ANP 1107 - Fluid Balance Flashcards
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ICF
- 2/3 of the body’s water
- within the cells (tiny compartments)
ECF
- External environment
(1) Plasma of blood
(2) Interstitial cells
Water
FOLLOWS SALT
Non-Electrolytes
- Usually have covalent bonds
- Do not dissociate
- Usually Organic
Electrolytes
- Dissociate
- Chemical compounds
- Conduct an electrical current
- Inorganic salts, acids and bases
Electrolytes have greater osmotic power because
They dissociate into two ions, more ions, more power
Key Electrolytes in ICF
K+
PO-3
Key Electrolytes in ECF
NA+
Cl-
Water Intake
- Enters body through ingested foods and liquids
- Includes metabolic water
Water Output
- vaporizes out of the lungs
- feces
- diffuses through the skin
- perspiration
- kidneys, urine (60%)
Dehydration
- RISE in plasma osmolarity
- Leads to release of ADH , kidneys conserve water and externe concentrated urine
Overhydration
- DECLINE is plasma osmolarity
- Inbits ADH
- Kidneys release dilute urine
Thirst Mechanism
Driving force for water intake
Osmoreceptors
Detect ECF changes vis changes in membrane stretch
Dry Mouth
- OP increases, salivary glands stop producing saliva
- Water goes to the blood instead
Baroreceptors
Detects changes in BV or BP, activates the thirst mechanism and angiotensin II
Sodium
Acts as a water magnet
Na, significance in OP
NaHCO3 and NaCl account for 90-94% of fluid in ECF
- Plasma membrane is impermeable to NA+
Aldosterone
When levels are high, Na+ is act. reabsorbed via DCT and CD
- Released by the AC via Angiotensin II
Effects of Aldosterone
- occur slowly
- increased reabsorption of Na+, increased secretion of K+
- decrease urinary output and increase BV
ANP
- Reduces BP and BV
- Inhibits vasoconstriction
- Triggered by stretch in heart cells
- Diuretic, slat-excreting effects
- Inhibits CT to reabsorb Na+
- Suppresses release of ADH, renin, aldosterone
Cardiovascular Baroreceptors
- Monitors Na+ content
- GFR increase, Na+ and water output
K+
- Required for neuromuscular function and metabolic activities
- Part of the body’s buffer system
- Opposite shifts of H+ to maintain cation balance
Too much K+
- Acidosis
- K+ leaves and H+ enters
- Decreases membrane potential
- Causes depolarization
- Reduced Excitability
Too little K+
- Alkalosis
- Hyperpolarization
- Non- responsiveness
- K+ will enter and H+ will leave
Calcium
- 99% found in bones
- Bones act as reservoir
- Calcium phosphate is regulated by PTH
Decline plasma Ca+ levels
- Release of PTH
- Increases Ca+ levels
(1) BONES: osteoclasts break down bone matrix, releases Ca++ HPO into blood
(2) KIDNEYS: increases Ca++ reabsorption in kidneys
(3) SMALL INTESTINE: increases intestinal absorption of Ca++ by making kidneys to make vitamin D
Most Ca++ is absorbed where
passively in the PTC by diffusion
Hypocalcemia
- Increased neuromuscular excitability
- Causes tetany
Hypercalcemia
- Inhibits neurons + muscle cells
- May cause life threatening cardiac arrhythmias
Phosphate
- 75% filtered in PCT (secondary active transport)
- Set by transport maximum
- PTH inhibits active transport by decreasing TM
- When ECF Ca++ levels are normal, PTH is inhibited, more phosphate retained
Normal Arterial pH
7.4
Normal Venous pH ( and IF)
7.35
Normal ICF pH
7
Lower pH means
greater amount of of acidic metabolites and CO2
Alkalosis
When arterial pH is more than 7.45
Acidosis
When arterial pH is less than 7.35
Chemical Buffers
- System of one or more compounds that resists changes in pH when strong acid or base is added
Basis of Chemical Buffer
- Binds to H+ when pH drops
- Releases H+ when pH rises
Acids
- Proton donors
- STRONG ACIDS: Dissociate completely, liberating H+ (dramatic change)
- WEAK ACIDS: Dissociate partially (smaller effect, more important)
Bases
- Proton acceptors
- STONG BASES: dissociate in water and tie up H+
WEAK BASES: Less likely to accept protons
Bicarbonate Buffer System
- Carbonic acid (weak) and sodium bicarbonate (weak base)
- Important in EFC
Phosphate Buffer System
- Nearly identical to bicarbonate suffer system
- Sodium salts of dihydrogen phosphate (weak acid) and mono hydrogen (weak base)
- Effective in urine and ICF
Protein Buffer System
- Proteins in plasma
- Linked to amino acids
Most Ca++ is absorbed where
passively in the PTC by diffusion
Hypocalcemia
- Increased neuromuscular excitability
- Causes tetany
Hypercalcemia
- Inhibits neurons + muscle cells
- May cause life threatening cardiac arrhythmias
Phosphate
- 75% filtered in PCT (secondary active transport)
- Set by transport maximum
- PTH inhibits active transport by decreasing TM
- When ECF Ca++ levels are normal, PTH is inhibited, more phosphate retained
Normal Arterial pH
7.4
Normal Venous pH ( and IF)
7.35
Normal ICF pH
7
Lower pH means
greater amount of of acidic metabolites and CO2
Alkalosis
When arterial pH is more than 7.45
Acidosis
When arterial pH is less than 7.35
Chemical Buffers
- System of one or more compounds that resists changes in pH when strong acid or base is added
Basis of Chemical Buffer
- Binds to H+ when pH drops
- Releases H+ when pH rises
Acids
- Proton donors
- STRONG ACIDS: Dissociate completely, liberating H+ (dramatic change)
- WEAK ACIDS: Dissociate partially (smaller effect, more important)
Bases
- Proton acceptors
- STONG BASES: dissociate in water and tie up H+
WEAK BASES: Less likely to accept protons
Bicarbonate Buffer System
- Carbonic acid (weak) and sodium bicarbonate (weak base)
- Important in EFC
Phosphate Buffer System
- Nearly identical to bicarbonate suffer system
- Sodium salts of dihydrogen phosphate (weak acid) and mono hydrogen (weak base)
- Effective in urine and ICF
Protein Buffer System
- Proteins in plasma
- Linked to AA have exposed groups of atoms (carboxyl groups)
- A single protein molecule can function reversibly as acid or base
Amphoteric
- A single protein molecule can function reversibly as acid or base
- Example: Haemoglobin
Respiratory Regulation of H+
- Respiratory system eliminates CO2 (acid) from blood, replenishes O2 supply
Physiological Buffer System
- Respiratory and renal buffer systems together
- Act slower than CB but have more power
Carbon Dioxide Retention
Hypoventilation –> acidosis
Carbon Dioxide Elimination
Hyperventialtion –> alkalosis
Ventilation
- Decreases CO2
- Moves reaction to the left
- Decreases H+
Decreased Ventilation
- Increased CO2
- Reaction moves to the right
- Increases H+
Renal Mechanisms of acid-base balance
- Kidneys
- Rid the body of acids generated by cellular metabolism (nonvolatile acids)
Nonvolatile Acids
Phosphoric, uric, lactic, and keytone body
Renal Mechanisms of acid-base balance
- Kidneys
- Rid the body of acids generated by cellular metabolism (nonvolatile acids)
Nonvolatile Acids
Phosphoric, uric, lactic, and keytone body