Chapter 3: The Cellular Environment: Fluids and Electrolytes, Acids and Bases Flashcards
What is the normal serum magnesium level?
1.5 to 2.5 mEq/L (p. 122)
Why can severe hypomagnesemia lead to hypokalemia?
Because magnesium inhibits potassium channels. Without magnesium “guards” stationed outside of the potassium channels, too much potassium escapes out of the cell and is excreted by the kidneys. (p. 122)
What does excessive magnesium do?
Depresses skeletal muscle contraction and nerve function.
(p. 122)
What is the normal range of serum phosphate?
- 5 to 4.5 mg/dl
(p. 121 - 122)
What equation explains the relationships among pH, pK, and the ratio of bicarbonate to carbonic acid?
the Henderson-Hasselbalch equation
(p. 123)
What is the Henderson-Hasselbalch equation?
pH = pK + log [HCO3- / H2CO3]
The body’s pH balance is maintained within a narrow range by ____, ________, and _____ function.
renal, hormonal, and neural
(p. 103)
Changes in the composition of ____________ affect __________ __________ of excitatory cells and cause shifts of fluid from one compartment to another that can affect cell function.
Fluid fluctuations also affect blood volume and therefore _____ ________.
electrolytes
electrical potentials
blood pressure
(p. 103)
___ of TBW is intracellular.
___ of TBW is extracellular.
2 main ECF compartments are ____________ fluid and _____________ fluid.
2/3
1/3
interstitial, intravascular
(p. 104)
Other ECF compartments include _____ and the transcellular fluids :
(3 gross fluids):
(4 GI fluids):
(6 other fluids):
lymph
saliva, sweat, urine
intestinal, biliary, hepatic, pancreatic
cerebrospinal fluid, intraocular, pericardial, peritoneal, pleural, synovial
(p. 104)
What are the 4 forces which determine the exchange of fluid between the capillary and interstitial space?
capillary hydrostatic pressure
capillary (plasma) oncotic pressure
interstitial hydrostatic pressure
interstitial oncotic pressure
(p. 105)
What is capillary hydrostatic pressure?
The pressure which facilitates the outward movement of water from the capillary to the interstitial space.
(p. 105)
What is the capillary (plasma) oncotic pressure?
The pressure which osmotically attracts water from the interstitial space back into the capillary.
(p. 105)
What is interstitial hydrostatic pressure?
The pressure which facilitates the inward movement of water from the interstitial space into the capillary.
(p. 105)
What is interstitial oncotic pressure?
The pressure which osmotically attracts water from the capillary into the interstitial space.
(p. 105)
The movement of fluid back and forth across the capillary wall is called ___ __________ and is best described by the ________ __________.
net filtration
Starling hypothesis
The Starling hypothesis states that
net filtration = (forces ________ __________) - (forces ________ __________)
favoring filtration
opposing filtration
(p. 105)
Forces favoring filtration =
capillary hydrostatic pressure and interstitial oncotic pressure
(p. 105)
Forces opposing filtration =
capillary oncotic pressure and interstitial hydrostatic pressure
Edema is the excessive accumulation of fluid within the interstitial space. It is often a problem of fluid ____________ and does NOT necessarily indicate a fluid ______.
distribution
excess
(p. 105)
What are the 4 most common mechanisms which cause edema?
- increased capillary hydrostatic pressure
- decreased plasma oncotic pressure
- increased capillary membrane permeability
- lymphatic obstruction
(p. 105)
Increased capillary hydrostatic pressure can result from ______ obstruction or ______ and _____ retention. Venous obstruction causes hydrostatic pressure to increase behind the obstruction, pushing fluid from the capillaries into the interstitial spaces. Venous blood clots, hepatic obstruction, right heart failure, tight clothing around the extremities, and prolonged standing are common causes of venous obstruction.
venous
sodium and water
(p. 106)
What are three conditions associated with excessive sodium and water retention, which in turn cause volume overload, increased venous pressure, and edema?
right congestive heart failure, renal failure, and cirrhosis of the liver
(p. 106)
Decreased plasma oncotic pressure results from ____ or __________ __________ of plasma albumin.
Decreased synthesis of plasma proteins may occur with _____ _______ or _______ ____________.
Losses of plasma proteins occur with __________ diseases like _________ syndrome, __________, and ______ drainage from open wounds or burns.
loss or diminished production
liver disease or protein malnutrition
glomerular, nephrotic, hemorrhage, serous
(p. 107)
Increased capillary permeability is usually associated with ____________ and the ______ ________. These responses are often the result of trauma like burns or crush injuries, neoplastic disease, allergic reactions, or infection. Edema caused by this is often very severe because a loss of proteins from the vascular space both ________ capillary oncotic pressure, and _______ interstitial oncotic pressure.
inflammation and the immune response
increase
increase
Dependent edema accumulates in _______-__________ areas of the body. It occurs in the feet and legs when standing and the ______ ____ and ________ when supine.
gravity-dependent
sacral area and buttocks
(p. 107)
The accumulation of fluid increases the distance required for nutrients, oxygen, and wastes to move between capillaries and cells in the tissues. This increased tissue pressure diminishes capillary blood flow, leading to ________. Therefore, edema contributes to slow _____ _______, and formation of pressure sores.
ischemia
wound healing
(p. 107)
Sodium balance is mediated hormonally by ___________ and ___________ ________. Water balance is regulated primarily by ___ from the _________ _________.
aldosterone, natriuretic peptides
posterior pituitary
Sodium account for __% of the ECF cations. As the most abundant ECF cation, along with its constituent anions ________ and ___________, sodium regulates extracellular osmotic forces and therefore regulates water balance.
90%
chloride
bicarbonate
The average dietary intake of sodium ranges from _ to _ g/day. The minimal daily requirement of sodium is ___ mg.
5 to 6
500
(p. 108)
When circulating blood pressure and renal blood flow, or serum sodium concentrations are reduced, renin, an ______ secreted by _______________ cells of the kidney is released.
Renin stimulates the formation of ___________, an ________ __________.
enzyme
juxtaglomerular
angiotensin I, inactive polypeptide
How does angiotensin I get converted to angiotensin II?
Angiotensin-converting enzyme in pulmonary vessels converts angiotensin I to angiotensin II.
(p. 109)
What are the 2 major functions of angiotensin II?
It causes vasoconstriction, which elevates BP,
and stimulates secretion of aldosterone.
Aldosterone promotes ______ and _____ reabsorption by the _______ tubules of the kidneys, thus conserving sodium, blood volume, and blood pressure. Aldosterone also stimulates secretion (and therefore _________) of potassium by the distal tubule of the kidney, reducing potassium concentrations in the ECF. The restoration of sodium levels, blood volume, and renal perfusion then inhibits further release of renin.
sodium and water
proximal
excretion
What are the 3 natriuretic peptides?
atrial natriuretic peptide
brain natriuretic peptide
urodilatin
The natriuretic peptides are natural antagonists to the…
…renin-angiotensin-aldosterone system.
(p. 109)
Chloride transport is generally passive and follows the ______ _________ of sodium, so that increases or decreases in chloride are proportional to changes in sodium. Chloride concentration tends to vary _________ with changes in the concentration of bicarbonate.
active transport
inversely
(p. 109)
What are baroreceptors?
Stretch receptors that are sensitive to changes in arterial volume and pressure.
(p. 109)
Baroreceptors can also stimulate the release of ADH by signaling the ____________ when atrial and arterial pressure drops.
hypothalamus
(p. 109)
One manner by which water balance is regulated is through the perception of thirst. Thirst is a sensation that stimulates water-drinking behavior. Thirst is experienced when water loss equals _% of an individual’s body weight or when there is an increase in osmolality. Dry mouth, hyperosmolality, and plasma volume depletion active hypothalamic _____________.
2%
osmoreceptors
(p. 109)
Water balance is also directly regulated by antidiuretic hormone (aka ________-___________), which is secreted when plasma osmolality increases or circulating blood volume decreases and blood pressure drops. Increased plasma osmolality occurs with a _____ _______ or sodium excess in relation to water. The increased osmolality stimulates hypothalamic osmoreceptors. In addition to causing thirst, the stimulated osmoreceptors signal the posterior pituitary to release ADH.
arginine-vasopressin
water deficit
The action of ADH is to increase the permeability of _____ _______ cells to water, increasing water reabsorption and promoting the restoration of plasma volume and blood pressure. Urine concentration _________, and the reabsorbed water decreases plasma osmolality, returning it toward normal.
renal tubular
increases
Like most hormones, ADH is regulated by a ________ _________. The restoration of plasma osmolality, blood volume, and blood pressure then inhibits ADH secretion.
feedback mechanism
(p. 109)
