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Intracellular fluid (ICF)
cytosol
Fluid within cells
2/3 of fluid
Extracellular fluid (ECF)
fluid outside of cells
1/3 of body fluid
Plasma membrane
separates intracellular fluid from surrounding interstitial fluid
Blood vessels
divides interstitial fluid from blood plasma
Water makes up ___% of total body mass
45-75%
Body water gain/day
2500 mL
Intestinal fluids- 1200
Ingested foods- 700
Metabolic water- 200
Gain
Thirst center of hypothalamus (urge to drink)
ADH reabsorbs__
Water
Angiotensin II & Aldosterone reabsorb__
Na & Cl
ANP excretes ___
Na & Cl
Changes in osmolarity is the cause of
Fluid imbalance
An increase in osmolarity of intestinal fluid will cause cells to __
Shrink (draws fluid out)
A decrease in osmolarity of interstitial fluid will cause cells to
Swell (draw fluid out)
Most common reason for changes in osmolarity is __
Changes in Na (this is why IV fluids have NaCl)
Electrolyte balance (general functions):
Control the osmosis of water between fluid compartments
Help maintain the acid-base balance
Carry electrical current (allows for action potentials & hormone secretion)
Serves as cofactors for enzyme activity (important minerals)
Cation= (+)
Anion= (-)
Sodium cation
most abundant cation ECF
90% of ECF cations
Half of ECF osmolarity
Important in fluid/electrolyte balance
Needed for action potentials in muscle & nerve tissue
Chloride anion
most abundant anion in ECF
Moves easily between ICF & ECF
Chloride shift to balance anions
Part of HCl in gastric juice
Potassium cation
most abundance cation in ICF
Important in rest potentials & repolarization in neurons & muscle fibers
Exchanged for H+ to regulate pH
Aldosterone causes secretion of K
Aldosterone causes secretion of __
K (potassium)
Bicarbonate anion
abundant in ECF
Increases in capillary beds due to CO2 exchange
Concentration decreases as CO2 is exhaled
Kidneys regulated HCO3
Important in acid-base balance
Calcium cation
MOST ABUNDANT MINERAL IN THE BODY DUE TO BONES!!
98% is found in bones & teeth
Important roles in blood clotting & nerve & muscle tissue
Controlled by PTH & calcitriol
What increases blood calcium levels?
PTH
What lowers blood calcium levels
calcitonin
Phosphate anion
Found with Ca in bones & teeth
Acts an important buffer
Binds in organic molecules (DNA, RNA, ATP)
Magnesium cation
50% in bone
50% in iCF
Needed for neuromuscular activity
Cofactor for enzymes
Buffer Systems
keeping H+ concentrations stable
Quickly binding to H+, but not removing it from the body
Uses a weak acid & its salt as a weak base to bind to hydrogen ions
The 3 types of buffer systems
Protein
Carbonic acid-bicarbonate
Phosphate
Protein buffer system
very abundante
Works in both ICF & ECF compartments
Contains a (-COOH & -NH2)
3 examples of protein buffer system
Hemoglobin (RBCs)
Albumin (plasma protein)
Amino acids
Carbonic acid-bicarbonate buffer system
Acts mostly on ECFs
HCO3= weak base
Binds to free H in low pH
H2CO3= gives up H in high pH
Phosphate buffer system
H2PO4= weak acid
HPO4 will bind to free H
Exhalation of CO2
CO2+H2O← → H2CO3→H + HCO3
Decreases in pH→ breathing __
Faster
Increase in pH→ breathing ___
Slows
Kidney excretion of H+
ability to secrete H as Na is reabsorbed
Intercalates cells can secrete H against a concentration gradient, also HCO3 (when pH is high)
Kidney cells can also form H2PO4 (phosphate ion), NH4 (ammonia ion) to rid the body of H ions by passing in urine
Normal body pH
7.35-7.45
Below 7.35 is __
Acidosis
Above 7.45 is __
Alkalosis
Respiratory compensation
the use of the respiratory system to correct pH imbalance
Renal compensation
using kidneys to secrete H+ or reabsorb HCO3 to correct pH imbalance
Respiratory acidosis
**most common challenge
Decreases in pH (causes= hypoventilation, COPD)
Increase in CO2 (Corrections= excrete H+, reabsorb HCO3)
Respiratory alkalosis
***not an emergency
Increase in pH (causes= hyperventilation, anxiety)
Decreases in CO2 (corrections= decrease less H+, reabsorb less HCO3)
Metabolic acidosis
**2nd most common
Decrease in pH (Causes= loss of bicarbonate ion, renal dysfunction)
Increase in HCO3 (corrections: hyperventilation)
Metabolic alkalosis
**rare
Increase in pH (causes= loss of acid, vomiting, anti acid drugs)
increase in HCO3 (corrections= hypoventilation)