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

NCERT Solutions for Class 11 Biology Chapter 18: Examinations can be intimidating. But with the help of the right resources, you can overcome your fears and face them confidently. NCERT solutions are one of the best tools to prepare for the exams, especially when it comes to Biology.

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NCERT Solutions for Class 11 Biology Chapter 18 about Body Fluids and Circulation. It is a part of the unit, Human Physiology.

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

 

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Download NCERT Class 11 Biology Chapter 18 Solutions

NCERT solutions help clear things up for students. The design is simple and easy to understand, as the chapters are logical. Chapter 18 discusses concepts related to the fluids that are present in the human body, their functions, and their circulation through the bloodstream.

What will you learn in Class 11 Biology Chapter 18 – Body Fluids and Circulation?

Body Fluids and Circulation is the 18^th chapter in Biology for CBSE class 11. It has six concepts that talk about various aspects of the heart, blood, and the circulatory system.

Blood is a substance that mostly consists of plasma and other cellular material. Plasma is of straw color and is a viscous fluid that makes up for 55 percent of the blood. The blood has two major types of cells present in it, namely, the white blood cells and the red blood cells. While red blood cells live for about 120 days, white blood cells have a lifespan of only three or four days.

Red blood cells are the ones that carry the hemoglobin pigment, which gives the blood its color.

The chapter also talks about the human circulatory system that handles the flow of blood throughout the body. The primary organ of the human circulatory system is the heart. The heart pumps blood to the other parts of the body and has four parts. Two of them are the atria, and the other two are the ventricles.

The heart is a muscular organ that contracts and expands to function. And this contraction and expansion at regular intervals are known as the ‘cardiac cycle.’ The cardiac cycle consists of two phases, namely, the diastole and systole. During the diastole phase, the heart ventricles relax. Similarly, during the systole phase, they contract and pump blood into the arteries.

The autonomous nervous system controls the contraction and relaxation of the heart. When the heart contracts, the sympathetic nervous system acts to increase cardiac activity by increasing the heart rate and the strength of the ventricular contractions. Likewise, during the relaxation phase, the parasympathetic nervous system plays a prominent role in decreasing the heart rate and the strength of the ventricular contractions.

The normal diastolic pressure of the heart is 80 mm Hg, while the expected systolic pressure is 120 mm Hg. Also, when these two pressures cross 90 mm Hg and 140 mm Hg, respectively, the person suffers from Hypertension.

Similarly, when the arteries become narrow, a condition called coronary heart disease occurs. Coronary heart disease decreases the supply of blood to various other parts of the body.

If there is a clog in the heart, then it can lead to a cardiac arrest, where the heart ceases to function.

Benefits of NCERT Solutions for Biology Chapter 18

NCERT solutions offer a way for students to understand the concepts of chapter 18 in Biology, which talks about the heart and the circulatory system. You can find below various benefits of going through NCERT solutions for class 11 Biology Chapter 18.

1. Logical Flow

The chapter explains all the concepts logically so that the students will find it easier to understand them.

2. Designed by Experts

The teachers who design NCERT solutions are experts in Biology. So, they will be able to explain all the concepts concisely.

Access NCERT Solution For Class 11 Biology Chapter 18

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

The components of the formed elements in blood are as follows:

• Erythrocytes or Red blood cells – They carry oxygen and contain the pigment, hemoglobin. Hemoglobin reacts with oxygen to form Oxyhemoglobin that carries oxygen to areas that are deprived of oxygen in the body.
• Leucocytes or white blood cells – Lymphocytes are known to synthesize antibodies that neutralizes or kills germs. Neutrophils acts as a defense mechanism against bacteria known as phagocytosis.
• Thrombocytes or blood platelets – They aid in coagulation of blood

2. What is the importance of plasma proteins?

Significance of plasma proteins:

Some of the plasma proteins are

• Globulins – They are involved in the defense mechanism of the body, and are also referred to as immunoglobulins
• Albumins –They aid in maintaining the osmotic balance of the body
• Fibrinogens – it plays a significant role in blood coagulation

3. Match Column I with Column II :

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

Blood is a connective tissue as it is mesodermal derived and contains an extra-cellular matrix known as plasma. It is abundant and a widely distributed tissue in the body. Connective tissues link and bind, providing support to other organs of the body thereby transporting oxygen and other nutrients within the body, eliminating waste products from the body and flows throughout the body. Hence, it is considered as a connective tissue.

5. What is the difference between lymph and blood?

The difference between lymph and blood is as follows:

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

Double circulation, as the name suggests, is where the blood circulates twice in the heart. Double circulation is possible as the heart is divided into four chambers, the right and the left halves by the atrio-ventricular septum.

The two circulations are:

1. Pulmonary circulation
   • Blood in the right ventricle is pumped into the pulmonary arteries
   • For oxygenation, these pulmonary arteries transport deoxygenated blood to the lungs
   • The oxygenated blood is then sent to the left atrium from the lungs through the pulmonary veins
   • This type of circulation of blood is referred to as pulmonary circulation where blood is pumped via pulmonary blood vessels.

2. Systemic circulation
   • It is a term used to refer to the major circulation of the body
   • Oxygenated blood is pumped from the left ventricle into the aorta
   • Furthermore, it is carried by the arteries, arterioles and the linkage of blood capillaries
   • Simultaneously, deoxygenated blood is accumulated in the right atrium through the inferior and superior vena cava
   • This circulation supplies nutrients and oxygen and carries away carbon dioxide and other toxic substances for elimination

Importance of double circulation:

• This type of circulation checks and prevents the mixing of oxygenated and deoxygenated blood
• In double circulation, oxygen is utilized efficiently

7. 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

The differences are as follows:

(a) Blood and Lymph

(b) Open and Closed system of circulation

(c) Systole and Diastole

(d) P-wave and T-wave

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

An evolutionary change in the pattern of heart among the vertebrates has been observed through careful analysis. Vertebrates possess a muscular heart, it is chambered. They have evolved from having a two-chambered heart(fish) to possessing a four-chambered heart(mammals).

A fish has a two-chambered heart. It pumps deoxygenated blood to the gills where it is oxygenated and sent to the body. The blood that is oxygenated is then carried to the heart.

Three-chambered hearts are found in amphibians – a ventricle and 2 atria(left atrium and right atrium). The left atrium receives oxygenated blood from the respiratory organs while deoxygenated blood is received by the right atrium from the organs of the body. But, both types of blood are eventually mixed in the ventricle, hence the body receives mixed blood.

Half septum in reptiles divides the ventricle partially. But in birds, crocodiles and mammals, the heart is completely segregated into halves hence deoxygenated and oxygenated blood are separated.

A structural modification in the hearts of fish up till mammals is observed checking that oxygen-rich blood is supplied to the body while the four-chambered heart ensures that the blood flow is synchronized. As the structure of heart has evolved, the type of circulation also depends on it, if it is single or double circulation.

9. Why do we call our heart myogenic?

The term ‘myo’ refers to muscle and ‘genic’ refers to originating from. The altered cardiac muscles or the nodal tissues of the heart – the sino-atrial or the sinus node (SA node) is capable of generating an impulse that extends over the heart wall which results in a heartbeat. As the cardiac impulse initiates in the cardiac muscles, it is referred to as myogenic.

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

The sino-atrial or the sinus node (SAN) is a specialized bundle of neurons generating action potential which produces a cardiac impulse without any exterior stimuli i.e., it is auto excitable. SAN can generate a maximum action potential of approximately 70 to 75 in a minute. It is responsible to initiate and maintain the rhythmic contractile activity of the heart. Due to these capabilities, SAN is referred to as the pacemaker.

11. What is the significance of atrio-ventricular node and atrio-ventricular bundle in the functioning of heart?

The atrio-ventricular bundle (AV) originating from the AV-node passes the cardiac impulse to the walls of the ventricles whereas the atrio-ventricular node(AVN) conveys the impulse from the SA node. Both AVN and AV are triggered by the action potential that is originated by the sino-atrial node thereby conducting the stimulus to the other parts of the heart. This causes a heart beat which is conducted to various other parts of the heart.

12. Define a cardiac cycle and the cardiac output.

Cardiac cycle:

• The alternate contraction and relaxation of the chambers of the heart causes the blood to circulate in the heart.
• Relaxation or expansion phase is also referred to as diastole whereas contraction is also referred to as systole
• Every systole is followed by a diastole
• Cardiac cycle is the series of events that take place in one complete heart beat. It lasts for about 0.8 seconds

Cardiac output:

• It is the amount of blood that is pumped by each of the ventricle in a minute
• It is given by:

Cardiac output = stroke volume x number of heart beats per minute

13. Explain heart sounds.

A heart beat generates two sounds – lub and dub, produced in every cardiac cycle. The sound is produced in a sequence, in-sync with every heartbeat. ‘Lub’ is the first sound and is low pitched. It is caused when the bicuspid valve and the tricuspid valve closes. ‘Dub’ is the second sound which arises when the semi-lunar valve closes. This sound is high- pitched. Both the sounds are significant in the diagnosis of any disorder of the heart.

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

The graphical representation of the cardiac cycle that is generated by the electrograph is known as the electrocardiogram or ECG. The diagram below depicts a standard ECG:

In the ECG, each peak indicated by the letters ‘P’ to ‘T’ relates to a particular electrical activity of the heart. The first peak ‘P’ represents the atrial contraction or the atrial depolarization. The subsequent QRS complex indicates the depolarization of the ventricles or the ventricular contraction. Finally, the T-wave indicates the ventricular relaxation or ventricular repolarization.

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