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PY352 > Adrenal Medulla > Flashcards

Adrenal Medulla Flashcards

1
Q

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

A

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

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2
Q

What is the adrenal gland comprised of?

A

Adrenal cortex:

  • zona glomerulosa
  • zona fasiculata
  • zona reticularis
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3
Q

What hormones does the adrenal MEDULLA secrete?

A

Adrenaline
Noradrenaline
Dopamine

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4
Q

Where are adrenaline, noradrenaline and dopamine cells made?

A

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

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5
Q

What type of neurotransmitter do chromaffin cells synthesise?

A

Chromaffin cells synthesise catecholamines.

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6
Q

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

A

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

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7
Q

Where is adrenaline and noradrenaline stored?

A

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

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8
Q

How is adrenaline and noradrenaline secreted? Through what stimulation?

A

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

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9
Q

Name three catecholamine hormones

A

Adrenaline
Noradrenaline
Dopamine

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10
Q

How are catecholamines made?

What percent of catecholamine production is adrenaline?

A

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.

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11
Q

Wha enzyme converts Tyrosine to Dihydroxyphenylalanine(DOPA)?

A

Tyrosine hydroxylase

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12
Q

Wha enzyme converts Dihydroxyphenylalanine (DOPA) to Dopamine?

A

DOPA decarboxylase

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13
Q

Wha enzyme converts Dopamine to Noradrenaline?

A

Dopamine beta hydroxylase

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14
Q

Wha enzyme converts Noradrenaline to Adrenaline?

A

PNMT

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15
Q

What does PNMT enzyme stand for?

A

phenylethanolamine-N-methyltransferase

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16
Q

Dopamine beta hydroxylase allows the conversion of ______ to ______

A

Dopamine

Noradrenaline

17
Q

Tyrosine hydroxylase allows the conversion of ______ to ______

A

Tyrosine

Dopa (Dihydroxyphenylalanine)

18
Q

Dopa decarboxylase allows the conversion of ______ to ______

A

DOPA

Dopamine

19
Q

PNMT allows the conversion of ______ to ______

A

Noradrenaline

Adrenaline

20
Q

How are the physiological effects of adrenaline and noradrenaline initiated?

A

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.

21
Q

What receptors does adrenaline act on?

A

alpha 1, alpha 2, beta 1, beta 2

22
Q

What receptors does noradrenaline act on?

A

alpha 1, alpha 2, beta 1

23
Q

what is the effect of ligand binding to each receptor?

A

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

24
Q

Why do you get complex physiological responses from medullary stimulation?

A

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

25
Q

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

A

by differential binding of various agonists and antagonists

26
Q

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

A
  • 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)
27
Q

Define phaeochromocytoma

A

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.

28
Q

Give examples of the ten percent rule of phaeochromocytomas:

A
  • 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)
29
Q

8 clinical symptoms of phaeochromocytoma:

A
  • headache
  • weight loss
  • tiredness
  • pallor
  • excessive sweating
  • dyspnoea
  • palpitations
  • panic attacks/ anxiety
30
Q

3 clinical signs of phaeochromocytomas:

A
  • postural hypotension
  • paroxysmal hypertension
  • sustained hypertension
31
Q

Diagnosis of phaeochromocytomas include:

A
  • 24 hour measurement of urine catecholamine levels and

- imaging

32
Q

Treatment of phaeochomocytoma:

A

Surgery cures approximately 90% of cases

33
Q

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

  • Phentolamine
  • Doxazocin
  • Prazosin
  • Phenoxybenzamine
A

Phenoxybenzamine

PY352 (25 decks)

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