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Beep!…Beep!…Beep! is the audible rhythmic sound made as the strength of the heart muscle is measured. The signal cadence has a characteristic record that varies in every individual. This record is called an electrocardiogram, or ECG.In the body, an array of systemic neural responses constantly occur, emitting electric currents. The electric currents can be detected on the surface of the body, and if a person is hooked to an amplifier, these impulses are recorded by an electrocardiograph. Most of the information obtained is about the heart because the heart sends out electric currents in waves. This “wave of excitation†spreads through the heart wall and is accompanied by electric changes. The wave takes place in three distinct steps.Initially, the “wave of excitation†accompanied by an electric change lasts for approximately 1 to 2 seconds after the contraction of the cardiac muscle. The electric impulses are discharged rhythmically from the sinoatrial (SA) node, the pacemaker of the heart. This spread of excitation over the muscle of the atrium indicates that the atrium has contracted.Next, the peak of the ECG reading is due to the atrioventricular (AV) node, causing the ventricle to become excited.<p>Finally, the ventricles relax, and any changes in the wave indicate to trained medical staff any abnormalities within the heart.
What are the three steps of the 'wave of excitation'?
- A. The discharge from the SA node, the peak ECG, and the excitement of the ventricle.
- B. The excitement of the ventricle, the relaxing of the ventricle, and the systemic neural response.
- C. The contraction of the atrium, the relaxation of the atrium, and the contraction of the ventricle.
- D. The excitation of the atrium, the excitement of the ventricle, and the relaxing of the ventricle.
Correct Answer: D
Rationale: The correct steps of the 'wave of excitation' are the excitation of the atrium, excitement of the ventricle, and relaxation of the ventricle. In the described process, the 'wave of excitation' starts with the discharge from the SA node, leading to the excitation of the atrium. Next, the peak ECG corresponds to the excitement of the ventricle, not its relaxation. Finally, the wave concludes with the relaxation of the ventricle, not its contraction. Therefore, choices A, B, and C are incorrect as they do not accurately describe the sequential steps of the 'wave of excitation' as presented in the extract.
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The immune system is a network of cells, tissues, and organs that defends the body against attacks by foreign invaders. These invaders are primarily microbes—tiny organisms such as bacteria, parasites, and fungi—that can cause infections. Viruses also cause infections, but are too primitive to be classified as living organisms. The human body provides an ideal environment for many microbes. It is the immune system's job to keep the microbes out or destroy them.The immune system is amazingly complex. It can recognize and remember millions of different enemies, and it can secrete fluids and cells to wipe out nearly all of them. The secret to its success is an elaborate and dynamic communications network. Millions of cells, organized into sets and subsets, gather and transfer information in response to an infection. Once immune cells receive the alarm, they produce powerful chemicals that help to regulate their own growth and behavior, enlist other immune cells, and direct the new recruits to trouble spots.Although scientists have learned much about the immune system, they continue to puzzle over how the body destroys invading microbes, infected cells, and tumors without harming healthy tissues. New technologies for identifying individual immune cells are now allowing scientists to determine quickly which targets are triggering an immune response. Improvements in microscopy are permitting the first-ever observations of living B cells, T cells, and other cells as they interact within lymph nodes and other body tissues.In addition, scientists are rapidly unraveling the genetic blueprints that direct the human immune response, as well as those that dictate the biology of bacteria, viruses, and parasites. The combination of new technology with expanded genetic information will no doubt reveal even more about how the body protects itself from disease.
What is the meaning of the word 'ideal' as it is used in the first paragraph?
- A. thoughtful
- B. confined
- C. hostile
- D. perfect
Correct Answer: D
Rationale: In this context, 'ideal' means perfect. The human body provides a perfect environment for many microbes, as stated in the extract. It is the immune system's role to keep these microbes out or destroy them. The other choices are incorrect: 'thoughtful' does not fit the context of the sentence, 'confined' and 'hostile' are not synonymous with 'ideal' in this context.
Foodborne illnesses are contracted by eating food or drinking beverages contaminated with bacteria, parasites, or viruses. Harmful chemicals can also cause foodborne illnesses if they have contaminated food during harvesting or processing. Foodborne illnesses can cause symptoms ranging from upset stomach to diarrhea, fever, vomiting, abdominal cramps, and dehydration. Most foodborne infections are undiagnosed and unreported, though the Centers for Disease Control and Prevention estimates that every year about 76 million people in the United States become ill from pathogens in food. About 5,000 of these people die.Harmful bacteria are the most common cause of foodborne illness. Some bacteria may be present at the point of purchase. Raw foods are the most common source of foodborne illnesses because they are not sterile; examples include raw meat and poultry contaminated during slaughter. Seafood may become contaminated during harvest or processing. One in 10,000 eggs may be contaminated with Salmonella inside the shell. Produce, such as spinach, lettuce, tomatoes, sprouts, and melons, can become contaminated with Salmonella, Shigella, or Escherichia coli (E. coli). Contamination can occur during growing, harvesting, processing, storing, shipping, or final preparation. Sources of produce contamination vary, as these foods are grown in soil and can become contaminated during growth, processing, or distribution. Contamination may also occur during food preparation in a restaurant or a home kitchen. The most common form of contamination from handled foods is the calicivirus, also called the Norwalk-like virus.When food is cooked and left out for more than two hours at room temperature, bacteria can multiply quickly. Most bacteria don't produce an odor or change in color or texture, so they can be impossible to detect. Freezing food slows or stops bacteria's growth, but does not destroy the bacteria. The microbes can become reactivated when the food is thawed. Refrigeration also can slow the growth of some bacteria. Thorough cooking is required to destroy the bacteria.
What is the meaning of the word 'pathogens' as it is used in the first paragraph?
- A. diseases
- B. vaccines
- C. disease-causing substances
- D. foods
Correct Answer: C
Rationale: In the context provided, 'pathogens' refers to disease-causing substances such as bacteria and viruses. These microorganisms can contaminate food and lead to foodborne illnesses. Choice A ('diseases') is incorrect as pathogens themselves cause diseases but are not diseases. Choice B ('vaccines') is incorrect as vaccines are used to prevent diseases caused by pathogens. Choice D ('foods') is incorrect as pathogens are not foods, but rather contaminants that can be found in food.
The body is composed of systems that have evolved and diversified in order to maintain the natural functions and processes they regulate. One such system that has these regulators is the body's cardiovascular system. The body's pump, which regulates the flow of vitally needed oxygen to all cells of the body, as well as the discard of carbon dioxide and other waste products, is the heart. Because blood pressure varies at different points within the body, differing components are needed to keep the body's blood pressure regulated. Three of the basic components are baroreceptors, chemoreceptors, and the kidneys.<p>Baroreceptors are stretch receptors composed of fine branching nerve endings and are contained along the walls of the arteries near the heart and in other areas of the body as well. Impulses are related to this stretching along the arterial walls, which causes these baroreceptors to send out even more impulses to the heart, arteries, and veins, causing the blood pressure to go either up or down.Chemoreceptors are located along the walls of the arteries and monitor changes in oxygen level, carbon dioxide, and pH. Just think! A fall in oxygen causes receptors to send impulses to raise the blood pressure.The kidneys play a role in regulating blood pressure by absorbing salts and water and removing wastes. Hormones secreted by the adrenal cortex cause the kidney to keep or let go of any salt and water. This has an influence on blood volume and consequently on blood pressure.
What is the best summary of this passage?
- A. The heart regulates oxygen flow and waste disposal, with the kidneys aiding in salt and water absorption.
- B. The cardiovascular system regulates blood pressure through baroreceptors, chemoreceptors, and the kidneys.
- C. Baroreceptors send impulses to regulate blood pressure by affecting the heart, arteries, and veins.
- D. Chemoreceptors monitor oxygen levels to impact blood pressure.
Correct Answer: B
Rationale: The correct answer is B because it provides a comprehensive summary of the passage, explaining how the cardiovascular system regulates blood pressure through baroreceptors, chemoreceptors, and the kidneys. Choice A is incorrect as it only focuses on the heart and kidneys without mentioning the broader cardiovascular system. Choice C is incorrect as it solely emphasizes the role of baroreceptors in regulating blood pressure. Choice D is incorrect as it oversimplifies the role of chemoreceptors in monitoring oxygen levels without mentioning their impact on blood pressure regulation.
Beep!…Beep!…Beep! is the audible rhythmic sound made as the strength of the heart muscle is measured. The signal cadence has a characteristic record that varies in every individual. This record is called an electrocardiogram, or ECG.In the body, an array of systemic neural responses constantly occur, emitting electric currents. The electric currents can be detected on the surface of the body, and if a person is hooked to an amplifier, these impulses are recorded by an electrocardiograph. Most of the information obtained is about the heart because the heart sends out electric currents in waves. This “wave of excitation†spreads through the heart wall and is accompanied by electric changes. The wave takes place in three distinct steps.Initially, the “wave of excitation†accompanied by an electric change lasts for approximately 1 to 2 seconds after the contraction of the cardiac muscle. The electric impulses are discharged rhythmically from the sinoatrial (SA) node, the pacemaker of the heart. This spread of excitation over the muscle of the atrium indicates that the atrium has contracted.Next, the peak of the ECG reading is due to the atrioventricular (AV) node, causing the ventricle to become excited.<p>Finally, the ventricles relax, and any changes in the wave indicate to trained medical staff any abnormalities within the heart.
What is the best summary of the passage?
- A. Electric currents within the body are due to electrostatic charges set off by the heart. Medical staff are trained to recognize any abnormalities within the heart.
- B. Every individual has unique electric currents on the surface of the body. The ECG measures and records these electric currents.
- C. The ECG systematically and rather quickly measures the stages at which the 'wave of excitation' occurs within the heart and records them. This wave has three distinct steps that spread from the SA node to the AV node.
- D. The ECG measures the electric currents within the body. These currents are detected on the surface of the body when the body is connected to an amplifier.
Correct Answer: C
Rationale: The correct summary of the passage is option C. The passage explains how the ECG systematically measures and records the 'wave of excitation' that occurs within the heart in three distinct steps, spreading from the SA node to the AV node. This summary effectively captures the main focus of the passage. Option A is incorrect because it only mentions the detection of electric currents in the body and recognizing abnormalities by medical staff, missing the key information about the 'wave of excitation' and its stages. Option B is incorrect as it focuses solely on the measurement and recording of unique electric currents on the body's surface, neglecting the specific process described in the passage. Option D is also incorrect as it provides a general description of how the ECG measures electric currents without emphasizing the specific stages of the 'wave of excitation' as detailed in the passage.
The body is composed of systems that have evolved and diversified in order to maintain the natural functions and processes they regulate. One such system that has these regulators is the body's cardiovascular system. The body's pump, which regulates the flow of vitally needed oxygen to all cells of the body, as well as the discard of carbon dioxide and other waste products, is the heart. Because blood pressure varies at different points within the body, differing components are needed to keep the body's blood pressure regulated. Three of the basic components are baroreceptors, chemoreceptors, and the kidneys.<p>Baroreceptors are stretch receptors composed of fine branching nerve endings and are contained along the walls of the arteries near the heart and in other areas of the body as well. Impulses are related to this stretching along the arterial walls, which causes these baroreceptors to send out even more impulses to the heart, arteries, and veins, causing the blood pressure to go either up or down.Chemoreceptors are located along the walls of the arteries and monitor changes in oxygen level, carbon dioxide, and pH. Just think! A fall in oxygen causes receptors to send impulses to raise the blood pressure.The kidneys play a role in regulating blood pressure by absorbing salts and water and removing wastes. Hormones secreted by the adrenal cortex cause the kidney to keep or let go of any salt and water. This has an influence on blood volume and consequently on blood pressure.
What is the writer's primary purpose in writing this essay?
- A. To inform the reader about the dangers of high blood pressure
- B. To inform the reader how high blood pressure leads to a higher risk of heart attack
- C. To inform the reader how the cardiovascular system regulates blood pressure
- D. To persuade the reader that controlling one's blood pressure is important
Correct Answer: C
Rationale: The primary purpose of the essay is to inform the reader about how the cardiovascular system regulates blood pressure. The essay provides detailed explanations about the components of the cardiovascular system that regulate blood pressure, such as baroreceptors, chemoreceptors, and the kidneys. Choices A and B are incorrect because the essay does not focus on discussing the dangers of high blood pressure or its correlation with a higher risk of heart attack. Choice D is incorrect as the essay does not aim to persuade the reader to control their blood pressure but rather to educate them on the regulatory mechanisms of the cardiovascular system.