492 Chapter 14
- You are bicycling in a 100-mile benefit race because you
want to help the cause, but you didn’t count on such a hot,
humid day. You’ve gone through both water bottles and, in
the last 10 miles, you are thirsty again. Should you accept
the water that one bystander offers or the sports drink
offered by another? Explain your choice. - As the leader of a revolution to take over a large country,
you direct your followers to seize the salt mines. Why is this
important? When the revolution succeeds and you become
president, you ask your surgeon general to wage a health
campaign urging citizens to reduce their salt intake. Why? - Which type of exercise, isotonic contractions or isometric
contractions, puts more of a “strain” on the heart? Explain. - As described in chapter 8, functional magnetic resonance
imaging (fMRI) is based on the increased oxyhemoglobin
flowing to the more active brain regions. Explain the
physiological mechanisms that result in this effect when a
particular brain region becomes very active. - Suppose you feel the pulse of a person in circulatory shock,
and find that it is weak and rapid. You are also concerned
that the person has a very low urine output. Explain the
reasons for these observations. What treatments could be
given to raise the blood pressure? Explain. - Athletes often have a slower resting cardiac rate than the
average (a condition called athlete’s bradycardia ). What causes
the slower cardiac rate? What cardiovascular adaptations allow
the person to have athlete’s bradycardia and yet not have a
dangerously low blood pressure? What advantages might the
slower resting cardiac rate have for the athlete?
Test Your Quantitative Ability
Suppose an artery divides as it enters an organ into two branches
of equal radius. Use the equation for Poiseuille’s law (see p. 465
and fig. 14.15 ) to answer the following questions:- If branch A is twice the length of branch B, what is true
regarding the resistance in branch A compared to B? - If branch A now constricts to one-third its previous radius,
how does this affect the resistance in branch A? - Given that the pressure and viscosity of the blood are
constant, what will be true regarding the rate of blood flow
through branch A compared to branch B?
Refer to page 458 and figure 14.9 for information regarding the
calculation of Starling forces to answer the following questions,
given this information:
Hydrostatic pressure inside the capillary 5 34 mmHg
Colloid osmotic pressure of the blood plasma 5 27 mmHg
Hydrostatic pressure in the interstitial fluid 5 2 mmHg
Colloid osmotic pressure in the interstitial fluid 5 4 mmHg - What is the total pressure favoring filtration?
- What is the total pressure favoring absorption?
- What is the net effect of these forces on fluid movement
across the wall of the capillary?
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