The adrenal medulla

Question 1

summarise the adrenal medulla

Answer 1

• part of the ANS
• receives innervation from a long pre-ganglionic neurone
• Ach as NT
• involved in catecholamine synthesis
• main site of ad (ad predominates here)
• PNMT enzyme contained within chromaffin cells
• not essential for life unlike cortex
• Ad released via SNS input, pre-packaged hormones in vesicles released into blood

Question 2

the primitive neural crest differentiates into …

Answer 2

• sympathetic ganglia
• chromaffin cells
• via D and migration processes

Question 3

the RLS during NAd synthesis Is catalysed by

Answer 3

• tyrosine hydroxylase
• can be unregulated and downregulated via regulation of this enzyme
• inhibited by a-methyltyrosine and NAd (negative feedback)
• during high levels of catecholamines
• high rate of stimulation from SNS stimulates TH

Question 4

PNMT converts

Answer 4

NAd - Ad

Question 5

adrenaline secretion can be regulated via

Answer 5

stressors- hypoT- SNS activation

• ACTH/ cortisol (increase Ad secretion)
• no negative feedback system at play
• ACTH unregulates PNMT when blood supply passes through the cortex cells

Question 6

alpha R

beta R

Answer 6

• Adrenaline
• Noradrenaline
  increased activity from medulla - more beta mediated effects then SNS innervation

Question 7

metabolic inactivation of Ad/NAd

Answer 7

• occurs in the liver/kidney
• COMT (Ad- metadrenaline)
• MAO ( MetA- VMA)
• excreted via kidney
• elevated VMA levels indicative of XS levels
• hypertension/ pheochromocytoma

Question 8

effects of Ad on the CNS

Answer 8

• increased altertness
• arousal
• increased anxiety
• increased muscle tremor

Question 9

effects of Ad on the periphery

Answer 9

• increased HR (b1R) , contractility
• vasodilation of skeletal muscle vessels (cAMP)
• bronchodilation
• widespread activation of medulla - Ad dominates - B2R
  direct innervation (Nad from terminals) - a1 R - constriction

Question 10

effects on metabolism include

Answer 10

• muscle- glycogen breakness
• hepatic - glycogenolysis / glucneogenesis)
• adipose - mobilisation of free FA
• aims to elevate blood glucose levels

Question 11

why do we need a medulla?

Answer 11

• longer lasting effects than SNS
• SNS doesn’t innverate whole body whilst hormones release into the bloodstream do
• different affect than SNS- dominance of Ad over NAd

Question 12

pheochromocytoma

Answer 12

• XS catecholamines
• tumour of chromaffin cells
• chronic over secretion
• use of VMA levels as diagnostic technique
• iodinated tracers / scans

Question 13

symptoms of PC include

Answer 13

• episodes of high BP
• sudden severe headache
• palpitations and chest pain
• pallor of skin and sweating
• anxiousness

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Question 14

treatments of PC include

Answer 14

• ACE Inhibitors (reduces aldosterone production)
• anti- hypertensive drugs
• beta blockers
• surgical removal of just one gland (require atleast one for aldosterone production)