Physiology: The Heart

Thick tunica media

What physical feature of large systemic arteries (resistance vessels) makes them relatively more responsive to changes in intracellular calcium concentrations?

Atrioventricular valves are open

Which of the following is true of ventricular diastole?

857 ms

If the heart rate is 70 beats per minute, what is the total duration (in milliseconds, ms) of any individual cardiac cycle?

1/8

A given arteriole has a resistance of 2. What would the new resistance of this vessel be if its radius were to double?

depolarization of the ventricles

Considering a typical electrocardiogram (ECG), the QRS complex is associated with:

repolarization of the ventricles

Considering a typical electrocardiogram (ECG), the T wave is associated with:

occurs before the start of atrial contraction (i.e., before atrial systole)

Considering the electrocardiogram (ECG) and the events of the cardiac cycle, the start of the P wave:

occurs before the start of ventricular contraction (i.e., before ventricular systole)

Considering the electrocardiogram (ECG) and the events of the cardiac cycle, the start of the QRS complex wave:

occurs during the contraction of the ventricles (i.e., during ventricular systole)

Considering the electrocardiogram (ECG) and the events of the cardiac cycle, the start of the T wave:

Semilunar valves

Which heart valves are NOT actively closed by the contraction of muscular structures?

Left ventricle during ventricular systole

Within the cardiovascular system, the highest hydrostatic blood pressure is found in the:

3

The right atrioventricular (AV) valve has __________ cusp(s).

All valves are closed

At the instant following the second heart sound, which heart valves are open?

False

Blood oxygen content is higher in the pulmonary artery than in the pulmonary vein.

True

Blood oxygen content is lower in the pulmonary artery than in the pulmonary vein.

depolarization of Atria

Considering a typical electrocardiogram (ECG), the P wave is associated with:

SA node → AV node → Bundle of His → Bundle branches → Purkinje fibers

Choose the correct sequence of action potential conduction along the conductive tissues of the heart:

20%

During a typical cardiac cycle under resting conditions, approximately __________ of the volume of blood present in the ventricles just before ventricular contraction (referred to as end-diastolic volume), enters the ventricles as a result of atrial contraction.

80%

During a typical cardiac cycle under resting conditions, approximately __________ of the volume of blood present in the ventricles just before ventricular contraction (referred to as end-diastolic volume), enters the ventricles as a result of passive venous return of blood flowing through the atria and into the ventricles.

Hydrostatic pressure within the left ventricle rises rapidly. // There is a slight increase in the hydrostatic pressure within the left atrium.

During isovolumic contraction (also referred to as isovolumetric contraction) of the left ventricle:

7-8 mm Hg

During the cardiac cycle, contraction of the left atrium leads to an increase of approximately __________ in the hydrostatic pressure within the left atrium.

4-6 mm Hg

During the cardiac cycle, contraction of the right atrium leads to an increase of approximately __________ in the hydrostatic pressure within the right atrium.

flow of blood through the atrioventricular valves from the atria into the ventricles // a decrease in the hydrostatic pressure within the ventricles // a decrease in the hydrostatic pressure within the atria

During the cardiac cycle, opening of the atrioventricular valves following ventricular relaxation leads to:

Systole

During the cardiac cycle, the contraction phase is referred to as __________.

Diastole

During the cardiac cycle, the relaxation phase is referred to as __________.

The atrioventricular valves and semilunar valves are closed.

During the isovolumic contraction (also referred to as isovolumetric contraction) phase of the cardiac cycle:

The hydrostatic pressure in the left ventricle is higher than the hydrostatic pressure in the left atrium. // The hydrostatic pressure in the left ventricle is lower than the hydrostatic pressure in the aorta.

During the isovolumic contraction (also referred to as isovolumetric contraction) phase of the cardiac cycle:

The hydrostatic pressure in the left ventricle is higher than the hydrostatic pressure in the left atrium. // The hydrostatic pressure in the left ventricle is lower than the hydrostatic pressure in the aorta.

During the isovolumic relaxation (also referred to as isovolumetric relaxation) phase of the cardiac cycle:

The atrioventricular valves and semilunar valves are closed.

During the isovolumic relaxation (also referred to isovolumetric relaxation) phase of the cardiac cycle:

True

During the plateau phase of the cardiac action potential, membrane permeability to K+ (pK) is lower than its resting value.

isovolumic relaxation or isovolumetric relaxation

During ventricular diastole of the cardiac cycle, the period of time immediately after the closure of the semilunar valves until just before the opening of the atrioventricular valves is referred to as the __________ __________ period. Your response should contain two words.

isovolumic contraction or isovolumetric contraction

During ventricular systole of the cardiac cycle, the period of time immediately after the start of ventricular contraction when the atrioventricular valves close (when ventricular pressure exceeds atrial pressure) until just before the opening of the semilunar valves is referred to as the __________ __________ period. Your response should contain two words.

Vasoconstriction

How can the circulatory system promote heat retention/conservation, such as on a cold day?

70 mL

In a healthy 70-kg adult man, stroke volume is about __________.

120 mL

In a typical human cardiac cycle, the volume of blood in the left ventricle just before the start of ventricular systole is approximately __________. This volume if referred to as the end-diastolic volume.

50 mL

In a typical human cardiac cycle, the volume of blood remaining in the left ventricle at the end of ventricular systole is approximately __________. This is referred to as the end-systolic volume.

5%

In an individual at rest, approximately this percentage of total blood volume can be found in all capillaries:

65%

In an individual at rest, approximately this percentage of total blood volume can be found in the venous system:

20%

In cardiac muscle cells, approximately what percentage of cytoplasmic Ca2+ required for contraction enters the cardiac muscle cell from the extracellular fluid?

80%

In cardiac muscle cells, approximately what percentage of cytoplasmic Ca2+ required for contraction is released from the sarcoplasmic reticulum?

Both are closed

In terms of being open or closed, what is the state of the mitral and tricuspid valves (left and right atrioventricular valves, respectively) at the end of the first heart sound?

Cells of the sinoatrial (SA) node and Purkinje fibers

Of the conductive tissues of the heart, only these cells can directly stimulate cardiac myocytes to contract:

Na+ influx and Opening of If channels

Pacemaker potentials of the heart result from:

Aorta > artery > arteriole > capillary > venule > vein

Rank the following blood vessels in order of their average pressure, from highest to lowest: artery, vein, arteriole, venule, aorta, capillary.

The atria contract before the ventricles.

The cardiac events that occur from the beginning of one heart beat to the beginning of the next heart beat are called the cardiac cycle. During the cardiac cycle:

The left atrium and right atrium contract nearly simultaneously. // The left ventricle and right ventricle contract nearly simultaneously. // The atria contract before the ventricles.

The cardiac events that occur from the beginning of one heart beat to the beginning of the next heart beat are called the cardiac cycle. Which of the following is/are true?

Blood flows from the right atrium through the tricuspid valve, into the right ventricle, through the pulmonary semilunar valve, into the pulmonary trunk, and then into the pulmonary arteries.

The correct blood flow in reference to the right side of the heart?

Blood flows from the left atrium, through the bicuspid valve, into the left ventricle, through the aortic semilunar valve, and then into the aortic arch.

The correct flow of blood in reference to the left side of the heart?

2

The left atrioventricular (AV) valve has __________ cusp(s).

opening of voltage-gated Ca2+ channels

The plateau phase of the cardiac action potential is due to the:

lungs

The right ventricle is the chamber of the heart that pumps blood for the pulmonary circulation. Based on this information, blood from the right ventricle is on its way to the __________.

Opening of voltage-gated Ca2+ channels

The spike phase of the action potential of the sinoatrial node pacemaker cells of the heart is caused by:

Cells of the sinoatrial (SA) node

These cells are known as the primary pacemakers of the heart:

Bundle of His

These conductive fibers of the heart originate in the atrioventricular (AV) node and pass through the cardiac skeleton (thick connective tissue that separates the atria and the ventricles):

Chordae tendineae

These ligaments prevent the eversion of atrioventricular valves during ventricular systole.

Left atrioventricular (AV) valve / Bicuspid valve / Mitral valve

This cardiac valve separates the left atrium from the left ventricle.

Right atrioventricular (AV) valve / Tricuspid valve

This cardiac valve separates the right atrium from the right ventricle.

William Harvey

This famous physiologist discovered the circulation of blood:

Pulmonary semilunar valve

This one-way valve separates the right ventricle from the pulmonary artery:

True

Venous blood is commonly referred to as deoxygenated blood because its oxygen content is lower than the oxygen content of arterial blood.

False

Venous blood is commonly referred to as deoxygenated blood because its oxygen content is zero.

Endocardium

What layer of the heart would be most immediately susceptible to infections caused by bacteria circulating in the blood?

Pulmonary artery

What vessels carry deoxygenated blood away from the heart?

Diastole

When the heart rate increases, the duration of both systole and diastole of the cardiac cycle decreases. Which phase of the cardiac cycle decreases to a larger extent?

decreases

When the heart rate increases, the duration of each cardiac cycle __________.

decreases

When the heart rate increases, the duration of the diastolic phase of the cardiac cycle __________.

decreases

When the heart rate increases, the duration of the systolic phase of the cardiac cycle __________.

bicuspid

also knows as mitral valve