Physiology: The Adrenal Medulla

Question 1

Which nervous system regulates the adrenal medulla?

Answer 1

The sympathetic nervous system

Question 2

Name three hormones produced by the adrenal medulla.

Answer 2

Adrenaline
Noradrenaline
Dopamine

Question 3

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

Answer 3

Catecholamines

Question 4

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

Answer 4

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

Question 5

Name the enzyme that is important for the synthesis of catecholamines

Answer 5

L-Aromatic amino acid decarboxylase

Question 6

True or false:

Adrenal medulla is a modified sympathetic ganglion

Answer 6

True

Question 7

Which adrenoreceptor does noradrenaline responds strongly with?

Answer 7

Alpha receptor

Question 8

What are the effects of noradrenaline?(2)

Answer 8

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

Question 9

To which adrenoreceptors does adrenaline has greater affinity to?

Answer 9

Beta receptors

Question 10

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

Answer 10

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

Question 11

What hormone increases the likelihood of catecholamine release?

Answer 11

Thyroxine

Question 12

Give the relevant characteistics of alpha-1 receptor

Answer 12

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

Question 13

Give the relevant characteistics of alpha-2 receptor

Answer 13

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

Question 14

Give the relevant characteistics of beta-1 receptor

Answer 14

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

Question 15

Give the relevant characteistics of beta-2 receptor

Answer 15

• 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.

Question 16

Give the relevant characteristics of beta-3 receptor

Answer 16

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

Question 17

Explain the process of cardiac contraction by catecholamines.

Answer 17

*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).

Question 18

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

Answer 18

A. Causes vasoconstriction
B. Causes vasodilation

Question 19

What is the half life of catecholamines?

Answer 19

Seconds

Question 20

Name the enzymes that metabolizes catecholamines

Answer 20

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

Question 21

What are monoamine oxidase inhibitors used as?

Answer 21

Antidepressants

Question 22

What are COMT inhibitors used for?

Answer 22

Parkinson’s disease

Question 23

Name and define the condition caused by excess catecholamines

Answer 23

Pheochromocytoma- tumour of the chromaffin tissue