Chapter 26: Fluid, Electrolyte and Acid-Base Balance

Question 1

Water Content of the Body

Answer 1

influenced by age, body mass, fat content and sex; infants 73%, young male 60%, young female 50% (bc of higher fat), elderly 45%

Question 2

Intracellular Fluid Compartment

Answer 2

fluid within cells (cytoplasm) 40% of body weight

Question 3

Extracellular Fluid Compartment

Answer 3

fluid outside cells 20% of body weight 2 divisions- plasma (confined to blood vessels) and interstitial fluid (spaces between cells)

Question 4

Electrolytes

Answer 4

dissociate in water to form ions (such as NaCl + h20 = Na + Cl)

Question 5

Nonelectrolytes

Answer 5

do not dissociate in water; most are organic molecules (lipids, glucose etc)

Question 6

In ECF main cation and manin anion is

Answer 6

Na and Cl

Question 7

In ICF main cation and main anion is

Answer 7

K and HPO4

Question 8

Fluid MOvement Among Compartments

Answer 8

ions move selectively between compatments via facilitated diffusion or active transport; h20 moves passively (always) between compartments to equalize ECF and ICF osmolaties (solute concentration); h20 ALWAYS follows ECF osmolaity

Question 9

Increase in ECF osmolality =

Answer 9

h20 diffusing out of cells

Question 10

Decerease in ECF osmolality =

Answer 10

h20 diffuses into cells

Question 11

Dehydration

Answer 11

water loss exceeds intake; causes: homorrhage, severe burns, prolonged vomiting or diaherra, profuse sweating, water deprivation and dieuretic abuse; may lead to hypervolemic shok (not enough blood volume)

Question 12

Hypotonic Hydration

Answer 12

water gain exceed outtake which leads to cells swelling; causes: renal insufficiency or consuming large amounts of water too quickly results hyponatremia (liw ECF na); may lead to cerebral edma and death

Question 13

Edema

Answer 13

atypical accumulation of fluid in the interstitial fluid space which leads to tisses swelling; causes: pregnancy, increased NaCl, congestive heart failure, kidney disease; may impair diffusion of o2 and nutrients or blood circulation

Question 14

Electrolyte Balance

Answer 14

usually refers to salt balance in the body; maintained primarily by the kidneys

Question 15

Regulation of Na Balance

Answer 15

sodium required to maintain fluid balance, BP, nerve impulse conduction, and muscle contraction; na contraction and na body content are monitored indirectly

Question 16

What is the most important hormone for regulating Na?

Answer 16

aldosterone

Question 17

Renin-Angiotensin-Aldoesterone Mechanism

Answer 17

RAA; 90% of sodiu absorption is obligatory (65% from PCT and 25% from ascending limb); remaining 10% absorbed from DCT and collecting duct ONLY if aldosterone is present

Question 18

What triggers the RAA mechanism?

Answer 18

low body na content; increased potassium in ECF; low systemic BP

Question 19

Estrogens are similar too…

Answer 19

aldoesterone and leads to water retention

Question 20

How does addisons disease affect na balance?

Answer 20

autoimmune disorder that attacks adrenal cortex which inhibits aldoesterone which leads to a lot of urination (polyuria) and that can lead to releaseing too much na (and water)

Question 21

Atrial Natriuretic Peptide

Answer 21

ANP; reduces BP and volume by inhibting systemic vasoconstriction, na and h2o reabsorption

Question 22

Regulation of K Balance

Answer 22

potassium required for proper kidney and heart function, nerve impulses and muscle contraction; as with na 90% of K reabsorption is obligatory (65% from PCT and 25% from ascending limb); HOWEVER (unlike sodium) K is secreted into DCT and Collecting duct

Question 23

What two factors influence K secretion?

Answer 23

K concentration in ECF (most impt) (increasing K causes it to be secreted more and reverse); and Aldosterone (enhances K secretion into filtrate)

Question 24

Regulation of Ca and HPO4

Answer 24

99% of bodys calcium found in bones as calcium phosphate salts; ECF levels regulated by PTH; decreased ca in ECF stimulates PTH release

Question 25

Increased Ca reabsorption causes

Answer 25

decreased phosphate reabsorption in DCT; activates osteoclasts to break down bone ; stimulates kidneys to transform vit D to its active form enabling ca absorption from the small intestine

Question 26

Hyper/Hyponatremia

Answer 26

na excess/deficit

Question 27

Hyper/Hypokalemia

Answer 27

K excess/deficit

Question 28

Hyper/Hypophosphatemia

Answer 28

HPO4 excess/deficit

Question 29

Hyper/Hypocalemia

Answer 29

ca excess/deficit

Question 30

Acids

Answer 30

release H into solution

Question 31

Bases

Answer 31

remove H from a solution

Question 32

H of blood regulated by...

Answer 32

1) chemical buffers (act w/n secs); 2) brain stem respiratory centers (act within 1-3mins); 3) renal mechanism(takes hours to days to change blood pH)

Question 33

Chemical Buffer System

Answer 33

a mixture of compounds that minimize changes in pH when a strongacid or base is added; if pH drops, buffer system ties up (removes) h from solution; if pH increases buffer sys releases (adds) H to solution

Question 34

Bicarbonate Buffer System

Answer 34

impt buffer sys in ECF; mixture of carbonic acid (weak acid) and sodium bicarbonate (weak base)

Question 35

Phosphate Buffer System

Answer 35

impt buffer in urine and ICF; mixture of sodium dihydrogen phosphate (NaH2PO4) (weak acid) and sodium monohydrogen phosphate (Na2HPO4) (weak base)

Question 36

Protein Buffer System

Answer 36

most imp buffer in ICF; also operates in blood plasma; most protein molecules are amphoteric: if pH rises it can act as a acid and if it drops it can act as a base

Question 37

What is the most important buffer in RBCs

Answer 37

hemoglobin

Question 38

What systems are included in the physiological buffering system?

Answer 38

respiratory sys and renal sys

Question 39

Respiratory System H Regulation

Answer 39

adjusts pH by expelling or retaining co2

Question 40

Respiratory System response to Acidosis

Answer 40

decreased pH detected by central and peripheral chemoreceptors; which stimulates medullary respiratroy center to increase respiration which leads to a decrease in blood co2 which decreases H2CO3 which increases blood pH

Question 41

Respiratory System Response to Alkalosis

Answer 41

increased pH detected by central and peripheral chemoreceptors which inhibits the medullary respiratory center which results in decreased respiration this leads to increased blood co2 which increases blood H2CO3 which lowers pH

Question 42

Hypoventilation

Answer 42

co2 accumulation; leads to increased blood H levels which causes respiratory acidosis

Question 43

Hyperventilation

Answer 43

co2 elimination (a lot) leads to decreased blood H content which causes respiratory alkalosis

Question 44

Renal System Regulation of H

Answer 44

adjusts pH by regulating blood levels of HCO3

Question 45

Renal Response to Acidosis

Answer 45

if pH drops the kidneys conserve (reabsorb) filtered HCO3 from PCT and returns it to the peritubular capillaries

Question 46

Kidneys generate new...

Answer 46

HCO3 in PCT cells that moves into the peritubular capillaries; new HCO3 generated via buffering of secreted H by HPO4 OR new HCO3 generated via glutamine metabolism and NH4 secretion

Question 47

Renal Response to Alkalosis

Answer 47

if blood pH increaes kidneys excrete (secrete) HCO3 into collecting ducts to pass out in urine

Question 48

Respiratory Acidosis

Answer 48

most common cause of acid base imbalance; results from co2 retention; if uncompensated Pco2 >45 mmhg and ph <7.35; renal mechanism tries to compensate b retaining HCO3

Question 49

Respiratory Alkalosis

Answer 49

co2 eliminated faster than it is generated; if uncompensated Pco2 <35 mmhg and pH > 7.45; renal sys tries to compensate by eliminating HCO3

Question 50

Metabolic Acidosis

Answer 50

occurs when nonvolatile acids (such as lactic acid and ketone bodies) accumulate in blood or HCO3 is lost from body; if uncompensated HCO3 <22 mEq/L and pH < 7.35; respiratory sys attempts to compensate by increasing rate and depth of breathing

Question 51

Metabolic Alkalosis

Answer 51

occurs when HCO3 levels are excessive; if uncompensated HCO3 >26 mEp/L and pH >7.45; respiratory sys attempts to compensate by decreasing rate and depth of breathing

Question 52

Steps to Identifying Acidosis/Alkalosis

Answer 52

1) determine blood pH (if it is high or low); 2) check Pco2 and HCO3 levels for cause of blood pH; 3) check for compensation; if respiratory imbalance look at HCO3 and vice versa

Question 53

ADD VALUES FOR IDENTIFYNG