Physiology Unit 5 Hormonal and Diuretic Regulation

How much filtrate will be reabsorbed in the PCT?

65%

How much filtrate will be reabsorbed in the nephron loop?

20%

What can changes in individual solute concentrations be a marker of?

a potential pathology

What is the normal plasma osmolality?

285-295 (but 300mOsm)

How much can heavy exercise increase the mOsm?

10 mOsm

What is the range that homeostasis prevents the fluctuation of mOsm?

1-3%, (+ 2.85 to 8.55 mOsm)

Why is the rate of water leaving the collecting duct?

it is being regulated by ADH

What is the mOsm of the filtrate when it enters the collecting duct?

100mOsm

Is the 100mOsm filtrate entering the collecting duct hypotonic or hypertonic to the renal cortex?

hypotonic

What is the job of the collecting duct?

transports filtrate from the cortex through the renal pyramid/medulla

What drives water out of the collecting duct and into the interstitial space?

osmotic pressure

Where does water go when it leaves the collecting duct?

ascending vasa recta

What is it called when you do not reabsorb water?

excretion

What does ADH do?

decreases the excretion of water

Does ADH increase or decrease reabsorption?

increase

Where is ADH produced?

by neurons in the hypothalamus

Where is ADH stored?

posterior pituitary gland

When is ADH secreted?

in response to increased plasma osmolality

What is the range that osmoreceptors in the hypothalamus detect increases in mOsm?

0.5 - 5 mOsm

Would ADH make you thirsty or not thirsty?

thirsty

What positive ion concentration do osmoreceptors especially detect?

Na+

Where does ADH bind to target cells?

collecting duct

If ADH is added, will plasma osmolality increase or decrease?

decrease

What system does ADH sstimulate?

cAMP 2nd messenger system

What does ADH cause vesicles to translocate to?

cell surface, this increases aquaporin water channels in the cell membrane

ADH causes a switch fro simple diffusion alone to what?

passive transport

Does ADH result in increased or decreased blood volume?

increased

When urine concentration increases because of ADH, what does this do to urine?

less urine produced

When ADH is not present, what happens to the aquaporins?

endocytosis of the aquaporins

Absence of ADH does what?

decreases water retention so increases urine production

What molecule inhibits ADH secretion?

ethanol

What affect does ethanol have on ADH?

inhibits ADH secretion resulting in increased urine production and increased dehydration

Where is the juxtaglomerular apparatus?

region where the afferent arteriole contacts end of ascending limb of the nephron loop and beginning of DCT

What two main pieces are in the juxtaglomerular apparatus?

granular cells and macula densa

What portion of the juxtaglomerular apparatus does the macula densa make up?

wall of the tubule

What portion of the juxtaglomerular apparatus does the granular cells make up?

arteriole

What do granular cells in the juxtaglomerular apparatus stimulate?

RAAS

Granular cells stimulate RAAS in response to what?

low renal artery blood pressure, low blood volume, and sort’ve low NaCl concentration in filtrate

What secretes renin?

juxtaglomerular granular cells

What does renin do?

cleaves angiotensinogen into angiotensin 1

What needs to happen to angiotensin 1 to become angiotensin 2?

angiotensin 1 needs to come into contact with angiotensin-converting enzyme (ACE) to cleave 2 more amino acids

Where does the conversion of Angiotensin 1 to angiotensin 2 occur?

lung capillaries

Once angiotensin 2 is created, what does it do?

stimulates the release of aldosterone from the adrenal cortex

What is the primary effect of angiotensin 2?

increase blood pressure by vasoconstriction

How does Angiotensin 2 increase blood volume?

stimulates thirst center in hypothalamus and stimulates adrenal cortex to secrete aldosterone

What does aldosterone do?

decrease salt loss and thus water loss

What do ACE inhibitors do?

prevents the conversion of angiotensin 1 into angiotensin 2, thus promotes vasodilation to lower TPR and arterial blood pressure, common hypertension medicine

What does the macula densa in the tubule do?

senses increased NaCl and H₂O in filtrate

What does the macula densa inhibit the secretion of?

renin

When the macula densa releases ATP, what is this for?

stimulating afferent arteriole constriction, decreasing GFR and flow of NaCl and H₂O

Where is aldosterone secreted from?

adrenal cortex

What is aldosterone secretion indirectly secreted by?

Na+ and Cl- deprivation and low blood volume and low BP

What is the release of aldosterone directly stimulated by?

hyperkalemia

Where does aldosterone stimulate the reabsorption of salt?

in late DCT and collecting duct

What does aldosterone do to blood volume and thus pressure?

increases blood volume and then pressure

What is not changed with aldosterone secretion?

plasma osmolality, salt and water are retained in equal proportions

How does aldosterone partially function?

through interactions with ADH

Aldosterone reabsorbes the remaining 8-10% of what in mostly the collecting duct and some in the late DCT?

Na+

Without aldosterone what happens to the 2% or 30g of Na+ left over?

it is not absorbed and excreted in urine

If aldosterone is present what will happen to the remaining 10% of Na+?

all of it will be reabsorbed

What does the maximum aldosterone secretion do?

stimulates Na+/K+ pumps on basolateral surface of collecting duct epithelial cells, creates concentration gradient to drive Na+ out of collecting duct, Cl- follows passively

Where is 90% of K+ reabsorbed?

PCT and nephron loop

Where is K+ secreted?

into DCT and collecting duct, K+ secreted where Na+ is reabsorbed

What is the aldosterone-dependent K+ secretion (hyperkalemia)?

increased K+ secretion through Na+/K+ pumps on basolateral surface

What is the aldosterone independent K+ secretion?

hyperkalemia induces insertion of additional K+ channels (passive transport) into collecting duct

What is atrial natriuretic peptide ANP produced by?

atria

What stimulates the release of ANP?

increased venous return stimulates receptors in atrial wall

How does the production of ANP affect ADH?

ADH secretion is inhibited

What does ANP stimulate?

natriuresis (excretion of Na+) and vasodilation

What does ANP inhibit in the collecting duct?

Na+/K+ ATPase pumps in collecting duct

What are the main goals of ANP?

promotes excretion of Na+ ad thus water, lowers blood volume and pressure

What does a diuretic directly lower?

blood volume and blood pressure

What does a diuretic indirectly decrease?

edema, lowers interstitial fluid volume

What are the 3 major categories of diuretics?

NaCl and water reabsorption inhibitors, osmotic diuretics, K+ sparing diuretics