Calculate the partial pressure of oxygen at an atmospheric pressure of 500 mm Hg.
answer
105 mmHg. This value was determined by multiplying the atmospheric pressure, 500 mm Hg, by 0.21, the fraction of air that is O2.
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Where would oxygen partial pressure be the highest?
answer
Mountain stream. Cold water and heavy mixing creates conditions with high oxygen.
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Which of the following aquatic habitats has the highest oxygen content per unit area?
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A shallow river fed by a waterfall. Waterfalls are highly oxygenated aquatic environments because of the exposure of the water to air and the incorporation of air bubbles. Also, shallow streams tend to be better oxygenated than deep one
question
Voice sounds are produced by the _____.
answer
Larynx
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The primary functions of the _____ are to warm, filter, and humidify air.
answer
Nasal cavity
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Which feature is common to gills, lungs, and tracheae?
answer
Large surface area
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Air moves in and out of the tracheal system of an exercising insect by ______.
answer
ventilation of the tracheae due to contraction of muscles around the tracheae. The muscles compress and dilate the tracheae, producing pressure changes in gases.
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Which of the following is an accurate comparison of vertebrate lungs?
answer
Mammals have more alveolar surface area than frogs.
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Most carbon dioxide is carried from the body tissues to the lungs _____.
answer
as bicarbonate ions (HCO3 -). Most carbon dioxide released from body tissues combines with water to form carbonic acid, which then breaks up into hydrogen and bicarbonate ions.
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By picking up hydrogen ions, hemoglobin prevents the blood from becoming too _____.
answer
acidic. If not carried by hemoglobin, hydrogen ions would reduce the pH, or increase the acidity, of the blood.
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In the blood most of the oxygen that will be used in cellular respiration is carried from the lungs to the body tissues _____.
answer
Combined with hemoglobin.
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A shift to the right of the oxygen-hemoglobin equilibrium curve represents _____.
answer
increased oxygen delivery to a tissue. A shift to the right—representing a pH decrease—makes hemoglobin more likely to release oxygen to tissues with low pH.
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The majority of carbon dioxide is carried in blood as _____.
answer
Bicarbonate dissolved in plasma.
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Blood returns to the heart via the _____.
answer
Pulmonary veins
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From the pulmonary veins, blood flows to the _____.
answer
Left atrium
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From the anterior vena cava, blood flows to the _____.
answer
Right atrium
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From the capillaries of the abdominal organs and hind limbs, blood flows to the _____.
answer
Posterior vena cava
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Which of the following does NOT correctly represent blood flow through the heart?
answer
From the right ventricle to the left ventricle
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Which of the following is most likely to be found in a terrestrial animal with high activity rates?
answer
A four-chambered heart
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A blood vessel that takes blood to the heart is a(n) _____.
answer
Vein
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Which of the following animals has a three-chambered heart?
answer
frog
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Which of the following occurs in response to a drop in blood pressure?
answer
Veins constrict. This constriction shifts blood volume toward the heart and arteries, maintaining blood flow to vital organs.
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Which of the following respiratory systems is NOT closely associated with the blood supply?
answer
The tracheal system of an insect
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Circulatory systems compensate for _____.
answer
the slow rate at which diffusion occurs over large distances
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Air-breathing insects carry out gas exchange _____.
answer
Across the finest branches of trachea and cell membranes
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Hemoglobin and hemocyanin _____.
answer
Both transport oxygen
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Most of the carbon dioxide produced by humans is _____.
answer
Converted to bicarbonate ions by an enzyme in red blood cells
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When you hold your breath, which of the following blood gas changes first leads to the urge to breathe?
answer
Rising carbon dioxide
question
The only vertebrates in which blood flows directly from respiratory organs to body tissues without first returning to the heart are the _____.
answer
fish
question
Which of the following is the correct sequence of blood flow in birds and mammals?
answer
vena cava → right atrium → right ventricle → pulmonary artery
question
A rabbit taken from a meadow near sea level and moved to a meadow high on a mountainside would have some trouble breathing. Why?
answer
The partial pressure of oxygen in the air at high elevations is lower than at sea level
question
If other factors are equal, which of the following environments would have the highest level of dissolved oxygen?
answer
Cool freshwater at a low elevation
question
Countercurrent exchange in the fish gill helps to maximize _____.
answer
diffusion
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True or false? The lungs of humans form from the embryonic foregut.
answer
True. Digestive organs such as the stomach and part of the small intestine also develop from the foregut.
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True or false? The pressure inside the human chest cavity is always positive, so the lungs stay relatively inflated even upon exhalation.
answer
False. The lungs stay relatively inflated even upon exhalation because the pressure inside the chest cavity is always negative.
question
Which lung structure is a tiny sac that functions as an interface between air and blood?
answer
Alveolus
question
Which barrier(s) must O2 and CO2 cross to pass between air and blood inside lungs?
True or false? The driving force for the unloading of oxygen from hemoglobin into tissues is the difference in PCO2 levels between the blood and body tissues.
answer
False. The PCO2 levels affect the diffusion of carbon dioxide; the driving force for the diffusion of oxygen from hemoglobin into tissues is the difference in PO2 levels between the blood (100 mm Hg when oxygenated) and body tissues (40 mm Hg at rest).
question
How is most carbon dioxide transported from tissues to the lungs?
answer
As bicarbonate ions (HCO3−).
question
Which of the following statements about the oxygen-hemoglobin interaction is true?
answer
The binding of one oxygen molecule to hemoglobin stimulates the binding of other oxygen molecules.
question
When you are jogging, your muscles are using more oxygen and releasing more carbon dioxide into the blood than when you are at home on the couch. Which of the following would occur during your jog?
answer
The medullary respiratory center would detect rising carbon dioxide levels.
question
An decrease from pH 7.4 to pH 7.2 causes hemoglobin to _____.
answer
Give up more of its oxygen molecules
question
The Bohr shift on the oxygen-hemoglobin dissociation curve is produced by changes in _____.
answer
pH
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Why is the pharmacological reactivation of fetal hemoglobin in a patient with sickle-cell anemia often a successful treatment? Fetal hemoglobin _____.
answer
has a higher affinity for oxygen than does adult hemoglobin.
question
What is the function of a circulatory system?
answer
It brings a transport liquid into close contact with all cells in the body.
question
Why do the circulatory systems of land vertebrates have separate circuits to the lungs and to the rest of the body?
answer
The large decrease in blood pressure as blood moves through the lungs may prevent efficient circulation through the rest of the body.
question
True or false? The circulatory systems of land-dwelling vertebrates are composed of two pumping circuits: the systemic circulation, which is a lower-pressure circuit to the lung, and the pulmonary circulation, which is a higher-pressure circuit to the rest of the body.
answer
False. The pulmonary circulation is the lower-pressure circuit to the lung, whereas the systemic circulation is the higher-pressure circuit to the rest of the body.
question
What is the function of the left ventricle?
answer
It pumps oxygenated blood around the body via the systemic circulation.
question
Which of the following statements about blood circulation in the body is true?
answer
Valves prevent the backflow of blood into the atria and ventricles.
question
Which event occurs first during diastole?
answer
The atria and ventricles are relaxed, and blood flows into the atria.
question
Which event of the cardiac cycle occurs when systolic blood pressure is measured?
answer
The ventricles contract, carrying blood into the aorta, and blood flows into the relaxed atria.
question
An anthropologist discovers the fossilized heart of an extinct animal. The evidence indicates that the organism's heart was large, was well-formed, and had four chambers, with no connection between the right and left sides. A reasonable conclusion supported by these observations is that the _____.
answer
animal was endothermic and had a high metabolic rate
question
Which of the following promotes oxygen release from hemoglobin?
answer
A decrease in pH.
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