Fluid, Electrolyte and Acid Base Balance (chapter 26) Flashcards
66 % of total body water found here
Intracellular fluid (ICF)
33 % of remaining body water found here
Extracellular fluid (ECF)
What are the 2 sub compartments of ECF?
- Plasma
- Interstitial fluid (IF)
- Anything that dissociate into ions in water
- (+) or (-) charge
- most abundant solutes
- more responsible for fluid shifts/movement of water
- ex: inorganic salts, acids and bases, some proteins, Nacl
Electrolytes
- Do not dissociate in water
- No charge
- Make up the bulk of the body fluids (most of mass since they don’t dissociate)
- Ex: glucose, Urea, lipids, etc
Non-electrolytes
Optimal body water content depends on
- Age: infants and children have more water
- Sex: men have higher body water content than women
- Body fat %: fat is the least hydrated of all body tissues
Lungs, skin
Insensible water loss
Sweat, urine, feces
Sensible water loss
- Controls the thirst mechanism which is activated by Osmoreceptors, dry moth and decreasing blood volume/pressure
Hypothalamic thirst center
the body will always lose water, even if we never drink water
Obligatory water loss
Detect changing ECF osmolarity
Osmoreceptors
- decrease in ADH produced by hypothalamus or released by posterior pituitary (beginning of the brain)
- symptoms: polyuria, dilute urine, fatigue, dehydration
Central diabetes insipidus
ADH is produced and released in normal amounts, but the kidneys are unresponsive to it
Nephrogenic diabetes insipidus
influence water movement in body, essential for excitability, membrane permeability
Electrolyte balance
NaHCO3 and NaCl account for ….. of total ECF solute
280 mOsm
release causes increased reabsorption of Na+ in DCT and collecting ducts
aldosterone
release causes decreased reabsorption of Na+
Atrial Natriuretic peptide (ANP)
- estrogen exerts similar effect as aldosterone
- progesterone is slighlty diuretic
- more sodium being absorbe causes water to be absorbed too
sex hormones
- In high plasma levels, exerts very strong aldosterone like effects
- can contribute substantially to edema
- stress response hormone
glucocorticoids
- Na+ serum value is > 145 mEq/l
- caused by dehydration,exccessive intravenous NaCl administration
Hypernatremia
Na+ serum value is <135 mEq/L
hyponatremia
potassium secretion depends on
plasma concentration and aldosterone
optimal pH of arterial blood is
7.4
pH of 7.45 or higher
alkalosis
pH 7.35 or lower
physiological acidosis
one or more compounds that resist changes in pH when strong acids or bases are introduced
Chemical buffer system
- important for ECF
- Mixture of carbonic acid (weak acid) and bicarbonate salt (weak base)
- Bicarbonate salt ties up free H+ from a strong acidconverted to carbonic acid
BiCarbonate buffer system
important for ICF and urine
Phosphate buffer system
Important in ICF and blood plasma
Protein buffer system
- important for long term acid base balance
renal regulation
H2CO3 in tubule cells broken down into H+ and HC03-
Where does each go?
- H+ secreted into filtrate
- HCO3- generated in tubule cell is pumped into peritubular capillary
generate new bicarbonate ions to be pumped into plasma
PCT and type A intercalated cells
in collecting ducts can secrete bicarbonate ions while reclaiming H+ from filtrate
Type B intercalated cells
PCO2 > 45 mmHg
Respiration is shallow/slow (hypoventilation) (not taking as many breathes and not breathing deeply)
CO2 can’t be exposed of (trapped in body)
Caused by: many respiratory diseases/conditions
CO2 is too high, above 45 mm Hg – this much CO2 will cause the blood to be too acidic
respiratory acidosis
PCO2 < 35 mm Hg
Respiration is deep/fast (hyperventilation) –too many breathes per minute and breaths are too deep, so they are getting rid of too much CO2 that they need
Caused by: stress/anxiety, pain
Too little CO2 in blood, pH will become high or too basic
respiratory alkalosis
any acid base imbalce that does not involve CO2
metabolic acidosis and alkalosis
Low bicarbonate levels
Common causes: excessive alcohol intake, long-term diarrhea
pH is low
metabolic acidosis
High bicarbonate levels
Common causes: excessive vomiting, excessive base intake
Takes tums or pepto—> can shift the person to metabolic alkalosis
metabolic alkalosis
Blood pH below 6.8
CNS depression
coma and death
Blood pH above 7.8
overstimulated CNS
muscle tetany
Changes in respiratory rate & depth evident when lungs must compensate for metabolic imbalances
Respiratory compensation (not fixing the problem but is trying to balance)
Kidneys can compensate for acid-base imbalances of respiratory origins
renal compensation
For renal compensation of respiratory acidosis, the kidneys will…
kidneys conserve more bicarbonate ions, the more blood pH will increase back to normal level
For renal compensation of respiratory alkalosis, the kidneys will…
kidneys either secrete more bicarbonate ions or simply do not reabsorb it–shift pH back down so it becomes more acidic
For respiratory compensation
1. metabolic acidosis the lungs will…
2. Metabolic alkalosis the lungs will….
- respiratory rate + depth increase
This blows off excess CO2 to increase blood pH again (balancing out the low bicarbonate level) - respiratory rate + depth decrease
Conserves CO2 to decrease blood pH to desirable level
