Important Questions Class 11 Biology Chapter 15 Body Fluids and Circulation
Important Questions Class 11 Biology Chapter 15 Body Fluids and Circulation
Body Fluids and Circulation is Chapter 15 of Class 11 Biology. Blood and lymph are the body fluids that carry food, oxygen, hormones and waste materials to and from the cells. The chapter explains the composition of blood, blood groups, clotting of blood, lymph, the structure of the human heart, the cardiac cycle, the ECG (electrocardiogram), double circulation and disorders of the circulatory system.
This page gives 12 important questions from Body Fluids and Circulation with clear answers prepared by Extramarks experts. The questions cover the standard ECG, heart sounds, cardiac cycle and cardiac output, the SA node and AV node, double circulation, the difference between blood and lymph and erythroblastosis foetalis. Students can use them for school tests and CBSE (Central Board of Secondary Education) exam revision, and teachers and parents can use them for quick practice.
Important Questions Class 11 Biology Chapter 15 Body Fluids and Circulation
Body Fluids and Circulation
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Body Fluids and Circulation
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Body Fluids and Circulation
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Body Fluids and Circulation
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Body Fluids and Circulation
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Body Fluids and Circulation
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Body Fluids and Circulation
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Body Fluids and Circulation
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Body Fluids and Circulation
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Body Fluids and Circulation
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Body Fluids and Circulation
Medium
Body Fluids and Circulation
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Body Fluids and Circulation
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Body Fluids and Circulation
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Q1. Premarital medical screening is fast gaining ground these days wherein intending couples are tested for genetic, infectious and blood transmitted diseases to avoid unwanted future circumstances like life-threatening diseases or complications in babies. A couple underwent such an examination and was advised not to plan for more than one child as their blood
analysis showed that the condition can be fatal for the second pregnancy.
a. Interpret the suggestion of doctors and identify the condition the couple is affected with?
b. Explain why this condition is considered fatal for the second pregnancy.
c. The male partner did not agree with the suggestion because he has read that the situation can be avoided. Can you justify his perception.
Answer: a. The condition the couple might be affected with is erythroblastosis foetalis.
b. Erythroblastosis foetalis is a hemolytic disease of foetus and newborn. It is observed when a Rh+ man marries a Rh- woman. In such cases, the baby would be Rh+ as it is the dominant allele. During first pregnancy or at the time of delivery, the foetal antigen sensitises the maternal lymphocytes to produce the anti Rh antibody. At the time of second pregnancy, the antibodies present in maternal circulation enter the foetal circulation by crossing the placental barrier and attack the foetal RBC. This causes haemolysis or destruction of RBC in the foetal circulation. If the baby is born, he/she could suffer from severe anaemia and jaundice.
c. Yes, the perception of male partner was correct as erythroblastosis foetalis can be avoided if blood group of both parents is known so that anti-Rh antibodies can be administered to the mother immediately after the delivery of the first child.
Q2. Draw a standard ECG and explain the different segments in it.
Answer: Electrocardiogram (ECG) is the graphical representation of the cardiac cycle. It is produced by an electrocardiograph. The normal ECG indicating that the heart is functioning properly is shown below.
A typical human ECG includes the following waves:
- P-wave: It represents depolarization of the right and left atria. The impulse of contraction by the SA node is generated during this wave.
- QRS wave: It shows depolarization and contraction of the right and left ventricles. The contraction starts shortly after Q and indicates the beginning of systole.
- T-wave: It represents repolarization (return from excited to normal) and relaxation of the ventricles. Its end indicates the end of systole.
Waves P, R and T are above the base line and are called positive waves, while Q and S are below the base line and are known as negative waves.
Q3. Explain heart sounds.
Answer: When the valves of heart open and close during the cardiac cycle, they produce a sound known as heart sound. These sounds are lub and dub. Lub is the first sound and is produced by the vibrations of the heart when bicuspid and tricuspid valves (valves present between atria and ventricle) close at the beginning of systole (when ventricular muscles contract). It is followed by second sound dub which is produced by vibrations caused due to closing of semilunar valves (which guard the pulmonary artery and the aorta) at the end of the systole.
Q4. Define a cardiac cycle and the cardiac output.
Answer: A cardiac cycle refers to the complete cycle of events from the start of one heartbeat to the start of next. It includes diastole and systole that involves filling of the heart with blood and then pumping it out. During diastole, the heart relaxes and fills with the blood. During systole, the ventricle contracts and pumps out the blood.
Cardiac output is the amount of blood pumped out by each ventricle in a minute. It is calculated by multiplying stroke volume (volume of blood pumped by each ventricle in a cardiac cycle) and heart rate (beats per minute).
Q5. What is the significance of atrio-ventricular node and atrio-ventricular bundle in the functioning of heart?
Answer: Atrio-ventricular (AV) node is present in right auricle at the base of inter-auricular septum, which separates right auricle from the ventricle. From this node, a bundle of nodal fibres called AV bundle arises and it passes via the AV septa. Immediately, it divides into left and right bundle. These bundles give rise to Purkinje fibres, which penetrate into the myocardium. These fibres along with the bundles form the structure called the bundle of His. This nodal system is auto-excitable, that is, it possesses the ability to generate an action potential in the absence of electric impulse. The electrical impulse is then passed on to ventricle by the bundle of His and Purkinje fibres. This impulse leads to contraction of the ventricles.
Q6. Sino-atrial node is called the pacemaker of our heart. Why?
Answer: Sino-atrial node is called the pacemaker of heart because it is a specialized structure made up of cardiac myocytes that have both muscular and nervous characteristics. It is located in the upper side of right atrium. This structure has the ability to generate action potentials without any external stimuli. It initiates the impulse of contraction that subsequently spreads throughout the heart. It can generate a maximum of 70-75 action potentials per minute. It initiates and maintains rhythmic contraction of heart. Our heart usually beats around 70-75 times in a minute.
Q7. Why do we call our heart myogenic?
Answer: Our heart is called myogenic heart because it receives signals for contraction from specialized cells called cardiac myocytes found in it. Cardiac myocytes form a specialized structure, known as nodal tissue, that possesses both muscular and nervous characteristics. The human heart receives the signals for contraction from the nodal tissue.
Q8. Describe the evolutionary change in the pattern of heart among the vertebrates.
Answer: The heart is a hollow muscular organ that pumps blood to all the tissues of the body. This process provides oxygen to various body parts. Evolution of heart has helped in more efficient transport of oxygen in the body by preventing the mixing of oxygenated and deoxygenated blood as described below:
Fish: Fish have a very simple heart structure. Its heart is a two-chambered hollow tube-like structure. It has one atrium and one ventricle. Deoxygenated blood enters the atrium of the heart from where the blood is pumped into the ventricle. It then enters into the gills for oxygenation. The blood oxygenated in the gills is circulated across the body and finally, the deoxygenated blood from different body parts is transported back into the atrium of the heart.
Amphibians: Amphibians have a three-chambered heart: two auricles and one ventricle. Oxygenated blood from the lungs enters into the left auricle while deoxygenated blood from other body parts enters into the right auricle. Both auricles transfer blood to the ventricle. In the ventricles, the oxygenated and deoxygenated blood mixes and this mixed blood is circulated to different body parts.
Reptiles: Reptilians (except crocodiles) have an incomplete four-chambered heart. They have two auricles and a ventricle which is partially divided into two chambers. There is partial mixing of oxygenated and deoxygenated blood due to incomplete partitioning of the ventricles.
Mammals and birds: Mammals and birds have a four-chambered heart. This prevents the mixing of oxygenated and deoxygenated blood. Right atrium receives deoxygenated blood and transfers it into right ventricle. From the right ventricle, deoxygenated blood is pumped into lungs to get oxygenated. Oxygenated blood is returned to left auricle of the heart. From left auricle, the oxygenated blood flows into the left ventricle and is pumped to whole body.
Q9. 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
Answer: (a) Blood and Lymph
| Blood | Lymph |
|---|---|
| Blood is red due to the presence of haemoglobin in red blood cells (RBCs). | Lymph is colourless due to the absence of red blood cells (RBCs). |
| Blood contains RBCs, WBCs and platelets. | Lymph contains less number of WBCs and platelets. |
| Blood contains proteins. | It lacks proteins. |
| It transports digested food materials, respiratory gases and metabolic waste products. | It transports digested fats and fat-soluble vitamins and is involved in the defence mechanism. |
| The flow of blood in the vessels is fast. | Lymph flows slowly. |
(b) Open and Closed system of circulation
| Closed system | Open system |
|---|---|
| In the closed type of circulatory system, blood flows inside the blood vessels all the time. | In the open type of circulatory system, blood is directly pumped into the body cavity called sinuses. |
| There are valves to prevent backward flow of blood. | There are no valves to prevent backward flow of blood. |
| Oxygen and nutrients diffuse out from the blood vessels to nourish the surrounding tissues/organs. | Oxygen and nutrients are directly supplied to tissues/organs by the blood present in the body cavity. |
| Blood and interstitial fluids do not mix. | There is no distinction between blood and interstitial fluid. They are called as hemolymph. |
| Blood flows at relatively higher speed. | Blood (hemolymph) flows at very slow speed. |
| Closed system is present in annelids and chordates. | Open type circulatory system is present in molluscs and arthropods. |
(c) Systole and Diastole
| Systole | Diastole |
|---|---|
| Systole refers to the contraction of heart muscles. | Diastole refers to the relaxation of heart muscles. |
| During systole, blood is pumped into the aorta and pulmonary arteries. Right ventricle contracts to send blood to the lungs via pulmonary artery. Left ventricle pumps blood into aorta. | During diastole, the heart chambers come back to original size to receive the blood. Blood received by atria is released into ventricles. |
| Atrio-ventricular valves close and semilunar valves open. | Atrio-ventricular valves open and semilunar valves close to prevent backflow of blood into the atria. |
(d) P-wave and T-wave
| P-wave | T-wave |
|---|---|
| It indicates activation of Sino-atrial node. | It indicates ventricular relaxation. |
| P-wave represents atrial excitation (depolarization) that results in atrial contraction. | T-wave shows the return of ventricles from excited to normal state (repolarization). |
Q10. What is meant by double circulation? What is its significance?
Answer: Double circulation refers to the process wherein blood passes two times through the heart in one complete cycle. In this circulation, the blood circulates in two distinct and separate pathways/loops (pulmonary circulation and systemic circulation). It is observed in birds and mammals as they have a four-chambered heart.
Pulmonary circulation: The pumping of blood from the heart to the lungs forms the pulmonary circuit. The right atrium of the heart receives deoxygenated blood from all the body parts. The deoxygenated blood then moves to the right ventricle. This deoxygenated blood is carried to the lungs from the right ventricle of the heart via the pulmonary artery. The blood is oxygenated in the lungs and is transported back to the left atrium by the pulmonary vein.
Systemic circulation: Flow of oxygenated blood, from the left ventricle of the heart, via arteries, arterioles and capillaries to the tissues is known as a systemic circuit. In the lungs, deoxygenated blood acquires oxygen and goes into the left atrium of the heart. From the left atrium, the oxygenated blood goes to left ventricle. Thereafter, the blood moves into the aorta and is carried to different body tissues by a network of arterioles, arteries, and capillaries. The deoxygenated blood is then collected from body tissues by a system of venules, veins and vena cava and emptied into the right atrium. This forms the systemic circulation. Systemic circulation provides nutrients, oxygen and other necessary substances to various body parts and carries back carbon dioxide and other harmful waste products away for elimination from the body.
Significance: The importance of double circulation is that it does not allow the mixing of oxygenated and deoxygenated blood. Thus, it ensures the efficient oxygen supply to the body organs.
Q11. What is the difference between lymph and blood?
Answer:
| Lymph | Blood |
|---|---|
| Lymph is the component of the lymphatic system. | Blood is part of the circulatory system. |
| Lymph is colourless due to the absence of red blood cells (RBCs). | Blood is red due to the presence of haemoglobin containing RBCs. |
| Lymph contains plasma, a few number of WBCs (white blood cells) and platelets. | Blood contains RBCs, WBCs and platelets. |
| It lacks proteins. | Blood contains proteins like albumin, globulin and fibrinogen. |
| It is the part of the immune system and plays a major role in defense mechanism. | It circulates oxygen, carbon dioxide, hormones, nutrients, and metabolic waste products in the body. |
Q12. Why do we consider blood as a connective tissue?
Answer: Connective tissue supports and connects different types of tissues and organs of the body. Blood is considered as a connective tissue due to the following reasons:
a) It is mesodermal in origin like other connective tissues.
b) Like connective tissues, blood has plasma as the extracellular matrix in which various formed elements (cellular components) like erythrocytes, leucocytes and platelets are suspended.
c) It connects various body parts and organ systems. Nutrients, hormones, oxygen and other essential elements are transported from one part of the body to another through the blood. Blood also carries waste products from various organs to the site of excretion.
Related Study Material on Extramarks
- Important Questions for Class 11 Biology Chapter 1 The Living World
- Important Questions for Class 11 Biology Chapter 2 Biological Classification
- Important Questions for Class 11 Biology Chapter 3 Plant Kingdom
- Important Questions for Class 11 Biology Chapter 4 Animal Kingdom
- Important Questions for Class 11 Biology Chapter 5 Morphology of Flowering Plants
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Q.1 Bending of shoot tip in absence of light is
Marks:1
Ans
Bending of shoot tip in the absence of light is etiolation. It occurs when plants are grown in either partial or complete absence of light, and is characterized by long, weak stems, smaller & sparser leaves due to longer internodes and a pale yellow color.
Q.2 Rita has brought the stem cutting of an exotic variety of rose. In order to make her stem produce roots, she should use
Marks:1
Ans
auxin.
Auxins are growth hormones which promote growth of roots. It is used in horticulture for rooting of stem cuttings.
Q.3 Gibberellins promote
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Ans
Seed Germination.
Explanation:
Some light sensitive seeds, like Lectuca sativa (Lettuce), germinate in complete darkness with the help of Gibberellins which otherwise require specific light conditions.
Q.4 Mathematically ‘Relative Growth Rate’ can be expressed asÂ
Marks:1
Ans
Relative Growth Rate = (Increase in Volume / Initial Volume) X 100
Explanation:
Mathematically ‘Relative Growth Rate’ can be expressed as:
Relative Growth Rate = (Increase in Volume / Initial Volume) X 100.
Q.5 The phase of growth, where synthesis of more protoplasm, formulation of a central vacuole and addition and extension of wall material takes place, is known as
Marks:1
Ans
The phase of growth, where synthesis of more of protoplasm, formulation of a central vacuole and addition and extension of wall material takes place, is known as phase of elongation.