Chapter 6

Chapter 6. Renal Physiology and Acid-Base Balance

A 67-year-old woman involved in a motor vehicle accident lost 1 L of blood because of an open fracture of her left femur. Paramedics were able to prevent further bleeding. What changes to her intracellular fluid (ICF) and extracellular fluid (ECF) volumes would be observed 15 minutes after this blood loss?

A ECF volume smaller; ICF volume unchanged

B ECF volume smaller; ICF volume smaller

C ECF volume unchanged; ICF volume unchanged

D ECF volume unchanged; ICF volume smaller

A. Acute blood loss is an example of isosmotic volume contraction. Volume loss is from the ECF. No change in ECF osmolarity occurs; therefore no fluid movement between the ECF and ICF occurs.

The following pressure measurements were obtained from within the glomerulus of an experimental animal:

• Glomerular capillary hydrostatic pressure = 50 mm Hg

• Glomerular capillary oncotic pressure = 26 mm Hg

• Bowman's space hydrostatic pressure = 8 mm Hg

• Bowman's space oncotic pressure = 0 mm Hg

Calculate the glomerular net ultrafiltration pressure (positive pressure favors filtration; negative pressure opposes filtration).

A +16 mm Hg

B +68 mm Hg

C +84 mm Hg

D 0 mm Hg

E −16 mm Hg

F −68 mm Hg

G −84 mm Hg

A. Using Equation 6-3 (in the text): PUF = PGC – (πGC + PGC). PUF = 50 – (26 + 8) = +16 mm Hg (favoring filtration).

A novel drug aimed at treating heart failure was tested in experimental animals. The drug was rejected for testing in humans because it caused an unacceptable decrease in the glomerular filtration rate (GFR). Further analysis showed that the drug caused no change in mean arterial blood pressure but renal blood flow (RBF) was increased. The filtration fraction was decreased. What mechanism is most likely to explain the observed decrease in GFR?

A Afferent arteriole constriction

B Afferent arteriole dilation

C Efferent arteriole constriction

D Efferent arteriole dilation

D. An increase in RBF without an increase in blood pressure indicates a decrease in renal vascular resistance. Dilation of the efferent ...

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