Test Your Ability to Analyze and Apply Your Knowledge

1. Mannitol is a sugar that does not pass through the walls of blood capillaries in the brain (does not cross the "blood-brain barrier," as described in chapter 7). It also does not cross the walls of kidney tubules, the structures that transport blood filtrate to become urine (see chapter 17). Explain why mannitol can be described as osmotically active. How might its clinical administration help to prevent swelling of the brain in head trauma? Also, explain the effect it might have on the water content of urine.

Discuss carrier-mediated transport. How could you experimentally distinguish between the different types of carrier-mediated transport? Remembering the effect of cyanide (described in chapter 5), explain how you might determine the extent to which the Na+/K+ pumps contribute to the resting membrane potential. Using a measurement of the resting membrane potential as your guide, how could you experimentally determine the relative permeability of the plasma membrane to Na+ and K+?

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Essentials of Human Physiology

Essentials of Human Physiology

This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.

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  • marigold
    How can mannitol be described as osmotically active?
    8 years ago

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