Body Fluids And Circulation Class 11 Notes: CBSE Biology Chapter 15

Blood

It's a type of fluid connective tissue made up of liquid plasma (which serves as the matrix) and cellular components (RBCs, for example).WBCs and the platelets).

Plasma

The matrix of blood is a plasma-based fluid. It's a vicious, straw-coloured fluid that accounts for around 55% of the total volume of the blood.

Plasma contains a variety of proteins, including fibrinogen, globulins, and albumins. Fibrinogens aid in the clotting of blood.

Albumins serve to keep the body's osmotic equilibrium in check. Globulins are anti-inflammatory proteins.

Minerals like sodium ions, calcium ions, magnesium ions, and bicarbonate ions aid in maintaining equilibrium as well as nutrient transport and uptake. In addition to these, plasma contains amino acids and glucose.

Formed Elements

Erythrocytes, leukocytes, and blood platelets are examples of formed elements. Many blood cell kinds play various roles. RBCs (Red Blood Cells) are also known as erythrocytes. They make up the majority of the blood cells. The production of red blood cells takes place in the bone marrow. They are present in biconcave form and are enucleated (no nucleus). RBC's graveyard is known as Spleen.

White blood cells are also known as leukocytes. Because they lack haemoglobin, they appear colourless. They have a three-to-four-day lifespan. Granulocytes and agranulocytes are the two categories.

Granulocytes include neutrophils, basophils, and eosinophils. Agranulocytes include lymphocytes and monocytes.

Polymorphonuclear leukocytes are the same as neutrophils. Neutrophils are the most numerous of the three granulocytes. They're called phagocytic cells because they eat other cells. In comparison to other granulocytes, basophils are the smallest. They secrete serotonin, histamine, and basophils. So, basophils are involved in inflammatory reactions. Eosinophils are involved in allergic reactions.

Platelets, commonly known as thrombocytes, are blood platelets. Megakaryocytes manufacture them in the bone marrow. They play a role in the coagulation of blood. Any drop in platelet count might result in blood loss from the body.

Groups of Blood

ABO and Rh blood groups are the two types of blood groups.

The ABO Blood Grouping System

The presence or absence of specific antigens on the surface of RBCs determines ABO blood grouping. The two main surface antigens present in the red blood cells are A and B. There are 4 types of blood groups A, B, AB, and O groups.

Diagram of Blood Groups and Antigen on Red Blood Cells

The above table depicts blood groups and donor compatibility recipients.

Because the O blood group has no surface antigen, they are called universal donors, but the AB blood group is considered universal recipients because they have both surface antigens. Blood transfusion is done safely based on the blood group of the donor and recipients.

Rhomboid Classification

Rh is an antigen that is comparable to that found in Rhesus monkeys. Individuals who have Rh antigen on their RBCs are Rh-positive, while individuals who do not have Rh antigen are Rh-negative. If an Rh -ve person receives Rh +ve blood, the Rh -ve person will begin to produce antibodies against the Rh +ve blood. As a result, before a blood transfusion, the Rh group should be evaluated as well. When an Rh -ve pregnant mother carries an Rh +ve foetus, an important case of Rh mismatching has been discovered. Due to a barrier known as the placenta, the foetus' Rh antigens are not exposed to the mother's Rh-ve blood during the first pregnancy.

However, there is a chance that the mother's blood will mix with the child's during the birth of the first child. Mother begins to manufacture antibodies against the Rh antigen as a result of this. The Rh antibodies from the Rh -ve mother can leak into the blood of the Rh +ve foetus and damage the foetal RBCs if the mother conceives again. Agglutination of red blood cells occurs as a result of this. Erythroblastosis foetal is the name for this condition. The foetus will be anaemic and have jaundice. To avert this, the mother should be injected with anti-Rh antibodies as soon as the first kid is born.

Coagulation of Blood 

It is a condition in which blood clots. Blood coagulation is another term for blood clotting. Any type of injury or trauma causes blood clotting. This helps to prevent excessive blood loss. When a person is hurt, a reddish-brown scum forms at the site of the injury after a period of time. The clot is the medical term for this. Fibrils are a network of threads that make up a clot.

This network comprises blood that has been created but is dead or damaged. Fibrils are generated when inactive fibrinogen is converted in the presence of the enzyme thrombin. Platelets release certain substances that cause blood to clot. During blood coagulation, calcium ions play a critical function.

Lymph

Lymph, in addition to blood, is another fluid found in the body. In tissues, blood circulates through blood capillaries. Some water, as well as some water-soluble compounds, leaks into the interstitial spaces. Tissue fluid, also known as interstitial fluid, is a type of fluid found in the body. The lymphatic system is a collection of tubes that collect interstitial fluid and discharge it to the main veins. Lymph is a fluid found in the lymphatic system. Lymph contains lymphocytes, which are an essential type of immune cell.

Lymph Node

Pathways of Circulation

The open circulatory system and the closed circulatory system are the two types of circulatory channels found. When blood flows in lacunae and sinuses, it is known as the open circulatory system. It is found in molluscs, arthropods, etc. The heart is a muscular, pumping organ found in vertebrates. Fishes' hearts are divided into two chambers. Except for crocodiles, all amphibians have three-chambered hearts (4 chambered hearts). Humans, birds, and reptiles all have four-chambered hearts.

The Circulatory System of the Human Body

The heart, blood arteries, and blood make up the human circulatory system. The heart is a mesodermal organ. It is located between the two lungs in the thoracic cavity. The heart is surrounded by a double membrane called the pericardium. The pericardium is a tissue ring that surrounds the pericardial fluid and protects it. There are four chambers in the heart: two atria and two ventricles. A small wall separates the left and right atria. The intra-atrial septum is what it's called. The left and right ventricles are separated by a strong interventricular septum.

Human Heart

The tricuspid valve protects the entrance between the right atrium and the right ventricle. The mitral valve, also known as the bicuspid valve, protects the entrance between the left atrium and the left ventricle. Semilunar valves are found at the entrances of the right and left ventricles into the pulmonary artery and aorta, respectively.

The heart is a musculoskeletal organ. Cardiac muscles are the muscles that make up the heart. The heart also contains specialised cardiac muscle known as nodal tissue. The sinoatrial node, or SA node, is located in the top right corner of the right atrium. The atrioventricular node, or AV node, is located in the upper left corner of the right atrium.

The atrioventricular bundle (AV bundle) extends from the AVN and divides into a right and left bundle after passing through the atrioventricular septa. Purkinje fibres are tiny fibres that grow from these branches. Because it has the ability to get excited and generate an action potential, the SA node is known as the heart's pacemaker.

Cardiac Cycle of the Heart

The cardiac cycle is the sequence of electrical and mechanical events that occur throughout each heartbeat. Diastole and systole are the two stages of the heartbeat. The heart ventricles relax during diastole, allowing blood to flow into them. The ventricles contract during systole to pump blood into the arteries. The Contraction of the right and left atria is followed by electrical stimulation in the atrial systole. The blood pressure in both the left and right atria rises as a result of this. In order for blood to be pushed into the ventricles. AV valves are open while semilunar valves are closed during this time. It takes roughly 0.1 seconds to complete.

Ventricular systole is characterised by the contraction of both the right and left ventricles, followed by electrical stimulation. During ventricular systole, the AV valves close and the semilunar valves open. It takes roughly 0.3 seconds to complete. Cardiac diastole occurs when the heart relaxes in order to fill the blood vessels. Complete cardiac diastole occurs when the atria and ventricles relax together. The pressure in the ventricles decreases below the left atrial pressure during ventricular diastole, the mitral valve opens, and the left ventricle fills with blood.

When the pressure in the right ventricle falls below that in the right atrium, the tricuspid valve opens, allowing blood to flow into the right ventricle. During diastole, the pressure inside the left ventricle is lower than in the aorta, allowing blood to circulate within the heart via the coronary arteries. When the pressure in the right ventricle falls below that in the right atrium, the tricuspid valve opens, allowing blood to flow into the right ventricle. During diastole, the pressure inside the left ventricle is lower than in the aorta, allowing blood to circulate within the heart via the coronary arteries.

The Sound of the Heart

The heartbeat is said to as a "lubb-dubb" sound. When the mitral and tricuspid valves collapse at the start of ventricular systole, the first heart sound lubb is produced. When the aortic and pulmonary valves seal at the conclusion of ventricular systole, the second sound dubb is produced.

ECG 

ECG stands for electrocardiograph and is a graphical representation of the electrical activity of the heart during the cardiac cycle. Various peaks are denoted by letters P through T in a typical ECG.

ECG Wave Representation

• P-Wave: Represents atrioventricular electrical stimulation. The atrial depolarization is visible.
• QRS Complex: The ventricular depolarization is represented by this complex. Ventricular contraction begins as a result of this. Soon after Q, the contraction begins.
• T-Wave: The T-Wave represents the repolarization of the ventricles. After excitation, it denotes the restoration of ventricles to their natural state. The end of the T-Wave indicates that the ventricular systole has ended.

Double Circulation: This is a circulation system in which blood circulates twice through the heart in a single cycle. It is divided into two parts: pulmonary and systemic circulation.

Blood Circulation between the heart and the lungs is referred to as pulmonary circulation. The heart's deoxygenated blood enters the lungs for oxygenation, and the oxygenated blood returns to the heart. A circulation system in which blood passes twice through the heart in a single cycle is known as double circulation. It is split into two sections: pulmonary circulation and systemic circulation. Pulmonary circulation is the exchange of blood between the heart and the lungs. The deoxygenated blood from the heart is oxygenated in the lungs before returning to the heart.

The Autonomous Nervous System (ANS) regulates heart activity through the neural centre in the medulla oblongata. The sympathetic nervous system raises heart rate and ventricular contraction strength, increasing cardiac output. Certain adrenal medullary hormones can also affect cardiac output.

Circulatory System Disorders:

Hypertension, often known as high blood pressure, is a condition in which a person's blood pressure is higher than usual. Blood pressure should be 120/80 mm Hg. The systolic pressure is 120 mm Hg, while the diastolic pressure is 80 mm Hg.

Coronary Heart Disease, also known as atherosclerosis, is characterised by a narrowing of the artery lumen due to calcium, fat, cholesterol, and fibrous tissue deposition. It has an effect on the heart muscle's blood supply.

Angina: Also known as angina pectoris, angina is a type of chest pain caused by a lack of oxygen reaching the heart muscles.

Heart Failure is the inefficient pumping of blood by the heart, which is mainly caused by heart congestion. As a result, it's also known as congestive heart failure.

Some Frequently Asked Questions for Exam from Chapter 15 Body Fluids And Circulation

Section–A (1 Mark Questions)

1. Name the component of blood which is a viscous and straw-coloured fluid.

Ans. The viscous and straw-coloured fluid which constitutes blood is called plasma.

2. Name the vascular connection that exists between the digestive tract and the liver.

Ans. The vascular connection between the digestive tract and the liver is called the hepatic portal system.

3. Given below are the abnormal conditions related to blood circulation. Name the disorders.

(i) Acute chest pain due to failure of oxygen supply to heart muscles.

(ii) Increased systolic pressure.

Ans.

(i) The condition involving acute chest pain due to failure of oxygen supply to the heart is called Angina.

(ii) Systolic pressure increases during Hypertension.

4. Fill in the blanks.

1. The serum in the plasma is without __________ factors.

2. In an ECG, one determines the heart rate by counting the number of ______.

Ans.

1. Clotting

2. QRS segment.

5. Given below is the diagrammatic representation of a standard ECG. Label its different peaks.

Ans. The different peaks observed in an electrocardiogram ECG are as follows:

Section–B (2 Mark Questions)

6. State the functions of the following in blood 

a. Fibrinogen 

b. Globulin 

c. Neutrophils 

d. Lymphocytes

Ans. 

a. Fibrinogen: It is an important clotting factor present in plasma responsible for the formation of blood clots.

b. Globulin: They primarily are involved in the defence mechanisms of the body.

c. Neutrophils: They are responsible for phagocytic activity.

d. Lymphocytes: They are responsible for antibody formation hence in the defence mechanism.

7. What physiological circumstances lead to erythroblastosis fetalis?

Ans. Erythroblastosis fetalis is caused by Rh incompatibility or mismatching, which is observed between the Rh-negative blood of a pregnant mother and with Rh-positive blood of the foetus. This could cause anaemia or even the death of the foetus.

8. Why do we call our heart myogenic?

Ans. 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.

9. Define the cardiac cycle and the cardiac output.

Ans. The sequential event in the heart which is cyclically repeated is called the cardiac cycle and it consists of the contraction of both atria and ventricles which is called systole and the relaxation of both the atria and ventricle which is called diastole.

Cardiac output is the amount of blood that is pumped by the heart in one minute. It is the product of the heart rate, which is the number of beats per minute, and the stroke volume, which is the amount of blood pumped from the ventricles per beat.

Cardiac Output = heart rate x stroke volume.

10. Write a short note on heart failure.

Ans. It is a state of heart when the heart does not pump blood effectively enough to meet the needs of the body. It is sometimes called congestive heart failure because congestion of the lungs is one of the main symptoms of this disease.

5 Important Topics of Biology Class 11 Chapter 15 You Shouldn’t Miss!

Importance of Biology Chapter 15 Body Fluids and Circulation Class 11 Notes

• Understanding the circulatory system helps students learn how the heart, blood vessels, and blood work together to keep the body functioning.

• Class 11 Body Fluids And Circulation Notes explain how oxygen and nutrients are transported to all cells, helping students grasp the importance of circulation in maintaining life.

• Learning about blood components like red blood cells, white blood cells, and platelets makes it easier to understand how the body fights infections and heals wounds.

• The topic of blood groups and compatibility in transfusions is essential for understanding real-life medical practices.

• Students gain knowledge about how the lymphatic system supports immune function and removes waste from tissues from Body Fluids And Circulation Class 11 Short Notes.

• By studying circulation, students can understand how issues like hypertension and heart disease develop, which is useful for health awareness.

• Body Fluids And Circulation PDF Notes help in recognising the role of various body fluids like plasma and lymph in maintaining balance in the body.

• Understanding how waste products are removed from the body helps students see how the body maintains cleanliness and health.

Tips for Learning the Class 11 Biology Chapter 15 Body Fluids and Circulation

• Start by understanding the basic functions of body fluids, like blood and lymph, and how they help transport nutrients and oxygen in the body.

• Focus on the structure and function of the human heart. Learn how blood flows through different chambers and the role of valves in maintaining proper circulation.

• Break down the different types of blood vessels (arteries, veins, capillaries) and their specific roles in the circulatory system.

• Pay attention to the components of blood, such as red blood cells, white blood cells, platelets, and plasma, and understand their functions.

• Study the process of blood clotting to understand how the body prevents excessive blood loss during injuries.

• Learn about the lymphatic system, its role in fluid balance, and how it works alongside the circulatory system.

• Use diagrams to visualise the circulatory pathways, especially the systemic and pulmonary circulations, for better retention.

• Practice answering questions related to blood groups, their antigens, and how transfusions work based on compatibility.

Conclusion

The study of CBSE Class 11 Biology Chapter 15 - Body Fluids and Circulation offers insights into the mechanisms facilitating fluid circulation in the human body. The chapter covers topics such as blood composition, heart structure and function, and circulation processes. Free PDF downloads of Class 11 Biology Chapter 15 notes provide comprehensive resources for students. These notes include explanations, diagrams, and illustrations on blood plasma, cells, heart structure, cardiac cycle, and cardiac activity regulation. The accessible format allows students to study at their own pace, aiding exam preparation. These notes promote an understanding of cardiovascular health, homeostasis, and physiological interconnectedness, enhancing knowledge and exam performance.

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