6Respiratory and skins systems test w solutions

BIOLOGY TOPICAL: Respiratory and Skin Systems Test Time: 21 Minutes* Number of Questions: 16 * The timing restrictions for the science topical tests are optional If you are using this test for the sole purpose of content reinforcement, you may want to disregard the time limit MCAT DIRECTIONS: Most of the questions in the following test are organized into groups, with a descriptive passage preceding each group of questions Study the passage, then select the single best answer to each question in the group Some of the questions are not based on a descriptive passage; you must also select the best answer to these questions If you are unsure of the best answer, eliminate the choices that you know are incorrect, then select an answer from the choices that remain Indicate your selection by blackening the corresponding circle on your answer sheet A periodic table is provided below for your use with the questions PERIODIC TABLE OF THE ELEMENTS H 1.0 He 4.0 Li 6.9 Be 9.0 B 10.8 C 12.0 N 14.0 O 16.0 F 19.0 10 Ne 20.2 11 Na 23.0 12 Mg 24.3 13 Al 27.0 14 Si 28.1 15 P 31.0 16 S 32.1 17 Cl 35.5 18 Ar 39.9 19 K 39.1 20 Ca 40.1 21 Sc 45.0 22 Ti 47.9 23 V 50.9 24 Cr 52.0 25 Mn 54.9 26 Fe 55.8 27 Co 58.9 28 Ni 58.7 29 Cu 63.5 30 Zn 65.4 31 Ga 69.7 32 Ge 72.6 33 As 74.9 34 Se 79.0 35 Br 79.9 36 Kr 83.8 37 Rb 85.5 38 Sr 87.6 39 Y 88.9 40 Zr 91.2 41 Nb 92.9 42 Mo 95.9 43 Tc (98) 44 Ru 101.1 45 Rh 102.9 46 Pd 106.4 47 Ag 107.9 48 Cd 112.4 49 In 114.8 50 Sn 118.7 51 Sb 121.8 52 Te 127.6 53 I 126.9 54 Xe 131.3 55 Cs 132.9 56 Ba 137.3 57 La * 138.9 72 Hf 178.5 73 Ta 180.9 74 W 183.9 75 Re 186.2 76 Os 190.2 77 Ir 192.2 78 Pt 195.1 79 Au 197.0 80 Hg 200.6 81 Tl 204.4 82 Pb 207.2 83 Bi 209.0 84 Po (209) 85 At (210) 86 Rn (222) 87 Fr (223) 88 Ra 226.0 89 Ac † 227.0 104 Unq (261) 105 Unp (262) 106 Unh (263) 107 Uns (262) 108 Uno (265) 109 Une (267) * 58 Ce 140.1 59 Pr 140.9 60 Nd 144.2 61 Pm (145) 62 Sm 150.4 63 Eu 152.0 64 Gd 157.3 65 Tb 158.9 66 Dy 162.5 67 Ho 164.9 68 Er 167.3 69 Tm 168.9 70 Yb 173.0 71 Lu 175.0 † 90 Th 232.0 91 Pa (231) 92 U 238.0 93 Np (237) 94 Pu (244) 95 Am (243) 96 Cm (247) 97 Bk (247) 98 Cf (251) 99 Es (252) 100 Fm (257) 101 Md (258) 102 No (259) 103 Lr (260) GO ON TO THE NEXT PAGE as developed by Respiratory and Skin Systems Test Passage I (Questions 1–5) All birds and mammals are able to maintain relatively constant body temperatures despite fluctuations in external temperature These animals have evolved thermoregulatory mechanisms that help them adapt to their environments One such mechanism involves metabolic rates A plot of the rate of oxygen consumption versus body weight for various mammals reveals that metabolic rate is inversely proportional to body weight (Figure 1) However, metabolic rate and the transfer of heat to the environment are directly proportional to the surface area-to-volume ratio of the animal For instance, a shrew has a higher metabolic rate and a greater surface area-to-volume ratio than a horse, which means that the shrew generates more internal heat per gram of body weight and loses more heat to the environment This makes it especially difficult for small animals to maintain a constant body temperature in cold weather A thermoregulatory mechanism often used by mammals to lose excess body heat in hot weather is sweating, but this requires a large supply of readily available water Mammals inhabiting environments that are both hot and dry have had to evolve alternative means of handling the heat generated by metabolism For example, gazelles possess retia, vascular structures that enable them to maintain organ-specific temperatures Gazelles have been found to have brain temperatures as much as 2.9°C lower than their body core temperatures The existence of a vascular structure that thermally isolates the head from the rest of the animal means that scarce water is used only to cool the head, while body temperature is allowed to rise Local cooling of the head occurs via panting Relative metabolic rate Harvest mouse Cactus mouse House mouse Flying squirrel Rabbit Rat Cat Human Dog Horse 0.01 0.1 A Huddling increases the effective surface area-tovolume ratio, thereby decreasing the loss of body heat B Huddling decreases the effective surface area-tovolume ratio, thereby decreasing the loss of body heat C Huddling decreases the effective surface area-tovolume ratio, thereby increasing the loss of body heat D Huddling increases the effective surface area-tovolume ratio, thereby increasing the loss of body heat Based on the information in the passage, it can be reasonably inferred that: A gazelles have evolved beyond the need for thermoregulation B the primary object of thermoregulation in gazelles is the maintenance of a constant brain temperature C gazelles have not successfully adapted to their environment D gazelles tolerate large water losses Which of the following is most likely true of an animal that must keep all of its vital organs at approximately the same temperature? Shrew It has often been observed that small animals, such as baby penguins, huddle together when it is cold outside What is the most likely explanation for this phenomenon? 10 A It could not survive in a desert environment B It sweats excessively and becomes dehydrated in hot weather C Its body temperature is dictated by the most temperature-sensitive organ D It must always have a large supply of water 100 1,000 Body weight (kilograms) Figure GO ON TO THE NEXT PAGE KAPLAN MCAT The main advantage that the gazelle has over mammals (inhabiting the same environment) that cool themselves primarily by sweating is: A the ability to maintain a lower brain temperature B the ability to tolerate higher external temperatures C lower metabolic requirements D more efficient water conservation Many Arctic animals have a countercurrent heat exchange mechanism in their extremities that prevents excessive heat loss from dissipation Veins returning from the extremities with cold venous blood are in direct contact with arteries carrying warm blood to the extremities By which of the following mechanisms is heat transferred from the arteries to the veins? A B C D Conduction Convection Radiation Evaporation GO ON TO THE NEXT PAGE as developed by Respiratory and Skin Systems Test Passage II (Questions 6–11) Emphysema is a lung disease characterized by marked destruction of the alveolar walls, leading to the permanent enlargement of the alveoli The condition arises most commonly as a consequence of heavy cigarette smoking Smoking irritates the bronchi and bronchioles, resulting in chronic infection Furthermore, it causes partial paralysis of the cilia of the epithelial lining of the respiratory tract, disabling the mechanism for mucus removal from the passageways Finally, it stimulates mucus secretion and inhibits the alveolar macrophages The resulting infection and excess mucus, along with inflammatory edema (accumulation of fluid in the epithelial tissue), lead to obstruction of many of the smaller airways, making it difficult for the patient to move air out of the lungs The subsequent entrapment of air stretches the alveoli and contributes to the destruction of the alveolar walls Expiration becomes difficult in emphysematous patients because bronchiolar obstruction increases airway resistance This resistance is already elevated during expiration due to the compressive force on the outside of the lung Slowing of forced expiration is the most reliable indicator of chronic emphysema The significant loss of functional lung tissue that often results from chronic emphysema has two important physiological effects First, it causes a decrease in the diffusion capacity of the lung, which is the ability of the respiratory membrane to exchange gases between the alveoli and the pulmonary capillaries Second, it decreases the number of pulmonary capillaries through which blood can pass As a result, the pulmonary vascular resistance increases markedly, causing pulmonary hypertension Oxygen moves from the alveoli into the pulmonary capillaries and carbon dioxide moves from the pulmonary capillaries into the alveoli via: A B C D active transport facilitated diffusion simple diffusion osmosis The decrease in the number of pulmonary capillaries due to the loss of functional lung tissue will most likely cause a pressure overload in the: A B C D right atrium right ventricle left atrium left ventricle A clinical test for emphysema is the forced expiratory vital capacity maneuver, in which the person first inspires to total lung capacity and then expires as rapidly as possible Which of the following graphs best illustrates the difference in test results between a normal individual and one with emphysema? normal emphysema A C lung volume lung volume seconds seconds The inhibitory effect of cigarette smoking on the alveolar macrophages will most directly contribute to which of the following? A Increase in bacteria and solid particles in the alveoli B Increase in the number of paralyzed cilia C Decrease in the destruction of alveolar walls D Decrease in the amount of functional lung tissue B D lung volume lung volume seconds seconds GO ON TO THE NEXT PAGE KAPLAN MCAT Based on the information in the passage a patient with severe emphysema who is breathing at a normal rate will exhibit: A B C D low PCO2 and high PO2 in the blood low PCO2 and low PO2 in the blood high PCO2 and high PO2 in the blood high PCO2 and low PO2 in the blood 1 In an individual with emphysema, new, larger alveolar chambers are formed as the walls of the original alveoli dissolve and the alveoli coalesce However, the diffusing capacity of the lung is greatly reduced What best accounts for this phenomenon? A The total volume of the alveolar chambers is decreased B The total surface area of the respiratory membrane is decreased C The total number of alveolar chambers available during respiration is decreased D The thickness of the respiratory membrane is increased GO ON TO THE NEXT PAGE as developed by Respiratory and Skin Systems Test 1 When an animal pants, it breathes rapidly in and out, causing large quantities of new air to come into contact with the upper portions of the respiratory passages The function of this mechanism is to: Questions 12 through 16 are NOT based on a descriptive passage Air entering the lungs of a tracheotomy patient through a tracheostomy (a tube inserted directly into the trachea) is colder and dryer than normal, which often causes lung crusting and infection This occurs primarily because the air: A enters the respiratory system too rapidly to be filtered B is not properly humidified by the larynx C does not flow through the nasal passageways D does not flow past the mouth and tongue The graph below shows the relationship between O2 consumption and total alveolar ventilation (the rate at which air reaches the alveoli) during exercise What is the net effect of exercise on arterial PO2? rapidly increase CO2 expiration moisten the mucosa of the respiratory passages minimize the movement of respiratory muscles decrease body heat via evaporation Heat conduction to the skin is controlled by the degree of vasoconstriction of the arterioles that supply blood to the skin Which of the following controls the vasoconstriction of these arterioles? A B C D Autonomic nervous system Sensory nervous system Somatic nervous system Spinal cord A person unacclimatized to hot weather will often lose as much as 15 – 30 g of salt each day for the first few days due to profuse sweating After to weeks of acclimatization, however, the same person will lose only – g of salt per day This decrease in salt loss is caused by: 110 100 Total alveolar ventilation (L/min) A B C D 80 60 A B C D 40 20 1.0 2.0 3.0 increased ADH secretion decreased ADH secretion increased aldosterone secretion decreased aldosterone secretion 4.0 O2 consumption (L/min) END OF TEST A P O remains the same, because ventilation increases as metabolism increases B P O increases markedly, because ventilation increases as metabolism decreases C P O decreases, because oxygen consumption increases D P O initially decreases and then rebounds, because ventilation increases KAPLAN MCAT ANSWER KEY: B B C D A 10 A C B A D 11 12 13 14 15 B C A D A 16 C as developed by Respiratory and Skin Systems Test RESPIRATORY AND SKIN SYSTEMS TEST TRANSCRIPT Passage I (Questions 1-5) Choice B is the correct answer An animal's primary "goal" when it's cold outside is to keep warm It wants to limit the amount of heat lost to the environment, because the more heat it loses, the colder the animal feels Realizing that, you should have eliminated choices C and D immediately, since the last part of both statements says, "thereby increasing the loss of body heat." So now you've narrowed it down to either choice A or B The amount of heat transferred from a body to its external environment is directly proportional to the amount of surface area (a.k.a skin) exposed to the external environment If you couldn't recall this, the information was provided for you in the passage If heat is lost through exposed surface area, then it follows that the more surface area exposed, the greater the amount of heat lost According to the passage, smaller animals have a tougher time than larger ones trying to maintain a constant internal body temperature, because smaller animals have a greater surface area-to-volume ratio and a higher metabolic rate than large ones Therefore, smaller animals generate more heat and lose more heat to their environment When the external temperature is lower than the animal's internal temperature, heat is transferred to the external environment via radiation Radiation is defined as the transfer of heat between objects that are not in direct contact So, as I already said, it follows that the more surface area exposed, the more heat lost This means that if a group of small animals can somehow decrease their collective surface area-to-volume ration, then they will lose less heat as a unit Huddling accomplishes this when a group of small animals huddle together in the cold, they are decreasing the total surface area exposed, as a group, to the environment In other words, huddling decreases the effective surface area-to-volume ration, thereby decreasing the loss of body heat per individual baby penguin So, choice A is wrong and the correct answer is choice B Choice B is the correct answer It's apparent from the question stem that this is a reading comprehension-type question, obviously dealing with gazelles, since that's the subject that all four answer choices deal with According to the passage, gazelles have evolved structures called retia, which are vascular structures that allow them to maintain organ-specific temperatures Thus, right off the bat, you should have eliminated choice A, because we know that the gazelle has evolved specific adaptations for thermoregulation; it has not evolved beyond the need for thermoregulation no animal has The gazelle's retia are located in the carotid arteries, which are located in the next region, and afford the gazelle the luxury of having a brain temperature almost degrees cooler than its body core temperature This also means that the gazelle doesn't lose valuable water trying to cool down its head, so water is conserved which is a particularly useful adaptation in a hot, arid climate From this, it can reasonably be inferred from the passage that one of the primary objects of thermoregulation in gazelles is the maintenance of a constant brain temperature So, choice B is the right answer According to the passage, the gazelle's head is cooled by panting, which involves rapid, short, shallow breaths that allow air to pass over the tongue and evaporate saliva Unlike sweating, panting does not incur a great loss of water, salt, and other essential ions So choice D is wrong And this also makes it clear that choice C is not a valid conclusion, because the evolution of such complex and unique thermoregulatory mechanisms implies that the gazelle has successfully adapted to its desert-like environment Again, choice B is the right answer Choice C is the correct answer You're being asked to draw a conclusion about what it means for all organs, including the brain, to have a single body temperature In the passage you're told that gazelles evolved retia to deal with a climate that is both hot and dry Water loss is kept at a minimum by only cooling the head, while body temperature is allowed to rise This seems to imply that the gazelle brain is a temperature-sensitive organ that must be maintained at a particular temperature for proper functioning, regardless of external temperature and the temperature of the rest of the body Now, if an animal must keep ALL of its vital organs at the same temperature, and if one particular organ, such as the brain, is the most temperature-sensitive organ, then the animal is obligated to maintain its body temperature at the temperature required by that organ So choice C is the right answer Let's look at the remaining choices You don't know at what temperature the most temperature-sensitive organ in this hypothetical animal must be maintained, so you can't conclude that this animal can't survive in a desert, or that it will sweat very heavily in hot weather So choice A and B can be ruled out As for choice D all animals need water to survive, including humans But whether or not the animal needs a large supply of water depends on how efficient its thermoregulatory mechanisms are; for instance, camels don't need much water even though they live in a hot, dry environment Again, choice C is the correct answer Choice D is the correct answer This is another question about the gazelle, and it requires you to infer what advantage the gazelles with their retia have over other mammals in the same or similar habitat a hot dry environment According to the passage, the main advantage to retia is water conservation An animal that sweats in hot weather begins to so when internal heat production rises When the sweat evaporates, it cools the body, but at the expense of a great water loss Gazelles, on the other hand, cool themselves by panting, and by allowing their body temperature to rise, thereby conserving water So in a hot, dry environment, the gazelle will lose less water than mammals who cool themselves by sweating So, choice D is the correct answer Animals that sweat not necessarily have higher metabolic rates, higher brain temperatures, or a lower tolerance to high environmental temperatures There's not enough information in either the passage KAPLAN MCAT or the question stem for you to conclude any of these things Hence, choices A, B, and C are all incorrect Again, choice D is the right answer Choice A is the correct answer This is one of those questions that is peripherally related to the passage topic, which is thermoregulation, but that can really be answered without reading the passage at all To answer it you have to rely entirely on your outside knowledge of the methods by which heat is transferred from one object or surface to another So let's discuss the answer choices one by one Conduction, choice A, is the transfer of thermal energy, or heat, between the molecules of two bodies that are in direct physical contact and differ in temperature Heat is transferred from the warmer body to the colder body In the countercurrent heat exchange mechanism found in animals inhabiting cold environments, such as the Arctic fox, the warm arteries are in direct physical contact with the cold veins, allowing for the transfer of heat from the arteries to the veins So choice A is the answer to this question Choice B, convection, is the movement of air or water in currents to or from the body's surface For example, when a person sweats on a breezy day, the evaporation of the sweat warms the air above the skin; when air is warmed, it rises, and new, colder air now comes into contact with the surface of the skin Radiation, choice C, refers to the transfer of energy between objects that are NOT in direct physical contact by way of electromagnetic waves All objects with temperatures above absolute zero produce radiation Thermal radiation occurs when an animal's body temperature is warmer or colder than air temperature Heat is exchanged between the animal and the air as electromagnetic waves Choice D, evaporation, is the loss of heat from the surface of a liquid as liquid molecules evaporate into gaseous molecules Every gram of water that evaporates dissipates over 500 calories, thus cooling the surface from which it evaporates Again, the correct answer is choice A Passage II (Questions 6-11) The correct choice is A The alveolar macrophages, which are present in the alveolar walls, engulf bacteria, dead cells, and particles that become trapped in the alveoli The alveolar macrophages are white blood cells that fight to prevent infection and are, therefore an integral component of the lung's defense system Since, according to the passage, smoking inhibits the alveolar macrophages and prevents them from doing their job, the amount of bacteria and the number of solid particles in the alveoli will increase, and so choice A is correct Even if you weren't familiar with the role macrophages play in the alveoli, you could have deduced the right answer It can be inferred from the passage that inhibition of the alveolar macrophages promotes infection Among the choices, the only one that would lead directly to infection is choice A While it is true that smoking causes an increase in the number of paralyzed cilia of the lung epithelium (choice B) and a decrease in the amount of functional lung tissue (choice D), these effects are not the direct consequence of the inhibition of macrophages Choice C makes no sense because smoking causes an increase, not a decrease, in the destruction of alveolar walls Again, choice A is the right answer The correct answer is choice C First, let's review each of the mechanisms of transport Active transport, choice A, is the net movement of dissolved particles against their concentration gradient with the help of carrier molecules Active transport requires energy in the form of ATP An example of active transport is the sodium-potassium pump You can eliminate active transport right away because the passage refers to the "diffusion capacity" of the lung Facilitated diffusion, choice B, is the net movement of dissolved particles along their concentration gradient with the help of carrier molecules It does not require energy input An example of facilitated diffusion is glucose transport in the nephron Simple diffusion, choice C, is the net movement of dissolved particles down their concentration gradient Diffusion is a passive process An excellent example of simple diffusion is gas exchange in the lungs Oxygen diffuses from the alveoli, where it is highly concentrated, into the pulmonary capillaries, where there is a low concentration of oxygen, without the help of carrier molecules; carbon dioxide diffuses from the pulmonary capillaries into the alveoli, down its concentration gradient Thus choice C is the correct answer Choice D, osmosis, is the simple diffusion of water from a region of lower solute concentration to a region of higher solute concentration since we are obviously not talking about the movement of water in this question, you can eliminate choice D right away as well Again, choice C is the right answer The correct answer is choice B The right ventricle of the heart pumps deoxygenated blood into the lungs via the pulmonary arteries Remember, arteries carry blood away from the heart When the loss of functional lung tissue reduces the number of pulmonary capillaries through which blood can flow, the resulting pressure overload leads to right ventricular enlargement, a condition known as cor pulmonale The right atrium, choice A, pumps deoxygenated blood returning from the body into the right ventricle The left atrium, choice C, receives oxygenated blood from the lungs via the pulmonary veins, and pumps the blood into the left ventricle, choice D Again, choice B is the right answer The correct answer is choice A The passage stresses than an emphysematous patient has a great deal of difficulty with expiration, or exhaling In fact, we're told that "slowing of forced expiration is the most reliable indicator of chronic emphysema." We can therefore predict that the graph of an emphysematous patient performing the forced expiratory vital capacity maneuver will show lung volume declining more slowly over time during expiration than it would in a normal individual, while inhalation is the same in both individuals Choice A, graph A, is the graph that most accurately reflects this, and is our right answer 10 as developed by Respiratory and Skin Systems Test Graph B shows the emphysematous patient having difficulty both with inhalation and exhalation Choice B can thus be eliminated because the passage never says that patients with emphysema have difficulty with inhalation According to graph C, the emphysematous patient is able to exhale more rapidly than the normal individual, which is clearly not the case, and so choice C is wrong Graph D indicates that both inspiration and expiration are quicker in the emphysematous patient This is the exact opposite of what we would predict from the passage and so choice D is wrong Again, choice A is the right answer 10 The correct answer is choice D According to the passage, an emphysematous patient's lungs have severely reduced diffusing capacity This means that oxygen won't diffuse into the pulmonary blood at the normal rate, nor will carbon dioxide be able to diffuse out of the pulmonary blood at the normal rate As a result, the blood of someone with severe emphysema will exhibit high PCO2 and low PO2, which is choice D 11 The correct answer is choice B The diffusing capacity of the lung depends on the respiratory membrane, since this is the membrane across which the diffusion of gases occurs If there is any loss of respiratory membrane that is, if the total surface area of the membrane is reduced by some sort of damage the diffusing capacity of the lung will be reduced When the alveoli coalesce, or consolidate, as occurs with emphysema, the new alveolar chambers may be larger, but the total surface area of the respiratory membrane is reduced, thus decreasing the diffusing capacity of the lung So, choice B is the right answer Choices A and C are wrong because neither the total volume of the alveolar chambers nor the total number of alveolar chambers is directly relevant to diffusing capacity Furthermore, the total volume of the alveolar chambers will most likely be increased, not decreased, in the emphysematous patient that's why these patients are often barrel chested The number of alveolar chambers will certainly decrease, not increase, as small alveoli coalesce into larger ones As for choice D, there is no evidence in the passage that the dissolution of alveolar walls has any impact on the thickness of the respiratory membrane Again, choice B is the right answer Discretes (Questions 12-16) 12 Choice C is the correct answer When a patient breathes through a tracheostomy, the air entering the respiratory system bypasses a very important area: the nasal cavities In a normal-breathing individual, the extensive surfaces of the nasal passageways warm and almost completely humidify the air, and particles are filtered out by a nasal air turbulence mechanism Since the air reaching the lungs of a tracheotomy patient has not been warmed or humidified, lung crusting and infection often result The speed with which air enters the lungs, choice A, is not what prevents the air from being filtered properly The air does bypass the larynx (choice B) and the mouth and tongue (choice D) in a tracheotomy patient, but this is irrelevant, since air is primarily warmed and humidified by the nasal passageways So, choices A, B, and D are wrong, and choice C is the right answer 13 Choice A is correct The rate of alveolar ventilation is directly related to the partial pressure of O2 in the blood: the greater the rate of ventilation, the more oxygen there will be in the alveoli to diffuse across the respiratory membrane into the pulmonary capillaries It makes sense that alveolar ventilation increases during exercise (when you breathe more deeply and rapidly) because metabolism is accelerated and there is a greater need for oxygen Judging from the graph, alveolar ventilation increases almost exactly in step with increased metabolism (represented by O2 consumption) The increasing supply of oxygen is in balance with the increasing demand for it, so you can infer that the partial pressure of O2 in the arteries will be about the same as the rest Thus, choice A is correct Choice B is out because ventilation increases as metabolism increases, not as it decreases Choice C does not take into account the effect of increased alveolar ventilation, so it's wrong Choice D would only be true if alveolar ventilation did not increase step for step with metabolism Again, choice A is the right answer 14 Choice D is correct Many animals not have sweat glands, so sweating cannot be a means of evaporative heat loss The panting mechanism, which is described in the question stem, serves as a substitute or as a complement to sweating The large amounts of air that come into the upper respiratory passages permit water evaporation from the mucosal surfaces, thereby allowing for heat loss Panting is turned on by thermoregulatory centers of the brain that monitor blood temperature Thus, choice D is correct Choice A is wrong because an animal's rapid breaths during panting are not deep enough to have a significant impact on the rate of carbon dioxide expiration Choice B is the opposite of what actually happens, so it's wrong Choice C is irrelevant; while your respiratory muscles probably move faster during panting, this movement does not serve a thermoregulatory function Again, choice D is the right answer 15 Choice A is correct This is a pure outside knowledge question The autonomic nervous system regulates the internal environment by controlling involuntary actions and processes It innervates the heart, smooth muscle in blood vessels and the digestive tract, and the endocrine, excretory, reproductive, and respiratory systems The sympathetic division of the autonomic nervous system controls the vasoconstriction of the arterioles in response to changes in temperature, so choice A is the one you want If you weren't sure about the answer right away, you could have eliminated the wrong answers The KAPLAN 11 MCAT job of the sensory nervous system, choice B, is to convert stimuli into action potentials; it includes the eye and the ear, as well as skin, taste, and olfactory receptors The somatic nervous system, choice C, innervates skeletal muscles in response to external stimuli The spinal cord, choice D, integrates simple motor responses and relays information to and from the brain None of these is directly involved in the vasoconstriction of arterioles, and so choices B, C, and D are wrong Again, choice A is the right answer 16 Choice C is the right answer Aldosterone, which is produced by the adrenal cortex, increases the rate of Na+ reabsorption by the kidney and sweat ducts Aldosterone secretion is stimulated by a decrease in blood volume, such as the decrease caused by profuse and prolonged sweating in hot weather Increased aldosterone secretion after a few weeks of acclimatization to hot weather would therefore significantly reduce the loss of salt, and so choice C is correct Decreased aldosterone secretion would increase the loss of salt, so choice D is incorrect ADH (antidiuretic hormone), which is also known as vasopressin, increases water reabsorption by acting on the kidney to increase its permeability to water ADH secretion is stimulated by a rise in plasma osmolarity Neither an increase in ADH secretion nor a decrease in ADH secretion would reduce the loss of salt, so choices A and B are wrong Again, choice C is the right answer 12 as developed by ... decreases and then rebounds, because ventilation increases KAPLAN MCAT ANSWER KEY: B B C D A 10 A C B A D 11 12 13 14 15 B C A D A 16 C as developed by Respiratory and Skin Systems Test RESPIRATORY AND. .. accurately reflects this, and is our right answer 10 as developed by Respiratory and Skin Systems Test Graph B shows the emphysematous patient having difficulty both with inhalation and exhalation Choice... involuntary actions and processes It innervates the heart, smooth muscle in blood vessels and the digestive tract, and the endocrine, excretory, reproductive, and respiratory systems The sympathetic