Lecture 38: Homeostasis in Action

Question 1

Increasing glucose level, ______ responds to high glucose by secreting _____. This causes _____, skeletal muscle, and ___ ____ to ….

Answer 1

• Pancreas
• Insulin
• Liver
• Other tissues
• Take up more glucose

Question 2

Control of blood glucose is mainly by _____ _____.

Answer 2

• Negative feedback

Question 3

Insulin can be thought of as…

Answer 3

• Signalling that the body has been fed

- i.e promotes uptake and storage of nutrients

Question 4

If there’s no insulin around then the body is going to act as if…

Answer 4

• It’s “starved”
• Breaking down stores of glycogen and releasing that glucose to other tissues in the body
• Gluconeogenesis = liver is taking non carbohydrate sources (break down of amino acids) to make new glucose
• Breaking down fat stores to increase lipid levels in blood
• Increase ketone production which can be ‘glucose sparing’.

Question 5

Diabetes derived from Greek….

Mellitus derived from Latin…

Answer 5

• “Passing through”

- “Honey” or “Sweet”

Question 6

Diabetes is historically referred to a disease state characterized by…

Answer 6

• Polyuria (passing large volumes of urine)
• Polydipsia (excessive thirst)
• Polyphagia (excessive hunger)

Question 7

Type 1 Diabetes Mellitus:

Answer 7

• Little or NO INSULIN
• Typically younger onset (children or teenagers)
• May be associated with prior viral illness and subsequent autoimmune response that destroys pancreatic Beta Cells
  Environmental agent + genetic predisposition ^^^
• Treatment = Insulin
• HYPO only occurs if they’ve been overtreated with insulin

Question 8

Type II Diabetes Mellitus:

Answer 8

• Insulin Resistance
• Cells aren’t responding to the insulin
• May have higher than normal levels of insulin, because glucose ends up staying in blood, which means lots and lots of insulin
• Eventually insulin level may drop off because pancreas has had enough
• May be related to:
  Ageing
  Obesity
  » Reduced numbers or function of insulin receptors
  » Altered intracellular signalling in target cells
• Other conditions (eg Cushing’s disease, PCOS)
• Hyperglycemia but diff to Type I, insulin levels may still be adequate to suppress lipolysis and ketogenesis but not sufficient to control BGL
• Treatment: Exercise, Weight Loss, Oral Drugs, Insulin if needed

Question 9

Oral Hypoglycemic Drug Classes are used for ____ ____ Diabetes people. These include:

Answer 9

• Type II
• Sulphonylureas : increase insulin secretion by beta cells, can cause hypoglycemia if not eating or overdose
• Metformin : reduces glucose output from liver by inhibiting gluconeogenesis
• Thiazolidinediones : increase insulin sensitivity of cells

Question 10

Diabetes Insipidus:

Answer 10

• Lots of dilute urine but no glucose in it!!!
• Due to altered secretion of ADH or decreased responsiveness to it
• Often associated with brain injury or tumour in region of pituitary gland

Question 11

Gestational Diabetes (important):

Answer 11

• Can affect women during pregnancy
• May resolve after pregnancy or not
• Large baby increased risk of birth injuries, neonatal hypoglycemia, congenital malformations, child/adult obesity?

Question 12

Hyperglycemia is due to:

Answer 12

• Inability of most cells (not brain) to absorb glucose
  » glucose stays in blood, can’t enter cells, decreased production
• Increased output of glucose by liver
  » Glycogenolysis and gluconeogenesis

Question 13

Glycosuria is when…

Answer 13

• Renal tubes can’t reabsorb the excessive glucose being filtered

Question 14

Polyuria…

Answer 14

• Excessive thirst

Question 15

Acute Consequences…

Answer 15

• Breakdown of protein and fat
• (Diabetic) Ketoacidosis (DKA) : ketones are acidic and cause acidosis when produced in excess
• Acetone-like smell on breath and can also be detected in urine
• Acidosis causes hyperventilation
• Acidosis can cause hyperkalemia

Question 16

Need to be careful when administering insulin in DKA - why?

Answer 16

• Increases uptake of amino acid and potassium

- Potassium is back in cells, total K is depleted

Question 17

Chronic hyperglycemia can predispose blood vessels and nerves to damage. This includes:

Answer 17

• Cardiovascular disease
• Renal failure
• Retinal damage
• Poor wound healing
• Peripheral nerve damage
• Susceptibility to infection

Question 18

Treatment of Type I Diabetes Mellitus:

Answer 18

• Insulin : Banting + best at UOT developed methods for extracting and purifying insulin from cattle pancreases.
• Now a much greater range of insulin types available
• Human insulin modifies to slow absorption

Question 19

Homeostatic mechanisms restoring blood pressure and volume after haemorrhage

Answer 19

• Activation of platelets and the coagulation cascade
• Drop in pressure detected by sensors
• Info sent by nerves to cardiovascular control centres in brainstem
• Nerve impulses sent from brain to heart to increase HR and force of contraction

Question 20

Signs typically associated with physiological shock…But what about blood volume?

Answer 20

• Looks pale and skin cool ‘clammy’
• Vasoconstriction to blood vessels in skin and other organs
• Decreased blood pressure detected by stretch receptors in walls of renal arterioles
• Specialised cells in the kidney (integrator) cause the formation of a hormone (control signal) in the blood (communication pathway)
• Hormone 1 can (1) stimulate adrenal glands –> Aldosterone –> Na+ reabsorption by kidney
  (2) stimulate ADH glands

Question 21

Blood pressure and blood volume are restored but what about the lost RBCs?

Answer 21

• A few weeks