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What lies superior to each kidney in the retroperitonial space and have a flattened pyramidal shape?
The adrenal glands
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During embryonic development, the adrenal glands differentiate into 2 structurally and functionally distinct regions. They are:
Adrenal cortex and adrenal medulla
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The adrenal medulla is located where according to the adrenal cortex?
centrally located
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What covers the adrenal gland?
a connective tussue capsule
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are the adrenal glands vascularized or not?
yes they are highly vascularized
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What hormones does the adrenal cortex produce that are essential to life?
steroid hormones
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What would happen if you did not have working adrenal hormones?
death
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Why would you die if you did not have working adrenal hormones?
you would die due to dehydration and electrolyte imbalances in a few days to a few weeks
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How could you correct adrenal hormone loss?
by hormone replacement therapy
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What catecholamine hormones does the adrenal medulla produce?
NE, epinephrine and a small amount of dopamine
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what are the 3 zones the adrenal cortex is divided into?
zona glomerulosa, the zona fasciculata and the zona reticularis
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What is the outer zone called in the adrenal cortex?
the outer zone is just deep to the connective tissue capsule and is called the zona glomerulosa
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What hormones do the zona glomerulosa secrete?
mineralocorticoids
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How are the cells of the zona glomerulosa arranged?
they are closely packed and arranged in spherical clusters and arched columns
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Why are the mineralocorticoids hormones that are secreted by the zona glomerulosa called by that name?
because they affect mineral homeostasis
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What is the middle zone of the adrenal cortex called?
zona fasciculata
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What is the arrangement of the zona fasciculata?
It is the widest of the 3 zones and consists of cells arraged in long, straight columns.
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What hormones does the zona fasciculata secrete?
mainly glucocorticoids
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Why are glucocorticoids, which are secreted by the zona fasciculata, given that name?
Because they affect glucose homeostasis
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What is the name of the inner zone of the adrenal cortex?
the zona reticularis
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how is the zona reticularis arranged?
they are arranged in branching cords
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What hormone does the zona reticularis synthesize?
small amounts of weak androgens
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What are androgens?
steroid hormones that have masculinizing effects
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What is the major mineralocorticoid?
Aldosterone
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What does aldosterone regulate?
homeostasis of 2 mineral ions, namely sodium ions (Na+) and potassium ions (K+) and helps adjust blood pressure and blood volume
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Besides regulating (Na+) and (K+), what else does aldosterone do?
promotes excretion of H+ in the urine
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What does excretion of urine help prevent?
Since the urine helps remove acids from the body, it helps prevent acidosis (blood pH below 7.35)
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What pathway controls secretion of aldosterone?
the renin-angiotensin-aldosterone or RAA pathway
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What do glucocorticoids regulate?
metabolism and resistance to stress
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What are the glucocorticoids?
cortisol, corticosterone and cotisone
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What secretes the glucocorticoids?
the zona fascuculata
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What is the most abundant glucocorticoid secreted by the zona fasciculata?
Cortisol, accounting for about 95% of glucocorticoid activity
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What type of system controls glucocorticoid secretion?
the typical negative feedback system
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What is the typical pathway of the negative feedback system for the glucocorticoids?
low blood levels of glucocorticoids, mainly cortisol, stimulate neurosecretory cells in the hypothalamus to secrete corticortropin-releasing hormone (CRH)
CRH promotes the release fo ACTH from the anterior pituitary.
ACTH flows in the blood to the adrenal cortex, where it stimulates glucocorticoid secretion
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What are the 6 effects glucocorticoids have?
1. protein breakdown
2. glucose formation
3. lipolysis
4. Resistance to stress
5. anti-inflammatory effets
6. depression of immune responses
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How does glucocorticoids work in protein breakdown?
they increase the rate of protein breakdow, mainly in muscle fibers, and thus increase the liberation of amino acids into the bloodstream. The amino acids may be used by body cells for synthesis of new proteins or for ATP production.
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How does glucocorticoids work in glucose formation?
Upon stimulation by glucocorticoids, liver cells may convert certain amino acids or lactic acid to glucose, which neurons and other cells can use for ATP production.
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How does glucocorticoids work in lipolysis?
they stimulate lipolysis, the breakdown of triglycerides and release of fatty acids from adipose tissue into the blood.
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What is lipolysis?
the breakdown of triglycerides
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what is gluconeogenesis?
conversion of a substance other than glycogen or another monosaccharide into glucose
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How does glucocorticoids work in resistance to stress?
The additional glucose supplied by the liver cells provides tissues with a ready source of ATP to combat a range of stresses, including exercise, fasting, fright, temperature extremes, high altitude, bleeding, infection, surgery, trauma, and disease. Because glucocorticoids make blood vesses more sensitive to other hormones that cause vasoconstriction, they reaise blood pressure. This effect would be an advantage in cases of severe blood loss, which causes blood pressure to drop.
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How does glucocorticoids work with anti-inflammatory effects?
They inhibit white blood cells that participate in inflammatory responses. Unfortunately, glucocorticoids also retart tissue repair, and as a result, they slow wound healing. Although high doses can cause severe mental disturbances, glucocorticoids are very useful in the treatment of chronic inflammatory disorders such as rheumatoid arthritis.
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What is the major androgen secreted by the adrenal gland?
dehydroepiandrosterone (DHEA)
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In males, when is the androgen testosterone also released in much greater quantity by the testes?
after puberty
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the amount of androgens secreted by the adrenal gland in males is usually so ___ that their effects are ____
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In females what do androgens do?
promote libido (sex drive) and are converted into estrogens by other body tissues
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When does all female estrogens come from conversion of adrenal androgens?
after menopause
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How do adrenal androgens affect boys and girls in prepuberty?
stimulate growth of axillary and pubic hair and contribute to the prepubertal growth spurt.
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What is the main hormone that stimulates the secreting action of adrenal androgens?
ACTH
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What is the inner region of the adrenal gland called?
adrenal medulla
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What is the modified sympathetic ganglion of the autonomic nervous system (ANS)?
adrenal medulla
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What part of the adrenal gland does not have axons?
Adrenal medulla
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Rather than a neurotransmitter, what do the cells of the adrenal medulla secrete?
hormones
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What are the hormone producing cells of the adrenal medulla?
chromaffin cells
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How do the chromaffin cells work?
they are innervated by sympathetic preganglionic neurons of the ANS.
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Why does the release of the hormones of the chromaffin cells occur very quickly?
Because the ANS exerts direct control over the chromaffin cells
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What are the 2 major hormones synthesized by the adrenal medulla?
epinephrine and NE
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What is another name of NE and epinephrine?
adrenalin and noradrenaline
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The chromaffin cells of the adrenal medulla secrete an unequal amount of the hormones NE and epinephrine, what is the percentages?
80% epinephrine and 20%NE
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Are the hormones from the adrenal medulla essential for life?
no
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What hormones greatly augment the fight or flight response?
epinephrine and NE
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How do epinephrine and NE incresae output of the heart?
by increasing heart rate and force of contraction.
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What increase blood flow to the heart, liver, skeletal muscles, and adipose tissue: dialate airways to the lungs; and increase blood levels of glucose and fatty acids?
epinephrine and NE
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