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MNSR > MNSR 43 - Islets of Langerhans Adrenal glands > Flashcards

MNSR 43 - Islets of Langerhans Adrenal glands Flashcards

1
Q

pancreas

A

organ with both a digestive exocrine and endocrine function

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2
Q

Exocrine

A

secretes digestive juices containing enzymes and bicarbonate

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3
Q

2 major hormones released from pancreas as endocrine

A
  • two major hormones insulin and glucagon
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4
Q

what cells in pancreas secrete insulin and glucagon

A

These are secreted by the cells of the Islets of Langerhans which are scattered throughout the exocrine
acinar tissue.

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5
Q

how are islets of langerhans arranged in pancreas

A

islets, the cells are arranged in irregular chains

and cords separated by a rich blood supply;

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6
Q

3 main cell types

A

alpha -20%
beta - 70%
sigma - 10%

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7
Q

what hormone does alpha cell secrete

A

glucagon - more peripherally arranged

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8
Q

what hormone does beta cell secrete

A

insulin

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9
Q

what hormone does sigma cell secrete

A

somatostatin

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10
Q

what does insulin and glucagon regulate

A

glucose levels - main target organ is liver

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11
Q

what causes diabetes

A

cause when body is state of hyperglycaemia - blood has glucose levels over renal threshold of 180mg/100ml

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12
Q

describe insulin structure

A

small protein made of 2 linked peptides
21 and 30 aa
effects carbohydrate metabolism

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13
Q

name three methods in which insulin decreases blood glucose levels

A
  1. Glucose transport is increased across all cell membranes in the body particularly muscle and liver
  2. Excess glucose is converted into glycogen in muscle and liver and into fatty acids in the liver
  3. Gluconeogenesis - the production of glucose from amino acids and glycerol in the liver, is reduced
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14
Q

what does glucagon hormone consist of

A

hormone consists of a single chain

protein of 29 amino

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15
Q

how is glucagon made

A

Synthesised as proglucagon, which is cleaved by protease enzymes to release active glucagon as well as several other signalling proteins

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16
Q

functions of glucagon

A

Glycogen breakdown in the liver is promoted,
glycogenolysis;
Gluconeogenesis (the production of glucose) is increased;
Lipolysis (breakdown of lipids) within adipose tissue is
promoted.

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17
Q

how does body react when there is a rise in blood glucose levels

A

beta cells are stimulated and release insulin
decrease in alpha cells secreting glucagon
liver takes up glucose - stored as glycogen
blood glucose levels decline

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18
Q

How does body react when there is a drop in blood glucose levels

A

alpha cells stimulated and release glucagon in blood
decrease in activity of beta cells - lowers release of insulin
blood glucose levels rise

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19
Q

how is glucose stored

A

stored as glycogen thru process of glycogenesis or stored as fats thru process lipogenesis

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20
Q

describe histology of adrenal medulla

A

a relatively homogenous,
well vascularised tissue with irregularly arranged cells often referred to as
chromaffin cells
contain small granules of hormone molecules in cytoplasm
lot of myelinated fibres of sympathetic nervous system

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21
Q

cell type of adrenal medulla

A

modified postganglionic neurons (neuroendocrine)

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22
Q

how fast or slow is adrenal medulla and why

A

The response of the medulla is very rapid due to the direct

sympathetic innervation.

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23
Q

what does adrenaline bind to

A

binds and activates both a and b adrenergic receptors to cause the following effects;

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24
Q

what effect does adrenaline have in the body when adrenaline activates alpha and beta adrenergic receptors

A

• Increased cardiac output (b1-adrenoreceptors)
• Increased lipolysis and glycogenolysis (a1 & b1-
adrenoreceptors)
• Bronchodilatation and vasodilatation (b 2 adrenoreceptors
in smooth muscle in the bronchial tree and skeletal blood
vessels)

25
Q

what are adrenaline and noradrenaline derived from and what are they referred to as

A

Adrenalin(e) [epinephrine] and noradrenalin(e) [norepinephrine] which,
like thyroxine, are derivatives of tyrosine and often referred to as
catecholamines

26
Q

what percentage of the secretion is adrenlaine and what %age is noradrenaline

A

80%adrenaline

20%noradrenalien

27
Q

physiological effect of secretion of hormones of adrenal medulla

A
  1. Bronchodilation
  2. Decreased peristalsis in GIT
  3. Increased heart beat
  4. Increased blood flow to brain and muscle
  5. Decreased blood flow to skin and GIT
  6. Increased mental alertness
  7. Increased lipolysis and glycogenolysis
28
Q

3 layers of adrenal cortex

A 
zona reticularis (inner)
zona fasciculata 
zona glomerulosa (outer)
29
Q

how many steroids have been isolated from adrenal cortex

A

30

30
Q

3 groups of adrenocortical hormones

A

glucocorticoids
mineralcorticoids
androgens

31
Q

site of production and hormone released from glucocorticoids group

A

Produced in zona fasciculata.

The major hormone is cortisol (hydrocortisone) the minor, corticosterone

32
Q

site of production and hormone released from mineralocorticoid group

A
  • Produced in
    zona glomerulosa. The major
    hormone is aldosterone
33
Q

site of production and hormone released from androgen group

A

Produced in zona
reticularis. A minor hormone -
androstenedione.

34
Q

what causes 95% of the glucocorticoid activity of adrenal

A

cortisol

35
Q

main glucocorticoid effect of cortisol

A

stimulation of gluconeogenesis and reduction in glucose utilization by cells
rise in blood glucose levels
promotes breakdown of protein in all cells except liver where it is increased
amino acid transport in muscles decrease but in liver increase

36
Q

when is the cortisol hormone released

A 
pain
injury
blood loss
fear
must release ACTH first
37
Q

therapeutic effect of cortisol

A

decrease in inflammatory response - treat certain immune response
treat eczema or anaphylaxis

38
Q

aldosterone accounts for what %age of mineralcorticoid

A

95%

39
Q

what effect does corticosterone and cortisol have

A

have a weak effect

40
Q

main effect of aldosterone

A

The main effect is to increase sodium reabsorption in the distal convoluted tubule and
the collecting duct while promoting the secretion of potassium and hydrogen ions
• Also prevents Na+ loss by the sweat glands, the salivary glands and the colon

41
Q

what controls aldosterone secretion

A

Aldosterone secretion is controlled by the circulating blood volume

42
Q

how does body react when Aldosterone drops

A

When this falls, the hormone is secreted along with pituitary ADH
• The renin-angiotensin system also stimulates aldosterone release

43
Q

renin-angiotensin system

A

drop in blood pressure and fluid volume
renin release from kidney and angiotensinogen released from liver
renin + angiotensinogen = angiotensin I
ACE (angiotensin-converting enzyme) from lungs + angiotensin I = angiotensin II
Angiotensin II acts on adrenal gland - release aldosterone
Aldosterone acts on kidney and start reabsorption of salt and water
Angiotensin II also acts on blood vessels - vasoconstriction

44
Q

what is the main male hormone secreted by cortex

A

androstenedione

45
Q

effects of androstenedione

A

Precursor in the synthesis pathways of both androgens (testosterone) as well as oestrogens (estrone)
• Exerts weak androgenic activity on its own

46
Q

example of hypoactivity in adrenal cortex

A

glucocorticoid insufficiency - addison’s disease

47
Q

causes of addisons disease

A

caused by an autoimmune destruction of the cortex; a third of cases are due to tuberculosis

48
Q

prevalence of addison’s disease and female:male ratio

A

Found in 3 per 100,000 (0.003%) population;

female/male ratio 2:1.

49
Q

symptoms of addison’s disease

A
  • Hypotension, sodium and fluid loss, hypoglycaemia, nausea, vomiting, diarrhoea and coma
  • The acute state (adrenal crisis) may be fatal in 24 hours
  • Slower onset may result in increased ACTH secretion which can increase skin pigmentation (MSH release)
50
Q

treatment of Addison’s disease

A

Replacement therapy with oral synthetic steroids

such as hydrocortisone

51
Q

example of hyperactivity of adrenal cortex

A

conn’s syndrome - hyperaldosteronism
increased secretion of aldosterone
cushing’s syndrome - increased secretion of glucocorticoids

52
Q

causes of hyperaldosteronism

A

This may be caused by a tumour within the zona glomerulosa

53
Q

prevalence of hyperaldosteronism

A

Occurs in less than 0.2% of the population, onset between 30 – 60 years

54
Q

symptoms of hyperadlosteronism

A

Hypertension due to sodium and fluid retention and overstimulation of the renin-angiotensin system
• Muscle weakness due to potassium deficiency

55
Q

at what age is cushing’s syndrome commonly present

A

30-40years

56
Q

causes of cushing’s syndrome

A

75% of cases due to overproduction of ACTH, one third of these are due to a pituitary tumour
• 20% are due to an adrenal cortical tumour

57
Q

symptoms of cushing’s syndrome

A

Hyperglycaemia, which may lead to excessive urine production (polyuria) which leads to excessive thirst (polydipsia)
• Muscle loss occurs due to protein usage for gluconeogenesis

58
Q

physical characteristics of of cushing’s syndrome

A

thin limbs fat in abdomen and enlargement of torso
moon face
protein removal of bone - osteoporosis
increased body hair in females

59
Q

treatment of conn’s and cushing’s syndrome

A

For both conditions surgical removal of the tumour

and hormone replacement therapy

MNSR (17 decks)

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