renal 3 Flashcards by Colt Moller

isoosmotic

having an osmolarity equal to that of normal ECF (300 milliosmoles per liter)

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hyperosmotic

having an osmolarity greater than normal ECF

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hypoosmotic

having an osmolarity less than normal ECF

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the kidneys produce a small volume of _______ urine when the ADH secretion rate if high

hyperosmotic (concentrated)

(this is a major reason why one can stay alive with limited water intake)

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the normal daily excretion of urea, sulfate, phosphate, and other wastes and ions amounts to about

600 mOsmol

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it is not possible for urine osmolarity to exceed about

1300 mOsmol/L

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how is the concentrating of urine to the hyperosmotic value of 1300 mOsmol/L achieved?

in juxtamedullary nephrons, sodium and chloride are actively pumped out of the ascending limb of the loop of Henle and into

water is unable to follow, as the ascending limb is mostly

this creates a _______ renal medullary interstitial fluid that is more and more concentrated as one moves deeper into the renal medulla

this above effect is “multiplied” by the countercurrent flow through the descending and ascending limbs of the loop of Henle, creating a _______ ________ _______ that concentrates the renal medullary interstitium to a maximum of about 1400 mOsmol

urea put into the renal medullary interstitium also contributes to its

the interstitial fluid that surrounds the loop

impermeable to water

hyperosmotic

countercurrent multiplier system

hyperosmolarity

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the blood supply of the renal medulla, called the _____ ______, has a countercurrent construction that prevents the “washing out” by the blood of the hyperosmolarity present in the renal interstitial fluid

vasa recta

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urine concentration: if blood ADH levels are high, water

diffuses out of the (medullary) CDs into the renal medullary interstitial fluid due to its hyperosmolarity, and then enters the capillaries of the renal medulla to be carried away in venous blood

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when blood ADH levels are low, water

is not reabsorbed as the filtrate flows through the CD, and a large volume of hypooosmotic urine is formed

(cortical and medullary CDs are impermeable to water)

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mechanism of formation of a dilute urine

decreased ADH release and reduced water permeability in distal and collecting tubules

(also continued electrolyte reabsorption)

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Na+ excreted =

Na+ filtered minus Na+ reabsorbed

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the receptors for the reflexes that control body sodium are

baroreceptors (pressure receptors) in the cardiovascular system and sensors in the kidney that monitor the filtered load of sodium

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the amount of sodium (by far the most abundant cation in the ECF) in the body is a major determinant of

ECF volume

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low total body sodium → ___________ → low arterial and venous blood pressure

low ECF volume → low plasma volume → low arterial and venous blood pressure

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low blood pressure leads to several corrective reflexes:

control of GFR (and thus of the amount of sodium filtered): the reflexes are set into motion by cardiovascular baroreceptors; thus the regulation of mean systemic arterial pressure (MAP) by the baroreceptors simultaneously achieves regulation of

total body sodium

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the amount of sodium in the body determines ECF volume, the plasma volume component of which helps determine MAP, which in turn initiates the responses that control

sodium excretion

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control of sodium reabsorption is ______ important than control of GFR for regulating control of total body sodium

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renin

an enzyme that catalyzes the conversion within the blood of the plasma protein angtiotensinogen into angiotensin I is secreted by juxtaglomerular cells which are part of the juxtaglomerular apparatus of the kidney

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angtiotensinogen

made by and put into the blood by the liver

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angiotensin-converting enzyme (ACE or converting enzyme)

found in epithelial cells of blood capillaries especially in the lungs catalyzes a reaction that transforms angiotensin I into angiotensin II as blood flows through the lungs

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angiotensin II

stimulates the adrenal cortex to secrete the hormone aldosterone into the blood

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aldosterone

acts on the late DT and CDs of the kidneys to increase Na+ reabsorption

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in the absence of aldosterone, 65 percent of the total filtered sodium is reabsorbed in the _______ , with another 30-32 percent reabsorbed in the _______

proximal tubule

loop of Henle and first part of the distal tubule

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when aldosterone levels are high, nearly 100 percent of filtered sodium is

reabsorbed (with the remaining sodium being reabsorbed in the late DT and CD) \*rate limiting step = renin secretion

_inputs to juxtaglomerular (JG) cells that increase renin secretion:_ 1. 2. 3.

1. sympathetic Nn (activated by the baroreceptor reflex) to the JG cells 2. baroreceptors within the kidney (activated by decreased stretch resulting from decreased blood pressure within the kidney 3. paracrine factors released from the macula densa (in response to a decreased volume and/or concentration of sodium in the tubular fluid flowing past the macula dense cells)

increased sodium in the body causes water to be reabsorbed also due to osmotic considerations; this water, together with the retained sodium, increases ECF (and thus plasma) volume and plays an important role in the long-term regulation of

arterial blood pressure

decreased converting enzymes → __________ → decreased blood pressure

decreased angiotensin II → decreased aldosterone → decreased sodium reabsorption → decreased blood volume → decreased BP

by causing vasoconstriction in many body regions, angiotensin II helps regulate: which also contributes to the control of:

total peripheral resistance arterial blood pressure

high plasma volume → ______ of atria of heart → _____ atrial natriuretic peptide (ANP) secretion by atria → ______ plasma ANP → kidney tubules: _______ and kidney vessels: _______ → ______ Na+ excretion

increased distention increased increased kidney tubules: decreased Na+ reabsorption kidney vessels: dilation of afferent arterioles and constriction of efferent arterioles (results in increased GFR) increased Na⁺ excretion

cardiac hormone atrial natriuretic peptide (ANP)

decreases sodium reabsorption by directly inhibiting aldosterone secretion

unwanted changes in total-body water with no corresponding change in total-body sodium are compensated for by altering

water excretion without altering sodium excretion

unlike sodium which stays in the ECF when added to the body, water distributes throughout all the body fluid compartments, with ______ entering the intracellular compartment

2/3

pure water gains/losses ______ influence blood pressure (and thus baroreceptors)

slightly

reflexes that alter water excretion without altering sodium excretion are: 1. initiated by 2. mediated by

1. sensory receptors in the hypothalamus called osmoreceptors that detect ECF osmolarity (and to a lesser extend, baroreceptors that detect blood pressure) 2. the posterior pituitary hormone ADH (vasopressin)

the hypothalamic osmoreceptors are neurons that

increase their frequency of action potentials when they shrink, which they do when ECF osmolarity is above normal (which causes water to be pulled out of the cells and into the ECF by osmosis)

the osmoreceptors synapse on neurons that have cell bodies

in the hypothalamus and have axons that travel down into (and release ADH from) the posterior pituitary

ingestion of excess water pathway:

decreased ECF osmolarity (increased [H2O] → inhibition of (decreased firing by) hypothalamic osmoreceptors → decreased ADH secretion from posterior pituitary → decreased plasma ADH → decreased permeability of renal collecting ducts to water → decreased water reabsorption → increased water excretion

input from arterial barorecptors and other cardiovascular baroreceptors can also influence ______ secretion rates; this is _______ important than osmoreceptor input under normal circumtances but can become important in scenaries such as hemorrhage

ADH less

alcohol inhibits

ADH → decreased water reabsorption → increased urine production

ADH also causes widespread ______ of arterioles which influences

constriction total peripheral resistance in the CV system

the regulation of ECF osmolarity requires the separation of

water excretion from sodium excretion

the kidneys need to be able to excrete a concentrated urine when: and a dilute urine when:

water is in short supply water is in excess

to excrete a concentrated urine, ______ renal interstitial fluid coupled with collecting ducts made permeable to water by lots of _______ which allows water reabsorption without concurrent sodium reabsorption

hyperosmotic ADH

to excrete a dilute urine, collecting ducts that are not water permeable coupled with

a lack of ADH secretion

in heart failure, the portions of the reflexes that raise heart rate and TPR are initially beneficial in restoring blood pressure. but over time, these reflexes bring about ________ \_\_\_\_\_\_\_\_\_ sometimes massive, of the ECF volume. this is because the _______ components of these reflexes cause the kidneys to ______ their excretion of sodium and water

fluid retention hormonal reduce

the failing heart cannot move the retained (extra) fluid, and it initially goes mostly into the _____ and backs up into the _____ ; excess fluid then leaves the capillaries into tissue spaces, so that the fluid retained by the kidneys ends up as extra interstitial fluid rather than extra plasma

veins capillaries

_the response to severe sweating:_ although sweat is salty, it is _______ relative to ECF, so sweating causes a sodium loss and an even relatively greater ______ loss

hypoosmotic water

normally, almost none of the filtered potassium is excreted in urine because

all but a tiny amount of filtered potassium gets reabsorbed

the CD (its cortical, rather than its medullary portion) can secrete potassium at a rate that is regulated

according to need

_potassium depletion:_ no secretion of potassium. thus, it is ______ , not ______ potassium that is excreted

filtered secreted

_when potassium intake rises:_ secreted potassium can be added to this tiny bit of filtered-and-not-reabsorbed potassium, and the amount excreted in urine goes up to a

variable degree according to need

mechanism of potassium secretion:

the sodium/potassium pump moves potassium from renal interstitial fluid across the basolateral membrane of tubule cells into the cells. potassium then moves by diffusion through potassium channels across the luminal membrane and into tubular fluid

_regulation of potassium secretion:_ aldosterone acts on _______ cells to increase their rate of potassium secretion

_regulation of potassium secretion:_ the aldosterone-secreting cells of the adrenal cortex can sense the concentration of potassium in the surrounding ECF. when the concentration is higher than normal, they

increase their secretion rate

increased potassium intake → __________ → increased potassium excretion

increased plasma potassium → adrenal cortex: increased aldosterone secretion → increased plasma aldosterone → renal CD: increased potassium secretion → increased potassium excretion

the sodium/potassium pumps in the basolateral membranes of CD cells are stimulated by potassium. when potassium levels in the interstitial fluid rise, there is

increased pumping of potassium into the CD cells (and thus increased diffusion of potassium out of the cells across their luminal membranes )

hyperkalemia

higher than normal potassium in the ECF

hypokalemia

lower than normal potassium in the ECF

Ca++ is important in

* cell division * functioning of many enzymes (internal messaging systems) * heart electrical activity * neurotransmitter secretion * hormone secretion * oocyte activation * removal of inhibition of muscle contraction * blood clotting * formation of bones and teeth

hypercalcemia

higher-than-normal Ca++ in the ECF (depresses nervous system and muscle activity)

hypocalcemia

lower-than-normal Ca++ in the ECF (causes nervous system excitement and tetany)

about 0.1 percent of total body calcium is in the ______ , about 1 percent is within _______ , and the rest is in \_\_\_\_\_\_

ECF cells and their organelles bones

bones are reservoirs, storing ________ , and releasing it when \_\_\_\_\_\_\_

excess calcium its ECF concentration is low

regarding calcium in plasma, ______ percent is ionized (Ca++) , ______ percent is combined with anions such as citrate and phosphate, and ______ percent is bound to plasma proteins

50 9 41

total [Ca++] in ECF is _______ total [Ca++] in cells

greater than

T/F ionized Ca++ and calcium bound with anions (such as citrate and phosphate) are filterable

T (they able to diffuse through the capillary membrane)

about 35 percent of dietary calcium is absorbed across the _______ (a process promoted by ______ ) ; the remainder is

intestinal wall vitamin D excreted in the feces

calcium absorption from the GI tract is unlike the absorption of ______ and ______ where the absorption from the GI track is normally near 100 percent

sodium and potassium

Ca++ absorption from the _______ is regulated according to need

small intestine

the organic matrix (non cellular) of bone is mostly

collagen fibers plus a homogeneous gelatinous substance called ground substance

\_\_\_\_\_\_\_ and _______ salts are deposited in a crystalline form (as long, flat plates) in the organic matrix of bone. the main crystalline salt is called \_\_\_\_\_\_\_

calcium and phosphate hydroxyapatite

if ECF calcium is low, calcium can be removed from bone matrix and added to the ECF by increasing the activity of

bone-resorbing cells called osteoclasts

osteoclast activity is stimulated indirectly by

parathyroid hormone (PTH)

when activated, osteoclasts secrete proteolytic enzymes that

digest the organic elements of bone matrix, and acids that dissolve the bone salts

PTH's effect of increasing the resorption of bone also causes ______ ions to leave the bone matrix and enter the \_\_\_\_\_\_

phosphate ECF

in the absence of active vitamin D, the effect of ______ in causing bone resorption is \_\_\_\_\_\_

PTH reduced

if excess bone calcium is present in the ECF, some of it can become incorporated into

bone matrix by the activity of bone-depositing cells called osteoblasts

PTH binds to receptors on ______ , causing them to release a substance that binds to ______ cells; the binding triggers

osteoblasts preosteoclast cells preosteoclasts to differentiate into mature osteoclasts

PTH may inhibit the production of a molecule that inhibits

bone resorption

about 59 percent of the calcium in plasma is available for

glomerular filtration (the rest is bound to blood proteins) (50 percent ionized + 9 percent bound to anions)

on average, 99 percent of the filtered calcium is

reabsorbed

over 80 percent of Ca++ reabsorption occurs in the: and is mostly not under:

proximal tubule, loop of Henle, and early distal tubule hormonal control (this is similar to Na+ and H2O)

reabsorption in the late DT and early collecting duct is regulated: low plasma Ca ²⁺ increases: PTH increases Ca²⁺ :

PTH secretion by the parathyroid glands reabsorption in the DT/CD

about 59 percent of the calcium in plasma is available

for glomerular filtration (50 percent ionized and 9 percent bound to anions)

on average, ______ percent of the filtered calcium is reabsorbed

for vitamin D3 and D2 to become active, both undergo

a reaction in the liver and then final activation in the kidney

1,25 dyhydroxyvitamin D , often considered to be a hormone, is carried by the blood to

the intestine, where it increases the absorption into the body of dietary calcium and phosphate ion

active vitamin D3 has complex effects on bone, some of which are indirect via its influence on

PTH's effect on bone resorption

calcitonin

a thyroid hormone that decreases ECF calcium concentration and is of little importance in the normal calcium regulation in humans

to become active, vitamin D3 and D2

undergo a reaction in the liver and then final activation in the kidney

most plasma phosphate that is filtered is

reabsorbed in the proximal tubule

even a tiny increase in blood Ca++ concentration above normal causes

decreased PTH secretion and increases calcium excretion in the urine markedly

PTH activates an enzyme that catalyzes the conversion (within the kidney) of

inactive vitamin D into active vitamin D (1,25 dihydroxycholecalciferol, or 1,25 dihydroxyvitamin D)

ultraviolet radiation in sunlight transforms a

cholesterol derivative present in skin into inactive vitamin D3. Vitamin D2 is dietary (as is some inactive D3)

for vitamin D3 and D2 to become active, both undergo

a reaction in the liver and then final activation in the kidney

active vitamin D3 has complex effects on bone, some of which are indirect via its influence on

PTH's effect on bone resorption

inorganic phosphate in the plasma is mainly in 2 forms:

HPO₄^2- and H2PO₄^-

about half of the plasma phosphate is

filterable

most plasma phosphate that is filtered is

reabsorbed in the proximal tubule

phosphate is a part of bone matrix that is involved in controlling \_\_\_\_\_\_\_\_ and is a part of:

acid-base balance ATP, ADP, cAMP, GTP, cGMP, DNA, RNA, and some proteins

renal reabsorption of phosphate ion is _______ by PTH

decreased

when blood calcium is low and PTH secretion levels and calcium reabsorption are increased as a result, phosphate ion excretion in urine is \_\_\_\_\_\_\_

increased

renal 3 Flashcards

(103 cards)