Life: The Science of Biology

David Sadava, David M. Hills, H. Craig Heller

Chapter 50

Circulatory Systems - all with Video Answers

Educators

Chapter Questions

Problem 1

Which statement about vertebrate circulatory systems is not true?
a. In fish, oxygenated blood from the gills returns to the heart through the left atrium.
b. In mammals, deoxygenated blood leaves the heart through the pulmonary artery.
c. In amphibians, deoxygenated blood enters the heart through the right atrium.
d. In reptiles, the blood in the pulmonary artery has a lower oxygen content than the blood in the aorta.
e. In birds, the pressure in the aorta is higher than the pressure in the pulmonary artery.

Zachary Papazian

Zachary Papazian

Numerade Educator

Problem 2

Which statement about the human heart is true?
a. The walls of the right ventricle are thicker than the walls of the left ventricle
b. Blood flowing through atrioventricular valves is always deoxygenated blood.
c. The second heart sound is due to the closing of the aortic valve
d. Blood returns to the heart from the lungs in the vena cava.
e. During systole, the aortic valve is open and the pulmonary valve is closed

Zachary Papazian

Zachary Papazian

Numerade Educator

Problem 3

The pacemaker action potentials in the heart
a. are due to opposing actions of norepinephrine and acetylcholine.
b. are generated by the bundle of His.
c. depend on the gap junctions between the cells that make up the atria and those that make up the ventricles.
d. are due to spontaneous depolarization of the plasma membranes of modified cardiac muscle cells.
e. reflect large depolarizations of membrane potential due to opening of voltage-gated $\mathrm{Na}^{+}$ channels.

Zachary Papazian

Zachary Papazian

Numerade Educator

Problem 4

Blood velocity through capillaries is slow because
a. much blood volume is lost from the capillaries.
b. the pressure in venules is high.
c. the total cross-sectional area of capillaries is larger than that of arterioles.
d. the osmotic pressure in capillaries is very high.
e. erythrocytes must pass through in single file.

Zachary Papazian

Zachary Papazian

Numerade Educator

Problem 5

Autoregulation of blood flow to a tissue is due to
a. sympathetic innervation.
b. the release of ADH by the hypothalamus.
c. increased activity of baroreceptors.
d. chemoreceptors in the aorta and the carotid arteries.
e. the effect of the local chemical environment on arterioles.

Zachary Papazian

Zachary Papazian

Numerade Educator

Problem 6

At the beginning of a race, cardiac output increases immediately before there is any change in blood $\mathrm{O}_{2}$ or $\mathrm{CO}_{2}$ concentrations. Explain two factors that contribute to this effect. Include the Frank-Starling law in your answer.

Zachary Papazian

Zachary Papazian

Numerade Educator

Problem 7

Is there a time in the mammalian cardiac cycle when all four heart valves are open? Explain.

Zachary Papazian

Zachary Papazian

Numerade Educator

Problem 8

A sudden and massive loss of blood results in a decrease in blood pressure. Describe several mechanisms that help return blood pressure to normal and how they do so.

Zachary Papazian

Zachary Papazian

Numerade Educator

Problem 9

The hearts of most mammals stop beating when their temperature falls more than a few degrees below $20^{\circ} \mathrm{C}$, but the hearts of hibernating mammals can beat at $0^{\circ} \mathrm{C}$. What adaptations of cardiac muscle might explain this capacity of the hearts of hibernators?

Zachary Papazian

Zachary Papazian

Numerade Educator

Problem 10

You can describe the cycle of events in a ventricle of the heart by a graph that plots the pressure in the ventricle on the $y$ axis and the volume of blood in the ventricle on the $x$ axis. Draw such a graph for a left ventricle using maximum and minimum pressures of 125 and $25 \mathrm{mm} \mathrm{Hg}$ and maximum and minimum ventricular volumes of 130 and 60 ml. Where would the heart sounds be on this graph? How would the graph differ for the left and the right ventricles?

Eric Goldman

Numerade Educator