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MODULE 3 - Gastrointestinal System > ENDOCRINOLOGY - Glucose Homeostasis > Flashcards

ENDOCRINOLOGY - Glucose Homeostasis Flashcards

1
Q

What is the key factor of blood glucose regulation?

A

The ratio between insulin and glucagon secretion

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2
Q

What are the Islets of Langerhans?

A

Islets of langerhans are groups of pancreatic cells which secrete glucose regulating hormones

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3
Q

Which structure allows islet of langerhans hormone secretion into the systemic circulation?

A

The network of fenestrated capillaries

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4
Q

List the four main pancreatic cells contained within the islets of langerhans? What do each of these cells secrete?

A

Alpha cells: Secrete glucagon
Beta cells: Secrete insulin
Delta cells: Secrete somatostatin
F-cells: Secrete pancreatic polypeptides

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5
Q

What type of hormones are insulin and glucagon?

A

Insulin and glucagon are peptide hormones

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6
Q

Where are the beta cells mainly located in the islets of langerhans?

A

In the centre

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7
Q

Where are the alpha cells mainly located in the islets of langerhans?

A

In the periphery

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8
Q

What is the main physiological stimulus for insulin secretion?

A

Hyperglycaemia stimulates insulin secretion

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9
Q

Which hormone inhibits insulin secretion?

A

Somatostatin

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10
Q

Which molecule stimulates insulin secretion from the beta cells?

A

Calcium stimulates insulin secretion

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11
Q

Describe the process of insulin secretion due to extracellular calcium stimulation

A
  1. Excess glucose enters the beta cells via GLUT 2 proteins
  2. Glucose enters the citric acid cycle to produce ATP
  3. ATP stimulates ATPase K+ channels allowing K+ to enter the cell, altering the membrane potential
  4. Altered membrane potential opens voltage gated Ca2+ channels, moving Ca2+ into the beta cells to stimulate insulin release from secretory vesicles
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12
Q

Describe the process of insulin secretion due to intracellular calcium stimulation

A
  1. Excess glucose binds to G-protein coupled receptors on the beta cell surface causing a conformational change
  2. Conformational change alters cAMP and IP3 levels within the cells stimulating Ca2+ release
  3. Ca2+ stimulates insulin release from secretory vesicles
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13
Q

Describe the two phases of insulin secretion (biphasic response)

A

Initial acute phase: release of stored insulin in the beta cells

Chronic phase: insulin is now being actively produced and secreted

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14
Q

What is the function of the insulin hormone?

A

Lower blood glucose levels through stimulating anabolic reactions reactions which store energy and to inhibit catabolic reactions which break down energy stores

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15
Q

What are the three anabolic reactions stimulated by insulin?

A

Glycogenesis
Protein synthesis
Triacylglycerol (TAG) synthesis

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16
Q

What are the four catabolic reactions inhibited by insulin?

A

Glycogenolysis
Gluconeogenesis
Lipolysis
Protein degradation

17
Q

What are the three cell types targeted by insulin?

A

Hepatocytes
Skeletal muscle cells
Adipose cells

18
Q

How long is the half life of insulin?

A

10 minutes

19
Q

What is the main physiological stimulus for glucagon secretion?

A

Hypoglycaemia stimulates glucagon secretion

20
Q

Which hormone inhibits glucagon secretion?

A

Somatostatin

21
Q

What is the function of glucagon?

A

Glucagon raises blood glucose levels by stimulating catabolic reactions which break down energy stores and inhibits anabolic reactions

22
Q

What are the three catabolic reactions stimulated by glucagon?

A

Glycogenolysis
Gluconeogenesis
Lipolysis

23
Q

Which anabolic reaction is inhibited by glucagon?

A

Glycogenesis

24
Q

What are the two cell types targeted by glucagon?

A

Hepatocytes
Adipose cells

25
Q

Where in the body is glucagon produced other than in alpha cells?

A

Glucagon is also produced in the stomach

26
Q

What is the half life of glucagon?

A

5 minutes

27
Q

Where are insulin and glucagon metabolised?

A

Liver and kidneys

28
Q

What are two glucose homeostasis disorders?

A

Hypoglycaemia
Hyperglycaemia

29
Q

List two causes of hypoglycaemia

A

Excessive insulin administration
Insulinoma (pancreatic tumour secreting excess insulin)

30
Q

List seven clinical signs of hypoglycaemia

A

Tachycardia
Sweating
Pallor
Tremors
Seizures
Unconsciousness
Death

31
Q

What is the most common cause of hyperglycaemia?

A

Diabetes

32
Q

If left untreated, what serious condition can be caused secondary to hyperglycaemia?

A

Secondary ketoacidosis

33
Q

How can ketoacidosis secondary to hyperglycaemia lead to death?

A

Ketoacidosis causes dehydration, nausea, vomiting and anorexia leading to hypovolaemia. Stress hormones in response to hypovolaemia cause further hyperglycaemia, eventually leading to death

MODULE 3 - Gastrointestinal System (17 decks)

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