Question 1

The fact that an increase in end-diastolic ventricular volume increases the stroke volume of the heart is an illustration of the

Accepted Answer

The Frank-Starling law of the heart states that an increase in end-diastolic ventricular volume leads to an increase in stroke volume. This is due to the stretch that occurs in the myocardial fibers, leading to a more forceful contraction and an increased ejection of blood. The other options, such as the influence of the parasympathetic nervous system or blood pressure, may also have an impact on cardiac output, but they are not directly related to the observed increase in stroke volume with increased end-diastolic volume.

Question 2

The relationship between cardiac output and metabolic rate is

Accepted Answer

The relationship between cardiac output and metabolic rate is linear. As the metabolic rate increases, the demand for oxygen and nutrients in the body's tissues also increases, which is met by an increase in cardiac output. This relationship is essential for maintaining homeostasis during varying levels of physical activity.

Question 3

In order to meet the increased oxygen demands of muscle during exercise,two major adjustments in blood flow must be made:

Accepted Answer

During exercise, the body needs to deliver more oxygen to the working muscles. This is achieved through an increase in cardiac output (the amount of blood pumped by the heart per minute) and a redistribution of blood flow from inactive tissues (such as the gut and kidneys) to the skeletal muscles. This allows for a greater delivery of oxygen and nutrients to the working muscles, allowing them to produce energy more efficiently. Therefore, option C best describes the adjustments in blood flow that occur during exercise. Option A is incorrect because an increase in diastolic blood pressure (the pressure in the arteries when the heart is relaxed) is not necessary for increased oxygen delivery to muscles during exercise. Option B is also incorrect, as blood flow to the brain and gut may actually decrease during exercise as blood flow is redirected to the working muscles. Option D is incorrect since the liver plays a relatively minor role in oxygen delivery during exercise compared to the skeletal muscles.

Question 4

The cardiovascular control center is located in the

Accepted Answer

The cardiovascular control center is located in the medulla oblongata, a part of the brainstem that regulates autonomic functions such as blood pressure, heart rate, and breathing. The medulla oblongata is responsible for receiving and integrating sensory information from baroreceptors, chemoreceptors, and other receptors throughout the body to maintain cardiovascular homeostasis.

Question 5

All gas exchange between the vascular system and tissues occurs in

Accepted Answer

Gas exchange between the vascular system and tissues occurs in the smallest blood vessels called capillaries. Oxygen diffuses out of the capillaries and into the tissues, while carbon dioxide diffuses out of the tissues and into the capillaries for transport back to the lungs.

Question 6

The decrease in maximal heart rate with age in adults can be estimated via

Accepted Answer

The most commonly used formula to estimate maximal heart rate is HR max = 220 - age, which means that maximal heart rate decreases by one beat per minute for every year of age.

Question 7

An increase in parasympathetic outflow to the heart results in

Accepted Answer

Parasympathetic outflow to the heart is responsible for slowing down heart rate, so an increase in parasympathetic outflow would result in a decrease in heart rate. Arterial blood pressure may decrease slightly due to the decreased cardiac output, but there would not be any significant increase in blood pressure or subsequent increase in heart rate as seen in choices C and D.

Question 8

The muscle of the heart is referred to as the

Accepted Answer

The muscle of the heart is the myocardium, which is responsible for the contraction and relaxation of the heart, allowing it to pump blood throughout the body. The pericardium is a double-layered membrane that surrounds the heart, while the epicardium is the outermost layer of the heart wall. The endocardium is the innermost layer of the heart wall, lining the chambers and valves.

Question 9

The primary purpose of the cardiovascular system is to

Accepted Answer

The primary purpose of the cardiovascular system is to deliver adequate levels of oxygen and remove wastes from body tissues. This is accomplished through the circulation of blood, which carries oxygen and nutrients to body tissues and removes carbon dioxide and other metabolic wastes. The kidneys are responsible for removing metabolic wastes from the body, but this is not the primary function of the cardiovascular system.

Question 10

During exercise,the time spent in diastole and systole

Accepted Answer

During exercise, the heart rate increases, which reduces the time spent in both diastole and systole. However, the greater reduction occurs in diastole. This is because during exercise, the demand for oxygen and nutrients by the muscles increases, and the heart responds by increasing its pumping rate, which reduces the amount of time spent in diastole, the relaxing phase of the cardiac cycle.

Question 11

Backflow of blood from the arteries into the ventricles is prevented by the

Accepted Answer

Backflow of blood from the arteries into the ventricles is prevented by the semilunar valves. The semilunar valves are located at the base of the two large vessels (pulmonary artery and aorta) leaving the heart and function to prevent the backflow of blood into the ventricles during relaxation of the heart.

Question 12

In most subjects,stroke volume continues to increase during incremental exercise up to approximately

Accepted Answer

Stroke volume typically increases with exercise intensity up to about 40% of VO2 max, after which it plateaus in most individuals.

Question 13

The __________ represents ventricular repolarization during a recording of the electrical activity (i.e. ,ECG)of the heart.

Accepted Answer

The T wave on an ECG represents ventricular repolarization, which is the recovery period of the ventricles following depolarization (as represented by the QRS complex). The P wave represents atrial depolarization, while the R wave represents ventricular depolarization.

Question 14

The contraction phase of the heart is called

Accepted Answer

Systole refers to the contraction phase of the heart. Diastole refers to the relaxation phase. Atrial contraction is a sub-phase within the cardiac cycle, which consists of both systole and diastole. Therefore, option C is the best choice.

Question 15

In a healthy heart,the time spent in systole is generally

Accepted Answer

In a healthy heart, the time spent in diastole is generally longer than systole. During diastole, the heart is relaxed and filling with blood, while during systole, the heart is contracting and pumping blood out to the body. Therefore, choice C, that systole is generally shorter than diastole, is the correct answer.

Question 16

The normal pacemaker of the heart is the

Accepted Answer

The sinoatrial node (SA node) is the normal pacemaker of the heart. It is located in the right atrium and initiates each heartbeat, setting the rhythm for the rest of the heart.

Question 17

The difference between systolic and diastolic blood pressure is called the

Accepted Answer

Pulse pressure is the difference between systolic and diastolic blood pressure.

Question 18

The most important variable that determines resistance to blood flow is

Accepted Answer

The diameter or radius of the blood vessel is the most important variable that determines resistance to blood flow. This is due to the fact that resistance to blood flow is inversely proportional to the fourth power of the radius of the vessel according to Poiseuille's law. Therefore, even a slight change in diameter can significantly alter the resistance to blood flow. The viscosity, length, and blood pressure do play a role in resistance to blood flow, but they are not as significant as the diameter of the vessel.

Question 19

Electrical impulses are conducted between heart muscle cells by

Accepted Answer

Intercalated discs are specialized junctions between cardiac muscle cells that allow for the rapid conduction of electrical impulses between cells. They contain gap junctions, which are channels that allow for the movement of ions between cells, allowing depolarization to rapidly spread throughout the heart muscle. Intermediate junctions and active transport of sodium between cells are not involved in the conduction of electrical impulses in the heart. Purkinje fibers are specialized cardiac muscle cells that are involved in transmitting electrical impulses to the ventricles of the heart, but they are not directly involved in the conduction of impulses between individual heart muscle cells.

Question 20

The increase in cardiac output that occurs during exercise is due to

Accepted Answer

The increase in cardiac output during exercise is attributed to both an increase in mean arterial pressure and a decrease in vascular resistance. This combination allows for more blood to be pumped by the heart to meet the increased oxygen and nutrient demands of the body during physical activity.

Quiz 10: Circulatory Responses to Exercise