Flashcards in usmle part1 Deck (300)
Factors that affect rate of diffusion
Concentration, surface area, solubility, membrane thickness, molecular weight
Conditions that increase membrane thickness
Lung fibrosis, pulmonary edema, pneumonia, membranous glomerulonephritis
Conditions that affect surface area of the membrane
Exercise (increases SA), emphysema (decreases SA)
Osmoles Vs. mole Vs. mEq
150 mM of NaCl = 300 mOsm. Moles yield osmoles. 10 mOsm Ca++ = 20 mEq
Characteristics of protein-mediated transport
More rapid than diffusion, transport can be saturated (Tm), is chemically specific, substances compete for transporter
Types of protein transport
Facilitated (down a concentration gradient), active (against gradient, requires ATP)
Primary active transport
ATP consumed directly by the transporter. E.g. Na/K countertransport
Secondary active transport
Depends indirectly on ATP. E.g. Na/glucose cotransporter in the renal tubule depends on Na/K countertransporter
Vesicles are continuously fusing with the cell membrane
The ligand binds receptor near clathrin-coated pits. More rapid and specific than constitutive endocytosis.
Simple diffusion curve in a graph
Linear. Slope increases if diffusion area or concentration increases. Slope decreases if membrane thickness increases
Facilitated diffusion curve in a graph
Reaches a plateau which represents Tm. Adding more transporters raises Tm, shifts curve up and right.
Amount of total body water
60% of weight in kg. 70kg = 42 L
Amount of intracellular fluid
2/3 of total body water or 40%. 42 L --> 28 L ICF
Amount of extracellular fluid
1/3 of total body water or 20%. 42 L --> 14 L ECF
Amount of interstitial fluid
2/3 of ECF. 14 L --> 10 L ISF
Amount of plasma volume
1/3 of ECF. 14 L --> 4 L plasma
Represented by non-penetrating solutes such as Na. If effective osmolarity increases, cells shrink and vice versa.
Are freely permeable to substances dissolved in plasma except proteins. Separate ISF and plasma.
Isotonic fluid loss diagram
Decreased ECF, no change in ICF. Causes: hemorrhage, isotonic urine, diarrhea, vomiting
Loss of hypotonic fluid diagram (hypovolemia)
Decreases ECF and ICF, increases osmolarity. Causes: dehydration, sweating, diabetes insipidus.
Gain of hypertonic fluid diagram
Increases osmolarity and ECF, decreases ICF. Causes: salt tablets, mannitol, hypertonic saline, aldosterone
Gain of hypotonic fluid diagram
Decreases osmolarity, increases ECF and ICF. Causes: SIADH, drinking tap water, primary polydipsia.
Gain of isotonic fluid diagram
Osmolarity stays the same, ECF increases. Causes: isotonic saline infusion.
Loss of hypertonic fluid diagram
Osmolarity decresaes, ECF decreases, ICF increases. Causes: mineralocorticoid deficiency
?ECF, no change in osmolarity or ICF, isotonic urine
Loss of isotonic fluid. Causes: hemorrhage, diarrhea, vomiting
?ECF, ?osmolarity, ?ICF
Loss of hypertonic fluid or hyponatremic hypovolemia. Aldosterone deficiency.
?ECF, ?osmolarity, ?ICF, little concentrated urine
Loss of hypotonic fluid or hypernatremic hypovolemia. Cause: Dehydration
?ECF, ?osmolarity, ?ICF, lots of diluted urine
Loss of hypotonic fluid or hypernatremic hypovolemia. Cause: diabetes insipidus