2/3 of all fluids reside inside the cell
Intracellular fluid
Intracellular fluids major cation is
K+
Intracellular fluids major anion is
low Na+, low Cl
1/3 of all body fluids reside outside the cell. includes the subcompartments: plasma and intersitial fluid
Extracellular fluid
Extracellular fluids major cation is
Na+
Extracellular fluids major anion is
Cl-
Water serves as the _____ _____ in which a variety of solutes are dissolved
Universal solvent
Solutes may be classified broadly as:
electrolytes and nonelectrolytes
Have bonds (usually covalent) the prevent them fom dissociating in solution. They are usually organic molecules - glucose, lipds, creatinine, and urea, for example
Nonelectrolytes
Chemical compounds that DO dissociate into ions in water. Because ions are charged particles, they can conduct an electrical current. Includes inorganic salts, both inorganic and organic acids and bases, and some proteins
Electrolytes
Electrolytes have much (lesser/greater) osmotic power than nonelectrolytes because each electrolyte molecule dissociates into at least 2 ions
Greater
Water moves according to osmotic gradients - from an area of (lesser/greater) osmality to an area of (lesser/greater) osmality
Lesser, greater
Exchanges between plama and interstitial fluid (IF) occur across
Capillary walls
Exchanges between the IF and intracellular fluid (ICF) occur across
Plasma membranes
ICF and ECF volumes are always changing because all the nutrients are being absorbed by blood. However, osmolalities remain _____
Equal
Increasing the ECF solute causes osmotic and volume changes in the ICF. Conversely, decreasing ECF osmolality causes water to move into the cells. THUS:
ECF solute concentration (osmolality) determines ICF volume (H2O)
Osmolality ↑, H2O ↓
Osmolality ↓, H2O ↑
The amount of water reabsorbed in the renal collecting ducts is proportional to
ADH release
When ADH levels are low, water reaching the collecting ducts is not reabsorbed and simply flows through resulting in
Dilute urine and a reduced volume of body fluids
When ADH levels are high nearly all filtered water is reabosrbed resulting in
A small volume of concentrated urine is excreted
_____ of the hypothalamus sense the ECF solute concentration and trigger or inhibit ADH release from the posterior pituitary accordingly
Osmoreceptors
Large changes in blood volume or blood pressure also influence secretion of this
ADH
A (decrease/increase) in blood pressure increases ADH release both directly via baroreceptors and indirectly via the renin-angiotensin-aldosterone mechanism
Decrease
Na is (always/never) secreted from blood to filtrate
Never
H2O (always/never) follows sodium
Always
_____ affects all functional proteins and biochemical reactions
pH
Normal pH of body fluids
Arterial blood: pH 7.4
Venous blood & IF fluid: pH 7.35
ICF: pH 7.0
Less than pH 7
Acidic
Greater than pH 7
Basic
Alkalosis or alkalemia
arterial pH > 7.45
Acidosis or acidemia
arterial pH < 7.35
Most H+ is produced by
metabolism
Concentration of hydrogen ions regulated sequentially by:
1- Chemical buffer systems: rapid, first line of defense
2- Brain stem respiratory centers: 1-3 min
3- Renal mechanisms: most potent, but requires hours to days to effect pH changes
Acid & Base acceptor and changes it to its own pH
Buffer
Chemical buffer systems:
1- Bicarbonate buffer system
2- Phosphate buffer system
3- Protein buffer system
Bicarbonate buffer in the blood
H2O + CO2 ==> H2CO3 (carbonic acid)
H2CO3 ==> H+ + HCO3 (carbonate)
H2O + CO2 ⇔ H2CO3 ⇔ H+ + HCO3
Bicarbonate buffer scenario:
↑ CO2 → More acidic (H+)
what does the body do to fix this?
Body ↑ HCO3 (carbonate) which combines w/ H+ to form H2CO3
Bicarbonate buffer scenario:
↑ HCO3 → more basic
What does the body do to fix this?
Body ↑ H+ which combines w/ HCO3 to form H2CO3
Hormone steroids:
Estrogen, Progesterone, and Glucocorticoids
↑ NaCl reabsorption (like aldosterone), retains H2O
Estrogen
Blocks aldosterone
Progesterone - pregnancy hormone
Releases aldosterone
Glucocorticoids (Z.G.)
If bp ↑, this inhibits SNS stimulation and dilates the afferent artery ==> ↑ GFR
Baroreceptors
PCO2 below 35 mm Hg
Respiratory alkalosis
- Common result of hyperventilation dues to stress/pain
- CO2 is being eliminated faster than produced
Low blood pH and HCO3
Metabolic acidosis
-Ingestion of too much alcohol
Blood pH below 6.8 → depression of CNS → coma →…
Death
Blood pH above 7.8 → excitation of nervous system → …
Muscle tetany, extreme nervousness, convulsions, death often from respiratory arrest