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38 Cards in this Set
- Front
- Back
Water is approximately what percent of body mass? |
50-60 % in a healthy adult of average weight |
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In the body, ways in which fluid is gained and ways in which fluid is lost:
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Gained: via intestinal tract (mainly) and metabolic generation Lost: via kidneys, insensible loss (lungs, skin), feces, sensible loss [perspiration {variable}] |
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What is the axiom regarding gains and losses of fluid in the body?
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Gains must equal losses.
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Define the fluid compartments in the body. Which has the greater volume , ECF or ICF?
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Extracellular Fluid -Intravascular fluid (plasma) -Interstitial fluid -Compartmentalized fluid Intracellular Fluid. ICF has greater volume than ECF. |
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The cell membranes of the body cells are freely permeable or selectively permeable?
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Selectively permeable
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Do ECF and ICF have the same composition? The same osmotic concentration?
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No, they do not have the same composition; each normally contains ions and molecules in concentrations that are peculiar to ECF and ICF respectively. Yes, the osmotic concentrations of EFC and ICF are, however, normally the same, through the passive movement of water (osmosis) --- which, at equilibrium, equalizes the osmotic concentrations on either side of the cell membrane. |
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Two exceptions to occurrences of osmosis:
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Ascending limb loop of Henle (impermeable to water) In collecting duct in absence of ADH (no water reabsorption in absence of ADHhere, in spite of osmotic gradient) |
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In fluid movement, the main concern is fluid movement between _____________________, _________________ and _____________________.
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cells of soft tissue interstitial fluid plasma |
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Continuous exchange and mixing of body fluids is regulated by these two kinds of pressure:
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Hydrostatic pressure Osmotic pressure |
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Water moves freely between compartments along ____________________ gradients.
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Osmotic
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True or False: Anything that changes the solute concentration in any compartment leads to net water flows across cell membranes.
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True
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ICF volume is determined by _____________ (ICF/ECF) solute concentration.
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ECF
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Why are solutes unequally distributed in fluid compartments?
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Because of variance in size, electrical charge or dependence on transport proteins
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Is water movement across cell membranes an active or a passive process?
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Water movement is a passive process.
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State two ways in which water moves: 1) On the basis of water molecule concentration and 2) On the basis of solute concentration.
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1) Water moves from an area of high water molecule concentration to an area of lower water molecule concentration. 2) Water molecules move from an area of lower solute concentration to an area of higher solute concentration. |
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If there is no net movement of water across cell membrane, the ECF and the ICF are said to be ___________________.
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Isotonic
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What are electrolytes?
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Soluble, mainly inorganic, compounds that disassociate into ions that will conduct an electrical current in solution.
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Do electrolytes contribute to the osmotic concentration gradients of solutions?
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Yes Example: Adding salt (NaCl) to ECF increases the solute load (osmotic concentration gradient) of ECF compared to ICF. Water movement will be out of ICF into ECF. |
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What are the units of expression of electrolyte concentration and how is this determined (the formula)?
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Units: mEq/L How determined: mEq/L = Ion concentration (mgm/L) in a solution X # of electrical charges on one ion / atomic weight of the element (mgm/mmol) |
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True or False: Since electrolytes are in fact solutes, they affect water balance (through water movement by osmosis).
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True
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What is the axiom regarding electrolyte gains and losses in the body.
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Gains must equal losses
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Ions are of two types relative to the state of the electrons in their outermost electron shell. Ions with positive charges are called _________________, and ions with negative charges are called ______________________.
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Cations Anions |
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The most important Cations? The most important Anions?
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Cations : Na+, K+, Ca++, Mg++ Anions: Cl -, HCO-, HPO-, SO- |
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The main/most important/dominant cation of ECF:
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Na+
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The main contributor to osmotic concentration in ECF is this cation:
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Na+
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There is a three-word axiom that describes the movement of water in relation to salt. Complete the axiom _______________ follows _________________ .
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water follows salt
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The stem-natr refers to sodium (Na+). In someone who is hypernatremic the sodium level concentration in ECF (as in blood) would be __________________ (higher/lower) than normal.
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Higher
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In someone who is hyponatremic the sodium concentration in ECF (as in blood) would be ______________________________ (Higher/lower) than normal.
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lower
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When we are under hydrated (hypovolemic), plasma is typically (hypernatremic/hyponatremic), causing water to move (into/out of) cells.
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hypernatremic / out of
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When we are over hydrated (hypervolemic), plasma is typically (hypernatemic/hyponatremic), causing water to move (into/out of) cells.
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Hyponatremic / into
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Of someone who has a serum sodium concentration of 150mEq/L: 1) Would this present a hypernatremic (hypertonic) or a hyponatremic (hypotonic) condition? 2) Which way would water move between ECF and ICF in this situation? 3) how would the body correct this condition? |
1) Hypernatremic 2) out of ICF into ECF 3) Water reabsorption to "dilute" the concentrated ECF. Works this way : Rising osmolality of the blood is detected by osmoreceptors in the hypothalamus ==> hypothalamus stimulates release of ADH from posterior pituitary gland ==> ADH causes water reabsorption in distal DCT and in collecting duct of kidney ==> decreases osmolality of blood (returns to normal as solute concentration of blood returns to normal due to reabsorption of water) ==> hypothalamic osmoreceptors detect the change ==> ADH secretion stops |
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Where in the CNS is the osmolality of blood monitored?
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Hypothalamus
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How are minor changes in Na+ concentration in the ECF handled?
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Changes in Na+ concentration in ECF and related fluid shifts are controlled by osmoreceptors in the hypothalamus, and the hypothalamus controls release of ADH (antidiuretic hormone) from the posterior pituitary gland. ADH acts to increase water reabsorption at the distal DCT and the collecting duct of kidney when solute concentration (mainly Na+ concentration) of ECF is increased. When solute concentration of ECF (blood) is lower than normal, ADH is not released, thus no water reabsorption by the DCT and collecting duct; the result is increased excretion of dilute urine.
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How are major changes in Na+ concentration in the ECF handled?
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Via the same mechanisms that regulate blood volume and blood pressure in situations of significant loss of blood volume and significant drop in systemic arterial blood pressure.
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Traditionally, people with high blood pressure or congestive heart failure are advised to restrict the amount of salt in their diets. Why?
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increase NaCl intake ==> increases NaCl absorption from small intestine ==> solute (NaCl) concentration in ECF/blood ==> increase intravascular volume ==> increase venous return ==> increase EDV (end diastolic volume) ==> increase stress/strain on weakened heart to pump increase volume ==> ESV (end systolic volume) ==> increase back pressure in pulmonary veins (increase pulmonary capillary hydrostatic pressure) ==> fluid extravasation into alveoli (pulmonary edema) ==> inhibits O2 uptake ==> hypoxia==> further impairment of cadiac function
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The main Cation of ICF : |
K+
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Where in the kidneys can K+ be reabsorbed?
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PCT, loop of Henle and collecting ducts
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K+ balance is accomplished mainly by changing the amount of K+ _________________ (reabsorbed /secreted) _____________________(into/out of) the filtrate.
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secreted into |