Download Challenge Questions

1. You have access to a set of pigments that can be added to blood and a colorsensitive machine to measure these pigments within the body. If you injected red
pigment into the systemic circulation and yellow into the pulmonary circulation,
in which of the following organisms could the pigments mix to create an orange
signal?
a. Birds
b. Mammals
c. Amphibians
d. Crocodilians
The correct answer is c—
A. Answer a is incorrect. Birds have two ventricles and mixing does not occur.
The correct answer is c—
B. Answer b is incorrect. Mammals have two ventricles and mixing does not occur.
The correct answer is c—Amphibians
C. Answer c is correct. Amphibians have an incomplete separation between ventricles
such that blood from the respiratory system mixes with blood from the body.
The correct answer is c—
D. Answer d is incorrect. Crocodilians have complete separation of the ventricles and
therefore there is no overlap.
2. Advantages of a closed circulatory system include all of the following except—
a. separation of circulating and extracellular fluids
b. transport of oxygen
c. efficient delivery to specific areas of the body
d. increased body size and complexity
The correct answer is b—
A. Answer a is incorrect. Closed circulatory systems allow the separation of
circulatory and extracellular fluids.
The correct answer is b—transport of oxygen
B. Answer b is correct. Transport of oxygen (and nutrients) is not a difference
between open and closed systems, in fact, it is a shared function.
The correct answer is b—
C. Answer c is incorrect. Closed circulatory systems are more efficient at delivering
material to specific areas of the body.
The correct answer is b—
D. Answer d is incorrect. Increased body size and complexity is a benefit of having a
closed circulatory system.
4. Systole is vitally important to heart function and begins in the heart with the—
a. activation of the AV node
b. activation of the SA node
c. opening of the voltage-gated potassium gates
d. opening of the semilunar valves
The correct answer is b—
A. Answer a is incorrect. The AV node is not activated at the beginning of
contraction.
The correct answer is b—activation of the SA node
B. Answer b is correct. The SA node begins the cardiac contraction cycle.
The correct answer is b—
C. Answer c is incorrect. It is the influx of Na+ that begins the depolarization
generated by the SA node.
The correct answer is b—
D. Answer d is incorrect. Systole does not begin with the opening of the semilunar
valves; in fact, the valves open after systole has begun.
5. Which of the following is the correct sequence of events in the circulation of
blood?
a. Heartarteries  arteriolescapillaries  venules lymph  heart
b. Heartarteries  arteriolescapillaries  veins  venules  heart
c. Heartarteries  arteriolescapillaries  venules veins heart
d. Heart arterioles  arteries capillaries  venulesveinsheart
The correct answer is c—
A. Answer a is incorrect. The proper sequence of events during circulation of the
blood does not include the lymph.
The correct answer is c—
B. Answer b is incorrect. The proper sequence of events during circulation of the
blood does not involve veins.
The correct answer is c—Heartarteries  arteriolescapillaries  venules veins heart
C. Answer c is correct. The proper sequence of events during an action potential
begins with the rising phase, followed by the falling phase, and finally the
undershoot.
The correct answer is c—
D. Answer d is incorrect. The proper sequence of events during an action potential
begins with the rising phase, followed by the falling phase, and finally the
undershoot.
6. Which of the following statements is NOT true?
a. Only arteries carry oxygenated blood.
b. Both arteries and veins have a layer of smooth muscle.
c. Both arteries and veins branch out into capillary beds.
d. Precapillary sphincters regulate blood flow through capillaries.
The correct answer is a—Only arteries carry oxygenated blood.
A. Answer a is correct. In addition to arteries, which carry oxygenated blood, the
pulmonary vein brings oxygenated blood from the lungs to the heart. Therefore,
answer a is false.
The correct answer is a—
B. Answer b is incorrect. Both arteries and veins have the same tissue layers.
Remember, the question is asking which answer is false.
The correct answer is a—
C. Answer c is incorrect. Both arteries and veins branch out into capillary.
Remember, the question is asking which answer is false.
The correct answer is a—
D. Answer d is incorrect. Precapillary sphincters do open to increase blood flow
through capillary beds and close to decrease blood flow through capillary beds.
Remember, the question is asking which answer is false.
7. The lymphatic system is like the circulatory system in that they both—
a. have nodes that filter out pathogens
b. have a network of arteries
c. have capillaries
d. are closed systems
The correct answer is c—
A. Answer a is incorrect. Only the lymphatic system has nodes that filter out
pathogens.
The correct answer is c—
B. Answer b is incorrect. Although the lymphatic and circulatory systems pump
lymph and blood, respectively, the lymphatic system does not have arteries.
The correct answer is c—have capillaries
C. Answer c is correct. Both lymphatic and circulatory systems have capillaries.
The correct answer is c—
D. Answer d is incorrect. The lymphatic system is an open system.
8.
A molecule of CO2 that is generated in the cardiac muscle of the left ventricle
would NOT pass through which of the following structures before leaving the
body?
a. Right atrium
b. Left atrium
c. Right ventricle
d. Left ventricle
The correct answer is b—
A. Answer a is incorrect. This molecule of CO2 would pass through the left ventricle
and travel out to the tissues; return to the heart via the superior vena cava; enter
the heart through the right atrium; and finally, exit the heart through the
pulmonary vein on its way to lungs in order to leave the body.
The correct answer is b—Left atrium
B. Answer b is correct. This molecule of CO2 would pass through the left ventricle
and travel out to the tissues; return to the heart via the superior vena cava; enter
the heart through the right atrium; and finally, exit the heart through the
pulmonary vein on its way to lungs in order to leave the body.
The correct answer is b—
C. Answer c is incorrect. This molecule of CO2 would pass through the left ventricle
and travel out to the tissues; return to the heart via the superior vena cava; enter
the heart through the right atrium; and finally, exit the heart through the
pulmonary vein on its way to lungs in order to leave the body.
The correct answer is b—
D. Answer d is incorrect. This molecule of CO2 would pass through the left ventricle
and travel out to the tissues; return to the heart via the superior vena cava; enter
the heart through the right atrium; and finally, exit the heart through the
pulmonary vein on its way to lungs in order to leave the body.
9. In vertebrate hearts, atria contract from the top, and ventricles contract from the
bottom. How is this accomplished?
a. The depolarization from the sinoatrial node proceeds across the atria from
the top, and the depolarization from the atrioventricular node is carried to
the bottom of the ventricles before it emanates over the ventricular tissue.
b. The depolarization from the sinoatrial node is initiated from motor
neurons coming down from our brain, and the depolarization from the
atrioventricular node is initiated from motor neurons coming up from our
spinal cord.
c. Gravity carries the depolarization from the sinoatrial node down from the
top of the heart, and contraction of the diaphragm forces the depolarization
from the atrioventricular node to move from the bottom up.
d. This statement is false; both contract from the bottom.
The correct answer is a—The depolarization from the sinoatrial node proceeds across the
atria from the top, and the depolarization from the atrioventricular node is carried to the
bottom of the ventricles before it emanates over the ventricular tissue.
A. Answer a is correct. The heart contains specialized self-depolarizing cells that can
initiate depolarization without neuronal activation. These cells form the sinoatrial
node.
The correct answer is a—
B. Answer b is incorrect. Motor neurons do not initiate heart contraction. The heart
contains specialized self-depolarizing cells that can initiate depolarization without
neuronal activation.
The correct answer is a—
C. Answer c is correct. Gravity and the diaphragm are not involved in heart
contraction.
The correct answer is a—
D. Answer d is incorrect. Atria contract from the top, and ventricles contract from
the bottom.
10. When you take a deep breath, your stomach moves out because—
a. swallowing air increases the volume of the thoracic cavity
b. your stomach shouldn’t move out when you take a deep breath because
you want the volume of your chest cavity to increase, not your abdominal
cavity
c. contracting your abdominal muscles pushes your stomach out, generating
negative pressure in your lungs
d. when your diaphragm contracts, it moves down, pressing your abdominal
cavity out
The correct answer is d—
A. Answer a is incorrect. Swallowing air does not increase the volume of the thoracic
cavity. The diaphragm contracts as it moves down, increasing the volume of the
thoracic cavity and pressing the abdominal cavity out.
The correct answer is d—
B. Answer b is incorrect. The volume of the abdominal cavity is not increasing. The
diaphragm contracts as it moves down, increasing the volume of the thoracic
cavity and pressing the abdominal cavity out.
The correct answer is d—
C. Answer c is incorrect. Contraction of the diaphragm, not the abdominal muscles,
generates negative pressure.
The correct answer is d—when your diaphragm contracts, it moves down, pressing your
abdominal cavity out
D. Answer d is correct. This action result generates negative pressure, which enables
air to be taken up by the lungs.
11. If you hold your breath for a long time, body CO2 levels are likely to
____________, and the pH of body fluids is likely to _____________.
a. increase; increase
b. decrease; increase
c. increase; decrease
d. decrease; decrease
The correct answer is c—
A. Answer a is incorrect. Although CO2 would increase, the pH would decrease. As
CO2 levels rise, production of carbonic acid (H2CO3) increases. Carbonic acid
dissociates into HCO3- and H+, increasing blood H+ concentration and thereby
decreasing the pH of body fluids.
The correct answer is c—
B. Answer b is incorrect. Holding your breath would result in an accumulation, or
increase of CO2 levels. As CO2 levels rise, production of carbonic acid (H2CO3)
increases. Carbonic acid dissociates into HCO3- and H+, increasing blood H+
concentration and thereby decreasing the pH of body fluids.
The correct answer is c—increase; decrease
C. Answer c is correct. As CO2 levels rise, production of carbonic acid (H2CO3)
increases. Carbonic acid dissociates into HCO3- and H+, increasing blood H+
concentration and thereby decreasing the pH of body fluids.
The correct answer is c—
D. Answer d is incorrect. Holding your breath would result in an accumulation of
CO2. As CO2 levels rise, production of carbonic acid (H2CO3) increases. Carbonic
acid dissociates into HCO3- and H+, increasing blood H+ concentration and
thereby decreasing the pH of body fluids.
12. Which pairing of structure and function is incorrect?
a. Erythrocytes: oxygen transport
b. Platelets: blood clotting
c. Plasma: waste transport
d. All of the above are correct
The correct answer is d—
A. Answer a is incorrect. It is not the only correct answer.
The correct answer is d—
B. Answer b is incorrect. It is not the only correct answer.
The correct answer is d—
C. Answer c is incorrect. It is not the only correct answer.
The correct answer is d—All of the above are correct
D. Answer d is the correct answer. All of the pairings are correct.
13. Increased efficiency of gas exchange in vertebrates has been brought about by all
of the following mechanisms except—
a. cutaneous respiration
b. unidirectional air flow
c. cross-current blood flow
d. cartilaginous rings in the trachea
The correct answer is d—
A. Answer a is incorrect. Cutaneous respiration is an adaptation in amphibians and
aquatic reptiles that maximizes exchange efficiency by increasing surface area for
exchange.
The correct answer is d—
B. Answer b is incorrect. Unidirectional air flow is an adaptation in birds that
maximizes gas exchange efficiency by increasing the amount of exposure time
between air and lung.
The correct answer is d—
C. Answer c is incorrect. Cross-current blood flow is an adaptation in birds that
increases the efficiency of gas exchange by moving blood at right angles to the
lung.
The correct answer is d—cartilaginous rings in the trachea
D. Answer d is correct. Cartilage rings within the trachea keep it open during the
changes in pressure associated with breathing. However they do not serve a
mechanism that directly increases gas exchange efficiency.
14. Which of the following is the primary method by which carbon dioxide is
transported to the lungs?
a. Dissolved in plasma
b. Bound to hemoglobin
c. As carbon monoxide
d. As bicarbonate
The correct answer is d—
A. Answer a is incorrect. Although 8% of the carbon dioxide does travel to the lungs
dissolved in plasma, this is not the primary mode of transport.
The correct answer is d—
B. Answer b is incorrect. Although 20% of the carbon dioxide travels to the lung
bound to hemoglobin, this is not the primary mode of transport.
The correct answer is d—
C. Answer c is incorrect. Carbon monoxide is a poison that prevents hemoglobin
from picking up oxygen. It does not occur naturally in the body as part of cell
metabolism and is not a mode of transport for carbon dioxide.
The correct answer is d—As bicarbonate
D. Answer d is correct. About 72% of the carbon dioxide released by cells travels to
the lungs as bicarbonate. This is the primary means of transport for carbon
dioxide.
Challenge Questions
1. Dr. Hearthealth is so impressed with your knowledge of cardiovascular
physiology that he asks you to help with a particularly difficult case. He proceeds
to tell you that his patient has a prolonged PQ wave in their electrocardiogram
(ECG), which you know means that the delay between the atrial contraction and
ventricle contraction is too long. What heart structure is likely causing this
problem? Why?
Answer—The atrioventricular node provides the only pathway for the conduction of the
depolarization from the atria to the ventricles. If the atrioventricular node is not
functioning properly it may lead to an increased delay between the atrial contraction and
ventricle contraction.
2. Humans have a number of mechanisms that help to maintain blood pressure,
particularly when it falls too low. Explain how the kidney and the endocrine
systems help to maintain blood pressure.
Answer—Antidiuretic hormone (ADH) is secreted by the posterior pituitary but has its
target cells in the kidney. In response to the presence of ADH, the kidneys increase the
amount of water reabsorbed. This water eventually returns to the plasma where it causes
an increase in volume and subsequent increase in blood pressure. Another hormone,
aldosterone, also causes an increase in blood pressure by causing the kidney to retain
Na+, which sets up a concentration gradient that also pulls water back into the blood.
3.
Explain why a sparrow can fly above a mountain peak at a height of 6000 m, but a
mouse of similar size would expire from lack of oxygen.
Answer—Birds have a unidirectional flow of air, more similar to a set of tubes than the
mouse’s saclike lung. This allows for an increase in the exchange rate between air and
blood. In addition, birds also have cross-current flow, which allows for greater exchange
time between air and blood because the blood moves at right angles across the lungs.
These adaptations allow the bird to harvest sufficient amounts of oxygen even at very
high altitudes.
4.
Your roommate has just returned from a 5-km run. She is breathing rapidly and
sweating profusely. At the beginning of her run her body began using more
glucose and releasing more carbon dioxide than when she was at rest. How does
the body compensate for this increase in CO2 during exercise?
Answer—As the amount of CO2 increases, the chemoreceptors in her body register a
decrease in pH (CO2 is converted into H2CO3 in the blood). The change in pH will cause
an increase in ventilation rate, and her hemoglobin will release oxygen more readily.
Both of these mechanisms will ensure that she has enough oxygen to metabolize her
glucose stores effectively and that CO2 buildup does not cause damage within the body.