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Electrocardiogram
Beep!Ć¢Ä‚¬Ā¦Beep!Ć¢Ä‚¬Ā¦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 Ć¢Ä‚¬Å“wave of excitationĆ¢Ä‚¬Ā¯ spreads through the heart wall and is accompanied by electric changes. The wave takes place in three distinct steps.
Initially, the Ć¢Ä‚¬Å“wave of excitationĆ¢Ä‚¬Ā¯ 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.
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' during an electrocardiogram?
- 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 sequence of the 'wave of excitation' during an electrocardiogram includes the excitation of the atrium (contraction), the excitement of the ventricle (peak ECG), and the relaxing of the ventricle. This process starts with the discharge from the SA node, followed by the peak ECG due to the AV node, and ends with the relaxation of the ventricles. Understanding this sequence is crucial for interpreting ECG readings accurately and identifying any abnormalities within the heart.
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Blood Pressure Regulators 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. 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 primary purpose of this text?
- 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 a 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 this text is to provide information on how the cardiovascular system regulates blood pressure. The passage discusses the role of different components like baroreceptors, chemoreceptors, and the kidneys in maintaining blood pressure. It explains how these components work together to regulate blood pressure within the body. The text does not focus on dangers of high blood pressure, risks of heart attacks, or persuading the reader, making choice C the most appropriate answer.
The Water Cycle
Water is needed to sustain practically all life functions on planet Earth. A single drop of this compound is composed of an oxygen atom that shares its electrons with each of the two hydrogen atoms.
The cycle starts when precipitation, such as rain, snow, sleet, or hail, descends from the sky onto the ground. Water that is not absorbed immediately from the precipitation is known as runoff. The runoff flows across the land and collects in groundwater reservoirs, rivers, streams, and oceans.
Evaporation takes place when liquid water changes into water vapor, which is a gas. Water vapor returns to the air from surface water and plants.
Ultimately, condensation happens when this water vapor cools and changes back into droplets of liquid. In fact, the puffy, cotton clouds that we observe are formed by condensation. When the clouds become heavily laden with liquid droplets, precipitation ensues.
Which of the following words is an antonym for the word 'comprised'?
- A. Incorporate
- B. Encompass
- C. Exclude
- D. Embody
Correct Answer: C
Rationale: The term 'comprised' means to include or contain. An antonym would be a word that signifies the opposite of including or containing. The correct answer, 'Exclude,' means to leave out or omit, which is the opposite of comprising.
Blood Pressure Regulators
The body comprises systems that have evolved and diversified to maintain essential functions and processes. One such system is the cardiovascular system, which includes critical regulators of blood pressure. The heart serves as the body’s pump, ensuring a steady flow of vital oxygen to all cells while facilitating the removal of carbon dioxide and other waste products. Given that blood pressure varies at different points throughout the body, various components are necessary to regulate it effectively.
Three primary components involved in blood pressure regulation are baroreceptors, chemoreceptors, and the kidneys. Baroreceptors, which are stretch receptors made up of fine branching nerve endings, are located along the walls of arteries near the heart and in other areas of the body. When these baroreceptors detect stretching in the arterial walls, they send impulses to the heart, arteries, and veins, leading to an increase or decrease in blood pressure.
Chemoreceptors, found along the walls of the arteries, monitor changes in oxygen levels, carbon dioxide, and pH. For instance, a drop in oxygen levels triggers these receptors to send impulses that raise blood pressure. The kidneys also play a crucial role in blood pressure regulation by absorbing salts and water while eliminating waste. Hormones secreted by the adrenal cortex influence the kidneys to retain or excrete salt and water, thereby affecting blood volume and, consequently, blood pressure.
What is a major difference in the way baroreceptors and chemoreceptors work from the way the kidneys work?
- A. Baroreceptors and chemoreceptors both work within the walls of the arteries, sending out impulses to raise or lower blood pressure, whereas the kidneys help control blood volume.
- B. Baroreceptors and chemoreceptors both work to help maintain blood volume, whereas the kidneys take care of salts, water, and waste removal.
- C. Baroreceptors and chemoreceptors must work together to control blood pressure, whereas the kidneys work with the adrenal cortex.
- D. Baroreceptors and chemoreceptors are both located near the adrenal cortex, whereas the kidneys are located near the heart.
Correct Answer: A
Rationale: Baroreceptors and chemoreceptors function within the walls of the arteries, monitoring and sending impulses to regulate blood pressure based on stretch and oxygen levels. In contrast, the kidneys play a role in controlling blood volume by absorbing salts, water, and removing wastes. The major difference lies in the functions: baroreceptors and chemoreceptors focus on regulating blood pressure, while the kidneys primarily manage blood volume. Therefore, choice A is correct as it highlights this distinction clearly.
Blood Pressure.The heart produces a characteristic "lub-dub" sound, which results from the rapid contraction and relaxation of its chambers. Each contraction, known as ventricular contraction, ejects approximately 70 mL of blood into the vascular system, which varies in volume and pressure. Blood pressure specifically refers to the pressure within the arterial system, commonly measured at the brachial artery in the arm, as pressure levels can differ at various points along the circulatory pathway. Essentially, blood pressure is the force exerted by blood in all directions within a specific area, driving the flow of blood from the heart, throughout the body, and back again. It is typically expressed as a ratio of systolic pressure over diastolic pressure. Systolic pressure, or the "high peak" pressure, occurs when the ventricles contract and push blood into the arteries, while diastolic pressure, or the "low peak" pressure, is the pressure in the arteries just before the next contraction. An increase in blood pressure may arise if arterial walls lose some elasticity due to aging or disease.
Which of the following statements is not supported by the passage?
- A. Ventricular contracting injects roughly 70 mL of blood into the vascular system.
- B. Blood pressure is typically measured in the brachial artery of the arm.
- C. Blood pressure is usually represented as a ratio of systolic pressure to diastolic pressure.
- D. Loss of arterial wall elasticity is always caused by disease.
Correct Answer: D
Rationale: The correct answer is D. The passage states that an increase in blood pressure can occur if the arterial walls lose some of their elasticity due to age or disease, not necessarily always by disease. Therefore, the statement that loss of arterial wall elasticity is always caused by disease is not supported by the passage. Choices A, B, and C are all facts supported by the information provided in the passage.
People of Hispanic origin were on the North American continent centuries before settlers arrived
from Europe in the early 1600s and the thirteen colonies joined together to form the United
States in the late 1700s. The first census of the new nation was conducted in 1790, and counted about four million people, most of whom were white. Of the white citizens, more than 80%
traced their ancestry back to England. There were close to 700,000 slaves and about 60,000 "free Negroes". Only a few Native American Indians who paid taxes were included in the census count, but the total Native American population was probably about one million. By 1815, the population of the United States was 8.4 million. Over the next 100 years, the
country took in about 35 million immigrants, with the greatest numbers coming in the late 1800s and early 1900s. In 1882, 40,000 Chinese arrived, and between 1900 and 1907, there were more
than 30,000 Japanese immigrants. But by far, the largest numbers of the new immigrants were
from central, eastern, and southern Europe. An enormous amount of racial and ethnic assimilation has taken place in the United States. In 1908, play-write Israel Zangwill first used the term "melting pot" to describe the concept of a place where many races melted in a crucible and re-formed to populate a new land. Some years during the first two decades of the 20th century, there were as many as one million new
immigrants per year, an astonishing 1 percent of the total population of the United States.
In 1921, however, the country began to limit immigration, and the Immigration Act of 1924
virtually closed the door. The total number of immigrants admitted per year dropped from as many as a million to only 150,000. A quota system was established that specified the number of
immigrants that could come from each country. It heavily favored immigrants from northern and western Europe and severely limited everyone else. This system remained in effect until 1965, although after World War II, several exceptions were made to the quota system to allow in
groups of refugees.
How many immigrants were taken in over the 100 years leading up to 1915?
- A. Probably about 1 million
- B. About 35 million
- C. 8.4 million
- D. About 4 million
Correct Answer: B
Rationale: The correct answer is B: About 35 million. The text mentions that over the 100 years leading up to 1915, the United States took in approximately 35 million immigrants. This period saw a significant influx of immigrants, with the largest numbers coming in the late 1800s and early 1900s. The Immigration Act of 1924 later limited immigration, reducing the number of immigrants admitted per year. Answer choices A, C, and D do not align with the information provided in the text regarding the influx of immigrants during this period.