Chapter 15 concept questions Flashcards
Would you expect to find valves in the veins leading from the brain to the heart? Defend your answer.
Veins from the brain do not require valves because blood flow is aided by gravity.
If you check the pulse in a person’s carotid artery and left wrist at the same time, would the pressure waves occur simultaneously? Explain.
The carotid wave would arrive slightly ahead of the wrist wave because the distance from heart to carotid artery is shorter.
Who has the higher pulse pressure, someone with blood pressure of 90/60 or someone with blood pressure of 130/95?
Pressure of 130/95 has the higher pulse pressure (35 mm Hg).
If heart rate increases, the relative time spent in diastole decreases. In that case, the contribution of systolic pressure to mean arterial pressure increases, and MAP increases.
If heart rate increases, the relative time spent in diastole decreases. In that case, the contribution of systolic pressure to mean arterial pressure increases, and MAP increases.
Peter’s systolic pressure is 112 mm Hg, and his diastolic pressure is 68 mm Hg (written 112/68). What is his pulse pressure? His mean arterial pressure?
Pulse pressure is 112−68=44 mm Hg.
MAP is 68+1/3(44)≈ 83 mm Hg.
Resistance to blood flow is determined primarily by which? (a) blood viscosity, (b) blood volume, (c) cardiac output, (d) blood vessel diameter, or (e) blood pressure gradient.
d
The extracellular fluid concentration of K+ increases in exercising skeletal muscles. What effect does this increase in K+ have on blood flow in the muscles?
Extracellular K+ dilates arterioles, which increases blood flow (see Tbl. 15.2).
What happens when epinephrine combines with beta1- receptors in the heart? With beta-2 receptors in the heart? (Hint: “in the heart” is vague. The heart has multiple tissue types. Which heart tissues possess the different types of beta-receptors.
Epinephrine binding to myocardial beta 1 receptors increases heart rate and force of contraction. Epinephrine binding to beta-2 receptors on heart arterioles causes vasodilation.
Skeletal muscle arterioles have both
alpha and beta receptors on their smooth muscle. Epinephrine can bind to both. Will these arterioles constrict or dilate in response to epinephrine? Explain.
alpha-receptors have a lower affinity for epinephrine than beta-2 receptors so the beta-2 receptors dominate and arterioles dilate.
Use Fig. 15.12 to answer these questions. (a) Which tissue has the highest blood flow per unit weight? (b) Which tissue has the least blood flow, regardless of weight?
(a) The kidney has the highest blood flow per unit weight. (b) The heart has the lowest total blood flow.
Baroreceptors have stretch-sensitive ion channels in their cell membrane. Increased pressure stretches the receptor cell membrane, opens the channels, and initiates action potentials. What ion probably flows through these channels and in which direction (into or out of the cell)?
The most likely ion is Na+ moving into the receptor cell.
Use the map in Fig. 15.14b to map the reflex response to orthostatic hypotension.
This map should look exactly like Fig. 15.14b except that the directions of the arrows are reversed.
In the classic movie Jurassic Park, Dr. Ian Malcolm must flee from the T. rex. Draw a reflex map showing the cardiovascular response to his fight-or-flight situation. Remember that fight-or-flight causes epinephrine secretion as well as output from the cardiovascular control center. (Hints: What is the stimulus? Fear is integrated in the limbic system.)
Stimulus: sight, sound, and smell of the T. rex. Receptors: eyes, ears, and nose. Integrating center: cerebral cortex, with descending pathways through the limbic system. Divergent pathways go to the cardiovascular control center, which increases sympathetic output to the heart and arterioles. A second descending spinal pathway goes to the adrenal medulla, which releases epinephrine. Epinephrine on Beta2-receptors of liver, heart, and skeletal muscle arterioles causes vasodilation of those arterioles. Norepinephrine onto alpha receptors in other arterioles causes vasoconstriction. Both catecholamines increase heart rate and force of contraction.
A man with liver disease loses the ability to synthesize plasma proteins. What happens to the colloid osmotic pressure of his blood? What happens to the balance between filtration and absorption in his capillaries?
Loss of plasma proteins will decrease colloid osmotic pressure. As a result, hydrostatic pressure will have a greater effect in the filtration-absorption balance, and filtration will increase.
Why did this discussion refer to the colloid osmotic pressure of the plasma rather than the osmolarity of the plasma?
Using osmotic pressure rather than osmolarity allows a direct comparison between absorption pressure and filtration pressure, both of which are expressed in mm Hg.
