The Adrenal Gland And Adrenal Hormones (week3) Flashcards
Function of aldosterone
It governs the extra cellular volume (ECV) due to its action on Na retention/ absorption by the kidney. Arginine vasopressin (AVP) - also known as anti diuretic hormone (ADH) - regulates osmolality because of its effect on free water balance (indirectly affects Na concentration)
Osmolality meaning
Osmolality is the measure of solute particles in a solution.
It quantifies the number of osmoles ( a unit of measurement for the concentration for the solute particles.
Osmolarity meaning
Concentration of solute particles in a solution per 1L of solvent
Where is aldosterone synthesised and what from
The adrenal gland. Zona glomerulosa
Cortisol
What are the only cells that contain aldosterone synthase
Glomerulosa cells, these cells are exclusive site of aldosterone synthesis
How quickly is aldosterone released
Secretion of aldosterone is limited by the rate at which the glomerulosa cells can synthesise the hormone
What stimulates the production of aldosterone in the glomerulosa
ACTH, extracellular [K+][Na+] and the peptide hormone ANG II
How does ACTH, K+, and ANG II enhance secretion
By increasing the activity of enzymes acting as rate-limiting steps in aldosterone synthesis.
These include the SCC enzyme (common to all steroid-producing cells) and aldosterone synthase (unique to glomerulosa cells and involved in the final stops of formation)
What is the major action of aldosterone
To stimulate the kidney to reabsorb Na+ and water and to enhance K+ secretion. Aldosterone has similar actions in the colon, salivary glands and sweat glands.
Is aldosterone hydrophobic or hydrophilic
Hydrophobic so transported in the blood with albumin
aldosterone class and location of synthesis
class: mineral corticoids
location of synethesis: synthesised and released by the outer layer (the zona glomerulosa) of the adrenal cortex
epinephrine(adrenaline) class and location of synthesis
class: catecholamine
location of synethesis: synthesised and released by the adrenal medulla, inner part of the adrenal gland
norepinephrine(noradrenaline) class and location of synthesis
class: catecholamine adrenergic hormone
location of synthesis: synthesised and released by the adrenal medulla, inner part of the adrenal gland
regulation of aldosterone synethesis
Na and water levels feedback through the RAS
Ang II binds to receptor
Gaq to PLC to DAG anf IP3
Ca increase, Ca-dependent enzymes increase
Depolarises glomerulosa cells, voltage-gated Ca channels open
Ca rises, stimulants
what is the stimulus for the release of renin
renin is released from juxtaglomerular cells in the kidney
low blood pressure
decreased blood volume
low sodium levels in the distal tubules of the kidneys
how is angiotensinogen converted to angiotensin I
Renin acts on a plasma protein called angiotensinogen, which is produced by the liver, to convert it into angiotensin I.
how is angiotensin II converted to angiotension II
through angiotensin converting enzyme(ACE) primarily found in the lungs, this conversion occurs in the blood stream
stimulation of aldosterone
angiotensin II acts directly on the adrenal cortex, primarily the zona glomerulosa
negative feed back
as blood pressure and blood volume increase in response to aldosterones actions, there is a negative feedback loop that inhibits further release of renin. This helps prevent excessive sodium retention and fluid accumulation
what does the adrenal cortex develop from
mesmodermal cells into steroidogenic cells that produce mineralocorticoids, glucocorticoids, and adrenal androgens.
what is the influence of cortisol
chromaffin cells have the potential of developing into post ganglionic sympathetic neurons and synthesize the norepinphrine from tyrosine, however the cells of the adrenal medulla are exposed to high local concentrations
what are the hormones secreted by catechlomines
dopamine
epinephrine
norepinephrine
synthesis of catechlomines
epinephrine and some norepinphrine stored in chromaffin granule complex with ATP.
70-80% of the cells of the adrenal medulla secrete epinephrine and the remaining 20-30% secrete norpinephrine.
regulation of catechlomines
autonomic centers that initiate sympathetic responses reside in the hypothalamus and the brain steam and they receive inputs from the cerebral cortex, the limbic system, and other regions of the hypothalamus and brain steam.
ACh increases the activity of the rate-limiting enzyme, tyrosine hydroxylase, and of dopamine beta-hydroxylase and stimulates exocytosis of the chromaffin granules.
degradation of catechlomines
the biological response if very brief, approximatley 10 seconds, circulating catehlomines degraded.
what are the twp primary enzymes involved in the degradation of catechlomines.
monoamine oxidase (MAO) - the predominant enzyme in neuronal mitochodria
catechol-O- methyltansferase -(COMT)
physiologic actions of catechlomines
Because the adrenal medulla is directly innervated by the autonomic nervous system, adrenomedullary responses are very rapid
Because of the involvement of several centers in the CNS adrenomedullary responses canprecede onset of the actual stress (i.e., responses can be anticipated
increased blood flow to muscles
increased glucose availability
decreased energy demand by visceral smooth muscle
what is Pheochromocytoma
An uncommon tumor caused by hyperplasia of adrenal medulla or other chromaffin tissue.
Excessive, unregulated production of catecholamines
what are some symptoms of Pheochromocytoma
Sudden outburst of hypertension,
headaches,
episodes of sweating,
anxiousness,
tremor and glucose intolerance
