Endorcine System IV

Question 1

The pancreas
Length
Location
Parts

Answer 1

15-25cm long
Location: retro-peritoneum
Parts: head, neck, body and tail

Question 2

Pancreas main functions

Answer 2

Primarily involved with the digestive system (exocrine)

Role in regulating blood glucose concentrations (endocrine)

Question 3

Histology of pancreatic tissue

25%, 60%, 10%

Answer 3

• islets observed as relatively pale staining population
• extremely rich capillary supply
• 25% glucagon producing cells (alpha)
• 60% insulin producing cells (beta)
• 10% somatostatin producing cells (delta)
• Ghrelin producing cells

Question 4

Islets of langerhans

Answer 4

• different cell types within an islet not randomly distributed
• betal cells occupy the central portion of the islet and are surrounded by a rind of alpha and delta cells
• adult humans have 2000-3000 beta cells with approx 1 mill islets scattered through pancreas

Question 5

Insulin

Answer 5

• a peptide hormone highly conserved sequence among most vertebrates
• insulin mRNA is translated as a single chain precursor called pre-proinsulin and remove of its signal peptide generates pro-insulin
• cleavage of pro-insulin by enzymes -> generates mature form of insulin plus C peptide

Question 6

Insulin function

Answer 6

• acts on tissues (liver, skeletal muscles, adipose) to increase uptake of glucose and amino acids
• increases glycogen production
• stimulates lipid synthesis from free fatty acids
• increased activity of glucose transporters = move glucose into cells
• control of intermediary metabolism

Question 7

Regulation of insulin release

Answer 7

• major stimulus: increased blood glucose levels
• amino acids and keto acids also stimulate insulin
• some neural stimuli
• inhibited by stress-induced responses

Question 8

Blood glucose concentration

Answer 8

• the normal fasting blood glucose concentration in humans and most mammals is 80-90mg per 100 mL
• glucose is liberated from dietary carbohydrate within the SI, then absorbed into the blood
• almost immediately after the infusion begins, plasma insulin levels increase

Question 9

Glucagon

Answer 9

• a 29 AA polypeptide hormone that is a potent hypoerglycaemic agent
• synthesised as pro-glucagon and proteolytic ally processed to yield glucagon within alpha cells of the pancreatic islets
• promotoes breakdown of triglycerides from adipose tissue and release of fatty acids into the blood

Question 10

Glucagon processes

Answer 10

• promotes breakdown of glycogen in the liver

- promoted synthesis of glucose from simpler molecules - process called gluconeogenesis

Question 11

Regulation of glucagon secretion

Answer 11

• produced by alpha cells in the pancreas
• increased blood glucose levels inhibit glucagon release
• amino acids stimulate glucagon release
• stress: epinephrine acts on beta-adrenrgic receptor on alpha cells, increasing glucagon release
• insulin inhibits glucagon secretion
• remember glucocorticoids
• stimulate gluconeogenesis and lipolysis

Question 12

Somatostatin

Answer 12

• named for its effect of inhibiting secretion of growth hormone
• GH secretion is controlled by the interaction of SS and GHRH
• appears to act primarily in a paracrine manner to inhibit the secretion of both insulin and glucagon
• injection of SS into the brain leads to arousal, decreased sleep and impairment of some motor responses
• it is also sometimes used to treat gigantism and acromegaly

Question 13

Blood glucose regulation

Answer 13

• control involves liver (makes and exports glucose) and pancreas (released insulin and glucagon)
• parasympatheis nervous system: stimulated insulin secretion
• sympathetic nervous system: stimulates glucagon secretion

Question 14

Type 1 diabetes

Answer 14

• aka insulin dependent diabetes mellitus
• diabetes currently affects aroung 200 million people -> 10% of these cases type 1 diabetes
• require insulin delivery
• results in hyperglycaemia
• glucose cannot enter the adipose cells
• juvenile onset = genetic susceptibility
• immune system destroys beta cells in pancreas

Question 15

Type 1 diabetes symptoms and consequences

Answer 15

• polyuria and polydipsia
• polyphagia
• diabetic retinopathy
• nephropathy
• diabetric neuropathy, damage to nerves, especially in peripheral tissues
• increased risk of myocardial infarction and stroke
• circulatory problems which can lead to gangrene
• foot problems

Question 16

Type 1 diabetes treatments/cures

Answer 16

• type diabetics require multiple insulin injections daily
• insulin injection is the only way to mamage the disease
• continuous glucose monitors and insulin pumps: automatic and continuous motorins

Question 17

Transplant of beta cells

benefits and limitations

Answer 17

• benefits:
  reduces hypoglycaemia, reduces long term risk of complications, help achieve good glycaemic control
• limitations:
  shortage of islets, immune suppressive theraphy, high costs, long-term insulin dependence

Question 18

Stem cell treatments

Answer 18

• appear to have significant success in some people
• Costly procedures
• immune rejection

Question 19

The appetite and hunger hormones

Leptin

Answer 19

• mediator of long-term regulation of energy balance
• decreases hunger
• secreted primarily from adipose tissue
• some obese patients are leptin-resistant

Question 20

The appetite and hunger hormones

Ghrelin

Answer 20

• Fast-acting hormone
• secreted primarily in stomach lining when stomach is empty
• also produced in e-cells of pancreas
• plays a role in meal initiation
• increases hunger