A&p: Fluid, Electrolyte, And Acid-Base Balance

Front 1

water

Back 1

cells rely on this as a diffusion medium for the distribution of gases, nutrients, and wastes.

-when content is low: proteins denature, enzymes cease functioning, and cells die.

Front 2

extracellular fluid (ECF)

Back 2

the interstitial fluid, plasma, and other bodily fluids.

-minor components = lymph, CSF, synovial fluid, serous fluids (pleural, pericardial, peritoneal), aqueous humor, perilymph, and endolymph.

-not much variation in composition.

Front 3

intracellular fluid (ICF)

Back 3

the cytosol (fluid inside a cell)

-has the greatest variation as a result of the differences in the content of fat vs muscle.

Front 4

concentrations of K and Ca ions in the ECF become too high

Back 4

cardiac arrhythmias develop and death can result.

Front 5

power of hydrogen (pH)

Back 5

-if this is too high, can break chemical bonds and change the shapes of complex molecules, disrupt plasma membranes, and impair tissue functions.

Front 6

Fluid balance

Back 6

-amount of water gained each day is equal to the amount lost to the environment.

-maintenance involves regulating the content and distribution of body water in the ECF and ICF.

-cells transport ions and create concentration gradients that are then eliminated by osmosis.

Front 7

Electrolytes

Back 7

-ions released when inorganic compounds dissociate.

-can conduct electrical current in solution.

-gained from food and drinks.

Front 8

electrolyte balance

Back 8

-gains and losses of electrolytes are equal.

-involves balancing the rates of absorption across the GI tract with rates of loss by the kidneys (and sweat).

-important because: total electrolyte conc. directly affect water balance and the conc. of individual electrolytes can affect cell function.

Front 9

acid-base balance

Back 9

-production of hydrogen ions in your body is precisely off-set by their loss.

-pH is maintained in normal limits (preventing a decrease in the pH is the primary problem)

-secretion of H ions takes place primarily in the DCT + collecting ducts of kidneys, along with generating buffers.

-lungs eliminate CO2.

Front 10

Body composition (Female vs. Male)

Back 10

Front 11

clinical surveillance of water comp.

Back 11

-safe to estimate that 2/3 of total body water is in ICF.

-portions of the ECF (water in bone, in many dense connective tissues, and in minor components) are relatively isolated so fluid exchange occurs more slowly here than that between plasma and other interstitial fluids.

-attention usually focused on rapid fluid and solute movements that accompany the administration of blood, plasma, or saline solutions to counteract blood loss or dehydration.

Front 12

exchange among the subdivisions of the ECF

Back 12

-occurs primarily across the endothelial lining of capillaries.

-may also travel from the interstitial spaces to plasma through lymphatic vessels and drain into the venous system.

Front 13

cations and anions in fluid compartments

Back 13

Front 14

plasma membranes are selectively permeable:

Back 14

-ions can enter or leave the cell only by specific membrane channels.

Front 15

osmotic concentrations of ICF and ECF

Back 15

-identical, despite the differences in the concentration specific substances.

-osmosis eliminates minor differences in concentration almost at once, because most plasma membranes are freely permeable to water. (except along the ascending limb of nephron loop, DCT, and collecting duct)

Front 16

Four Basic Principles of Fluid and Electrolyte Balance:

Back 16

1. all the homeostatic mechanisms that monitor and adjust the composition of body fluids respond to changes in the ECF, not in the ICF.

2. no receptors directly monitor fluid or electrolyte balance.

3. cells cannot move water molecules by active transport.

4. the body's content of water or electrolytes will increase if dietary gains exceed losses to the environment, and will decrease if losses exceed gains.

Front 17

receptors monitoring the composition of ECF

Back 17

-detect significant changes in their composition or volume and trigger appropriate neural and endocrine responses.

-change in one ECF component spreads rapidly because it is not isolated via plasma membranes.

Front 18

three hormones that mediate physiological adjustments to fluid/electrolyte balance:

Back 18

1. Antidiuretic hormone (ADH)

2. aldosterone

3. natriuretic peptides (ANP & BNP)

Front 19

osmoreceptors

Back 19

-special cells in the hypothalamus that monitor the osmotic concentration of ECF.

-sensitive to subtle changes.

-includes neurons that secrete ADH near fenestrated capillaries in the posterior lobe of the pituitary gland. (higher osmotic concentration = more ADH release)

Front 20

increased release of ADH:

Back 20

1. stimulates water conservation by the kidneys, reducing urinary water loss and concentrating the urine.

2. stimulates the hypothalamic thirst center.

Front 21

aldosterone

Back 21

-secreted by the adrenal cortex (synth in the liver).

-major role in determining the rate of Na absorption and subsequent K loss along the DCT and collecting system.

(more = Na conservation, which also means water retention..."water follows salt")

-increase sensitivity of salt receptors on tongue to increase uptake.

-released in response to increased K or decreased Na levels in the blood reaching the adrenal cortex or response to activated RAAS.

Front 22

rennin release in response to:

Back 22

1. decrease in plasma blood volume/pressure at Juxt complex.

2. decrease in the osmotic conc. of tubular fluid @ DCT.

3. decrease Na or increase K conc. in renal circulation.

Front 23

natriuretic peptides

(ANP and BNP)

Back 23

-released by cardiac muscle cells in response to abnormal stretching of the heart walls caused by increased blood pressure or volume.

-reduce thirst and block the release of ADH and aldosterone.

Front 24

diuresis

Back 24

fluid loss by the kidneys with release of natriuretic peptides.

-decreases blood pressure and plasma volume, eliminating heart wall overstretching.

Front 25

water vs. electrolyte balance

Back 25

-considered separately even though closely related.

-regulatory mechanisms are quite different.

-distinction is necessary clinically when there are problems with fluid balance and electrolyte balance that must be identified.

Front 26

hydrostatic pressure

Back 26

-forces water out of blood plasma and into interstitial space.

-some of that water may be reabsorbed in the distal portion of the capillary bed and the rest enters lymphatic vessels for transport to the venous circulation.

Front 27

fluid movement among the minor components of the ECF

Back 27

-is continuous.

Front 28

flow rate of water moving back and forth across the mesothelial surfaces that line the cavities:

Back 28

-significant

-but the actual volume present at any one time is very small.

Front 29

Na / water ratio

Back 29

provides useful clues to the state of water balance.

Front 30

interstitial fluid and fluid compartments contain approx:

Back 30

80% of the ECF volume and plasma contains the other 20%.

Front 31

edema

Back 31

any factoring altering the net hydrostatic pressure or the net colloid osmotic pressure will alter the distribution of fluid within the ECF resulting in this.

Front 32

causes of edema:

Back 32

-increase blood pressure

-decreased blood colloid osmotic pressure

(advanced starvation, plasma protein decrease)

-damaged capillary wall

-constriction of regional venous circulation

-blockage of lymphatic drainage

Front 33

fluid gains and losses

Back 33

Front 34

metabolic generation of water

Back 34

-production of water within cells, primarily as a result of oxidative phosphorylation in mitochondria.

-diet in US: 46% carbs, 40%lipid, 14% protein = 300 mL of water per day (12% daily requirement)

Front 35

Fluid Shift

Back 35

-rapid water movement between the ECF and ICF in response to an osmotic gradient.

-occur quickly in response to changes in osmotic concentration of the ECF and reach equilibrium within minutes to hours.

Front 36

dehydration

Back 36

"water depletion"

-develops when water losses outpace water gains.

-body fluids become more concentrated and sodium ion conc. become abnormally high (hypernatremia)

-if this imbalance remains unchecked, the loss of water will produce severe thirst, dryness, and wrinkling of the skin.

-shock may develop if severe enough.

Front 37

First week of dieting

Back 37

-may seem unproductive because your body is conserving water and catabolizing lipids.

Front 38

causes of hyperhydration

Back 38

-drinking too much water or infusion of a hypotonic sol.

-inability to eliminate excess water in urine (chronic renal failure, heart failure, cirrhosis, etc)

-endocrine disorders (too much ADH prod.)

Front 39

first signs of hyperhydration

Back 39

-effects on CNS.

-individual acts drunk (water intox)

-can be deadly.

Front 40

equivalent (eq)

Back 40

electrolytes in the body fluids are measured in terms of this.

-amount of positive or negative ion that supplies one mole of electrical charge.

Front 41

two general rules concerning sodium and potassium balance worth noting:

Back 41

1. the most common problems with electrolyte balance are caused by an imbalance between gains and losses of sodium ions.

2. problems with K balance are less common but significantly MORE dangerous than problems related with Na.

Front 42

Homeostatic regulation of increased [Na] in ECF

Back 42

Front 43

Homeostatic regulation of decreased [Na] in ECF

Back 43

Front 44

Fluid Volume regulation and [Na] in Body fluids

(increasing blood pressure and volume)

Back 44

Front 45

Fluid Volume regulation and [Na] in Body fluids

(decreasing blood pressure and volume)

Back 45

Front 46

baroreceptors at the carotid sinus, aortic sinus, and the right atrium.

Back 46

-homeostatic mechanisms can monitor ECF volume indirectly by monitoring blood pressure via these receptors.

Front 47

rate of tubular secretion of K varies based on three factors:

Back 47

1. changes in the [K] of ECF.

2. changes in pH.

3. aldosterone levels

Front 48

major factors involved in disturbances of potassium balance

Back 48

Front 49

volume depletion

Back 49

occurs when athletes sweat lose much more water than they do sodium.

(increase [Na] in ECF)

-kidney function is impaired because this occurs at the same time that blood is being shunted away from the kidneys.

-wastes accumulate in the blood.

Front 50

calcium

Back 50

-the most abundant mineral in the body.

-99% is in the skeleton

-also play role in muscular and neural activities, blood clotting, as cofactors for enzymatic reactions, and as second messengers.

Front 51

increase [Ca]

Back 51

-parathyroid hormone

-calcitriol

Front 52

decrease [Ca]

Back 52

calcitonin.

Front 53

magnesium

Back 53

-required as a cofactor for several important enzymatic reactions, including phosphorylation of glucose within cells and the use of ATP by contracting muscle fibers.

Front 54

phosphate ions

Back 54

-required for bone mineralization

-inside cells, required for the formation of high-energy compounds, the activation of enzymes, and the synthesis of nucleic acids.

Front 55

chloride ions

Back 55

-most abundant anions in the ECF.

Front 56

Electrolyte balance in Adults

Back 56

Front 57

acid-base terminology

Back 57

Front 58

carbonic acid

Back 58

-a weak acid.

-at the normal pH of ECF, and equilibrium exists:

Front 59

acidosis

Back 59

-acidemia that exists when the pH of the blood falls below 7.35.

Front 60

alkolosis

Back 60

-alkemia that exists when the blood pH rises about 7.45.

Front 61

severe acidosis

Back 61

-effects primary the CV and nervous systems.

1. CNS function deteriorates and the person can become comatose.

2. cardiac contractions grow weak and irregular, and signs/symptoms of heart failure develop.

3. peripheral vasodilation produces a dramatic decrease in blood pressure, potentially producing circulatory collapse.

Front 62

Three classes of Acids that can THREATEN pH balance

Back 62

Front 63

carbonic anhydrase is found...

Back 63

in the cytoplasm of RBCs, liver, and kidney cells, parietal cells of the stomach, etc.

Front 64

P(CO2) is inversely related to the pH

Back 64

Front 65

Buffer Systems in Body Fluids

Back 65

Front 66

buffers

Back 66

-dissolved compounds that stabilize the pH of a solution by adding or removing H ions.

-include weak acid and its conjugate base.

Front 67

Phosphate Buffer System

Back 67

-plays a supporting role in ECF pH regulation

-very important in regulating ICF pH and that of urine.

Front 68

protein buffer systems

Back 68

depend on the ability of amino acids to respond to pH changes by accepting or releasing protons. (amphoteric)

Front 69

plasma proteins

Back 69

-contribute to the buffering capabilities of the blood.

Front 70

interstitial fluid and pH regulation

Back 70

-contains extracellular protein fibers and dissolved amino acids that assist in this.

Front 71

ICF of active cells

Back 71

-structural or other proteins provide an extensive buffering capability.

-buffering prevents destructive changes in pH when cellular metabolism produces organic acids such as lactic acid or pyruvic acid.

-acid from the ECF can come here to get buffered.

Front 72

Hb Buffer System

Back 72

-the only Intracellular buffer system that can have an immediate effect on the pH of the ECF.

-helps prevent drastic changes in pH when the plasma P(co2) is increasing or decreasing.

Front 73

Carbonic Acid-Bicarbonate Buffer System

Back 73

-primary role is to prevent changes in H caused by organic acids and fixed acids in the ECF.

-reaction is freely reversible.

Front 74

Important limitation of the carbonic acid-bicarbonate buffer system

Back 74

1. it cannot protect the ECF from changes in pH that result from increased or decreased levels of CO2. (its own weak acid)

2. it can function only when the respiratory system and the respiratory control centers are working normally.

3. the ability to buffer acids is limited by the availability of bicarbonate ions.

Front 75

bicarbonate reverse

Back 75

-readily available supply of HCO3-

Front 76

preserving homeostasis through acid-base balance

Back 76

-buffers only render the H ions as harmless.

(body's supply of buffer is limited)`

-captured H ions must ultimately be either permanently tied up in water molecules, through the removal of carbon dioxide by the lungs, or removed from the body fluids, through secretion by the kidneys.

Front 77

respiratory compensation

Back 77

-change in the respiratory rate that helps stabilize the pH of ECF.

-takes place whenever the body pH strays out of normal limits.

-respiratory activity has a direct effect on the carbonic acid-bicarbonate buffer system.

Front 78

chemoreceptors of the carotid and aortic bodies

Back 78

-these are sensitive to the Pco2 if circulating blood.

-a rise in Pco2 stimulates these receptors leading to an increase in the respiratory rate.

Front 79

renal compensation

Back 79

-change in the rates of H+ and HCO3- secretion or reabsorption by the kidneys in response to changes in plasma pH.

Front 80

the ability to eliminate a large number of hydrogen ions in a normal volume of urine

Back 80

-depends on the presence of buffers in the urine.

-secretion of H+ can only continue until the pH of the tubular fluid reaches 4-4.5 (the point at which H+ concentration gradient is too high and they leak out as fast as they are pumped in)

Front 81

if the tubular fluid lacked buffer

Back 81

-the kidneys would secrete less that 1% of the acid it produced each day before the pH reached its limit.

-buffers keep the pH high enough for H+ secretion to continue.

Front 82

secretion of H+ ions by the kidney tubules

Back 82

Front 83

generation of ammonia within the kidney tubules

Back 83

In a starving person, tubule cells break down amino acids yielding ammonium ions that are pumped into the tubular fluid, bicarbonates to help buffer ketone bodies in the blood, and carbon chains for catabolism.

Front 84

the response of the kidney tubule to alkalosis

Back 84

1. the rate of H+ secretion by the kidneys declines.

2. tubule cells do not reclaim the bicarbonates in the tubular fluid

3. the collecting system transports HCO3- into the tubular fluid while releasing a strong acid into the peritubular fluid.

Front 85

Interactions among the Carbonic Acid-Bicarbonate Buffer System and Compensatory Mechanisms in the Regulation of Plasma pH

(acidosis)

Back 85

Front 86

Interactions among the Carbonic Acid-Bicarbonate Buffer System and Compensatory Mechanisms in the Regulation of Plasma pH

(alkalosis)

Back 86

Front 87

More serious and prolonged disturbances of acid-base balance can result under the following circumstances:

Back 87

-any disorder affecting circulating buffers, respiratory performance, or renal function.

(emphysema and renal failure)

-cardiovascular conditions

(heart failure or hypertension cause fluid shifts and change GFR)

-conditions affecting the CNS

(affect respiratory and cardiovascular reflexes that are essential to pH regulation)

Front 88

respiratory acid-base disorders

Back 88

-result from a mismatch between carbon dioxide generation in peripheral tissues and carbon dioxide excretion by the lungs

-carbon dioxide levels in ECF are abnormal

Front 89

metabolic acid-base disorders

Back 89

-caused by the generation of organic acids or fixed acids or by conditions affecting the concentration of HCO3- in the ECF.

Front 90

respiratory acidosis

Back 90

-develops when the respiratory system cannot eliminate all the CO2 generated by the peripheral tissues. (hypercapnia)

-most common challenge to acid-base equilibrium.

-tissues generate CO2 rapidly, so this occurs within a few minutes of hypoventilation.

Front 91

acute respiratory acidosis

Back 91

-an immediate, life-threatening condition in which chemoreceptors do not respond, breathing rate cannot be increased, or the circulatory supply to the lungs is inadequate.

-reversal of this is probably the major goal in the resuscitation of cardiac arrest or drowning victims.

Front 92

chronic respiratory acidosis

Back 92

-develops when normal respiratory function has been compromised, but the compensatory mechanisms have not failed completely.

-chronic hypoventilation of people who have had CNS injuries.

-conditions fostering this include: emphysema, congestive heart failure, and pneumonia.

(also pneumothorax and respiratory muscle paralysis)

Front 93

respiratory alkalosis

Back 93

-respiratory activity lowers blood Pco2 to below normal levels. (hypcapnia)

-can be produced by hyperventilation which can increase the pH to around 8.0.

-this generally corrects itself because the reduction in Pco2 halts the stimulation of chemoreceptors.

Front 94

common causes of hyperventilation

Back 94

-physical stresses such as pain, or psychological stresses such as extreme anxiety.

symptoms

-symptoms that occur include tingling of the hands, lips, and feet, also light-headed.

-person may lose consciousness which removes psychological stimulation and the breathing rate decreases.

Front 95

rebreathe

Back 95

this may be required if a person is hyperventilating.

-air is breathed out into a bag and the CO2 is recirculated upon the next inhalation.

Front 96

three major causes of metabolic acidosis

Back 96

1. production of large number of fixed acids or organic acids.

2. impaired ability to excrete H+ by the kidneys.

3. severe bicarbonate loss.

Front 97

glomerulonephritis

Back 97

severe kidney damage that can result in severe metabolic acidosis.

Front 98

metabolic acidosis from increased acid production/decreased secretion.

Back 98

Front 99

lactic acidosis

Back 99

-can develop after strenuous exercise or prolonged tissue hypoxia as active cells rely on anaerobic respiration.

Front 100

ketoacidosis

Back 100

-results from the generation of large quantities of ketone bodies during the postabsorptive state of metabolism.

-problem in starvation and potentially lethal complication of poorly controlled diabetes mellitus.

-peripheral tissues cannot obtain adequate glucose from the bloodstream and they begin metabolizing lipids and ketone bodies.

Front 101

metabolic acidosis from loss of bicarbonate ions

Back 101

-this buffer system is rendered less effective and acidosis soon develops.

-this is most commonly the result of chronic diarrhea.

Front 102

respiratory and metabolic acidosis

Back 102

-typically linked because oxygen-starved tissues generate large quantities of lactic acid, and because sustained hypoventilation leads to decreased arterial PO2

Front 103

metabolic alkalosis

Back 103

-occurs when [HCO3-] are elevated.

-bicarbonate ions then interact with H+ in solution forming H2CO3.

-this is rare.

Front 104

alkaline tide

Back 104

-due to the influx into the ECF of large numbers of bicarbonate ions associated with the secretion of HCl by the gastric mucosa.

-temporarily increased the HCO3- concentration in the ECF during meals.

Front 105

vomitting

Back 105

may bring about serious metabolic alkalosis because the stomach continues to generate stomach acids to replace those that are lost.

Front 106

treatment of acute metabolic alkalosis

Back 106

-administering ammonium chloride

-metabolism of ammonium ion liberates a H+

Front 107

ACID-BASE DISORDERS

Back 107

Front 108

changes in blood chemistry associated with the major classes of ACID-BASE DISORDERS

Back 108

Front 109

identifying possible causes of the problem and distinguishing compensated from uncompensated conditions

Back 109

-steps may include determining the anion gap, plotting blood test results on a numerical graph (nomogram), or using a diagnostic chart.

Front 110

Aging affects several aspects of fluid, electrolyte, and acid-base balance

Back 110

-total body water gradually decreases

-decrease in GFR and #nephrons

-lack of ability to concentrate urine, so more water is lost.

-reduction in ADH and aldosterone sensitivity

-net loss in body mineral content as muscle mass and skeletal mass decrease.

-reduction in vital capacity.

-disorders affecting major systems become more common with increasing age.