NCERT Solutions for Class 11 Biology Chapter 18 Body Fluids and Circulation

Q1. Name the components of the formed elements in the blood and mention one major function of each of them.

Answer:

The formed elements found in the blood are as follows:

(1) Erythrocytes- These are the most abundant cells (red blood cells) and they contain the red pigment called haemoglobin that imparts a red colour to these cells. Erythrocytes carry oxygen to all parts of the body. These are produced continuously in some parts of the body such as the marrow of long bones, ribs, etc. There are about 4 — 6 million RBCs per cubic millimetre of blood.

(2) Leukocytes- These are colourless cells that do not contain haemoglobin. They are the largest cells of the body and are divided into two main categories.

(a) Granulocytes- These leucocytes 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.

Q2 What is the importance of plasma proteins?

Answer:

Plasma is the colourless fluid of blood which constitutes about 55% of the blood. It helps in the transport of food, C02, waste products, and salts etc. About 6.8% of the plasma is constituted by proteins such as fibrinogens, globulins, and albumins. Fibrinogen is a plasma glycoprotein synthesised by the liver. It plays a role in the clotting of blood. Globulin is a major protein of the plasma and it protects the body against infecting agents. Albumin is a major protein of the plasma that maintains the fluid volume within the vascular space.

Q3. 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

Q4. Why do we consider blood as a connective tissue?

Answer:

We consider blood as connective tissue because of these reasons:

• Connective tissues bind, link or support the other organs of the body.
• They are the most abundant and widely distributed tissue in the body.
• Blood transports gases, nutrients, and hormones from one body organ to the other.
• It flows throughout the body.
• Hence, blood is considered connective tissue.

NCERT solutions for class 11 biology chapter 18 body fluids and circulation:

Q5. What is the difference between lymph and blood?

Answer:

Blood

1. Blood is red liquid connective tissue.

2. It flows through blood vessels—arteries, veins and capillaries and it also contains hemoglobin, red blood cells, white blood cells and platelets.

4. It transports gases and other nutrients in the body

Lymph

1. Lymph is a white tissue fluid

2. It flows in the lymph vessels and it also contains white blood cells called lymphocytes.

4. Exchange of gases and nutrients between the blood and the cells occurs through the lymph.

Q6. What is meant by double circulation? What is its significance?

Answer:

Double circulation is a process during which blood passes twice through the heart during one complete cycle. This type of circulation is found in amphibians, reptiles, birds, and mammals. However, it is more prominent in birds and mammals as in them the heart is completely divided into four chambers —

• the right atrium,
• the right ventricle,
• the left atrium, and
• the left ventricle.

The movement of blood in an organism is divided into two parts:

(i) Systemic circulation

(ii) Pulmonary circulation

Systemic circulation involves the movement of oxygenated blood from the left ventricle of the heart to the aorta. It is then carried by the blood through a network of arteries, arterioles, and capillaries to the tissues. From the tissues, the deoxygenated blood is collected by the venules, veins, and vena cava, and is emptied into the left auricle. Pulmonary circulation involves the movement of deoxygenated blood from the right ventricle to the ulmon arte which then carries blood to the lungs for oxygenation.

Significance of double circulation: The separation of oxygenated and deoxygenated blood allows a more efficient supply of oxygen to the body cells. Blood is circulated to the body tissues through systemic circulation and to the lungs through the pulmonary circulation.

Q7. (1) Write the differences between : Blood and Lymph

Answer:

Blood

1. Blood is red liquid connective tissue.

2. It flows through blood vessels—arteries, veins, and capillaries and it also contain hemoglobin, red blood cells, white blood cells and platelets.

4. It transports gases and other nutrients in the body

Lymph

1. Lymph is white tissue fluid.

2. It flows in the lymph vessels and it also contains white blood cells called lymphocytes.

4. Exchange of gases and nutrients between the blood and the cells occurs through the lymph.

Q7. (3) Write the differences between : Systole and Diastole

Answer:

Systoles:

1. It is the contraction of heart chambers.
2. It increases the blood pressure inside the heart.
3. Blood is pumped out of the chambers which are in systole.

Diastole:

1. It is the relaxation of heart chambers.
2. The blood pressure in the heart falls.
3. Blood is received by the chambers which are in diastole.

Q7 (4) Write the differences between : P-wave and T-wave

Answer:

P-Wave:

1. P-Wave represents the depolarisation or electrical excitation of atria.
2. Blood is pumped into the ventricles.

T-Wave

1. T-Wave represents the repolarisation of ventricles.
2. Blood is received by the atria.

NCERT solutions for class 11 biology chapter 18 body fluids and circulation:

Q8 Describe the evolutionary change in the pattern of heart among the vertebrates.

Answer:

The evolutionary change in the pattern of heart among the vertebrates are given below:

1. The vertebrate heart has evolved from a two-chambered heart of a fish to a four-chambered heart of mammals and birds.
2. The heart of the fish is two-chambered. The heart pumps deoxygenated blood to the gills where it is oxygenated and sent to the body. The deoxygenated blood is carried to the heart.
3. In amphibians, there are three chambers—
   1. the left atrium
   2. the right atrium, and
   3. a ventricle.
4. The left atrium receives the oxygenated blood from the gills, the lungs or the skin. The right atrium receives deoxygenated blood from the body organs. However, eventually, both types of blood are mixed in the ventricle and the body is supplied with the mixed blood.
5. In the case of reptiles, there is half septum which divides the ventricle incompletely. Here, oxygenated and deoxygenated blood do not mix.
6. In crocodiles, birds, and mammals, the heart is completely divided into halves which keep the oxygenated and deoxygenated blood separate.
7. There is a structural modification in the heart from fish to mammals, which ensures the supply of oxygenated blood to the body. At the same time, the four-chambered structure makes sure that the flow of blood is regulated.

Q9. Why do we call our heart myogenic?

Answer:

Because the cardiac impulse originates in the heart muscles, which is called myogenic. Modified cardiac muscles or the nodal tissue of the heart—the SA node—can generate an impulse which spreads over the walls of the heart.

This results in the beating of the heart.

The meaning of ‘myo’ is ‘muscle’ and ‘genic’ is ‘originating from’.

Q10. Sino-atrial node is called the pacemaker of our heart. Why?

Answer:

Because of the property of originating a cardiac impulse, the sino-atrial node is called the pacemaker of the heart. The sino-atrial node generates the action potential and produces cardiac impulse. This cardiac impulse then spreads over atria and ventricles causing them to contract or relax.

The SA node can generate a maximum number of action potentials which is about 70−75 per minute. It also controls the rhythmic contractile activity of the heart.

Q11. What is the significance of the atrio-ventricular node and atrio-ventricular bundlein the functioning of heart?

Answer:

The significance of the atrioventricular node and the atrioventricular bundle in the functioning of the heart is :

• The atrioventricular node picks up the cardiac impulse from the SA node.
• The atrioventricular bundle which originates from the AV-node conveys the cardiac impulse further towards the walls of the ventricles.

NCERT Solution for class 11 biology chapter 18 body fluids and circulation:

Q12. Define a cardiac cycle and the cardiac output.

Answer:

Cardiac Cycle:

• The circulation of blood in the heart occurs because of the alternate contraction and relaxation of the heart chambers and the contraction is also known as systole , while relaxation is known as diastole .
• Each contraction phase (systole) is followed by a relaxation or expansion phase (diastole).
• The series of events which occur during one complete beat of the heart is called the cardiac cycle and the duration of one cardiac cycle is 0.8 seconds.

Cardiac Output:

• The amount of blood pumped by each ventricle per minute is called the cardiac output.

Q13. Explain heart sounds

Answer:

Heart Sound:

1. They occur in sequence with each heartbeat.
2. Two sounds, lub, and dub, are heard during each cardiac cycle.
3. The first sound lub is caused by the closure of the bicuspid and tricuspid valves. It is low pitched.
4. The second sound dub is caused by the closure of semi-lunar valves. It is high pitched.
5. Both sounds are important in the clinical diagnosis of any heart-related disorder.

Q14. Draw a standard ECG and explain the different segments in it.

Answer:

ECG is a graphical representation of heart activities during a cardiac cycle. ECG is Electrocardiograph. Suppose a patient is connected to the machine with three electrical leads that is one to each wrist and to the left ankle and it continuously monitors the heart activity. For a detailed evaluation of the heart's function, multiple leads are attached to the chest region.

Each peak in the ECG is identified with a letter from P to T that corresponds to a specific electrical activity of the heart.

P-wave: It represents the electrical excitation (or depolarization) of the atria, which leads to the contraction of both the atria.

QRS complex: It represents the depolarization of the ventricles, which initiates the ventricular contraction. The contraction starts shortly after

T-wave: It represents the return of the ventricles from excited to the normal state (repolarisation).

The end of the T-wave marks the end of the systole. Obviously, by counting the number of QRS complexes that occur in a given time period, one can determine the heartbeat rate of an individual. Since the ECGs obtained from different individuals have roughly the same shape for a given lead configuration, any deviation from this shape indicates a possible abnormality or disease. Hence, it is of great clinical significance.