipogenesis

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15
Q

What is the affect of increased protein synthesis?

A

Growth and maintenance

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16
Q

What factors regular glucagon release from alpha cell?

A

Decreased blood glucose

Certain amino acids

GI tract hormones

PSNS stimulation

Beta adrenergic stimulation

Alpha adrenergic stimulation

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17
Q

What factors regular glucagon release from alpha cell?

A

Decreased blood glucose

Certain amino acids

GI tract hormones

PSNS stimulation

Beta adrenergic stimulation

Alpha adrenergic stimulation

ALL INCREASE GLUCAGON

absorption of high protein meal in the GI tract

18
Q

How does beta cell affect alpha cell?

A

Insulin inhibits release of glucagon

19
Q

How does delta cell affect beta cells?

A

Somatostatin inhibits release of alpha

20
Q

What are the physiological actions of glucagon?

A

Decrease insulin leading to decreased lipogenesis and increased lipolysis, leading to increased free fatty acids and glycerol

Increased glycogenolysis leading to increased blood glucose

Increased cortisol leading to increased gluconeogenesis leading to increased blood glucose

21
Q

What causes diabetes mellitus?

A

Insulin deficiency or insulin insensitivity

22
Q

Symptoms of hyperglycemia?

A

Glucosuria- tubular fluid exceeds renal threshold

Polyuria- osmotic diuresis due to glucose in tubular fluid

Polydipsia- due to dehydration increasing angiotensin II levels which acts as a dipsogen on thirst centres in the brain

Increased blood amino acids due to increased protein catabolism

Increased blood FFA and glycerol

Ketoacidosis

23
Q

What are the different steps in the development of ketoacidosis?

A

FFA/ ketogenic

Acetyl CoA

Beta-OH-butyrate

Acetone

Increase plasma ketones

Ketonaemia

Ketonuria

24
Q

Describe type 1 diabetes?

A

Insulin dependent

Destruction of pancreatic beta cell

25
Q

How to treat type 1 diabetes?

A

Insulin administration and restricted carbohydrate diet

26
Q

Describe type II diabetes?

A

Capacity of beta cell to produce insulin decreased or decreased number and affinity of insulin receptors results in reduced insulin responsiveness

Related to obesity

27
Q

How to treat type II diabetes?

A

Treated by restricted diet

Sulphonylureas

Biguanides

Insulin injection

28
Q

Why would diabetics take sulphonylureas?

A

Increase beta cell response to glucose

29
Q

Why would diabetics take biguanides?

A

Stimulate glucose uptake in muscle

30
Q

What are the main acute effects of diabetes mellitus?

A

Increased hepatic glucose output

Decreased glucose uptake by cells

Decreased triglyceride synthesis

Increased lipolysis

Decrease aa uptake by cells

Increased protein degradation

31
Q

See slide 13

A

lecture

32
Q

Example of long term pathologies associated with diabetes mellitus?

A

Diabetic atherosclerosis

Hypertension

CVS disease

Angina

Arrhythmias

Renal disease

33
Q

What leads to diabetic athersclerosis?

A

Loss of arterial compliance caused by

Damage/ loss of vascular endothelium (loss of NO) caused by

Modification of structural protein in arteries and arterioles caused by both

increased fat metabolism and blood glucose

34
Q

What leads to hypertension?

A

Loss of arterial compliance caused by

Damage/ loss of vascular endothelium (loss of NO) caused by

Modification of structural protein in arteries and arterioles caused by both

increased fat metabolism and blood glucose

35
Q

Where does the thymus gland develop?

A

Pharyngeal pouch

36
Q

Where is the thymus?

A

Migrates inferiorly to the superior mediastinum and loses connection with the pharynx

37
Q

Where does the thymus get its function from?

A

Lymphoid thymocytes derived from bone marrow invade and colonise the gland

38
Q

Function of thymus?

A

Development and education of T lymphocytes

Secretes several hormones that promote the maturation of different cells of the immune system

39
Q

Function of amylin?

A

Amylin is a peptide hormone that is cosecreted with insulin from the pancreatic β-cell and is thus deficient in diabetic people. It inhibits glucagon secretion, delays gastric emptying, and acts as a satiety agent

40
Q

What is the glucose tolerance test?

A

A glucose tolerance test checks how well the body processes blood sugar (glucose). It involves comparing the levels of glucose in the blood before and after drinking a sugary drink. The results of this test can help doctors to detect type 2 diabetes or pre-diabetes

MD4001 Week 9 (8 decks)

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