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NCERT Solutions for Class 11 Biology Chapter 15 Body Fluids and Circulation describe the major functions of blood and lymph in the body. Blood is a red fluid that transports oxygen, nutrients, and waste through blood vessels. It consists of plasma, red blood cells, white blood cells, and platelets. The chapter further discusses how blood clots are formed and why Blood Groups are important. It also includes important concepts such as the composition of blood, pathways of circulation, and the workings of the heart in a simple and organized way, along with the required diagrams to make understanding more clear.
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The human circulatory system is well-explained in easy language by describing the heart structure and function, the cardiac cycle, and double circulation. The regulation of cardiac activity and disorders of the circulatory system gives detailed knowledge of the transportation of nutrients and oxygen around the body. NCERT solutions provide clear explanations, helping students understand complex topics with ease. The NCERT Solutions for Class 11 Biology Body Fluids and Circulation explain concepts in a detailed and step-by-step manner, making them easy for students to understand.
Students can download the complete questions with detailed answers in a PDF of this chapter for better learning:
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The detailed answers to all the questions in this chapter are given below:
Question 1. Name the components of the formed elements in the blood and mention one major function of each of them.
Answer:
The following formed elements were discovered in the blood:
(1) Erythrocytes: The most prevalent type of red blood cells, erythrocytes are coloured red by the red pigment known as haemoglobin. Every part of the body receives oxygen from erythrocytes. Some body parts, like the marrow of long bones, ribs, etc., continuously produce these. Each cubic millimetre of blood contains roughly 4–6 million red blood cells.
(2) Leukocytes: These are colourless cells devoid of haemoglobin. They fall into two major categories and are the largest cells in the body.
(a) Granulocytes- These leukocytes have granules in their cytoplasm and include neutrophils, eosinophils, and basophils. Neutrophils are phagocytic cells that protect the body against various infecting agents. Eosinophils are associated with allergic reactions, while basophils are involved in inflammatory responses.
(b) Agranulocytes- Lymphocytes and monocytes are agranulocytes. Lymphocytes generate immune responses against infecting agents, while monocytes are phagocytic in nature.
(3) Platelets- These are small irregular bodies present in the blood. They contain essential chemicals that help in clotting. The main function of platelets is to promote clotting.
Question 2. What is the importance of plasma proteins?
Answer:
About 55% of blood is made up of plasma, the colourless fluid. It facilitates the transportation of waste materials, salts, food, and carbon dioxide, among other things. Proteins like albumins, globulins, and fibrinogens make up around 6.8% of plasma. The liver produces the plasma glycoprotein fibrinogen. It contributes to blood coagulation. One of the main proteins in plasma, globulin, shields the body from pathogens. One of the main proteins in plasma that keeps the fluid volume in the vascular space constant is albumin.
Question 3. Match Column I with Column II :
Column I | Column II |
---|---|
(a) Eosinophils | (i) Coagulation |
(b) RBC | (ii) Universal Recipient |
(c) AB Group | (iii) Resist Infections |
(d) Platelets | (iv) Contraction of Heart |
(e) Systole | (v) Gas transport |
Answer:
The correct matching is a- iii, b- v, c- ii, d-i, e- iv
Column I | Column II |
---|---|
(a) Eosinophils | (iii) Resist Infections |
(b) RBC | (v) Gas transport |
(c) AB Group | (ii) Universal Recipient |
(d) Platelets | (i) Coagulation |
(e) Systole | (iv) Contraction of Heart |
Question 4. Why do we consider blood as a connective tissue?
Answer:
For the following reasons, we view blood as connective tissue:
Question 5. What is the difference between lymph and blood?
Answer:
Blood
Lymph
Question 6. What is meant by double circulation? What is its significance?
Answer:
Double circulation occurs when blood flows through the heart twice in a single cycle. Although it can be found in birds, mammals, amphibians, and reptiles, it is most noticeable in birds and mammals because of their four-chambered hearts:
The circulation of blood is separated into:
Systemic circulation: Blood that has been oxygenated leaves the left ventricle and travels to the aorta, then passes through arteries to reach bodily tissues before returning to the right atrium as deoxygenated blood.
Pulmonary circulation: Blood that has lost oxygen travels from the right ventricle to the lungs for oxygenation before returning to the left atrium.
By separating oxygenated and deoxygenated blood, double circulation guarantees an effective oxygen supply.
Question 7. (1) Write the differences between Blood and Lymph
Answer:
Blood | Lymph |
Red liquid connective tissue that circulates in blood vessels. | White tissue fluid that circulates in lymphatic vessels. |
Red due to the presence of haemoglobin. | Colourless or pale yellow due to the absence of haemoglobin. |
Contains red blood cells (RBCs), white blood cells (WBCs), platelets, plasma, and haemoglobin. | Contains white blood cells (mainly lymphocytes), proteins, and plasma but lacks RBCs and platelets. |
Transports oxygen, nutrients, hormones, and waste products throughout the body. | Helps in immunity, removal of waste, and exchange of nutrients and gases between blood and cells. |
Travels through arteries, veins, and capillaries. | Travels through lymphatic vessels. |
Circulated by the heart. | Moves slowly without a central pump, relying on muscle movement and valves. |
Question 7. (2) Write the differences between Systole and Diastole
Answer:
Systoles:
Diastole:
Question 7. (3) Write the differences between P-wave and T-wave
Answer:
P-Wave:
T-Wave
Question 8. Describe the evolutionary change in the pattern of heart among the vertebrates.
Answer:
This development increases the availability of oxygen and effectively controls blood flow.
Question 9. Why do we call our hearts myogenic?
Answer:
Because the cardiac impulse starts in the heart's muscles, the organ is known as myogenic. The heart beats as a result of impulses produced by the SA node, a specialized cardiac tissue, spreading throughout the heart walls.
"Genic" means coming from, and "myo" means muscle.
Question 10. The sino-atrial node is called the pacemaker of the heart. Why?
Answer:
The sino-atrial node is referred to as the heart's pacemaker due to its ability to generate a cardiac impulse. The cardiac impulse and action potential are produced by the sinoatrial node. The atria and ventricles then contract or relax as a result of this cardiac impulse spreading throughout them.
The maximum number of action potentials that the SA node can produce is roughly 70–75 per minute. It also regulates the heart's rhythmic contractions.
Answer:
The atrioventricular node and atrioventricular bundle are important for the heart's operation because:
Question 12. Define the cardiac cycle and the cardiac output.
Answer:
The cardiac cycle
Question 13. Explain heart sounds
Answer:
Every heartbeat is followed by a series of heart sounds.
Question 14. Draw a standard ECG and explain the different segments in it.
Answer:
The heart's activity during a cardiac cycle is represented graphically by an ECG. Electrocardiograph, or ECG. Assume that a patient has three electrical leads attached to the device—one to the left ankle and one to each wrist—and that the device is continuously monitoring the patient's heart activity. Several leads are connected to the chest area for a thorough assessment of the heart's performance.
Every ECG peak is denoted by a letter, ranging from P to T, which represents a distinct electrical activity of the heart.
The P-wave is a representation of the electrical excitation (or depolarization) of the atria, which causes both atria to contract.
The QRS complex stands for the ventricles' depolarization, which starts the ventricular contraction. Shortly after, the contraction begins.
T-wave symbolizes the ventricles' repolarization or transition from an excited to a normal state.
The systole ends when the T-wave ends. Naturally, one can calculate a person's heartbeat rate by counting the number of QRS complexes that occur in a specific amount of time. For a given lead configuration, the ECGs from different people have a similar shape, so any deviation from this shape suggests a potential abnormality or illness. It is, therefore, very important from a clinical standpoint.
NCERT Solutions for Class 11 Subject-wise
The chapter explores the vital mechanisms by which essential substances like oxygen, nutrients, and hormones are transported throughout the body, highlighting the structure and function of the Human Circulatory System, including its components and associated disorders. Some important questions for better understanding are given below.
Question 1: Arrange the following blood vessels in descending order of their average pressure.
Aorta, artery, arteriole, capillary, venule, vein.
Choose the correct option:
A. Aorta > arteriole > venule > artery > vein > capillary.
B. Aorta > artery > arteriole > capillary > venule > vein.
C. Capillary > arteriole > venule > artery > vein > aorta.
D. Capillary > vein > venule > arteriole > artery > aorta.
Answer:
In terms of average pressure, the correct arrangement is as follows: Aorta > artery > arteriole > capillary > venule > vein. The aorta, being the largest artery, experiences the highest pressure as it receives blood directly from the left ventricle. The pressure gradually decreases as blood flows through the arteries, arterioles, and capillaries. The pressure is lowest in the venules and veins, where blood returns to the heart.
Hence, the correct answer is Option (2) Aorta > artery > arteriole > capillary > venule > vein.
Question 2: What is the definition of cardiac output?
Answer:
Cardiac output refers to the amount of blood pumped out of the ventricles of the heart per unit of time, typically measured in liters per minute. It represents the volume of blood ejected from the ventricles and delivered into the systemic circulation (aorta) and pulmonary circulation (pulmonary artery).
Question 3: Calculate the cardiac output (in liters per minute) for a heart with a stroke volume of 0.07 liters and a heart rate of 90 beats per minute.
Answer:
Cardiac output, a critical physiological parameter, represents the volume of blood ejected from the heart, particularly the left ventricle, within a minute. This measure effectively quantifies the heart's proficiency in delivering oxygen-rich blood throughout the body to meet metabolic demands and maintain systemic circulation.
Cardiac Output (CO) = Heart rate x Stroke volume of the Heart
CO = 90beats/min x 0.07L
CO = 6.3L/min
Question 4: What are the functions of the AV node and Purkinje fibres in the heart?
Answer:
The AV node delays ventricular depolarization relative to atrial depolarization, while the Purkinje fibres transmit the cardiac impulse to very small localized groups of ventricular fibres. The AV node acts as a gatekeeper, allowing a brief delay in the electrical signal to ensure proper coordination between the atria and ventricles. On the other hand, the Purkinje fibres rapidly transmit the electrical signal to ensure synchronized and efficient contraction of the ventricles. This combination of functions allows for the effective pumping of blood throughout the body.
Question 5: What happens to the mitral and tricuspid valves at the end of the first heart sound?
Answer:
At the end of the first heart sound (S1), both the mitral valve (left atrioventricular valve) and the tricuspid valve (right atrioventricular valve) are closed. The closure of these valves is responsible for producing the "lub" sound heard during auscultation.
The closure of the atrioventricular valves occurs during ventricular systole, which is the phase when the ventricles contract and pump blood out of the heart. The closure of these valves prevents the backflow of blood from the ventricles to the atria, ensuring that blood is ejected forward into the pulmonary artery and aorta.
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Listed below are some important tips that students must follow to understand the concepts clearly and solve their questions skillfully:
NCERT is the most important book for NEET, but to score higher and understand better, students should also study some extra topics and practice more questions beyond what’s in the book.
The NCERT Solutions for Class 11 Biology Chapter 15, Body Fluids and Circulation, help students understand how blood and lymph work in the body. This chapter explains the structure and function of the heart, blood vessels, and circulatory system. It also covers important topics like blood groups, blood clotting, and heart disorders. These solutions make learning easier by providing clear answers and step-by-step explanations. By studying this chapter, students can understand how nutrients, oxygen, and waste are transported in the body.
Below mentioned are the Chapter-wise solutions:
Important Topics Covered:
Blood has plasma, red blood cells (RBCs), white blood cells (WBCs), and platelets.
The liquid part of blood called plasma transports waste materials, hormones, and nutrients.
Additionally, it has proteins that support immunity and coagulation.
Red blood cells, or RBCs, use hemoglobin to carry oxygen and return carbon dioxide to the lungs.
White blood cells, or WBCs, protect the body from foreign substances and infections.
Hemoglobin in red blood cells binds to oxygen, which is then carried by arteries.
Carbon dioxide is returned to the lungs while oxygen is released for cellular respiration in tissues.
One heartbeat, lasting roughly 0.8 seconds, is included.
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