Physiology: The Adrenal Medulla Flashcards

1
Q

Which nervous system regulates the adrenal medulla?

A

The sympathetic nervous system

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2
Q

Name three hormones produced by the adrenal medulla.

A

Adrenaline
Noradrenaline
Dopamine

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3
Q

What are the hormones produced by the adrenal medulla generally called?

A

Catecholamines

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4
Q

Name the three regions of the adrenal gland as well as what they secrete

A

Zona glomerulosa- aldosterone
Zona fasciculata- Glococorticoids
Zona reticularis- sex hormones

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5
Q

Name the enzyme that is important for the synthesis of catecholamines

A

L-Aromatic amino acid decarboxylase

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6
Q

True or false:

Adrenal medulla is a modified sympathetic ganglion

A

True

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7
Q

Which adrenoreceptor does noradrenaline responds strongly with?

A

Alpha receptor

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8
Q

What are the effects of noradrenaline?(2)

A

Mydriasis( pupil dilation) , glycolysis, lipolysis and vasoconstriction.

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9
Q

To which adrenoreceptors does adrenaline has greater affinity to?

A

Beta receptors

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10
Q

What are the effects of adrenaline?(2,5)

A

-Arteriole dilation of skeletal vasculature.
- Bronchial muscle relaxation
- Positive inotropy and chronotropy.
- Glycolysis
- Lipolysis

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11
Q

What hormone increases the likelihood of catecholamine release?

A

Thyroxine

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12
Q

Give the relevant characteistics of alpha-1 receptor

A

•It is found in most sympathetic target tissues.
• It is mostly sensitive to Noradrenaline.
• It activates phospholipase C.

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13
Q

Give the relevant characteistics of alpha-2 receptor

A

•It is found in the GIT and pancreas.
•It has greater sensitivity for Noradrenaline.
• It decreases cAMP.

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14
Q

Give the relevant characteistics of beta-1 receptor

A

•It is found in the heart muscles, kidney.
• It has equal sensitivity for both adrenaline and noradrenaline.
• It increases cAMP.

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15
Q

Give the relevant characteistics of beta-2 receptor

A

• It is found in certain blood vessels and smooth muscles of certain organs.
• The sensitivity of adrenaline is greater than that of noradrenaline.
• It decreases cAMP.

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16
Q

Give the relevant characteristics of beta-3 receptor

A

• It is found in adipose tissue.
• It has greater sensitivity for noradrenaline than adrenaline.
• It increases cAMP.

17
Q

Explain the process of cardiac contraction by catecholamines.

A

*A and NA bind to Beta-1 receptor which activates cAMP.
*This leads to phosphorylation of voltage-gated calcium channels.
*More calcium enters the ECF.
*This increases calcium stores in the sarcoplasmic reticulum.
*Leading to high levels of calcium being released which causes a more forceful contraction (+inotropy).
*The activation of cAMP also phosphorylates phospholamban, this increases calcium ATPase on sarcoplasmic reticulum.
*Leading to more calcium stores in sarcoplasmic reticulum, more calcium being released which also causes a more forceful contraction.
*It also leads to calcium being removed faster from the cytosol, which decreases the Ca-troponin binding time.
*This leads to a shorter duration of contraction (chronotropy).

18
Q

What is the receptor response in blood vessels when adrenaline binds to them:
A. Alpha-receptor
B. Beta-2 receptor

A

A. Causes vasoconstriction
B. Causes vasodilation

19
Q

What is the half life of catecholamines?

A

Seconds

20
Q

Name the enzymes that metabolizes catecholamines

A

Catecholamine-O-methyl-transferase(COMT)
Monoamine oxidase(MAO)

21
Q

What are monoamine oxidase inhibitors used as?

A

Antidepressants

22
Q

What are COMT inhibitors used for?

A

Parkinson’s disease

23
Q

Name and define the condition caused by excess catecholamines

A

Pheochromocytoma- tumour of the chromaffin tissue