1. Adrenal Glands

2. Copyright © 2014 John Wiley & Sons, Inc. All rights reserved.
Adrenal Glands
The adrenal glands (suprarenal glands) are located on top of each kidney.
Ad= near; renal=kidney
Supra=above
Copyright © 2014 John Wiley & Sons, Inc. All rights reserved.

3. Adrenal Gland – 2 Glands in 1
Cortex (outer) – bulk of gland (75%); glandular tissue Medulla (inner) – nervous tissue; SNS
Mineralcorticoid: Defend the body content of sodium and potassium; controlled by the kidney’s secretion of Renin  Ang II
Glucocorticoids: Body Fuel Metabolism, responses to injury, and general cell function; controlled by the AP  ACTH
Androgens: similar to the hormone of the male gonad. Controlled by the AP  ACTH
Catecholamines: participate in a large variety of regulatory responses.

4. Cortex vs. Medulla Glandular vs. Nervous tissue
Remind you of another endocrine gland??
Blood flows from outside of adrenals inward
Adrenal Epi synthesis is dependent upon steroid hormone support

5. Adrenal Cortex Zones Cortex - divided histologically into 3 regions:
ZG - “salt”
Mineralcorticoids
ZF – “sugar”
Glucocorticoids
ZR – “sex”
Gonadocorticoids
Steroid hormones (steroidogenic tissue); slow-acting processes; Steroidogenic cells contain cholesterol
Vs.
Medulla – catecholamines (chromaffin tissue); fast acting “fight or flight”

6. Adrenal Cortex Hormones
The zona glomerulosa secretes:
Mineralocorticoids - used to regulate mineral homeostasis (electrolytes), Na2+ K+
Aldosterone
The zona fasciculata secretes:
Glucocorticoids - affect glucose homeostasis
Cortisol
The zona reticularis secretes:
Weak androgens
DHEA, androstenedione
Aldosterone- most abundant mineralcorticoid (95%), most potent, ESSENTIAL FOR LIFE!

7. Zona Glomerulosa - Mineralcorticoids
Aldosterone is the major mineralocorticoid.
Regulates sodium (Na2+) and potassium (K+) homeostasis.
Controlled by renin-angiotensin-aldosterone (RAA) pathway
A.k.a. Renin Angiotensin System (RAS)

8. Renin-Angiotensin-Aldosterone (RAA) Pathway
Copyright © 2014 John Wiley & Sons, Inc. All rights reserved.
Renin-Angiotensin-Aldosterone (RAA) Pathway
Negative feedback control of renin and angiotensin secretion. The monitored variable is blood volume detected as decreases in sodium chloride at the macula densa, decreased pressure in the afferent arterioles, and decreased pressure in the carotid sinuses, aortic arch, and thoracic low pressure receptors. Coordinated actions of angiotensin restore plasma volume and abolish the stimuli for renin secretion. Note that angiotensin II contributes directly and indirectly to maintenance of blood volume, but its influence in this regard is inadequate in the absence of aldosterone
Angiotensinogen from the liver
Renin from the kidneys
Aldosterone an adrenal steroid hormone. Secreted by the cells of the zona glomerulosa and acts on collecting ducts in kidney to promote reabsorption of sodium and excretion of potassium.
With the Na comes water too and an increase in interstitial and vascular volume.
In the absence of aldosterone, the ratio of K+ to Na+ increases; high K+ is a direct stimulus to aldosterone secretion.
Aldosterone secretion from the ZG is mainly controlled by angiotensin II, derived angiotensin I (ACE)
Angiotensin I is derived from a precursor protein, angiotensinogen (renin substrate) produced in the liver.
Conversion of angiotensinogen to AI results from enzymatic action of renin which is released from juxtaglomerular cells in the afferent arteriole of the vascular pole of the renal glomerulus.

11. Zona Fasciculata - Glucocorticoids
Stimulated by ACTH
Secretion of cortisol is regulated by negative feedback.
Glucocorticoids help control:
Protein breakdown
Glucose formation
Lipolysis
Resistance to stress
Inflammation
Immune responses
Liver: glucocort’s are anabolic
They increase a # of key enzymes in the gluconeogenic pathway within hepatocytes
SKM & AT: glucocort’s are catabolic
Catabolic actions may result because glucose uptake is inhibited by glucocorts.
Proteolysis of muscle proteins
Lipolysis of adipose tissue
Acts permissively to increase HSL
Copyright © 2014 John Wiley & Sons, Inc. All rights reserved.

12. Glucocorticoids Mostly permissive to actions of other hormones.
Epi is ineffective w/out cortisol
Under stress, w/out glucocorts, there is vascular collapse.
Maintain cardiac output; increase arteriolar tone; decrease endothelial permeability; maintain normal vascular resistance
Maintains normal BP (angiotensin II)
Modulate emotional tone, wakefulness; memory
High cortisol will ↓ muscle mass and bone formation
Inhibit inflammatory and immune response
Facilitate maturation of the fetus
Develops fetal enzyme systems
Growth and development

13. The FFA and a.a. that are released from these tissues become substrates fro gluconeogenesis in the liver.
Glucose produced is either stored as glycogen or released into the blood.
Excessive secretion of glucocorticoids is antagonistic to the actions of insulin and predisposes the person to diabetes mellitus as the glucocorts elevate BG.
Glucocorts also reduce the affinity of certain cells for insulin, which further aggravates the hyperglycemia.

14. Glucocorticoid Feedback Loop
Copyright © 2014 John Wiley & Sons, Inc. All rights reserved.
Glucocorticoid Feedback Loop

15. Zona Reticularis - Gonadocorticoids
Dehydroepiandrosterone (DHEA) – major androgen secreted.
In males, after puberty the hormone testosterone is secreted in much larger quantities so DHEA has virtually no effect.
In females, DHEA and other adrenal androgens play a major role in promoting libido and are converted to estrogens.
In menopausal women, all female estrogens come from adrenal androgens.

16. Adrenal Medulla
Stimulated by sympathetic preganglionic neurons of the autonomic nervous system (ANS).
Chromaffin cells store and secrete 2 catecholamines:
epinephrine (adrenaline)
norepinephrine (noradrenaline).
Both of which are involved in the fight-or-flight response.
E is produced primarily by the chromaffin tissue and NE by the sympathetic neurons but they both have similar structures and biological actions.

17. Catecholamines & Thyroid Hormone
Sympathoadrenal activity is enhanced under conditions of hyperthyroidism and depressed under conditions of low levels of thyroid hormones.
Major symptoms of patients with thyroid dysfunction relate to functional alterations of those organs regulated by the sympathetic nervous system.
Sympathoadrenal function: Any decrease in BP, BG, or O2 availability leads to an acute enhancement of the sympathoadrenal activity resulting in elevated catecholamines.