Exam 3 Lesson 20 Flashcards
What does aldosterone regulate?
electrolyte transport across epithelial cells
what is electrolyte transport?
Na+ resorption and K+ secretion
what are the main target tissues of aldosterone?
kidney, intestine, salivary and sweat glands
How does low sodium diet affect aldosterone secretion?
it increases it.
what happens to zona glomerulosa with a low sodium diet?
it doubles in thickness in 3 weeks
how much does sodium have to decline in plasma for aldosterone secretion to be stimulated?
About 20 mEq/L
how much does plasma K+ have to increase to stimulate aldosterone secretion?
Only 1 mEq/L
what secondary messengers are involved in the regulation of aldosterone secretion?
ACTH, angiotensin II, K+
intracellular mediator ACTH?
cAMP, PKA
intracellular mediator angiotensin II?
DAG, PKC
intracellular mediator K+?
Ca2+ via v-gated Ca2+ channels
Four parts of kidney
cortex, medulla, renal pelvis, ureter
how does blood flow in and out of glomerulus?
afferent arteriole from renal artery flows into glomerulus and efferent arteriole to renal vein flows out
what does aldosterone bind to?
intracellular aldosterone receptor in principal cell of collecting duct
where does aldosterone stimulate Na+ reabsorption?
across luminal membrane through epithelial Na+ channels
How does aldosterone upregulate Na+ reabsorption?
It upregulates open Na+ channels and increases the no of Na+K+ ATPase pumps in basolateral membrane
how do spironolactone and eplerenone act to inhibit aldosterone?
they compete directly with aldosterone for receptor
how do amiloride and triamterene inhibit aldosterone?
they indirectly inhibit aldosterone by closing the epithelial sodium channels
aldosterone receptor: what binds to aldosterone receptor besides aldosterone?
cortisol
aldosterone receptor: what happens when ligand binds to aldosterone receptor?
it loses its inhibitor and dimerizes, then translocates into the nucleus, binds with RE, and promotes mRNA transcription
How do the isozymes of 11Beta-HSD interact with cortisol?
11Beta-HSD2 is an exclusive dehydrogenase that acts in classical aldosterone tissues. It excludes cortisol from otherwise nonselective mineralocorticoid receptors. It inactivates cortisol, turning it to cortisone. 11Beta-HSD1 is an 11beta reductase that activates cortisol to increase local intracellular glucocorticoid concentrations
Where does 11beta-HSD2 work?(Tissue)
kidney, colon, sweat glands, salivary glands, placenta
where does 11beta-HSD1 work (Tissue)
skin, liver, adipose, CNS, placenta
How much higher is cortisol concentration in circulation than aldosterone circulation?
100x
what is the active component of licorice? What does it do?
glycyrrhetinic acid/ inhibits 11beta OHSD
what can happen when cortisol is in excess in circulation?
it can saturate 11beta OHSD and then interacts with aldosterone receptor
Renin-angiotensin and aldosterone secretion: what does aldosterone in distal nephron stimulate?
it stimulates increases Na+ resorption and K+ secretion and stimulates the juxtaglomerular apparatus to make renin
renin-angiotensin and aldosterone secretion: What is the purpose of renin?
renin turns angiotensinogen into angiotensin I
Renin-angiotensin and aldosterone secretion: how does angiotensin I turn into angiotensin II?
angiotensin converting enzyme
renin-angiotensin and aldosterone secretion: what is the target of angiotensin II?
adrenal gland
what part of the juxtaglomerular apparatus secretes renin?
juxtaglomerular cells
what is the role of the macula densa?
it modulates renin secretion
what does macula densa sense?
both flow and sodium delivery
what does renin secretion do?
it helps maintain total body sodium and glomerular filtration rate at an acceptable level
Feedback control by macula densa: what happens when macula densa senses increase in both flow and sodium delivery?
macula densa releases ATP (adenosine), which a. decreases GFR and maintains normal filtered load and b. decreases renin secretion and allows more sodium excretion
feedback control by macula densa: what happens when macula densa senses decrease in both flow and sodium delivery?
it releases NO, prostaglandins which a. increase GFR and maintains normal filtered load and b. increases renin secretion and conserves body sodium.
what are the two roles of the juxtaglomerular apparatus?
a. endocrine gland that secretes renin b. sensor of blood volume, tubular fluid composition
how do juxtaglomerular cells determine the need for renin release?
they are pressure transducers. The sense stretch of afferent arteriolar wall, or renal perfusion pressure. This pressure helps determine renin release necessary.
what makes up the macula densa?
a specialized group of convoluted distal tubular cells
what do macula densa cells do?
they function as chemoreceptors to monitor sodium and chloride in distal tubule. b. they monitor flow rate of fluid
how do macula densa cells work?
they release ATP, prostaglandin in a paracrine manner on neighboring jx. Cells
how does an increase in blood volume affect juxtaglomerular cells?
it stretches the cells, which may be stimulus that stops renin secretion
what works as substrate for renin?
angiotensinogen
how large is angiotensinogen?
it has 13+ aa
how large is angiotensin I?
it has 10 aa
how large is angiotensin II?
it has 8 aa
what three things stimulate the tubuloglomerular feedback system?
a. a depletion of the extracellular fluid compartment b. a decrease in renal blood pressure c. a decrease in NaCl concentration at the macula densa
what is the first indicator to the tubuloglomerular feedback system that blood pressure is low?
the afferent arteriole, which is a pressure receptor and detects low blood pressure due to low blood volume. This will induce the secretion of renin.
how does tubuloglomerular feedback mechanism work?
it links changes in NaCl concentration (sensed by macula densa) with the control of afferent and efferent arteriolar resistance to autoregulate renal blood flow and the GFR
what does angiotensin II stimulate (4)?
a. aldosterone secretion by the adrenal cortex b. arteriolar vasoconstriction c. ADH secretion and thirst d. reabsorption of NaCl by the proximal convoluted tubule
what does aldosterone stimulate?
the reabsorption of NaCl by the loop of Henle, the distal convoluted tubule, and the collecting tubule
how does antidiuretic hormone help raise blood pressure?
it helps increase water reabsorption in the collecting tubule.
why does prolonged action aldosterone require the continuous stimulation of renin secretion?
because both renin and aldosterone have short plasma half lives (approx 15 min).
what is the half life of angiotensin II?
less than a minute
three direct renal influences on cardiovascular system?
Red blood cell production, ECF volume, total peripheral resistance
how do kidneys produce red blood cells?
via erythropoeitin
what renal influences affect blood volume?
red blood cell production and control of extracellular fluid volume
what controls blood pressure?
blood volume and total peripheral resistance
what influences total peripheral resistance?
angiotensin II
effect of low salt diet on ANP, vasopressin, aldosterone, renin, urine and plasma Na+?
ANP, low – vasopressin, low – aldosterone, high – renin, high – urine Na+ low – plasma Na+ high
effect of normal salt diet on ANP, vasopressin, aldosterone, renin, urine and plasma Na+?
ANP, vasopressin, aldosterone all normal. Low renin. High Na+ in urine, normal plasma Na+.
effect of high salt diet on ANP, vasopressin, aldosterone, renin, urine and plasma Na+?
ANP, high – VP, high – aldosterone, low – renin, low – high urine and plasma Na+
what do natriuretic peptides do?
promote sodium excretion in urine
what are the natriuretic peptides and what is their main source?
ANP, BNP – heart
What does ANP inhibit?
a. renin release b. angiotensin II promotion of Na+ reabsorption c. medullary collecting dust Na+ absorption
what increases natriuretic peptide secretion?
atria distension, which can be due to plasma volume expansion
what is the fetoplacental unit concept
the placenta cannot make estrogen on its own, and the fetal adrenal gland cannot make progesterone. The placenta synthesizes progesterone, sends it to the fetal adrenal gland, which in turn makes DHEA/DHEAS, and resends that to the placenta. The placenta uses DHEA/DHEAS to make estrogen, which it the secretes.
what is the luteal-placental shift?
chorionic gonadotropin maintains the corpus luteum of pregnancy after LH secretion stops.
what molecules are imported by placenta (3)?
maternal immunoglobulins (intracellular R), ions (ATP dependent membrane R), glucose (facilitated diffusion)
how is gas exchanged through placenta (O2 and CO2)
simple diffusion
what does placenta excrete (3)
placental lactogen, estrogen, chorionic gonadotropin
what is the purpose of lactogen?
together with chorionic gonadotropin, it stimulates the mammary gland for postpartum lactogenesis
what are the layers of the placenta?
syncytiotrophoblast, cytotrophoblast
functions of fetal adrenal cortex
a. DHEA production during early gestation b. production of glucocorticoids, which are responsible for functionl hypothalamopituitary development, induction of thymic involution, and production of surfactant by alveolar cells of lung
