Q: What would be the heart rate of a person if the cardiac output is 5 L, blood volume in the ventricles at the end of diastole is 100 mL and the blood volume at the end of ventricular systole is 50 mL?

Cardiac output = stroke volume \times Heart rate \Rightarrow Cardiac output =5L or 5000 mL \Rightarrow Blood volume in ventricles at the end of diastole =100 ml \Rightarrow Blood volume in ventricles at the end of systole =50 mlStroke volume =100-50 =50 ml.So, 5000 ml =50 ml \times Heart rateSo, Heart rate =100 beats per minute.So, the correct answer is '100 beats per minute'

Question 1

Draw a standard ECG and explain the different segments in it.

Accepted Answer

Electrocardiogram is a graphical representation of the cardiac cycle produced by an electrograph. The diagrammatic representation of a standard ECG is shown below.A typical human electrocardiogram has five waves – P, Q, R, S, and T. The P, R, and T waves are above the base line and are known as positive waves. The Q and S waves are below the base line and are known as negative waves. The P wave is of atrial origin, while the Q, R, S, and T waves are of ventricular origin. (a) The P wave indicates atrial depolarization. During this wave, the impulse of contraction is generated by the SA node. The PQ wave represents atrial contraction.(b) The QR wave is preceded by ventricular contraction. It represents the spread of the impulse of contraction from the AV node to the wall of the ventricle. It leads to ventricular depolarization.(c) The RS wave represents the ventricular contraction of about 0.3 sec.(d) The ST wave represents the ventricular relaxation of about 0.4 sec. During this phase, the ventricles relax and return to their normal state.(e) The T wave represents ventricular relaxation.

Question 2

What would be the heart rate of a person if the cardiac output is  5 L, blood volume in the ventricles at the end of diastole is  100 mL and the blood volume at the end of ventricular systole is  50  mL?

Accepted Answer

Cardiac output  =  stroke volume  	imes  Heart rate \Rightarrow  Cardiac output  =5L  or  5000  mL \Rightarrow  Blood volume in ventricles at the end of diastole  =100  ml \Rightarrow  Blood volume in ventricles at the end of systole  =50 mlStroke volume  =100-50 =50 ml.So,  5000 ml  =50 ml  	imes  Heart rateSo, Heart rate  =100  beats per minute.So, the correct answer is '100 beats per minute'

Question 3

What prevents backflow of blood inside the heart during contraction?

Accepted Answer

Hint - Flow of blood in the heart is unidirectional in both right and left part of the heart.  This unidirectional flow is maintained by flaps like structure.Part 1 - Heart Heart is the blood-pumping organ that pumps blood throughout the body with the help of blood vessels of the circulatory system. The heart is divided into two halves: right and left. Both the halves have 1 atrium (upper chamber) and 1 ventricle (lower chamber) each.Part 2 - ValvesThe atrium and ventricle have valves in between the chambers to prevent the backflow of the blood.Between the right atrium and the right ventricle, the Tricuspid valve is present.Between the left atrium and the left ventricle, the Bicuspid valve is present.The semilunar valve is present between the ventricles and the pulmonary artery and the systemic aorta.Part 3 - ConclusionThe four valves present in the heart prevents the backflow of blood inside the heart.The thick muscular wall of ventricles (especially left ventricle) helps in sending blood to the entire body with pressure. The wall of atria is thinner than ventricles because they have to pump blood just to the ventricles and not to the body. Final step -  The Valves in heart prevent the backflow of blood inside the heart.

Question 4

The rhythmic expansion and contraction of the heart is called ________.

Accepted Answer

The cardiac cycle is the rhythmic contraction and relaxation of the heart.Contraction is called cardiac systole and Relaxation is called cardiac diastole. Both contraction and relaxation are together known as the cardiac cycle.The heart beats 72 times per minute, i.e., that many cardiac cycles are performed per minute.Hence the rhythmic expansion and contraction of the heart are called Cardiac cycle.

Question 5

Why do we call our heart myogenic?

Accepted Answer

In the human heart, contraction is initiated by a specially modified heart muscle known as the sinoatrial node. It is located in the right atrium. The SA node has the inherent power of generating a wave of contraction and controlling the heartbeat. Hence, it is known as the pacemaker. Since the heartbeat is initiated by the SA node and the impulse of contraction originates in the heart itself, the human heart is termed as myogenic. The hearts of vertebrates and mollusks are also myogenic.

Question 6

Ventricles have thicker walls than auricles. Give reasons.

Accepted Answer

Because ventricles have to do more work as compare to atria. Ventricles pump blood into various organs and the pressure of blood flowing in them is more than that of articles.

Question 7

If due to some injury the chordae tendineae of the tricuspid valve of the human heart is partially non-functional, what will be the immediate effect?

Accepted Answer

In the human heart, both the tricuspid and mitral valves are attached by means of thin fibrous threads to the wall of the ventricles. The function of these threads, called as the chordae tendineae, is to keep the valve flaps from flipping up into the atria, when the ventricles contract and thus causing a backflow of blood. If the chordae tendineae of the tricuspid valve of the human heart is partially non-functional; the flow of blood into the pulmonary artery will be reduced and if the chordae tendineae of the bicuspid valve is nonfunctional then flow of blood into aorta will be affected.So, the correct answer is option A.

Question 8

Explain cardiac cycle with the help of diagrams.

Accepted Answer

The cardiac cycle is the performance of the human heart, beginning from one heartbeat to the beginning of the next.It consists of two phases:- 1) Diastolic phase, 2) Systolic phase.In the diastolic phase,  the heart ventricles are relaxed and the heart fills with blood.In the systolic phase, the ventricles contract and pump blood out of the heart and to arteries.It further proceeds in the following steps:Atrial systole lasts about 0.1 seconds - both atria contract and forces the blood from the atria into the ventricles.Ventricular systole lasts about 0.3 seconds - both ventricles contract, blood is forced to the lungs via the pulmonary trunk and the rest of the body via the aorta.Atrial diastole lasts for about 0.7 seconds- relaxation of the atria, during which the atria fill with blood from the large veins (the vena cavae).Ventricular diastole lasts about 0.5 seconds - begins before atrial systole, allowing the ventricles to fill passively with blood from the atria.

Question 9

Which of the following shows correct sequence of conduction of action potential in the heart?

Accepted Answer

The conduction system of the heart. Left: Normal excitation originates in the sinoatrial (SA) node then propagates through both atria. The atrial depolarization spreads to the atrioventricular (AV) node, and passes through the bundle of His to the bundle branches/Purkinje fibers.

Question 10

The second heart sound (dubb) is associated with the closure of

Accepted Answer

The closing of different valves in the heart produces different characteristic sound commonly known as the lub-dub sounds. The lub sound is the first sound of the heart. The dub sound is the second sound of the heart that is produced by the closing of the semilunar valves in the heart.Thus, the correct answer is 'Semilunar valves.'

Revise with Concepts

Structure and Working of Heart

Cardiac Cycle

Conducting System in Human Heart

Electrocardiograph (ECG)

Learn with Videos

Quick Summary With Stories

Structure of Heart in Details

Important Questions

Draw a standard ECG and explain the different segments in it.

What would be the heart rate of a person if the cardiac output is $5$ L, blood volume in the ventricles at the end of diastole is $100$ mL and the blood volume at the end of ventricular systole is $50$ mL?

What prevents backflow of blood inside the heart during contraction?

The rhythmic expansion and contraction of the heart is called ________.

Why do we call our heart myogenic?

Ventricles have thicker walls than auricles. Give reasons.

If due to some injury the chordae tendineae of the tricuspid valve of the human heart is partially non-functional, what will be the immediate effect?

Explain cardiac cycle with the help of diagrams.

Which of the following shows correct sequence of conduction of action potential in the heart?

The second heart sound (dubb) is associated with the closure of

Revise with Concepts

Structure and Working of Heart

Cardiac Cycle

Conducting System in Human Heart

Electrocardiograph (ECG)

Learn with Videos

Quick Summary With Stories

Structure of Heart in Details

Important Questions

Draw a standard ECG and explain the different segments in it.

What would be the heart rate of a person if the cardiac output is 5L, blood volume in the ventricles at the end of diastole is 100mL and the blood volume at the end of ventricular systole is 50 mL?

What prevents backflow of blood inside the heart during contraction?

The rhythmic expansion and contraction of the heart is called ________.

Why do we call our heart myogenic?

Ventricles have thicker walls than auricles. Give reasons.

If due to some injury the chordae tendineae of the tricuspid valve of the human heart is partially non-functional, what will be the immediate effect?

Explain cardiac cycle with the help of diagrams.

Which of the following shows correct sequence of conduction of action potential in the heart?

The second heart sound (dubb) is associated with the closure of

What would be the heart rate of a person if the cardiac output is $5$ L, blood volume in the ventricles at the end of diastole is $100$ mL and the blood volume at the end of ventricular systole is $50$ mL?