Sodium Homeo

Question 1

changes in water secretion are controlled by?

Answer 1

ADH only

Question 2

changes in sodium secretion are determined by?

Answer 2

a variety of overlapping features in concert

Question 3

compared to water secretion, sodium secretion occurs more?

Answer 3

slowly

Question 4

you gain 1kg of water weight for every ____ sodium you retain

Answer 4

140 mEq

Question 5

if you increase sodium intake, it will take ___ days for your body to adjust and begin excreting equal to ingestion

Answer 5

4 days (slower than water excretion response to added H2O)

Question 6

when does ECF volume return to baseline after increased salt intake?

Answer 6

not until 4 days after reducing salt intake back to normal level (stays up if salt intake remains high)

Question 7

the body attempts to retain salt when?

Answer 7

the EABV is low (usually correlates with the ECF but is specific to organ blood flow)

Question 8

what detect changes in EABV?

Answer 8

high pressure baroreceptors in aortic arch, carotid sinus, LV of heart, JG apparatus in afferent arterioles of kidney (low pressure receptors less important)

Question 9

what percent of filtered sodium is reabsorbed in each region of the collecting duct

Answer 9

67% in proximal tubules, 25% ascending loops, 5% distal tubules, 3% collecting ducts

Question 10

normally about ___% of filtered sodium is reabsorbed

Answer 10

99.40%

Question 11

increased hydrostatic pressure from increased sodium intake results in?

Answer 11

increased glomerular filtration rate, increased pressure in peritubular capillaries (pressure natriuresis)–> increased sodium excretion (at higher body weight)

Question 12

increased EABV sensed by the JGA results in?

Answer 12

decreased renin, angiotension, and aldosterone

Question 13

increased EABV sensed by the aortic arch and carotid sinus results in?

Answer 13

decreased catecholamines and decreased sympathetic outflow

Question 14

increased EABV sensed by the cardiac atria results in?

Answer 14

increased atrial natriuretic factor

Question 15

how does angiotensin II increase sodium reabsorption?

Answer 15

directly at proximal tubule, indirectly by peripheral vasoconstriction which increases vascular resistance, stimulates production of aldosterone

Question 16

from where is aldosterone released?

Answer 16

cortex of adrenal gland

Question 17

where does aldosterone act?

Answer 17

promotes sodium reabsorption in exchange for potassium by activating sodium channels in CCT

Question 18

renin is released from?

Answer 18

juxtaglomerular cells in afferent arteriole

Question 19

how is release of renin controlled?

Answer 19

negative feedback through three major components: baroreceptors in afferent arterioles, chemoreceptors in macula densa, EABV and sympathetic nervous system

Question 20

how does the macula densa work?

Answer 20

located in the distal tubule where it detects the concentration of sodium in the urine and acts on JG cells that are right next door

Question 21

name 3 ways in which renal efferent nerves influence excretory function

Answer 21

regulation of GFR; release of renin; reabsorption from proximal and distal nephron segments

Question 22

at what point does an increase in ECF show signs of edema?

Answer 22

3L

Question 23

generalized edema is suggestive of an increase in ECF volume of ____ liters and a corresponding increase in sodium content of _____

Answer 23

4-5 L; 500-700mEq

Question 24

name three causes of salt and water retention by the kidneys that could occur in a state of normal or high ECF

Answer 24

heart disease, kidney disease, liver disease (perceived decreased in EABV due to increased fluid in venous system)

Question 25

why is interstitial hydrostatic pressure usually negative?

Answer 25

drainage of interstitial fluid into lymphatics

Question 26

what is the most common cause of increased movement of fluid from the intravascular compartment to the interstitium?

Answer 26

increased hydraulic pressure

Question 27

what is the main mechanism for edema formation in heart, liver, and kidney dz?

Answer 27

increased hydrostatic pressure in the intravascular compartment that comes from the venous end (where there is no sphincter to control flow)

Question 28

decreased plasma protein would result in?

Answer 28

decreased oncotic pressure and thus edema (increased fluid in interstitium)

Question 29

edema due to increased capillary permeability occurs in?

Answer 29

pregnancy, inflammatory and allergic reactions, sepsis, ARDS

Question 30

name three safeguards to prevent severe edema

Answer 30

increase in hydrostatic pressure of interstitium, increase in lymphatic flow, decrease in interstitial oncotic pressure (diluted by fluid entry)

Question 31

examples of high output heart failure

Answer 31

hyperthyroidism, AV fistula (output bypasses large sections of circulation)

Question 32

in the early phases of heart failure, RAAS and SNS activation are balanced out by ___ and ___

Answer 32

vasodilatory prostaglandins and atrial natriuretic peptide

Question 33

the SNS system stimulates nuclei in the ____ resulting in non-osmotic release of ADH

Answer 33

hypothalamus

Question 34

name 4 causes of ascites in liver disease

Answer 34

1. increased sinusoidal pressure and pooling of blood in splanchnic venous system; 2. peripheral vasodilation (increase NO); 3. hepatorenal reflex? (neural response to sinusoidal pressure); 4. hypoalbuminemia

Question 35

tx of sodium retention seen with liver disease

Answer 35

strict sodium and water restriction; careful use of diuretics

Question 36

overuse of diuretics in liver disease will result in metabolic ____ and ___kalemia

Answer 36

alkalosis; hypo-

Question 37

nephrotic syndrome is usually caused by disorders of the?

Answer 37

glomerulus

Question 38

what is the cause of protein permeability and loss in nephrotic syndrome?

Answer 38

loss of fixed negative charges in the glomerular capillary wall (with or without structural changes in the wall)

Question 39

cardinal features of nephrotic syndrome include?

Answer 39

hypoalbuminemia; peripheral edema; lipiduria; dyslipidemia (and associated atherosclerosis, venous thrombosis)

Question 40

the majority of evidence suggests that edema secondary to the nephrotic syndrome is primarily due to the (underfill/overfill) mechanism

Answer 40

overfill; unexplained increase in salt and water retention in the distal portions of the nephron occurs FIRST

Question 41

tx of nephrotic syndrome

Answer 41

reverse glomerular dz (corticosteroids, cytotoxic agents), sodium restriction, ?cautious use of diuretics, occasional infusion of albumin, ACE inhibitors to reduce proteinuria