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NCERT Solutions Class 11 Biology Chapter 15 - Body Fluids and Circulation
NCERT Solutions for Class 11 Biology Chapter 15 (Body Fluids and Circulation) explain how blood and lymph help transport oxygen, nutrients, hormones, and waste products throughout the human body. The chapter covers the composition and functions of blood and lymph, the structure of the human heart, and how blood flows through different parts of the circulatory system. Students can also learn about blood groups, blood clotting, the cardiac cycle, ECG, and double circulation.
NCERT Solutions for Class 11 Biology Chapter 15 by ALLEN provide clear explanations of important topics such as the cardiac cycle, ECG waves, and the pathway of electrical impulses through the heart. Students can understand the ABO and Rh blood group systems, the role of the conducting system of the heart, and the process of double circulation. These solutions follow NCERT Class 11 Biology Chapter 15 and help students revise important concepts and prepare for school exams and NEET.
1.0Class 11 Biology Chapter 15 Body Fluids and Circulation: Key Concepts
Class 11 Biology Chapter 15, Body Fluids and Circulation, explains how blood and lymph transport oxygen, nutrients, hormones, and other substances throughout the body. The chapter covers the composition of blood, blood groups, blood clotting, the human circulatory system, the structure and working of the heart, cardiac cycle, ECG, double circulation, and common heart-related disorders.
- Blood: Learn about plasma and formed elements of blood, including red blood cells, white blood cells, and platelets.
- Blood Groups: Understand the ABO blood group system and Rh factor, including their importance during blood transfusion and pregnancy.
- Blood Clotting: Learn how blood clotting takes place with the involvement of thrombin, fibrin, and calcium ions.
- Lymph: Understand the formation and functions of lymph and its role in transporting fats and maintaining fluid balance.
- Circulatory Systems: Learn the difference between open and closed circulatory systems and the structure of hearts with different numbers of chambers.
- Human Circulatory System: Study the structure of the human heart and the conducting system, including the sinoatrial node (SAN), atrioventricular node (AVN), and Bundle of His.
- Cardiac Cycle: Understand atrial and ventricular systole and diastole and how the heart produces the sounds "Lubb" and "Dupp".
- Electrocardiogram (ECG): Learn the meaning of the P-wave, QRS complex, and T-wave and their relation to the activity of the heart.
- Double Circulation: Understand pulmonary and systemic circulation and how blood moves between the heart, lungs, and different parts of the body.
- Regulation of Cardiac Activity: Learn how the autonomic nervous system and hormones such as adrenaline influence heart rate and cardiac activity.
- Circulatory Disorders: Study hypertension, coronary artery disease, angina, and heart failure, along with their basic causes and effects.
2.0Detailed NCERT Textbook Solutions : Class 11 Biology Chapter 15
- Name the components of the formed elements in the blood and mention one major function of each of them. Ans. Blood corpuscles are the formed elements in the blood, they constitute 45% of the blood. Formed elements are - (erythrocytes, RBCs or red blood corpuscles), (leucocytes, WBCs or white blood corpuscles) and thrombocytes or blood platelets. The major function of RBCs is to transport oxygen from lungs to body tissues and from body tissues to the lungs. White blood cells provide immunity to the body. Blood platelets play important role in blood clotting.
- What is the importance of plasma proteins? Ans. Plasma proteins constitute about 7 to 8% of plasma. These mainly include albumin, globulin, prothrombin and fibrinogen. Prothrombin and fibrinogen are needed for blood clotting. Albumins and globulins retain water in blood plasma and helps in maintaining osmotic balance. Certain globulins
- Match Column I with Column II.
Ans. (a) - (iii), (b) - (v), (c) - (ii), (d) - (i), (e) - (iv).
- Why do we consider blood as a connective tissue? Ans. A connective tissue connects different tissues or organs of the body. It consists of living cells and extracellular matrix. Blood is vascular connective tissue, of fluid matrix and free cells. Blood transports materials from one place to the other and thereby establishes connectivity between different body parts.
- What is the difference between lymph and blood? Ans. The differences between blood and lymph are given below:
- What is meant by double circulation? What is its significance? Ans. The type of blood circulation in which oxygenated blood and deoxygenated blood do not get mixed is termed double circulation. It includes systemic circulation and pulmonary circulation. The circulatory pathway of double circulation is given in the following flow chart.
- Write the differences between:
(a) Blood and lymph
(b) Open and closed system of circulation
(c) Systole and diastole
(d) P-wave and T-wave
Ans.
(a) The differences between blood and lymph are given below:
(b)
(c)
(d)
- Describe the evolutionary change in the pattern of heart among the vertebrates. Ans. All vertebrates possess a muscular chambered heart. Fishes have a 2-chambered heart with an atrium and a ventricle. Amphibians and the reptiles (except crocodiles) have a 3-chambered heart with two atria and a single ventricle, whereas crocodiles, birds and mammals possess a 4-chambered heart with two atria and two ventricles. In fishes the heart pumps out deoxygenated blood which is oxygenated by the gills and supplied to the body parts from where deoxygenated blood is returned to the heart (single circulation). In amphibians and reptiles, the left atrium receives oxygenated blood from the gills/lungs/skin and the right atrium gets the deoxygenated blood from other body parts. However, they get mixed up in the single ventricle which pumps out mixed blood (incomplete double circulation). In birds and mammals, oxygenated and deoxygenated blood received by the left and right atria respectively passes on to the ventricles of the same sides. The ventricles pump it out without any mixing up, i.e., two separate circulatory pathways are present in these organisms, hence, these animals have double circulation.
- Why do we call our heart myogenic? Ans. The heart of molluscs and vertebrates including humans is myogenic. It means heart beat is initiated in heart itself by a patch of modified heart muscle called sino-atrial node or pacemaker which lies in the wall of the right atrium near the opening of the superior vena cava.
- Sino-atrial node is called the pacemaker of our heart. Why? Ans. The SAN can generate the maximum number of action potentials, i.e., , and is responsible for initiating and maintaining the rhythmic contractile activity of the heart. Therefore, it is called the pacemaker. Our heart normally beats 70-75 times in a minute (average 72 beats ).
- What is the significance of atrio-ventricular node and atrio-ventricular bundle in the functioning of heart? Ans. The entire heart is made of cardiac muscles. The walls of ventricles are much thicker than that of the atria. A specialised cardiac musculature called the nodal tissue is also distributed in the heart (Figure 15.2). A patch of this tissue is present in the right upper corner of the right atrium called the sino-atrial node (SAN). Another mass of this tissue is seen in the lower left corner of the right atrium close to the atrio-ventricular septum called the atrio-ventricular node (AVN). A bundle of nodal fibres, atrioventricular bundle (AV bundle) continues from the AVN which passes through the atrio-ventricular septa to emerge on the top of the interventricular septum and immediately divides into a right and left bundle. These branches give rise to minute fibres throughout the ventricular musculature of the respective sides and are called purkinje fibres. The nodal musculature has the ability to generate action potentials without any external stimuli, i.e., it is autoexcitable. However, the number of action potentials that could be generated in a minute vary at different parts of the nodal system.
- Define a cardiac cycle and the cardiac output. Ans. This sequential event in the heart which is cyclically repeated is called the cardiac cycle and it consists of systole and diastole of both the atria and ventricles. As mentioned earlier, the heart beats 72 times per minute, i.e., that many cardiac cycles are performed per minute. From this it could be deduced that the duration of a cardiac cycle is 0.8 seconds. During a cardiac cycle, each ventricle pumps out approximately 70 mL of blood which is called the stroke volume. The stroke volume multiplied by the heart rate (no. of beats per min.) gives the cardiac output. Therefore, the cardiac output can be defined as the volume of blood pumped out by each ventricle per minute and averages 5000 mL or 5 litres in a healthy individual. The body has the ability to alter the stroke volume as well as the heart rate and thereby the cardiac output. For example, the cardiac output of an athlete will be much higher than that of an ordinary man.
- Explain heart sounds. Ans. During each cardiac cycle two prominent sounds are produced which can be easily heard through a stethoscope. The first heart sound (lub) is associated with the closure of the tricuspid and bicuspid valves whereas the second heart sound (dub) is associated with the closure of the semilunar valves. These sounds are of clinical diagnostic significance.
- Draw a standard ECG and explain the different segments in it. Ans. ECG is graphic record of the electric current produced by the excitation of the cardiac muscles. The instrument used to record the changes is an electrocardiograph. A normal electro gram (ECG) is composed of a P wave, a QRS wave (complex) and a T wave. The P Wave is a small upward wave that represents electrical excitation or the atrial depolarisation which leads to contraction of both the atria (atrial contraction). It is caused by the activation of SA node. The impulses of contraction start from the SA node and spread throughout the artia. The QRS Wave (complex) represents ventricular depolarisation (ventricular contraction). It is caused by the impulses of the contraction from AV node through the bundle of His and Purkinje fibres and the contraction of the ventricular muscles. Thus this wave is due to the spread of electrical impulse through the ventricles.
The T Wave represents ventricular repolarisation (ventricular relaxation). The potential generated by the recovery of the ventricle from the depolarisation state is called the repolarisation wave. The end of the T-wave marks the end of systole. ECG gives accurate information about the heart. Therefore, ECG is of great diagnostic value in cardiac diseases.
3.0NCERT Class 11 Biology – Chapter-Wise Solutions & Explanations
Get NCERT Solutions for Class 11 Biology chapter-wise, with answers to all textbook questions. Study important topics, revise the syllabus, and prepare well for your Biology exams.
4.0Key Features of NCERT Solutions for Class 11 Biology Chapter 15
- Cardiac Cycle: Understand the 0.8-second cardiac cycle, including atrial and ventricular systole and diastole, valve movements, and the flow of blood through the heart.
- ECG Explained: Learn what the P-wave, QRS complex, and T-wave represent and how they relate to the electrical activity of the heart.
- Blood Clotting: Understand the main steps of blood coagulation and the role of clotting factors, vitamin K, and calcium ions.
- Blood Group Compatibility: Learn about ABO and Rh blood groups and understand blood transfusion compatibility and the reasons for transfusion reactions.
- Prepared by ALLEN Expert Faculty: Get clear explanations of the anatomical structures and physiological processes covered in NCERT Class 11 Biology Chapter 15.
- Double Circulation: Understand pulmonary and systemic circulation and how blood moves between the heart, lungs, and different parts of the body.
- Complete NCERT Exercise Solutions: Get clear answers to NCERT exercise questions to revise important concepts from Body Fluids and Circulation and prepare for school exams and NEET.