Adrenal gland- Quick revision card
Adrenal gland – Two adrenal glands just above each kidney Each weigh about 4-6 gm , 3 cm wide , 5 cm high and 1 cm thick Adrenal cortex is the outer part which makes about 90 % of the gland Adrenal medulla is the inner region & makes < 10 % of the gland.
Adrenal cortex – Steroidogenesis – produces precursors for glucocorticoids , mineralocorticoids and androgens Made of 3 layers ○ zona glomerulosa the outermost layer ( Aldosterone ) ○ zona fasciculata middle layer ( Corticosteroids ) ○ zona reticularis innermost layer ( androgens ) Steroidogenesis is the complex pathway which leads to transform cholesterol into steroid hormones ACTH ( Adrenocorticotrophic hormone ) is the main hormone which regulates adrenal glucocorticoid biosynthesis and secretion.
Adrenal medulla – part of the autonomic nervous system activated by similar stimuli as the sympathetic nervous system as exercise , cold , stress , bleeding major cells are called chromaffin cells medulla secretes ○ epinephrine ( 80 % ) ○ norepinephrine ( 19 % ) ○ dopamine ( 1 % ) Others- acetylcholine , metenkephalin , chromogranin A considered as part of the sympathetic NS and is innervated by cholinergic paraganglion sympathetic NS
Aldosterone – regulates plasma concentration of minerals and salts – most importantly of ionic Na + and K + important regulators of aldosterone are the Renin angiotensin system ( RAS ) and potassium excretion released when Na conc is low and helps raise plasma Na+ conc by various mechanisms ( mainly by action on nephrons by directly impacting Na absorption and potassium excretion )
Glucocorticoids – cortisol is the major glucocorticoid long term stress hormone regulated by the HPA axis affects nearly all body functions such as mediating the stress response , regulating metabolism , inflammatory response & immune function.
Androgens- Adrenal androgens ( DHEA) require peripheral conversion to active sex steroids in the gonads and peripheral tissue
Catecholamine’s- enhances the effect of the sympathetic NS prepares the body for a stressful event two major catecholamines are the adrenaline ( epinephrine ) and noradrenaline ( norepinephrine ) derived from enzyme tyrosine act as hormone and neurotransmitters.
Epinephrines – more potent stimulator of the heart and metabolic activities actions of NA on the heart ( adrenaline rush ) is by its binding to beta adrenergic receptors causing an accelaration of heart rate , increasing BP by promoting vasoconstriction acts on all body tissues.
Norepinephrines – leads to peripheral vasoconstriction and increased arterial pressure along with epinephrine participates in the flight or fight response by increasing HR , releasing glucose from energy stores and increasing blood flow to skeletal muscles.
REFERENCES
- Clinical Practice Systems of life Endocrine System 4 : adrenal glands *210728-Endocrine-system-4-adrenal-glands1.pdf (emap.com)
- The adrenals by The Adrenals Part 1- anatomy and physiology (uniba.sk)
- What are the symptoms of adrenal gland disorders? What are the symptoms of adrenal gland disorders? | NICHD – Eunice Kennedy Shriver National Institute of Child Health and Human Development (nih.gov)
- Medicine 438’s Endocrine Physiology Lecture XIII : Physiology of Adrenal Medulla and Pheochromocytoma 13th Lecture_ Physiology of Adrenal Medulla and Pheochromocytoma – Endocrine Physiology .pdf (ksumsc.com)
