Cisco
CompTIA
ISC
EC-Council
EXIN
Fortinet
ITIL
Juniper
Microsoft
VMware
Avaya
SAP
Google
NVIDIA
Salesforce
Amazon
Palo Alto Networks
ISC2
Splunk
ServiceNow
All Vendors
  2. Home
  3. Exams
  4. Test Prep
  5. MCAT Test

Test Prep MCAT Test Exam
Medical College Admission Test: Verbal Reasoning, Biological Sciences, Physical Sciences, Writing Sample (Page 28 )

Updated On: 12-Jan-2026
Page 28 of 164
PDF with 811 Questions

The process of depolarization triggers the cardiac cycle. The electronics of the cycle can be monitored by an electrocardiogram (EKG). The cycle is divided into two major phases, both named for events in the ventricle:
the period of ventricular contraction and blood ejection, systole, followed by the period of ventricular relaxation and blood filling, diastole.
During the very first part of systole, the ventricles are contracting but all valves in the heart are closed thus no blood can be ejected. Once the rising pressure in the ventricles becomes great enough to open the aortic and pulmonary valves, the ventricular ejection or systole occurs. Blood is forced into the aorta and pulmonary trunk as the contracting ventricular muscle fibers shorten. The volume of blood ejected from a ventricle during systole is termed stroke volume.
During the very first part of diastole, the ventricles begin to relax, and the aortic and pulmonary valves close. No blood is entering or leaving the ventricles since once again all the valves are closed. Once ventricular pressure falls below atrial pressure, the atrioventricular (AV) valves open. Atrial contraction occurs towards the end of diastole, after most of the ventricular filling has taken place. The ventricle receives blood throughout most of diastole, not just when the atrium contracts.
: Electronic and pressure changes in the heart and aorta during the cardiac cycle.
Figure 1

Position P on the EKG of Fig. 1 probably correspond to:

  1. atrial contraction.
  2. ventricular contraction.
  3. the beginning of ventricular systole.
  4. the beginning of ventricular diastole.

Answer(s): A

Explanation:

This question requires you to incorporate information from the figure with information given in the passage.
Following vertically down from position P in Figure 1, note that it occurs during a period of diastole. In paragraph 3, sentence 4, the passage gives information concerning the actions of the heart during diastole which would lead to answer choice A. Alternatively, the answer can be deduced through information in the passage and figure. In paragraph 1, sentence 2, diastole is described as a period of ventricular relaxation, ruling out answer choice B. Position P in Figure 1 occurs during a period of diastole and it occurs at a point about halfway through that period, ruling out answer choices C and D.



The process of depolarization triggers the cardiac cycle. The electronics of the cycle can be monitored by an electrocardiogram (EKG). The cycle is divided into two major phases, both named for events in the ventricle:
the period of ventricular contraction and blood ejection, systole, followed by the period of ventricular relaxation and blood filling, diastole.
During the very first part of systole, the ventricles are contracting but all valves in the heart are closed thus no blood can be ejected. Once the rising pressure in the ventricles becomes great enough to open the aortic and pulmonary valves, the ventricular ejection or systole occurs. Blood is forced into the aorta and pulmonary trunk as the contracting ventricular muscle fibers shorten. The volume of blood ejected from a ventricle during systole is termed stroke volume.
During the very first part of diastole, the ventricles begin to relax, and the aortic and pulmonary valves close. No blood is entering or leaving the ventricles since once again all the valves are closed. Once ventricular pressure falls below atrial pressure, the atrioventricular (AV) valves open. Atrial contraction occurs towards the end of diastole, after most of the ventricular filling has taken place. The ventricle receives blood throughout most of diastole, not just when the atrium contracts.
: Electronic and pressure changes in the heart and aorta during the cardiac cycle.
Figure 1


The first heart sound represented in Fig. 1 is probably made when:

  1. During ventricular systole, blood in the ventricle is forced against the closed atrioventricular valve.
  2. During ventricular diastole, blood in the ventricles is forced through the aortic and pulmonary artery valves.
  3. During ventricular diastole, blood in the ventricle is forced against the closed atrioventricular valve.
  4. During ventricular systole, blood in the arteries is forced through the aortic and pulmonary artery valves.

Answer(s): A

Explanation:

This entire passage relies little on your previous knowledge or understanding of cardiovascular physiology;
rather, emphasis is on your ability to read a graph and, at times, correlate the information with the passage.
This question indicates that we should be looking at the graph representing "Heart sounds" in Figure 1. The graph for heart sounds can be described thus: a horizontal line is followed by a narrow burst of spikes or activity; prior to the spikes is the label "1st" implying that the spikes represent the 1st heart sound. The first heart sound begins immediately after the first long vertical line. By following this vertical line downwards, we can note any other events which may initiate or occur at the time as the first heart sound: beginning near the bottom of Figure 1, note that the first heart sound occurs (i) in phase 2 of the cardiac cycle; (ii) at the beginning of ventricular SYSTOLE; (iii) during a period that the aortic and pulmonary valves are not opened (i.e. closed); and (iv) the first heart sound begins exactly when the position of the AV valves just become closed. Therefore, strictly according to the figure, during ventricular systole the AV valves suddenly close just as the first heart sound is created. Thus, answer choice A is the only plausible answer.



The process of depolarization triggers the cardiac cycle. The electronics of the cycle can be monitored by an electrocardiogram (EKG). The cycle is divided into two major phases, both named for events in the ventricle:
the period of ventricular contraction and blood ejection, systole, followed by the period of ventricular relaxation and blood filling, diastole.
During the very first part of systole, the ventricles are contracting but all valves in the heart are closed thus no blood can be ejected. Once the rising pressure in the ventricles becomes great enough to open the aortic and pulmonary valves, the ventricular ejection or systole occurs. Blood is forced into the aorta and pulmonary trunk as the contracting ventricular muscle fibers shorten. The volume of blood ejected from a ventricle during systole is termed stroke volume.
During the very first part of diastole, the ventricles begin to relax, and the aortic and pulmonary valves close. No blood is entering or leaving the ventricles since once again all the valves are closed. Once ventricular pressure falls below atrial pressure, the atrioventricular (AV) valves open. Atrial contraction occurs towards the end of diastole, after most of the ventricular filling has taken place. The ventricle receives blood throughout most of diastole, not just when the atrium contracts.
: Electronic and pressure changes in the heart and aorta during the cardiac cycle.
Figure 1


Would the walls of the atria or ventricles expected to be thicker?

  1. Atria, because blood ejection due to atrial contraction is high.
  2. Atria, because blood ejection due to atrial contraction is low.
  3. Ventricles, because ventricular stroke volume is high.
  4. Ventricles, because ventricular stroke volume is low.

Answer(s): C

Explanation:

Thicker walls in a particular part of the heart would indicate that it is more muscular, and therefore is more
efficient or forceful during its contraction. This immediately rules out answer choices B and D, as they suggest that the thicker walled chamber would be less efficient or forceful. It should be known from the biology review (BIO 7.2) that the ventricles are more muscular (thicker-walled), but in the event that this is not initially known, information regarding the function of both the atria and the ventricles from the passage may help lead to this conclusion. First, systole, the period of contraction, refers to the period of contraction of the ventricles not the atria (paragraph 1, line 5). This would indicate that the contraction of the ventricles might be more relevant in some way. Second, during diastole, atrial contraction occurs after most of the ventricle is already filled (paragraph 3, sentence 4) and serves to push the small amount of blood necessary to complete the filling into the ventricles. Since the atrial contraction does not need to move a large amount of blood (the ventricle is already mostly full), it does not need to be as muscular.



The process of depolarization triggers the cardiac cycle. The electronics of the cycle can be monitored by an electrocardiogram (EKG). The cycle is divided into two major phases, both named for events in the ventricle:
the period of ventricular contraction and blood ejection, systole, followed by the period of ventricular relaxation and blood filling, diastole.
During the very first part of systole, the ventricles are contracting but all valves in the heart are closed thus no blood can be ejected. Once the rising pressure in the ventricles becomes great enough to open the aortic and pulmonary valves, the ventricular ejection or systole occurs. Blood is forced into the aorta and pulmonary trunk as the contracting ventricular muscle fibers shorten. The volume of blood ejected from a ventricle during systole is termed stroke volume.
During the very first part of diastole, the ventricles begin to relax, and the aortic and pulmonary valves close. No blood is entering or leaving the ventricles since once again all the valves are closed. Once ventricular pressure falls below atrial pressure, the atrioventricular (AV) valves open. Atrial contraction occurs towards the end of diastole, after most of the ventricular filling has taken place. The ventricle receives blood throughout most of diastole, not just when the atrium contracts.
: Electronic and pressure changes in the heart and aorta during the cardiac cycle.
Figure 1


The graph below shows the effects on stroke volume of stimulating the sympathetic nerves to the heart.


According to the graph, the net result of sympathetic stimulation on stroke volume is to:

  1. approximately double stroke volume at any given end diastolic volume.
  2. decrease stroke volume at any given end diastolic volume.
  3. increase stroke volume at any given end diastolic volume.
  4. leave stroke volume relatively unchanged.

Answer(s): C

Explanation:

This question is easily answered by reading the graph. Compared to the curve labeled 'control', the curve labeled 'sympathetic stimulation' is always at a higher stroke volume for a given end-diastolic volume. However, by looking at stroke volume values for both curves at any end-diastolic volume value (i.e. 200), it is clear that the stroke volume for sympathetic stimulation is always less than twice the control (i.e. 160 vs. 100), thus eliminating answer choice A. Thus, we are left with answer choice C.



The process of depolarization triggers the cardiac cycle. The electronics of the cycle can be monitored by an electrocardiogram (EKG). The cycle is divided into two major phases, both named for events in the ventricle:
the period of ventricular contraction and blood ejection, systole, followed by the period of ventricular relaxation and blood filling, diastole.
During the very first part of systole, the ventricles are contracting but all valves in the heart are closed thus no blood can be ejected. Once the rising pressure in the ventricles becomes great enough to open the aortic and pulmonary valves, the ventricular ejection or systole occurs. Blood is forced into the aorta and pulmonary trunk as the contracting ventricular muscle fibers shorten. The volume of blood ejected from a ventricle during systole is termed stroke volume.
During the very first part of diastole, the ventricles begin to relax, and the aortic and pulmonary valves close. No blood is entering or leaving the ventricles since once again all the valves are closed. Once ventricular pressure falls below atrial pressure, the atrioventricular (AV) valves open. Atrial contraction occurs towards the end of diastole, after most of the ventricular filling has taken place. The ventricle receives blood throughout most of diastole, not just when the atrium contracts.
: Electronic and pressure changes in the heart and aorta during the cardiac cycle.
Figure 1


The wall of the left ventricle is at least three times as thick as that of the right ventricle. This feature aids circulation by assuring that:

  1. blood entering the pulmonary artery is at a much higher pressure than blood entering the aorta.
  2. blood entering the aorta is at a much higher pressure than blood entering the pulmonary artery.
  3. the left ventricle has a higher blood capacity than the right ventricle at all times.
  4. the right ventricle has a higher blood capacity than the left ventricle at all times.

Answer(s): B

Explanation:

It is commonly known that as a rule, the size of a muscle is proportional to its strength. The heart, which is a muscle, contains a chamber which must pump blood into the aorta to perfuse the grand majority of the body's tissues. Clearly, this chamber (= the left ventricle) must contain thicker muscle (= stronger) than a chamber that pumps blood only to the lungs (= the right ventricle through the pulmonary artery). The stronger chamber pumps blood with a greater force which means a higher pressure (recall from physics: P = F/A).



Viewing page 28 of 164
Viewing questions 136 - 140 out of 811 questions



Post your Comments and Discuss Test Prep MCAT Test exam prep with other Community members:

Join the MCAT Test Discussion