a&e chap18 test_prep medic12
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What do all of the body's cell's rely on water for?
As a diffusion medium for the distribution of gases, nutrients, & waste products.
What happens if the water content of the body declines too far?
- Cellular activitites are jeopardized:
- 1)proteins denature
- 2)enzymes cease functioning
- 3)cells ultimately die.
In order to survive, the body must maintain a normal volume & composition in both...
ECF & ICF.
Extracellular Fluid (ECF)
- 1)interstitial fluid
- 3)other body fluids
Intracellular Fluid (ICF)
cytosol (fluid in a cell)
- 1)Amount of water you gain each day = to the amount you lose to the environment.
- 2)Involves regulating the content & distribution of water in ECF & ICF.
- 3)Reflects the creation of ion concentration gradients that are then eliminated by osmosis.
Ions released through the dissociation of inorganic compunds. (when in solution they they can conduct an electrical current)
How does the body gain electrolytes?
From the food & drink consumed.
How does the body lose electrolytes?
In urine, sweat, & feces excreted.
When does electrolyte balance exist?
When there is neither a net gain or nor a net loss of any ion in body fluids. It primarily involves balancing the rates of absorption across the digestive tract with rates of loss at the kidneys.
When are you in acid-base balance?
When the production of hydrogen ions is equal to their loss. The pH of body fluids remains within normal limits.
Why is it a problem to prevent a reduction in pH?
Because normal metabolic operations generate a variety of acids.
What organs play key roles in maintaining the acid-base balance of body fluids?
Kidneys & Lungs
Treatment of any serious illness that affects the nervous, cardiovascular, respiratory, urinary, or digestive system must always include what?
Steps to restore normal fluid, electrolyte, & acid-base balance.
What is the normal body limits of pH?
What % of the total body water content is found inside living cells, as the fluid medium of the intracllular fluid (ICF) (Cytoplasm)?
What % of the total body water content is in Extracellular fluid (ECF)?
What are the largest subdivisions of ECF?
- 1)interstitial fluid in the peripheral tissues
- 2)plasma of the circulating blood (capillary)
- 3)water in the ground substance of bone & dense connective tissue
What are the minor subdivisions of ECF?
- 2)cerebrospinal fluid (CSF)
- 3)synovial fluid
- 4)serous fluids
- 5)aqueous humor
- 6)fluids of the inner ear
How does exchange between the ICF & ECF occur?
Across cell membranes by osmosis, diffusion, & carrier-mediated processes.
How does exchange among the subdivisions of the ECF occur?
Primarily across the endothelial lining of capillaries.
What are the principal ions in in ECF?
sodium, chloride & bicarbonate
What does ICF contain an abundance of?
potasium, magnesium, & phosphate ions, plus large numbers of negatively charged proteins
Water movement between the ECF & ICF. Occurs relatively rapidly, & reach equilibrium within a period of minutes to hours.
osmotic concentration of a fluid
Why do fluid shifts occur?
In response to changes in the osmolarity of the ECF.
If ECF becomes more concentrated (hypertonic) w/ respect to ICF...
water will move from the cells into the ECF until equilibrium is restored.
If ECF becomes more dilute (hypotonic) with respect to ICF...
water will move from the ECF into the cells, & the volume of the ICF will increase accordingly.
When are you in electrolyte balance?
When the rates of gain & loss are equal for each electrolyte.
Why is electrolyte balance important?
- 1) A gain or loss of electrolytes can cause a gain or loss in water.
- 2) Concentrations of individual electrolytes affect a variety of cell functions. (effects of high or low calcium & potassium ion concentrations on cardiac muscle tissue)
- Na+ (sodium)
- K+ (potassium)
Why do the cations Na+ & K+ deserve attention?
- 1)they are major contributors to the osmotic concentrations of the ECF & ICF
- 2)they directly affect the normal functioning of all cells.
The dominant cation w/in the extracellular fluid. More than 90% of the osmotic concentration of the ECF results from the presence of sodium salts (principally, sodium chloride (NaCl) & sodium bicarbonate (NaHCO3)). Changes in the osmotic concentration of ECF usually reflect changes in the concentration of sodium ions.
The dominant cation in the ICF (ECF levels of this cation are normally low).
Most common problems involving electrolyte balance are caused by?
An imbalance between sodium gains & losses.
Problems with potassium balance...
are less common but significantly more dangerous than those related to sodium balance.
The amount of sodium in the ECF represents a balance between sodium ion absorption at the digestive tract and sodium ion excretion where?
At the kidneys & other sites.
Sodium ion uptake is a direct function of...
the amount of sodium included in the diet.
How do sodium ion losses occur?
Primarily by excretion in urine & through perspiration.
Kidneys respond to it by reabsorbing sodium ions (wh/ decreases sodium loss). Increases in it also strongly affect the loss of potassium ions.
Atrial Natriuretic Peptide
kidneys respond to it by increasing the loss of sodium ions
What % of the potassium content of the body lies within the ICF?
What is the K+ concentration in the ECF a function of?
- 1)rate of gain across the digestive epithelium
- 2)rate of loss in urine (strongly affected by aldosterone)
- 3)rate of gain proportional to the amount in the diet
How is urinary potassium loss controlled by adjustments in the rate of active secretion of aldosterone along the distal convoluted tubules of the kidneys?
- 1)ion pumps sensitive to aldosterone reabsorb sodium ions from the filtrate in exchange for potassium ions from the interstitial fluid
- 2)high plasma concentrations of potassium ions also stimulate aldosterone secretion directly
- 3)when potassium levels rise in the ECF, aldosterone levels climb, & additional potassium ions are lost in the urine.
How would eating a meal high in salt content affect the amount of fluid in the intracellular fluid compartment?
It would cause a reduction of fluid in the ICF; the ingested salt would temporarily increase the osmolarity of the ECF, so water would shift from the ICF to the ECF.
What effect would being lost in the desert for a day without water have on your blood osmotic concentration?
Fluid loss through perspiration, urine formation, & respiration would increase the osmolarity of blood & other body fluids.
What does pH deviation from the normal range cause?
- 1) disrupt stability of cell membranes
- 2) alter protein structure
- 3) change activities of important enzymes
- (you could not survive long below 6.8 or above 7.7)
pH of blood falls below 7.35
pH of blood exceeds 7.48
What occurs in severe acidosis (pH below 7.0)?
- 1) CNS function deteriorates - comatose
- 2) cardiac contractions grow weak & irregular - signs of heart failure develop
- 3) peripheral vasodilation produces dramatic drop in BP - circulatory collapse can occur
Carbonic Acid reaction sequence
CO2 + H2O <-> H2CO3 <-> H+ + HCO3-
- carbon dioxide: CO2
- water: H2O
- carbonic acid: H2CO3
- hydrogen ion: H+
- bicarbonate ion: HCO3-
carbonic acid breaks down into...
- at the lungs -> H2CO3 breaks down into CO2 & H2O (the CO2 diffuses into the aveoli)
- in the peripheral tissues -> CO2 in solution interacts w/ H2O to form H2CO3
- [occurs very rapidly in presence of carbonic anhydrase]
where is carbonic anhydrase found?
- 1) red blood cells
- 2) liver & kidney cells
- 3) parietal cells of the stomach
What is the relationship of PCO2 to pH
how when CO2 goes up pH goes down...
- CO2 rise...
- additional H+ & HCO3- released...
- pH goes down (more acidic because more H+)
What is the most important factor that affects the pH in body tissue?
What causes the pH to rise in the H2CO3 process?
At the alveoli, CO2 diffuses into the atmosphere and the number of H+ & HCO3- drops.
dissolved compunds that can provide or remove hydrogen ions (H+) (thereby stabilizing the pH of a solution)
- 1) weak acids that can donate H+
- 2) weak bases that can absorb H+
consists of a combination of a weak acid & its dissociation products: a hydrogen ion & an anion.
what are the 3 buffer systems of the body?
- 1) protein buffer system
- 2) carbonic acid-bicarbonate buffer system
- 3) phosphate buffer system
What effect would a decrease in the pH of body fluids have on the respiratory rate?
stimulate the respiratory center in the medulla ablongata, resulting in an increased breathing rate. as a result, more CO2 is eliminated, & pH rises.
How would a prolonged fast affect the body's pH?
fatty acids are catabolized, producing ketone bodies, wh/ are acids that lower the body's pH. The eventual result is called ketacidosis.
How does prolonged vomiting produce alkalosis?
- 1) large amounts of stomach acid (HCI) are lost from the body
- 2) to replace the lost H+, hydrogen ions & bicarb ions are fromed from CO2 & H2O withing the parietal cells
- 3) the release of bicar ions into the blood (in exchange for chloride ions) raises the body's pH, wh/ would cause metabolic alkalosis
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