A&P Exam 3 Fluid Balance

Intracellular compartment

AKA cytosol found in between the cells. Not limited to the area below the head but is present everywhere in body including the head.

Extracellular compartment

Fluid exterior to cells; includes the interstitial fluid, blood plasma, lymph.

Transcellular fluids

Specialized fluids found in specific compartments of the body. Cerebrospinal fluid synovial fluid (joints), aqueous humor (in the eye), and peri lymph (within the ear).

Excretion

Eliminating waste products. Urine production and feces.

Evaporation

Sweating and breathing

Water is distributed in the body through two compartments which are

Intracellular (inside cells) and extracellular (outside cells). The intracellular compartment contains 63% of the body’s water and the extracellular compartment includes interstitial fluid, plasma, lymph, and transcellular fluid which is about 37 %.

Dehydration

Increased thirst, ADH release, aldosterone release, reduced urine output.

Hyponatremia

A condition where the sodium level in the blood are abnormally low. Diuretic use and excessive intake of water.

Electrolytes

Bicarbonate and phosphate buffering systems; they neutralize excess acids or bases

pH

Measures the concentration of H+

sources of H+ ions

Acids when dissolved in water release hydrogen ions

Chemical buffering systems

Excreting H+ ions and reabsorbing bicarbonate.

Physiological buffering systems

Buffering system that helps maintain a stable pH in bodily fluids by absorbing or releasing hydrogen ions.

Bicarbonate buffering systems

Phosphate buffering systems

Uses sodium dihydrogen phosphate and sodium hydrogen phosphate to neutralize strong acids and bases.

Protein buffering systems

Respiratory excretion (role in pH)

When you exhale carbon dioxide, the blood pH increases because carbonic acid is very acidic so when you get rid of it, the blood is basic.

Renal excretion (role in pH)

Glomerular filtration

How is water distributed in the body?

Intracellular fluid and extracellular fluid

What are some examples of transcellular fluids?

Cerebrospinal fluid, synovial fluid, aqueous humor, peri lymph, pleural fluid.

What are two sources from which the body derives water? Which of these contributes the most to the body’s total water budget?

Ingested fluids such as drinking water and metabolic water (during cellular respiration). Ingested fluids are more significant as they contribute the most to the body’s total water budget.

What are the two ways the body loses water through excretion?

Urination and defecation

What are two ways the body loses water through evaporation?

Sweating and evaporation (perspiration and respiratory water loss)

What are the four water conservation mechanisms initiated by dehydration? Explain how each helps conserve water

Increased thirst, ADH, Aldosterone secretion, reduced urination, increased sodium reabsorption.

What are the three most important electrolytes in the body?

Sodium, potassium, and calcium. NA and K are regulated by aldosterone and calcium is regulated by parathyroid hormone and calcitonin

How does a chemical buffering system work?

By neutralizing excess acids or bases to maintain stable pH levels. For example, the bicarbonate ions (HCO3-) reacts with excess hydrogen ions (H+) to form carbonic acid(H2CO3), which can dissociate to release H+ when needed. A shift in pH can affect the buffering capacity. So, if pH decreases (becomes more acidic), the buffer can absorb H+ ions to stabilize pH.

How can respiratory excretion of CO2 help raise blood pH?

Helps raise blood pH by reducing carbonic acid levels in the blood. (carbonic acid is very acidic, it is the form when carbon dioxide is dissolved in water). When CO2 is exhaled, it decreases the concentration of carbonic acid (H2CO3), leading to a rise in pH (making the blood less acidic).

How do the kidneys regulate blood pH?

By excreting hydrogen ions (H+) and reabsorbing bicarbonate (HCO3-). When blood pH is low, the kidneys excrete more H+ and retain bicarbonate, which helps to increase pH. Conversely, when blood pH is high, the kidneys can excrete bicarbonate to lower pH.

Compare the speed of action of chemical versus physiological buffering systems

Chemical buffers act instantly while physiological buffers take hours to days to effect pH change.

What happens when the pH rises?

If the pH rises, the body will remove hydrogen ions by shifting the equilibrium to the right, leading to the dissociation of carbonic acid and the production of bicarbonate. Conversely, if the pH falls, the equilibrium shifts to the left, favoring the formation of carbonic acid. 

Where is most of the water in the human body found?

In the intracellular compartment

Which of the following is NOT considered a transcellular fluid?

Synovial fluid

Aqueous humor of the eye

Plasma

Serous fluid

Plasma

The main excretory mechanism by which the body sheds water is

Urination

Which of the following conservation measures will reduce respiratory evaporative loss of water?

increasing perspiration

hyperventilation

ceasing urine formation

ceasing perspiration

hyperventilation

What electrolyte is regulated by aldosterone?

Potassium

What is the correct definition of pH?

The inverse log of hydrogen ion concentration -log(H+)

Which of the following buffer system will be the slowest?

Respiratory excretion buffer

Protein buffer

Phosphate buffer

Bicarbonate buffer

Respiratory excretion buffer

Consider the bicarbonate buffer system. A rise in pH will favor

The dissolution of bicarbonate

The formation of carbon dioxide

The formation of carbonic acid

The dissociation of carbonic acid

The dissociation of carbonic acid

What is the best explanation for how respiratory excretion modulates pH?

The removal of CO2 from the blood eliminates the source of carbonic acid

Which of the following is an example of a physiological buffering system?

Phosphate buffer

Bicarbonate buffer

Protein buffer

Renal excretion

Renal excretion

What happens when the pH falls?

When the pH decreases, there is an increase in H+. The bicarbonate reacts with the excess H+ ions to form carbonic acid (H2CO3). This process helps to maintain a stable pH by preventing a drastic drop in pH, which could be harmful to the body.

How does the body maintain pH?

carbonic acid and bicarbonate

Look at the bicarbonate buffer system. If pH is rising, will that favor the formation or dissociation of carbonic acid?

Dissociation of carbonic acid to release Hydrogen ions to lower the pH.

If pH is falling, will formation or dissociation of carbonic acid be favored?

When the pH decreases (meaning more H+), the equilibrium shifts to the left, favoring the formation of carbonic acid.

Buffering:

The bicarbonate/carbonic acid system acts as a buffer, meaning it helps to resist changes in pH. When pH drops, the system absorbs excess H⁺ ions by forming carbonic acid, thus preventing a drastic drop in pH.