Chapter 3: The Cellular Environment: Fluids and Electrolytes, Acids and Bases

Question 1

What is the normal serum magnesium level?

Answer 1

1.5 to 2.5 mEq/L (p. 122)

Question 2

Why can severe hypomagnesemia lead to hypokalemia?

Answer 2

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)

Question 3

What does excessive magnesium do?

Answer 3

Depresses skeletal muscle contraction and nerve function.

(p. 122)

Question 4

What is the normal range of serum phosphate?

Answer 4

2. 5 to 4.5 mg/dl
   (p. 121 - 122)

Question 5

What equation explains the relationships among pH, pK, and the ratio of bicarbonate to carbonic acid?

Answer 5

the Henderson-Hasselbalch equation

(p. 123)

Question 6

What is the Henderson-Hasselbalch equation?

Answer 6

pH = pK + log [HCO₃^- / H₂CO₃]

Question 7

The body’s pH balance is maintained within a narrow range by ____, ________, and _____ function.

Answer 7

renal, hormonal, and neural

(p. 103)

Question 8

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 _____ ________.

Answer 8

electrolytes

electrical potentials

blood pressure

(p. 103)

Question 9

___ of TBW is intracellular.

___ of TBW is extracellular.

2 main ECF compartments are ____________ fluid and _____________ fluid.

Answer 9

2/3

1/3

interstitial, intravascular

(p. 104)

Question 10

Other ECF compartments include _____ and the transcellular fluids :

(3 gross fluids):

(4 GI fluids):

(6 other fluids):

Answer 10

lymph

saliva, sweat, urine

intestinal, biliary, hepatic, pancreatic

cerebrospinal fluid, intraocular, pericardial, peritoneal, pleural, synovial

(p. 104)

Question 11

What are the 4 forces which determine the exchange of fluid between the capillary and interstitial space?

Answer 11

capillary hydrostatic pressure

capillary (plasma) oncotic pressure

interstitial hydrostatic pressure

interstitial oncotic pressure

(p. 105)

Question 12

What is capillary hydrostatic pressure?

Answer 12

The pressure which facilitates the outward movement of water from the capillary to the interstitial space.

(p. 105)

Question 13

What is the capillary (plasma) oncotic pressure?

Answer 13

The pressure which osmotically attracts water from the interstitial space back into the capillary.

(p. 105)

Question 14

What is interstitial hydrostatic pressure?

Answer 14

The pressure which facilitates the inward movement of water from the interstitial space into the capillary.

(p. 105)

Question 15

What is interstitial oncotic pressure?

Answer 15

The pressure which osmotically attracts water from the capillary into the interstitial space.

(p. 105)

Question 16

The movement of fluid back and forth across the capillary wall is called ___ __________ and is best described by the ________ __________.

Answer 16

net filtration

Starling hypothesis

Question 17

The Starling hypothesis states that

net filtration = (forces ________ __________) - (forces ________ __________)

Answer 17

favoring filtration

opposing filtration

(p. 105)

Question 18

Forces favoring filtration =

Answer 18

capillary hydrostatic pressure and interstitial oncotic pressure

(p. 105)

Question 19

Forces opposing filtration =

Answer 19

capillary oncotic pressure and interstitial hydrostatic pressure

Question 20

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 ______.

Answer 20

distribution

excess

(p. 105)

Question 21

What are the 4 most common mechanisms which cause edema?

Answer 21

1. increased capillary hydrostatic pressure
2. decreased plasma oncotic pressure
3. increased capillary membrane permeability
4. lymphatic obstruction
   (p. 105)

Question 22

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.

Answer 22

venous

sodium and water

(p. 106)

Question 23

What are three conditions associated with excessive sodium and water retention, which in turn cause volume overload, increased venous pressure, and edema?

Answer 23

right congestive heart failure, renal failure, and cirrhosis of the liver

(p. 106)

Question 24

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.

Answer 24

loss or diminished production

liver disease or protein malnutrition

glomerular, nephrotic, hemorrhage, serous

(p. 107)

Question 25

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.

Answer 25

inflammation and the immune response

increase

increase

Question 26

Dependent edema accumulates in _______-__________ areas of the body. It occurs in the feet and legs when standing and the ______ ____ and ________ when supine.

Answer 26

gravity-dependent

sacral area and buttocks

(p. 107)

Question 27

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.

Answer 27

ischemia

wound healing

(p. 107)

Question 28

Sodium balance is mediated hormonally by ___________ and ___________ ________. Water balance is regulated primarily by ___ from the _________ _________.

Answer 28

aldosterone, natriuretic peptides

posterior pituitary

Question 29

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.

Answer 29

90%

chloride

bicarbonate

Question 30

The average dietary intake of sodium ranges from _ to _ g/day. The minimal daily requirement of sodium is ___ mg.

Answer 30

5 to 6

500

(p. 108)

Question 31

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 ________ __________.

Answer 31

enzyme

juxtaglomerular

angiotensin I, inactive polypeptide

Question 32

How does angiotensin I get converted to angiotensin II?

Answer 32

Angiotensin-converting enzyme in pulmonary vessels converts angiotensin I to angiotensin II.

(p. 109)

Question 33

What are the 2 major functions of angiotensin II?

Answer 33

It causes vasoconstriction, which elevates BP,

and stimulates secretion of aldosterone.

Question 34

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.

Answer 34

sodium and water

proximal

excretion

Question 35

What are the 3 natriuretic peptides?

Answer 35

atrial natriuretic peptide

brain natriuretic peptide

urodilatin

Question 36

The natriuretic peptides are natural antagonists to the…

Answer 36

…renin-angiotensin-aldosterone system.

(p. 109)

Question 37

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.

Answer 37

active transport

inversely

(p. 109)

Question 38

What are baroreceptors?

Answer 38

Stretch receptors that are sensitive to changes in arterial volume and pressure.

(p. 109)

Question 39

Baroreceptors can also stimulate the release of ADH by signaling the ____________ when atrial and arterial pressure drops.

Answer 39

hypothalamus

(p. 109)

Question 40

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 _____________.

Answer 40

2%

osmoreceptors

(p. 109)

Question 41

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.

Answer 41

arginine-vasopressin

water deficit

Question 42

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.

Answer 42

renal tubular

increases

Question 43

Like most hormones, ADH is regulated by a ________ _________. The restoration of plasma osmolality, blood volume, and blood pressure then inhibits ADH secretion.

Answer 43

feedback mechanism

(p. 109)