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

MNSR 43 - Islets of Langerhans Adrenal glands Flashcards

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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

Study These Flashcards
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
what are adrenaline and noradrenaline derived from and what are they referred to as
Adrenalin(e) [epinephrine] and noradrenalin(e) [norepinephrine] which, like thyroxine, are derivatives of tyrosine and often referred to as catecholamines
26
what percentage of the secretion is adrenlaine and what %age is noradrenaline
80%adrenaline | 20%noradrenalien
27
physiological effect of secretion of hormones of adrenal medulla
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
3 layers of adrenal cortex
``` zona reticularis (inner) zona fasciculata zona glomerulosa (outer) ```
29
how many steroids have been isolated from adrenal cortex
30
30
3 groups of adrenocortical hormones
glucocorticoids mineralcorticoids androgens
31
site of production and hormone released from glucocorticoids group
Produced in zona fasciculata. | The major hormone is cortisol (hydrocortisone) the minor, corticosterone
32
site of production and hormone released from mineralocorticoid group
- Produced in zona glomerulosa. The major hormone is aldosterone
33
site of production and hormone released from androgen group
Produced in zona reticularis. A minor hormone - androstenedione.
34
what causes 95% of the glucocorticoid activity of adrenal
cortisol
35
main glucocorticoid effect of cortisol
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
when is the cortisol hormone released
``` pain injury blood loss fear must release ACTH first ```
37
therapeutic effect of cortisol
decrease in inflammatory response - treat certain immune response treat eczema or anaphylaxis
38
aldosterone accounts for what %age of mineralcorticoid
95%
39
what effect does corticosterone and cortisol have
have a weak effect
40
main effect of aldosterone
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
what controls aldosterone secretion
Aldosterone secretion is controlled by the circulating blood volume
42
how does body react when Aldosterone drops
When this falls, the hormone is secreted along with pituitary ADH • The renin-angiotensin system also stimulates aldosterone release
43
renin-angiotensin system
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
what is the main male hormone secreted by cortex
androstenedione
45
effects of androstenedione
Precursor in the synthesis pathways of both androgens (testosterone) as well as oestrogens (estrone) • Exerts weak androgenic activity on its own
46
example of hypoactivity in adrenal cortex
glucocorticoid insufficiency - addison's disease
47
causes of addisons disease
caused by an autoimmune destruction of the cortex; a third of cases are due to tuberculosis
48
prevalence of addison's disease and female:male ratio
Found in 3 per 100,000 (0.003%) population; | female/male ratio 2:1.
49
symptoms of addison's disease
* 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
treatment of Addison's disease
Replacement therapy with oral synthetic steroids | such as hydrocortisone
51
example of hyperactivity of adrenal cortex
conn's syndrome - hyperaldosteronism increased secretion of aldosterone cushing's syndrome - increased secretion of glucocorticoids
52
causes of hyperaldosteronism
This may be caused by a tumour within the zona glomerulosa
53
prevalence of hyperaldosteronism
Occurs in less than 0.2% of the population, onset between 30 – 60 years
54
symptoms of hyperadlosteronism
Hypertension due to sodium and fluid retention and overstimulation of the renin-angiotensin system • Muscle weakness due to potassium deficiency
55
at what age is cushing's syndrome commonly present
30-40years
56
causes of cushing's syndrome
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
symptoms of cushing's syndrome
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
physical characteristics of of cushing's syndrome
thin limbs fat in abdomen and enlargement of torso moon face protein removal of bone - osteoporosis increased body hair in females
59
treatment of conn's and cushing's syndrome
For both conditions surgical removal of the tumour | and hormone replacement therapy

MNSR (17 decks)

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