URINARY SYSTEM

1
BALANCE
WATER ACID-BASE ELECTROLYTE
2
WATER BALANCE

• NORMAL WATER CONTENT OF BODY
• 75 AT BIRTH
• 55-60 YOUNG ADULTS
• MEN SLIGHTLY HIGHER THAN WOMEN
• (MORE FAT, LESS WATER)
• 45 IN ELDERLY, OBESE

3
WATER BALANCE

• TOTAL BODY WATER
• 40 LITERS
• SEVERAL FLUID COMPARTMENTS
• 65 INTRACELLULAR FLUID (ICF)
• 35 EXTRACELLULAR FLUID (ECF)
• 25 INTERSTITIAL FLUID (TISSUE FLUID)
• 8 BLOOD PLASMA AND LYMPH
• 2 TRANSCELLULAR FLUID
• SYNOVIAL, PLEURAL, PERICARDIAL, ETC.

4
WATER BALANCE

• TOTAL BODY WATER
• ENTERS BODY
• OSMOSIS FROM DIGESTIVE TRACT
• ALSO PRODUCED BY AEROBIC RESPIRATION
• ALSO PRODUCED BY CONDENSATION REACTIONS
• EXITS BODY
• URINARY, DIGESTIVE, RESPIRATORY, INTEGUMENTARY
  SYSTEMS

5
WATER BALANCE

• TOTAL BODY WATER
• FLUID EXCHANGED BETWEEN COMPARTMENTS
• CAPILLARY WALLS, PLASMA MEMBRANES
• DRIVEN BY TRANSIENT OSMOTIC GRADIENTS
• OSMOTIC GRADIENTS DEPENDENT ON SOLUTE MOLECULES
• MOST ABUNDANT SOLUTES ARE ELECTROLYTES
• WATER BALANCE AND ELECTROLYTE BALANCE ARE CLOSELY
  RELATED

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7
WATER BALANCE

• WATER BALANCE
• FLUID GAIN FLUID LOSS
• BOTH TYPICALLY 2500 ML / DAY

8
WATER BALANCE

• WATER GAIN
• TYPICALLY 2500 ML / DAY
• 1600 ML FROM DRINK
• 700 ML FROM FOOD
• 200 ML FROM METABOLISM
• AEROBIC RESPIRATION
• CONDENSATION REACTIONS
• A.K.A. DEHYDRATION REACTIONS

9
WATER BALANCE

• WATER LOSS
• TYPICALLY 2500 ML / DAY
• 1500 ML EXCRETED AS URINE
• 200 ML ELIMINATED IN FECES
• 300 ML EXPIRED IN BREATH
• 100 ML SECRETED AS SWEAT
• 400 ML LOST AS CUTANEOUS TRANSPIRATION
• DIFFUSES THROUGH EPIDERMIS, EVAPORATES

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12
WATER BALANCE

• WATER LOSS
• CAN VARY GREATLY
• INCREASED RESPIRATORY LOSS IN COLD WEATHER
• INCREASED SWEAT LOSS IN WARM WEATHER
• INCREASED RESPIRATORY AND SWEAT LOSS, DECREASED
  URINE OUTPUT DURING PHYSICAL EXERTION

13
WATER BALANCE

• WATER LOSS
• OBLIGATORY WATER LOSS
• RELATIVELY UNAVOIDABLE
• EXPIRED AIR, CUTANEOUS TRANSPIRATION, SWEAT,
  FECAL MOISTURE, MINIMUM URINE OUTPUT (400 ML/DAY)

14
WATER BALANCE

• REGULATION OF WATER INTAKE
• GOVERNED BY THIRST
• PROVOKED BY INCREASED PLASMA OSMOLARITY
• PROVOKED BY BLOOD LOSS
• THIRST CENTER IN HYPOTHALAMUS
• RESPONDS TO SIGNS OF DEHYDRATION
• ANGIOTENSIN II
• ANTIDIURETIC HORMONE (ADH)
• SIGNALS FROM OSMOCENTERS
• INHIBITS SALIVATION

15
WATER BALANCE

• REGULATION OF WATER INTAKE
• INHIBITED SALIVATION
• DRY MOUTH
• SENSE OF THIRST
• INGESTION OF WATER
• COOLS AND MOISTENS MOUTH
• DISTENDS STOMACH AND INTESTINES
• REHYDRATES BLOOD
• THIRST INHIBITED

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17
WATER BALANCE

• REGULATION OF WATER OUTPUT
• CONTROLLED VIA ALTERATIONS IN URINE VOLUME
• URINE VOLUME AFFECTED BY
• SODIUM REABSORPTION
• WATER FOLLOWS SODIUM REABSORPTION
• MORE LATER
• ANTIDIURETIC HORMONE (ADH)
• BLOOD VOLUME ?, Na ?, OSMORECEPTORS
  STIMULATED, PITUITARY RELEASES ADH
• AQUAPORINS PRODUCED IN KIDNEYS COLLECTING DUCTS
• FACILITATE REABSORPTION
• ALSO WORKS IN REVERSE

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19
WATER BALANCE

• WATER BALANCE DISORDERS
• FLUID DEFICIENCY
• VOLUME DEPLETION (HYOVOLEMIA)
• DEHYDRATION
• FLUID EXCESS
• VOLUME EXCESS
• HYPOTONIC HYDRATION
• FLUID SEQUESTRATION

20
WATER BALANCE

• WATER BALANCE DISORDERS
• FLUID DEFICIENCY HYPOVOLEMIA
• CAUSED BY PROPORTIONATE LOSS OF WATER AND SODIUM
  WITHOUT REPLACEMENT
• TOTAL BODY WATER DECREASED
• OSMOLARITY UNCHANGED
• CAUSES
• HEMORRHAGE
• SEVERE BURNS
• CHRONIC VOMITING OR DIARRHEA
• MAJOR CAUSE OF INFANT MORTALITY

21
WATER BALANCE

• WATER BALANCE DISORDERS
• FLUID DEFICIENCY DEHYDRATION
• CAUSED BY LOSS OF MORE WATER THAN Na
• TOTAL BODY WATER DECREASED
• ECF OSMOLARITY INCREASES
• CAUSES
• LACK OF DRINKING WATER
• DIABETES MELLITUS
• ADH HYPOSECRETION
• PROFUSE SWEATING
• OVERUSE OF DIURETICS

22
WATER BALANCE

• WATER BALANCE DISORDERS
• FLUID DEFICIENCY DEHYDRATION
• AFFECTS ALL FLUID COMPARTMENTS
• INFANTS MORE VULNERABLE THAN ADULTS
• HIGHER METABOLISM ? MORE WASTES
• MORE WASTES ? MORE URINE VOLUME
• IMMATURE KIDNEYS
• URINE LESS CONCENTRATED
• GREATER SURFACE AREA-TO-VOLUME RATIO
• GREATER WATER LOSS BY EVAPORATION

23
WATER BALANCE

• WATER BALANCE DISORDERS
• EFFECTS OF FLUID DEFICIENCY
• CIRCULATORY SHOCK
• DUE TO LOSS OF BLOOD VOLUME
• NEUROLOGICAL DYSFUNCTION
• DUE TO DEHYDRATION OF BRAIN CELLS

24
WATER BALANCE

• WATER BALANCE DISORDERS
• FLUID EXCESS
• LESS COMMON THAN FLUID DEFICIENCY
• KIDNEYS ARE TYPICALLY ABLE TO EXCRETE MORE URINE

25
WATER BALANCE

• WATER BALANCE DISORDERS
• FLUID EXCESS VOLUME EXCESS
• CAUSED BY PROPORTIONATE RETENTION OF EXCESS WATER
  AND SODIUM
• TOTAL BODY WATER INCREASED
• OSMOLARITY UNCHANGED
• CAUSES
• ALDOSTERONE HYPERSECRETION
• RENAL FAILURE

26
WATER BALANCE

• WATER BALANCE DISORDERS
• FLUID EXCESS HYPOTONIC HYDRATION
• WATER INTOXICATION, POS H20 BALANCE
• CAUSED BY RETENTION OF MORE WATER THAN SODIUM
• TOTAL BODY WATER INCREASED
• ECF OSMOLARITY DECREASES
• CAUSES
• REPLACEMENT OF WATER AND SALT WITH WATER
• LACK OF PROPORTIONATE INTAKE OF ELECTROLYTES
• ADH HYERSECRETION

27
WATER BALANCE

• WATER BALANCE DISORDERS
• EFFECTS OF FLUID EXCESS
• PULMONARY EDEMA
• CEREBRAL EDEMA

28
WATER BALANCE

• WATER BALANCE DISORDERS
• FLUID SEQUESTRATION
• EXCESS FLUID ACCUMULATES IN A PARTICULAR LOCATION
• TOTAL BODY WATER MAY BE NORMAL
• CIRCULATING VOLUME MAY DROP
• EXAMPLES
• EDEMA (IN INTERSTITIAL SPACES)
• HEMORRHAGE (LOST TO CIRCULATION)
• PLEURAL EFFUSION (IN PLEURAL CAVITY)

29
ELECTROLYTE BALANCE

• IMPORTANCE OF ELECTROLYTES
• SALTS
• E.G. NaCl, Ca3(PO4)2, ETC.
• INCLUDE IONS IN DEFINITION
• MANY ROLES
• INVOLVED IN METABOLISM
• DETERMINE ELECTRICAL MEMBRANE POTENTIALS
• AFFECT OSMOLARITY OF BODY FLUIDS
• AFFECT WATER CONTENT AND DISTRIBUTION
• ETC.

30
ELECTROLYTE BALANCE

• SODIUM
• PRINCIPAL EXTRACELLULAR CATION
• 90 95 OF OSMOLARITY FROM SODIUM SALTS
• ROLES
• DEPOLARIZATION
• MUSCLES, NERVES
• AFFECT TOTAL BODY WATER
• AFFECT WATER DISTRIBUTION
• COTRANSPORT
• GLUCOSE, AMINO ACIDS, CALCIUM, ETC.
• ETC.

31
ELECTROLYTE BALANCE

• SODIUM HOMEOSTASIS
• 0.5 G / DAY DIETARY REQUIREMENT
• RECEIVE 3 7 G / DAY FROM OUR DIET
• KIDNEYS EXCRETE EXCESS (5 G / DAY)
• EXCRETION REGULATED BY 3 HORMONES
• ALDOSTERONE
• ANTIDIURETIC HORMONE (ADH)
• ATRIAL NATRIURETIC FACTOR (ANF)

32
ELECTROLYTE BALANCE

• SODIUM HOMEOSTASIS
• REGULATION BY ALDOSTERONE
• SALT-RETAINING HORMONE
• STEROID HORMONE
• ALDOSTERONE SECRETION STIMULATED BY
• HYPONATREMIA
• HYPERKALEMIA
• HYPOTENSION

33
ELECTROLYTE BALANCE

• SODIUM HOMEOSTASIS
• REGULATION BY ALDOSTERONE
• TARGET CELLS
• DISTAL CONVOLUTED TUBULE
• COLLECTING DUCT
• TRANSCRIBE GENE FOR Na-K PUMP
• SODIUM REABSORPTION INCREASES
• H AND K SECRETION INCREASES
• URINE pH DROPS

34
ELECTROLYTE BALANCE

• SODIUM HOMEOSTASIS
• REGULATION BY ALDOSTERONE
• AVERAGE Na EXCRETION 5 G / DAY
• ALDOSTERONE REDUCES TO 0
• WATER REABSRBED PROPORTIONALLY
• SODIUM CONCENTRATION IN BODY UNCHANGED

35
ELECTROLYTE BALANCE

• SODIUM HOMEOSTASIS
• REGULATION BY ALDOSTERONE
• INHIBITED BY HYPERTENSION
• KIDNEYS THEN REABSORB LITTLE Na
• EXCRETION INCREASED TO 30 G / DAY

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ELECTROLYTE BALANCE

• SODIUM HOMEOSTASIS
• REGULATION BY ADH
• INDEPENDENTLY MODIFIES SODIUM AND WATER EXCRETION
• CAN CHANGE SODIUM CONCENTRATION
• HIGH BLOOD Na ? ADH SECRETION
• INCREASES WATER REABSORPTION
• SODIUM CONCENTRATION DECREASED
• ADH ALSO STIMULATES THIRST
• ALSO HAPPENS IN REVERSE

38
ELECTROLYTE BALANCE

• SODIUM HOMEOSTASIS
• REGULATION BY ANF
• HYPERTENSION ? ANF SECRETION
• INHIBITS ADH AND RENIN SECRETION
• INHIBITS SODIUM WATER REABSORPTION
• MORE SODIUM AND WATER EXCRETED
• BLOOD PRESSURE DECREASED

39
ELECTROLYTE BALANCE

• SODIUM HOMEOSTASIS
• REGULATION BY OTHER HORMONES
• ESTROGENS MIMIC ALDOSTERONE
• WATER RETENTION DURING PREGNANCY
• MENSTRUAL WATER RETENTION
• PROGESTERONE
• REDUCES SODIUM REABSORPTION
• DIURETIC AEFFECT
• GLUCOCORTICOIDS
• PROMOTE SODIUM REABSORPTION, EDEMA

40
ELECTROLYTE BALANCE

• SODIUM HOMEOSTASIS IMBALANCES
• RELATIVELY RARE
• HYPERNATREMIA
• CAN RESULT FROM IV SALINE
• CAUSES WATER RETENTION, HYPERTENSION, EDEMA
• HYPONATREMIA
• GENERALLY FROM WATER EXCESS
• HYPOTONIC HYDRATION
• CORRECTED BY EXCRETION OF EXCESS WATER

41
ELECTROLYTE BALANCE

• POTASSIUM
• PRINCIPAL INTRACELLULAR CATION
• AFFECTS INTRACELLULAR OSMOLARITY
• AFFECTS CELL VOLUME
• ROLES
• PRODUCES RESTING ACTION POTENTIALS
• COTRANSPORT
• THERMOGENESIS
• COFACTOR FOR PROTEIN SYNTHESIS

42
ELECTROLYTE BALANCE

• POTASSIUM HOMEOSTASIS
• HOMEOSTASIS LINKED TO THAT OF Na
• K AND Na COREGULATED BY ALDOSTERONE
• 90 OF K REABSORBED IN PCT
• REMAINDER EXCRETED IN URINE
• CONTROL IMPARTED IN DCT COLLECTING DUCT (CD)
• HIGH K ? SECRETE MORE INTO FILTRATE
• LOW K ? SECRETE LESS INTO FILTRATE
• EXCHANGED FOR Na

43
ELECTROLYTE BALANCE

• POTASSIUM HOMEOSTASIS
• REGULATION BY ALDOSTERONE
• HIGH K ? ALDOSTERONE PRODUCTION
• Na-K PUMP PRODUCED
• Na AND K COREGULATED
• INCREASE K SECRETION
• DECREASE Na SECRETION

44
ELECTROLYTE BALANCE

• POTASSIUM HOMEOSTASIS IMBALANCES
• MOST DANGEROUS ELECTROLYTE IMBALANCES
• HYPERKALEMIA
• EFFECTS DEPEND ON SPEED OF CONC RISE
• QUICK RISE ? NERVE/MUSCLE CELLS VERY EXCITABLE
• ? CARDIAC ARREST
• E.G., K RELEASED FROM INJURED CELLS
• E.G., TRANSFUSION WITH OLD BLOOD
• E.G., EUTHANASIA, CAPITAL PUNISHMENT LETHAL
  INJECTION
• K HAS LEAKED FROM ERYTHROCYTES
• SLOW RISE ? NERVE/MUSCLE CELLS LESS EXCITABLE
• (Na CHANNELS INACTIVATED)
• E.G., ALDOSTERONE HYPOSECRETION, RENAL FAILURE,
  ACIDOSIS
• E.G., SUPPLEMENTAL K TO RELIEVE MUSCLE CRAMPS

45
ELECTROLYTE BALANCE

• POTASSIUM HOMEOSTASIS IMBALANCES
• HYPOKALEMIA
• NERVE/MUSCLE CELLS LESS EXCITABLE
• MUSCLE WEAKNESS, LOSS OF MUSCLE TONE, DEPRESSED
  REFLEXES, IRREGULAR HEART ACTIVITY
• E.G., HEAVY SWEATING, CHRONIC VOMITING OR
  DIARRHEA, EXCESSIVE LAXATIVES, ALDOSTERONE
  HYPERSECRETION, ALKALOSIS
• E.G., DEPRESSED APPETITE, BUT RARELY FROM DIETARY
  INSUFFICIENCY

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ELECTROLYTE BALANCE

• CHLORIDE
• MOST ABUNDANT ANION IN ECF
• MAJOR CONTRIBUTION TO OSMOLARITY
• ROLES
• FORMATION OF HCl
• CHLORIDE SHIFT
• CO2 LOADING/UNLOADING
• REGULATION OF BODY pH

48
ELECTROLYTE BALANCE

• CHLORIDE HOMEOSTASIS
• Cl- STRONGLY ATTRACTED TO SOME CATIONS (E.G.,
  Na, K, Ca2)
• CANNOT KEEP THEM APART
• HOMEOSTASIS ACHIEVED AS AN EFFECT OF Na
  HOMEOSTASIS
• Cl- PASSIVELY FOLLOWS Na

49
ELECTROLYTE BALANCE

• CHLORIDE IMBALANCES
• HYPERCHLOREMIA
• RESULTS FROM DIETARY EXCESS
• RESULTS FROM INTERVENOUS SALINE ADMINISTRATION
• HYPOCHLOREMIA
• SIDE EFFECT OF HYPONATREMIA
• SIDE EFFECT OF HYPOKALEMIA
• KIDNEYS RETAIN K BY SECRETING Na, Cl- FOLLOWS
• EFFECTS
• ALTERED ACID-BASE BALANCE

50
ELECTROLYTE BALANCE

• CALCIUM
• ROLES
• STRENGTHENS BONE
• MUSCLE CONTRACTION
• SECOND MESSENGER FOR HORMONES
• ACTIVATES EXOCYTOSIS
• BLOOD CLOTTING

51
ELECTROLYTE BALANCE

• CALCIUM
• BINDS TO PHOSPHATE ION
• CAN FORM Ca3(PO4)2
• HIGH CONCENTRATIONS OF BOTH IONS WILL FORM
  PRECIPITATE CRYSTALS
• INTRACELLULAR Ca2 MUST BE KEPT LOW
• Ca2 PUMPED OUT INTO E.R.

52
ELECTROLYTE BALANCE

• CALCIUM HOMEOSTASIS
• REGULATED BY PTH CALCITROL
• ALSO BY CALCITONIN IN CHILDREN
• BLOOD Ca2 REGULATED VIA
• BONE DEPOSITION REABSORPTION
• INTESTINAL ABSORPTION
• URINARY EXCRETION

53
ELECTROLYTE BALANCE

• CALCIUM IMBALANCES
• HYPERCALCEMIA
• REDUCES EMBRANE PERMEABILITY TO Na
• INHIBITS DEPOLARIZATION OF NERVES/MUSCLES
• ? MUSCULAR WEAKNESS, CARDIAC ARRHYTHMI, ETC.
• RESULTS FROM
• ALKALOSIS
• HYPERPARATHYROIDISM
• HYPOTHYROIDISM

54
ELECTROLYTE BALANCE

• CALCIUM IMBALANCES
• HYPOCALCEMIA
• INCREASES EMBRANE PERMEABILITY TO Na
• NERVES/MUSCLES OVERLY EXCITABLE
• ? TETANUS IF CONCENTRATION DROPS TO LOW
• RESULTS FROM
• ACIDOSIS
• VITAMIN D DEFICIECY
• DIARRHEA
• PREGNANCY OR LACTATION
• HYPOPARATHYROIDISM
• HYPERTHYROIDISM

55
ELECTROLYTE BALANCE

• PHOSPHATES
• RELATIVELY CONCENTRATED IN ICF
• ROLES
• COMPONENTS OF BONES
• COMPONENTS OF DNA RNA
• COMPONENTS OF PHOSPHOLIPIDS
• ACTIVATE / DEACTIVATE ENZYMES
• BUFFER pH OF BODY FLUIDS

56
ELECTROLYTE BALANCE

• PHOSPHATES
• COMPONENTS OF
• NUCLEIC ACIDS (DNA, RNA)
• NTPs AND dNTPs (ATP, dATP, GTP, dGTP, etc)
• cAMP
• PHOSPHOLIPIDS
• VARIOUS OTHER PHOSPHORYLATED MOLECULES
• GENERATED VIA ATP HYDROLYSIS, ETC.
• EXIST AS MIXTURE OF THREE FORMS
• PO43- (PHOSPHATE ION)
• HPO42- (MONOHYDROGEN PHOSPHATE ION)
• H2PO4- (DIHYDROGEN PHOSPHATE ION)

57
ELECTROLYTE BALANCE

• PHOSPHATE HOMEOSTASIS
• DIET PROVIDES AMPLE PHOSPHATE
• READILY ABSORBED BY SMALL INTESTINE
• REGULATION
• RENAL TUBULES SITE OF REGULATION
• PTH INCREASES PHOSPHATE EXCRETION
• EXCRETION RATE AFFECTED BY URINE pH

58
ELECTROLYTE BALANCE

• PHOSPHATE IMBALANCES
• PHOSPHATE HOMEOSTASIS NOT VERY CRITICAL
• BODY CAN TOLERATE WIDE VARIATIONS OF PHOSPHATEE
  CONCENTRATION WITH LITTLE EFFECT

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ACID-BASE BALANCE

• ACIDS, BASES, AND pH
• ACID
• ANY SUBSTANCE RELEASING H
• H INCREASES (pH DECREASES)
• BASE
• ANY SUBSTANCE ACCEPTING H
• H DECREASES (pH INCREASES)
• pH
• A MEASURE OF H
• -LOG H
• SCALE 0 14, 7 IS NEUTRAL

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ACID-BASE BALANCE

• WHY IS ACID-BASE BALANCE IMPORTANT?
• METABOLISM REQUIRES NUMEROUS ENZYMES
• ENZYMES ARE PROTEINS
• pH AFFECTS PROTEIN STRUCTURE
• PROTEIN STRUCTURE AFFECTS FUNCTION
• DEVIATIONS FROM NORMAL pH CAN INACTIVATE ENZYMES
  AND SHUT DOWN METABOLIC PATHWAYS

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ACID-BASE BALANCE

• BLOOD pH
• BLOOD AND TISSUE pH 7.35 7.45
• ENZYMES FUNCTION WELL WITHIN THIS RANGE
• ENZYMES FUNCTION POORLY (OR NOT AT ALL) WHEN
  SIGNIFICANTLY OUTSIDE OF THIS RANGE
• THIS RANGE MUST BE MAINTAINED
• ACID-BASE BALANCE

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ACID-BASE BALANCE

• BUFFERS
• ANY MECHANISM OF RESISTING SIGNIFICANT CHANGES IN
  pH
• ACCOMPLISHED BY CONVERTING
• STRONG ACID ? WEAK ACID
• STRONG BASE ? WEAK BASE

64
ACID-BASE BALANCE

• BUFFERS
• PHYSIOLOGICAL BUFFER
• SYSTEM STABILIZING pH BY CONTROLLING BODYS
  OUTPUT OF ACIDS, BASES, OR CO2
• URINARY SYSTEM
• BUFFERS GREATEST QUANTITY
• REQUIRES HOURS OR DAYS TO EXERT EFFECT
• RESPIRATORY SYSTEM
• SMALLER EFFECT
• EXERTS EFFECT WITHIN MINUTES

65
ACID-BASE BALANCE

• BUFFERS
• CHEMICAL BUFFER SYSTEM
• COMBINATION OF WEAK ACID AND WEAK BASE
• BINDS TO H AS H RISES, AND
• RELEASES H AS H FALLS
• CAN RESTORE NORMAL pH ALMOST IMMEDIATELY
• THREE MAJOR CHEMICAL BUFFER SYSTEMS
• BICARBONATE SYSTEM
• PHOSPHATE SYSTEM
• PROTEIN SYSTEM

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ACID-BASE BALANCE

• BICARBONATE BUFFER SYSTEM
• CARBONIC ACID (H2CO3)
• WEAK ACID
• BICARBONATE ION (HCO3-)
• WEAK BASE
• CO2 H20 ? H2CO3 ? H HCO3-
• WORKS IN CONCERT WITH RESPIRATORY AND URINARY
  SYSTEM
• THESE SYSTEMS REMOVE CO2 OR HCO3-

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ACID-BASE BALANCE

• PHOSPHATE BUFFER SYSTEM
• DIHYDROGEN PHOSPHATE ION(H2PO4-)
• WEAK ACID
• MONOHYDROGEN PHOSPHATE ION (HPO42-)
• WEAK BASE
• H2PO4- ? H HPO42-
• STRONGER THAN BICARBONATE BUFFERING SYSTEM
• MORE IMPARTANT IN BUFFERING ICF AND RENAL TUBULES
  THAN IN ECF

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ACID-BASE BALANCE

• PROTEIN BUFFER SYSTEM
• PROTEINS ARE MORE CONCENTRATED THAN BICARBONATE
  AND PHOSPHATE BUFFERS
• ACCOUNTS FOR 75 OF ALL CHEMICAL BUFFERING OF
  BODY FLUIDS
• BUFFERING ABILITY DUE TO CERTAIN FUNCTIONAL
  GROUPS OF AMINO ACID RESIDUES
• CARBOXYL GROUPS
• --COOH ? -COO- H
• AMINO GROUPS
• --NH3 ? -NH2 H

69
ACID-BASE BALANCE

• RESPIRATORY CONTROL OF pH
• CO2 H20 ? H2CO3 ? H HCO3-
• ADDITION OF CO2 INCREASES H
• REMOVAL OF CO2 DECREASES H
• CAN NEUTRALIZE 2-3 X MORE ACID AS CHEMICAL BUFFERS

70
ACID-BASE BALANCE

• RENAL CONTROL OF pH
• CAN NEUTRALIZE MORE ACID OR BASE THAN BOTH
  RESPIRATORY SYSTEM AND CHEMICAL BUFFERS
• RENAL TUBULES SECRETE H
• H EXCRETED IN URINE
• EXCHANGED FOR SODIUM ION (Na)
• ONLY POSSIBLE WHEN H INSIDE TUBULE CELLS IS gt
  H IN TUBULAR FLUID

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ACID-BASE BALANCE

• ACID-BASE BALANCE DISORDERS
• AT pH 7.4, 201 HCO3-H2CO3 RATIO
• IF H2CO3 INCREASES, pH DROPS
• pH BELOW 7.35 ACIDOSIS
• IF HCO3- INCREASES, pH INCREASES
• pH ABOVE 7.45 ALKALOSIS

73
ACID-BASE BALANCE

• ACID-BASE BALANCE DISORDERS
• RESPIRATORY ACIDOSIS
• CO2 PRODUCTION EXCEEDS RESPIRATORY CO2
  ELIMINATION
• CO2 ACCUMULATES IN ECF
• pH DROPS
• RESPIRATORY ALKALOSIS
• RESPIRATORY CO2 ELIMINATION EXCEEDS CO2
  PRODUCTION
• EXCESSIVE VENTILATION (HYPERVENTILATION)
• pH RISES

74
ACID-BASE BALANCE

• ACID-BASE BALANCE DISORDERS
• METABOLIC ACIDOSIS
• INCREASED PRODUCTION OF ORGANIC ACIDS
• E.G., FERMENTATION ? LACTIC ACID
• E.G., ALCOHOLISM, DIABETES MELLITUS ? KETONE
  BODIES
• INGESTION OF ACIDIC DRUGS
• E.G., ASPIRIN
• LOSS OF BASE
• E.G., CHRONIC DIARRHEA, OVERUSE OF LAXITIVES
• METABOLIC ALKALOSIS
• RARE
• OVERUSE OF BICARBONATES
• E.G., ANTACIDS
• LOSS OF STOMACH ACID FROM CHRONIC VOMITING

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76
ACID-BASE BALANCE

• ACID-BASE BALANCE DISORDERS
• ACIDOSIS
• H PASSIVELY DIFFUSES INTO CELLS
• K DIFFUSES OUT
• ELECTRICAL BALANCE MAINTAINED
• H BUFFERED BY INTRACELLULAR PROTEINS
• NET LOSS OF CATIONS FROM CELL
• MEMBRANE IS NOW HYPERPOLARIZED
• NERVE MUSCLE CELLS DIFFICULT TO STIMULATE
• CENTRAL NERVOUS SYSTEM DEPRESSED
• CONFUSION, DISORIENTATION, COMA

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78
ACID-BASE BALANCE

• ACID-BASE BALANCE DISORDERS
• ALKALOSIS
• H PASSIVELY DIFFUSES OUT OF CELLS
• K DIFFUSES INTO CELLS
• GAIN IN POSITIVE INTRACELLULAR CHARGE
• MEMBRANE POTENTIAL SHIFTED
• NERVOUS SYSTEM HYPEREXCITABLE
• NEURONS FIRE SPONTANEOUSLY
• SKELETAL MUSCLES OVERSTIMULATED
• MUSCLE SPASMS, TETANY, CONVULSIONS, RESPIRATORY
  PARALYSIS

79
ACID-BASE BALANCE

• ACID-BASE IMBALANCE COMPENSATION
• RESPIRATORY SYSTEM COMPENSATION
• ADJUSTS PCO2 IN ECF
• CO2 EXCESS ? INCREASED VENTILATION
• CO2 DEFICIENCY ? DECREASED VENTILATION
• EFFECTIVE VS RESPIRATORY ACIDOSIS AND ALKALOSIS
• NOT VERY EFFECTIVE VS METABOLIC ACIDOSIS AND
  ALKALOSIS
• I.E., CANNOT RID BODY OF KETONE BODIES
• CAN CORRECT pH 7.0 TO 7.2 OR 7.3
• NOT ALL THE WAY TO 7.4

80
ACID-BASE BALANCE

• ACID-BASE IMBALANCE COMPENSATION
• RENAL SYSTEM COMPENSATION
• SLOWER TO RESPOND
• CAN FULLY RESTORE NORMAL pH
• URINE pH NORMALLY 5 6
• MAY DROP TO 4.5 WITH EXCESS H
• RESPONSE TO ACIDOSIS
• RENAL TUBULES INCREASE H SECRETION
• H IN URINE IS BUFFERED
• MAY RISE TO 8.2 WITH EXCESS HCO3-
• RESPONSE TO ALKALOSIS
• HCO3- CONCENTRATION IN URINE ELEVATED