Physiology: The Adrenal Medulla Flashcards
Which nervous system regulates the adrenal medulla?
The sympathetic nervous system
Name three hormones produced by the adrenal medulla.
Adrenaline
Noradrenaline
Dopamine
What are the hormones produced by the adrenal medulla generally called?
Catecholamines
Name the three regions of the adrenal gland as well as what they secrete
Zona glomerulosa- aldosterone
Zona fasciculata- Glococorticoids
Zona reticularis- sex hormones
Name the enzyme that is important for the synthesis of catecholamines
L-Aromatic amino acid decarboxylase
True or false:
Adrenal medulla is a modified sympathetic ganglion
True
Which adrenoreceptor does noradrenaline responds strongly with?
Alpha receptor
What are the effects of noradrenaline?(2)
Mydriasis( pupil dilation) , glycolysis, lipolysis and vasoconstriction.
To which adrenoreceptors does adrenaline has greater affinity to?
Beta receptors
What are the effects of adrenaline?(2,5)
-Arteriole dilation of skeletal vasculature.
- Bronchial muscle relaxation
- Positive inotropy and chronotropy.
- Glycolysis
- Lipolysis
What hormone increases the likelihood of catecholamine release?
Thyroxine
Give the relevant characteistics of alpha-1 receptor
•It is found in most sympathetic target tissues.
• It is mostly sensitive to Noradrenaline.
• It activates phospholipase C.
Give the relevant characteistics of alpha-2 receptor
•It is found in the GIT and pancreas.
•It has greater sensitivity for Noradrenaline.
• It decreases cAMP.
Give the relevant characteistics of beta-1 receptor
•It is found in the heart muscles, kidney.
• It has equal sensitivity for both adrenaline and noradrenaline.
• It increases cAMP.
Give the relevant characteistics of beta-2 receptor
• 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.
Give the relevant characteristics of beta-3 receptor
• It is found in adipose tissue.
• It has greater sensitivity for noradrenaline than adrenaline.
• It increases cAMP.
Explain the process of cardiac contraction by catecholamines.
*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).
What is the receptor response in blood vessels when adrenaline binds to them:
A. Alpha-receptor
B. Beta-2 receptor
A. Causes vasoconstriction
B. Causes vasodilation
What is the half life of catecholamines?
Seconds
Name the enzymes that metabolizes catecholamines
Catecholamine-O-methyl-transferase(COMT)
Monoamine oxidase(MAO)
What are monoamine oxidase inhibitors used as?
Antidepressants
What are COMT inhibitors used for?
Parkinson’s disease
Name and define the condition caused by excess catecholamines
Pheochromocytoma- tumour of the chromaffin tissue
