Adrenal Medulla

Question 1

Where are the adrenal glands located? What are they sometimes referred to? (in america)

Answer 1

adrenal glands are located above the kidneys, hence are sometimes called the suprarenal glands. They are retroperitoneal

Question 2

What is the adrenal gland comprised of?

Answer 2

Adrenal cortex:

• zona glomerulosa
• zona fasiculata
• zona reticularis

Question 3

What hormones does the adrenal MEDULLA secrete?

Answer 3

Adrenaline
Noradrenaline
Dopamine

Question 4

Where are adrenaline, noradrenaline and dopamine cells made?

Answer 4

These hormones are made by chromaffin cells that are derived from neuroectodermal tissue cells, which are present in the adrenal medulla.

Question 5

What type of neurotransmitter do chromaffin cells synthesise?

Answer 5

Chromaffin cells synthesise catecholamines.

Question 6

What is the structure of chromaffin cells and how are they arranged ?

Answer 6

They are columnar and are arranged in clusters around the medullary veins.

Question 7

Where is adrenaline and noradrenaline stored?

Answer 7

Adrenaline and noradrenaline is synthesised and stored in electron dense granules within chromaffin cells

Question 8

How is adrenaline and noradrenaline secreted? Through what stimulation?

Answer 8

These hormones are secreted by the stimulation of acetylcholine release from the preganglionic sympathetic fibres innervating the medulla.

Question 9

Name three catecholamine hormones

Answer 9

Adrenaline
Noradrenaline
Dopamine

Question 10

How are catecholamines made?

What percent of catecholamine production is adrenaline?

Answer 10

Synthesis of catecholamines begins with the amino acid Tyrosine which is taken up by chromaffin cells and converted to Adrenaline and Noradrenaline.

80% of catecholamine production by the adrenal medulla is adrenaline.

Question 11

Wha enzyme converts Tyrosine to Dihydroxyphenylalanine(DOPA)?

Answer 11

Tyrosine hydroxylase

Question 12

Wha enzyme converts Dihydroxyphenylalanine (DOPA) to Dopamine?

Answer 12

DOPA decarboxylase

Question 13

Wha enzyme converts Dopamine to Noradrenaline?

Answer 13

Dopamine beta hydroxylase

Question 14

Wha enzyme converts Noradrenaline to Adrenaline?

Answer 14

PNMT

Question 15

What does PNMT enzyme stand for?

Answer 15

phenylethanolamine-N-methyltransferase

Question 16

Dopamine beta hydroxylase allows the conversion of ______ to ______

Answer 16

Dopamine

Noradrenaline

Question 17

Tyrosine hydroxylase allows the conversion of ______ to ______

Answer 17

Tyrosine

Dopa (Dihydroxyphenylalanine)

Question 18

Dopa decarboxylase allows the conversion of ______ to ______

Answer 18

DOPA

Dopamine

Question 19

PNMT allows the conversion of ______ to ______

Answer 19

Noradrenaline

Adrenaline

Question 20

How are the physiological effects of adrenaline and noradrenaline initiated?

Answer 20

Adrenaline and Noradrenaline bind to adrenergic receptors present on the target cell. These receptors are an example of 7 transmembrane proteins which are coupled to G proteins. This will then either stimulate or inhibit the intracellular signalling pathway.

Question 21

What receptors does adrenaline act on?

Answer 21

alpha 1, alpha 2, beta 1, beta 2

Question 22

What receptors does noradrenaline act on?

Answer 22

alpha 1, alpha 2, beta 1

Question 23

what is the effect of ligand binding to each receptor?

Answer 23

alpha 1 - increased free calcium
alpha 2 - decreased cAMP
beta 1 - increased cAMP
beta 2 - increased cAMP

Question 24

Why do you get complex physiological responses from medullary stimulation?

Answer 24

Because we have multiple receptor types which are differentially expressed in different tissues and cells

Question 25

How were alpha and beta adrenergic receptors and their subtypes originally defined by?

Answer 25

by differential binding of various agonists and antagonists

Question 26

What are the effects of adrenaline (A) and noradrenaline (NA) in response of Fight or Flight?

Answer 26

- increased heart rate: NA/A - increased blood pressure: NA/A - increased lipid breakdown:NA/A - peripheral vasoconstriction NA/A - bronchial dilation (A) - coronary dilation (A) - muscle (glycogen) converted to muscle (glucose)

Question 27

Define phaeochromocytoma

Answer 27

Phaeochromocytoma is a benign tumour that is comprised of chromaffin tissue. It is a rare cancer which is highly vascular and so any handling or invasive procedure can result in the outpour of catecholamines; noradrenaline and adrenaline.

Question 28

Give examples of the ten percent rule of phaeochromocytomas:

Answer 28

- 10% are familial - 10% are malignant - 10% are paraganglionomas - 10% are bilateral - 10% are present in children - 10% will recur (come back after 5-10 years)

Question 29

8 clinical symptoms of phaeochromocytoma:

Answer 29

- headache - weight loss - tiredness - pallor - excessive sweating - dyspnoea - palpitations - panic attacks/ anxiety

Question 30

3 clinical signs of phaeochromocytomas:

Answer 30

- postural hypotension - paroxysmal hypertension - sustained hypertension

Question 31

Diagnosis of phaeochromocytomas include:

Answer 31

- 24 hour measurement of urine catecholamine levels and | - imaging

Question 32

Treatment of phaeochomocytoma:

Answer 32

Surgery cures approximately 90% of cases

Question 33

Which of the following is a powerful alpha-blocker that is effective in the management of phaeochromocytoma? - Phentolamine - Doxazocin - Prazosin - Phenoxybenzamine

Answer 33

Phenoxybenzamine