Adrenal Cortex & Medulla-Dr. Bracha
What is Cushing's?
What is addison's like disease?
What does it mean if your dog has a primary hyperadrenocorticism?
There is an adrenocortical tumor
What is Cushing's disease?
A pituitary dependent hyperadrenocorticism (Usually the result of a pituitary tumor)
What are some of the main symptoms of Cushings-like syndrome (for dogs)?
Lethary & Obesity
What are the main symptoms of Equine Cushing's disease?
From where is Aldosterone secreted?
The Zona glomerulosa of the adrenal cortex (SALT, Sugar, Sex)
There are 2 main functions of Aldosterone. What are they?
Conservation of Na+ (Which water follows)
Excretion of K+
What are 2 things that stimulate the release of Aldosterone?
Reduced volume of circulating fluid (Hypovolemia-->Renin-->Angiotensin-->Aldosterone)
Increased plasma K+
What are some factors associated with Aldosterone release? (in other words, what are some conditions that lead to hypovolemia or increased plasma k+?)
Trauma, Hemorrhage, Heart failure, Hyperkalemia, Angiotensin II & III, Low GFR, Liver Cirrhosis
What do Antiontensin II & III stimulate?
Aldosterone release (They are released from low GFR)
Explain the cascade that starts with a low GFR, and renin release and ends in increased blood volume.
Decreased GFR & Na+-->Renin release-->Angiotensin I & II-->Aldosterone-->Increased Na+ resorbtion-->Water follows-->Increased blood volume
What are 2 things that stimulate renin release?
Decreased NaCl in the tubules
What are the 3 cellular mechanisms that are triggered to increase Na+ re absorption after Aldosterone stimulation?
1) Increased pump action
2) Increased synthesis of Na+ channels/pumps
3) Pumps up the mitochondria to make ATP to support the channels
Explain why bilateral adrenalectomy is fatal (ie. Why is loss of Aldosterone fatal?)
Low Aldosterone-->Loss of Na+, Build up of K+ & H+-->Water doesn't follow Na+ out and is lost in the urine-->Hypovolemic shock-->Death
Angiotensions stimulate the release of Aldosterone. What else do they do?
Vasoconstriction (makes sense to do this to compensate for hypovolemia)
Promote ADH secretion
What are the 2 most common causes of Adrenocortical insufficiency (Addison's)?
Iatrogenic (Corticosteroid response)
What are the main symptoms of Addison's like-disease?
Decreased Na+/K+ ratio
What is the function of Natriuretic peptide?
To reduce blood volume!!!
Antagonizes aldosterone, ADH and Angiotensin II
Reduces Na+ & Fluid levels
Where is Natriuretic peptide made?
It is synthesized by atrial myocytes
What triggers release of Natriuretic peptide?
Plasma volume expansion in the atria
What is the function of ANP on peripheral blood vessels?
What are the 3 natriuretic peptides?
BNP-->Brain (Stimulated by ANP-->Vasodilation)
CNP-->CNS (Stimulated by ANP-->Vasodilation)
Which hormone causes ADH release, thirst, Vasocontriction and Aldosterone release?
Angiotensin II & III
If there is hypovolemia and hyperkalemia what hormone will be released?
What are the main causes of Secondary Hyporadrenocorticism (Addison's)?
Hypothalmic or Pituitary failure to release CRH & ACTH
Prolonged glucocorticoid administration
What are the main causes of primary Hyporadrenocorticism (Addison's)?
Immune mediated destruction of Adrenal cortex
Neoplasia, infection, trauma etc.. (Anything that could damage the adrenal cortex)
Adrenal suppressive drugs
The adrenal medulla is a modified sympathetic ______
What are released from the adrenal medulla?
Catecholamines (Epi & NorEpi)
What stimulates the release of E & NE from the Adrenal medulla?
Sympatheic nervous system activation
ie..emotional, biochemical or physical stress
When E & NE are released from the adrenal gland they produce a ______ response
fight or flight response
Which receptors respond more to NE?
Alpha 1 & 2s (Betas respond more to Epinephrine)
Which receptors respond more to E?
Beta2 (Alphas respond more to NE)
The adrenal medulla acts as both a ganglion and as an endocrine gland. Explain this.
NE release acts on target cells as the point of release
E travels, and acts on distant target cells
What are some of the physiological changes associated with the "fight or flight" response?
High Renin release
Vasodilation to skeletal muscles
Relax bronchiolar smooth muscle
Low insulin + High Glucagon
What are the 4 hormones that antagonize insulin?
Cortisol, GH, Epinephrine & Glucagon
Are catecholamines lipid soluble or water soluble? Where are their receptors?
They are water soluble (NOT lipid) so their receptors are on the cell membranes
What is a pheochromocytoma?
A catecholamine secreting tumor
90% are located in the adrenal glands
They are NOT intervated so release may be continuous or episodic