Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
111 Cards in this Set
- Front
- Back
|
Why is ECF and ICF volume and composition important to survival
|
We must maintain a normal volume and composition of the extracellular fluid (ECF) and the intracellular fluid (ICF - the cytosol)
|
|
|
What happens if the concentrations of calcium or potassium ions in the ECF become too high?
|
Cardiac arrhythmias develop and death can result
|
|
|
Why is a low pH especially dangerous?
|
because hydrogen ions break chemical bonds, change he shapes of complex molecules, disrupt cell membranes, and impair tissue functions
|
|
|
When is a body in fluid balance?
|
when the amount of water you gain each day is equal to the amount you lose to the environment
|
|
|
What is involved in the maintenance of normal fluid balance?
|
the regulation of content and distribution of body water in the ECF and ICF
|
|
|
What is the primary source of water gains?
|
the digestive system, with a small amount of additional water generated by metabolic activity
|
|
|
What is the primary route for water loss under normal conditions?
|
the urinary system
|
|
|
Electrolyte balance
|
involves balancing the rates of absorption across the digestive tract with rates of loss at the kidneys, although losses at sweat glands and other sites play a secondary role
|
|
|
Electrolytes
|
ions released through the dissociation of inorganic compounds, they are named so because they will conduct an electrical current in a solution
|
|
|
When is a body in acid-base balance?
|
when the production of hydrogen ions in your body is precisely offset by their loss
|
|
|
What is the primary problem in acid-base balance?
|
preventing a reduction in pH because your body generates a variety of acids during normal metabolic operations
|
|
|
What role do the kidneys play in acid-base balance?
|
kidneys play a major role by secreting hydrogen ions into the urine and generating buffers that enter the bloodstream
|
|
|
Where does the secretion of hydrogen ions occurr during acid-base balance?
|
in the distal segments of the distal convoluted tubule (DCT_ and along the collecting system
|
|
|
How do the lungs play a role in acid-base balance?
|
the lungs play a key role through elimination of carbon dioxide
|
|
|
What is the distribution of water in the average male and female?
|
Average Male: 60% of total body weight
Average Female: 50% of total body weight |
|
|
What contributes to the difference between male and female % of water in body?
|
Females: proportionately larger mass of adipose tissue which consists of 10% water
Males: greater average muscle mass which consists of 75% water |
|
|
In both sexes, which contains more of the total body water, ICF or ECF?
|
ICF, intracellular fluid contains more of the total body water than does ECF, extracellular fluid
|
|
|
What are the largest subdivisions of ECF?
|
Interstitial fluid of peripheral tissues and the plasma of circulating blood.
|
|
|
What are minor components of the ECF?
|
lymph, cerebrospinal fluid (CSF), synovial fluid, serous fluids, aqueous humor, perilymph, and endolymph
|
|
|
Why is there a large variation in the ICF in the precise measurements of total body water?
|
Because of the differences in the intracellular water content of fat versus muscle
|
|
|
What is the estimate of total body water in the ICF vs EDF?
|
2/3 of the total body water is in the ICF and 1/3 is in the ECF
|
|
|
Describe the rate of exchange between ECF and ICF versus fluid movement of plasma, blood, or saline?
|
Exchange between ECF and ICF occurs more slowly than does the exchange of plasma and other interstitial fluids
|
|
|
Why are the ECF and ICF called fluid compartments?
|
because they commonly behave as distinct entities
|
|
|
What enables a cell to maintain internal environments with a composition different from that of it's surroundings?
|
The presence of cell membrane and active transport at the membrane surface
|
|
|
What are the principle ions in the ECF?
|
sodium, chloride, and bicarbonate
|
|
|
What are the principle ions in the ICF?
|
postassium, magnesium, phosphate ions and a large number of negatively charged proteins
|
|
|
Where does exchange among the subdivisions of the ECF primarily occur?
|
across the endothelial lining of capillaries
|
|
|
Why doesn't diffusion continue until ions are evenly distributed across the membrane?
|
because cell membranes are not freely permeable, they are selectively permeable. Ions can enter or leave the cell only via specific membrane channels.
|
|
|
Compare the osmotic concentration of ECF and ICF
|
They are identical
|
|
|
Why are the regulation of fluid balance and that of electrolyte balance tightly intertwined?
|
Because changes in solute concentration lead to immediate changes in water distribution
|
|
|
Why are plasma volume and osmotic concentration good indicators of the state of fluid balance and electrolyte balance?
|
Because fluid continuously circulates between interstitial fluid and plasma, and because exchange occurs between the ECF and the ICF
|
|
|
Describe how water moves in the body
|
Our cells cannot move water molecules by active transport. All movement of water across cell membranes and epithelia occurs passively, in response to osmotic gradients established by the active transport of specific ions, such as sodium and chrloride.
|
|
|
What does the phrase "water follows salt" mean?
|
when sodium and chloride ions (or other solutes) are actively transported across a membrane or epithelium, water follows by osmosis
|
|
|
What accounts for water absorption across the digestive system and water conservation in the kidneys?
|
The principle that when sodium chloride ions are actively transported across a membrane or epithelium, water follows by osmosis
|
|
|
Major physiological adjustments affecting fluid balance and electrolyte balance are mediated by what 3 hormones?
|
1. antidiuretic hormone (ADH)
2. aldosterone 3. natriuretic peptides (ANP & BNP) |
|
|
What monitors the osmotic concentration in the ECF?
|
Special cells known as the osmoreceptors located in the hypothalamus
|
|
|
What kind of change will the osmoreceptors react to?
|
a 2% change in osmotic concentration (approximately 6 mOsml)
|
|
|
Where are osmoreceptors located?
|
these neurons are located in the anterior hypothalamus and their axons release ADH near fenestrated capillaries in the posterior lobe of the pituitary gland
|
|
|
Describe the rate release of ADH
|
varies directly with the osmotic concentration: the higher osmotic concentration, the more ADH released
|
|
|
Describe 2 important effects of increased ADH release
|
1. Stimulates water conservation at the kidneys, reducing urinary water losses and concentrating the urine
2. Stimulates the thirst center, promoting the intake of fluids |
|
|
What plays a major role in determining the rate of absorption and loss along the distal convoluted tubule and collecting system of the kidneys?
|
the secretion of aldosterone by the adrenal cortex; the higher the plasma concentration of aldosterone, the more efficiently the kidneys conserve water.
|
|
|
What triggers aldosterone secretion?
|
it occurs in response to rising or falling levels in the blood that reach the adrenal cortex or in response to the activation of the renin-angiotensin system.
|
|
|
When does renin release occur?
|
In response to:
1. a drop in plasma volume or blood pressure at the juxtaglomerular apparatus of the nephron 2. a decline in filtrate osmotic concentration at the distal convoluted tubules of the kidneys, or 3. falling or rising concentrations in renal circulation |
|
|
Why are the natriuretic peptides ANP and BNP released by cardiac muscle cells?
|
in response to abnormal stretching of the heart walls, caused by elevated blood pressure or an increase in blood volume
|
|
|
What are other effects of natriuretic peptides?
|
they reduce thirst and block the release of ADH and aldosterone that might otherwise lead to the conservation of water and salt.
|
|
|
Diuresis
|
Fluid loss at the kidneys, lowers both blood pressure and plasma volume, eliminating the source of the stimulation.
|
|
|
Fluid shift
|
Water movement between EDF and ICF.
|
|
|
Why does fluid shift occur?
|
Occurs rapidly in response to to changes is the osmotic concentration of the ECF and reach equilibrium within minutes to hours.
|
|
|
What happens if the osmotic concentration of your ECF increases?
|
that fluid will become hypertonic with respect to your ICF. Water will then move from the cells into the ECF until the osmotic equilibrium is restored.
|
|
|
What happens if the osmotic concentration of your ECF decreases?
|
that fluid will become hypotonic with respect to your ICF. Water will then move from the ECF into the cells and the ICF volume will increase
|
|
|
Why does the ICF act as a water reserve?
|
Because the volume of the ICF is much greater than that of the ECF
|
|
|
Do large or small changes occurr in the ECF and ICF?
|
small changes occur in both
|
|
|
What will happen if the osmotic concentration of the ECF changes?
|
a fluid shift between the ICF and ECF will tend to oppose the change
|
|
|
What happens to the osmotic concentration of the ECF when your body loses water, but retains electrolytes?
|
The osmotic concentration of the ECF rises through osmosis moving water out of the ICF and into the ECF until both solutions are isotonic
|
|
|
Why does the change in volume of ECF after fluid exchange seem relatively small?
|
Because ICF has twice the funcitonal volume of ECF, making the net change relatively small
|
|
|
What conditions cause severe water losses?
|
Excessive perspiraiton, inadequate water consumption, repeated vomiting, diarrhea
|
|
|
What responses restore homeostasis during severe water losses?
|
ADH and renin secretion
|
|
|
What happens to the water and electrolyte content of your body when you drink a glass of pure water?
|
the water content of your body increases without a corresponding increase in electrolytes
|
|
|
What happens to ICF and ECF during a water gain?
|
ECF increases in volume but becomes hypotonic with respect to ICF. A fluid shift then occurs and the volume of the ICF increases at the expense of the ECF.
|
|
|
Why is electrolyte balance so important?
|
Because the total electrolyte concentrations directly affect the water balance.
|
|
|
What happens during abnormal concentrations of electrolytes?
|
It can have an affect on neuron activity and cardiac muscle tissue.
|
|
|
What is the dominant cation in the ECF?
|
Sodium
|
|
|
More than 90% of the osmotic concentration of the ECF results from the presence of what 2 sodium salts?
|
Sodium chloride (NaCl) and sodium bicarbonate
|
|
|
What are normal osmotic concentraitons of sodium in the ECF?
|
136 - 142 mEql
|
|
|
What is the dominant cation in the ICF?
|
Potassium
|
|
|
What are normal concentrations of potassium in the ECF?
|
Very low, from 3.8 - 5.0 mEql
|
|
|
What are 2 general rules about sodum and potassium balance?
|
1. The most common problems with electrolyte balance are caused by the imbalance between gains and losses of sodium ions.
2. Problems with potassium balance are less common, but significantly more dangerous than those related to sodium balance. |
|
|
How do sodium ions enter the ECF?
|
By crossing the digestive epithelium through diffusion and carrier-mediated transport
|
|
|
How is the rate of absorption of sodium entering the ECF determined?
|
The rate of absorption varies directly with the amount of sodium in the diet.
|
|
|
How do sodium loses primarily occur?
|
Sodium losses occur primarily by excretion in urine and through perspiration
|
|
|
What are the most important sites for regulation of sodium?
|
The kidneys
|
|
|
How much sodium does a person in sodium balance gain and lose each day?
|
A person in sodium balance typically gains and loses 48-122mEq (1.1-3.3 g) each day.
|
|
|
What happens to ECF when sodium gains exceed losses, and vice versa?
|
When sodium gains exceed sodium losses, the total content of ECF goes up; when losses exceed gains, the content declines
|
|
|
What happens to water in your body when sodium intake or output changes?
|
When sodium intake or output changes, a corresponsing gain or loss of water tends to keep the concentration oconstant.
|
|
|
Hoes a change in the content of ECF produce a change in the concentration?
|
No
|
|
|
What happens to plasma when you consume a large amount of sodium?
|
If large amounts of salt are consumed without adequate fluid, the plasma concentration will rise temporarily
|
|
|
How does change in ECF volume affect plasma and blood volume?
|
When the ECF volume changes, so does plasma volume and, in turn, blood volume. If the ECF volume rises, blood volume goes up; if the ECF volume drops, blood volume goes down.
|
|
|
What receptors are involved in blood pressure regulation?
|
Baroreceptors at the carotid sinus, the aortic sinus, and the right atrium. A rise in bllod volume elevates blood pressure.
|
|
|
What system is activated when the ECF volume is inadequate and the blood volume and blood pressure decline?
|
The renin-angiotensis system
|
|
|
What happens when the plasma volume becomes abnormally large?
|
Venous return increases, stretching the atrial and ventricular walls of the heart and stimulating the release of atriuric peptides (ANP and BNP)
|
|
|
What percent of potassium content is located in the ICF?
|
Roughly 98%
|
|
|
What represents the concentration of potassium in ECF at any moment?
|
1. the rate of entry across the digestive epithelium
2. the rate of loss into urine |
|
|
How is potassium loss regulated in urine?
|
by controlling the activities of ion pumps along the distal portions of the nephron and collecting system of the kidneys
|
|
|
What happens when a sodium ion is reabsorped from the tubular fluid?
|
it generally is exchanged for a cation in the peritubular fluid
|
|
|
How are potassium losses in urine determined?
|
Urinary losses are usually limited to the amount gained by apsorption across the digestive epithelium, typically 50-150 mEq per day
|
|
|
How are the concentrations of potassium in the ECF controlled?
|
The concentration of postassium in the ECF is controlled by adjustments in the rate of active secretion along the distal convoluted tubule and collecting system of the nephron
|
|
|
What are 3 factors influencing K+ secretion?
|
1. Changes in concentration of the ECF
2. Changes in pH 3. Aldosterone Levels |
|
|
What determines the rate of secretion of K+?
|
the higher extracellular concentration of potassium, the higher the rate of secretion
|
|
|
When the pH of ECF falls, so does the pH of _________
|
Peritubular fluid
|
|
|
What happens when pH of the ECF falls?
|
the rate of potassium secretion then declines, because hydrogen ions, rather than potassium ions, are secreted in exchange for sodium ions in tubular fluid
|
|
|
Why is the rate at which K+ ost in the urine strongly affected by aldosterone?
|
because the ion pumps that are sensitive to this hormone reabsorb from filtrate in exchange for peritubular fluid
|
|
|
What stimulates aldosterone secretion?
|
Aldosterone secretion is stimulated by angiotensin II as part of the regulation of blood volume. High plasma concentrations also stimulate aldosterone secretion.
|
|
|
How does the influence of aldosterone affect the amount of sodium and postassium?
|
the amount of sodium conserved and the amount of potassium excreted in urine under the influence of aldosterone are directly related.
|
|
|
What happens when the plasma concentration of postassium falls below 2mEq/l?
|
extensive muscular weakness develops followed by eventual paralysis. This condition is called hypo-kalemia
|
|
|
What are causes of Hypokalemia?
|
1. Inadequate dietary intake
2. the admission of diuretic drugs 3. excessive aldosterone secretion 4. increase in the pH of ECF |
|
|
What are treatments for hypokalemia?
|
increasing the dietary intake of potassium by salting foods with potassium salts or by taking potassium tablets
|
|
|
What causes hyperkalemia?
|
high concentrations of potassium in the ECF
|
|
|
When can a severe arrhythmia occur from high concentrations of potassium in ECF?
|
when the concentration exceeds 9 mEq/l
|
|
|
What are causes of hyperkalemia?
|
1. Renal failure
2. the administration of diuretic drugs that block reabsorption 3. a decline in the pH of the ECF |
|
|
What are treatments for hyperkalemia?
|
1. elevation of ECF volume with a solution low in Na++
2. stimulation of loss in urine by using appropriate diuretics 3. cautious administration of buffers (generally sodium bicarbonate) that can control the pH of the ECF 4. restriction of the dietary intake of k+ 5. administratino of enemas or laxatives which contain compounds such as kayexolate, that promote loss across digestive lining 6. kidney dialysis |
|
|
What is the most abundant mineral in the body?
|
Calcium
|
|
|
What is the typical amount of calcium in the body?
|
1-2 kg with 99% in the skeleton
|
|
|
Why is calcium important to the body?
|
In addition to forming the crystaline component of bone, calcium ions play key roles in the control of muscular and neural activities, in blood clotting, as cofactors for enzymatic reactions, and as second messengers
|
|
|
What determines calcium homeostasis?
|
an interplay between reserves in the bone, the rate of absorption across the digestive tract, and the rate of loss at the kidneys
|
|
|
What hormones regular calcium homeostasis in the ECF?
|
parathyhroud (PTH) & calcitriol raise concentrations, and calcitonin opposes these actions
|
|
|
When does hypercalcemia occur?
|
When the ECF is above 11 mEq/l
|
|
|
What is the primary cause of hypercalcemia in adults?
|
hyperparathyroidism, less common causes are cancers of breast, lung, kidney, and bone marrow.
|
|
|
When does a body develop hypocalcemia?
|
when concentration is under 4 mEq/l, much less common than hypercalcemia
|
|
|
What causes hypocalcemia?
|
hypoparathyroidism, vitamin D deficiency, or renal failure
|
|
|
What are the most abundant anions in the ECF?
|
Chloride ions
|
|
|
What kinds of ions are required for bone mineralization?
|
Phosphate ions
|
