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

Transcription

1 CLASS XI BIOLOGY Body Fluids And Circulation 1. Name the components of the formed elements in the blood and mention one major function of each of them. Formed Elements in Blood And Their Functions: Erythrocytes or red blood cells (RBC): These molecules play a significant role in transport of respiratory gases. Leucocytes or white blood cells (WBC): They are of two types, viz. granulocytes and agranulocytes. as they are Neutrophils, eosinophils and basophils are different types of granulocytes, while lymphocytes and monocytes are the agranulocytes. Neutrophils and monocytes (6-8 per cent) are phagocytic cells which destroy foreign organisms entering the body. Basophils secrete histamine, serotonin, heparin, etc., and are involved in inflammatory reactions. Eosinophils (2-3 per cent) resist infections and are also associated with allergic reactions. Lymphocytes (20-25 per cent) are of two major types B and T forms. Both B and T lymphocytes are responsible for immune responses of the body. Platelets or thrombocytes: Platelets can release a variety of substances most of which are involved in the coagulation or clotting of blood. 2. What is the importance of plasma proteins? Plasma Proteins: Fibrinogen, globulins and albumins are the major proteins. Fibrinogens are needed for clotting or coagulation of blood. Globulins primarily are involved in defense mechanisms of the body and the albumins help in osmotic balance. 3. Match Column I with 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 Column I Eosinophils RBC AB Group Platelets Systole Column II Resist Infections Gas Transport Universal Recipient Coagulation Contraction of Heart

2 4. Why do we consider blood as a connective tissue? Connective Tissue: It is largely a category of exclusion rather than one with a precise definition, but all or most tissues in this category are similarly: (a) Involved in structure and support. (b) Derived from mesoderm, usually. (c) Characterized largely by the traits of non-living tissue. Blood is considered a connective tissue for two basic reasons: (1) embryologically, it has the same origin (mesodermal) as do the other connective tissue types and (2) blood connects the body systems together bringing the needed oxygen, nutrients, hormones and other signaling molecules, and removing the wastes. As the name implies, connective tissue serves a "connecting" function. It supports and binds other tissues. Unlike epithelial tissue, connective tissue typically has cells scattered throughout an extracellular matrix. Interestingly enough, blood is considered to be a type of connective tissue. Even though it has a different function in comparison to other connective tissues it does have an extracellular matrix. The matrix is the plasma and erythrocytes, leukocytes and platelets are suspended in the plasma. 5. What is the difference between lymph and blood? Lymph is the interstitial fluid found between the cells of the human body. It enters the lymph vessels by filtration through pores in the walls of capillaries. The lymph then travels to at least one lymph node before emptying ultimately into the right or the left subclavian vein, where it mixes back with blood. Lymph has a composition comparable to that of blood plasma, but it may differ slightly depending on the tissue served (drained). Lymph contains white blood cells. In particular, the lymph that leaves a lymph node is richer in lymphocytes. Likewise, the lymph formed in the digestive system called chyle is rich in triglycerides (fat), and looks milky white. 6. What is meant by double circulation? What is its significance? The double circulatory system of blood flow refers to the separate systems of pulmonary circulation and the systemic circulation in amphibians, birds and mammals (including humans.) In contrast, fish have a single circulation system

3 because they do not have lungs. All animals with lungs have a double circulatory system. For instance the adult human heart consists of two separated pumps, the right side with the right atrium and ventricle (which pumps deoxygenated blood into the pulmonary circulation), and the left side with the left atrium and ventricle (which pumps oxygenated blood into the systemic circulation). Blood in one circuit has to go through the heart to enter the other circuit. Double circulation system is more efficient as it prevents mixing of oxygenated and deoxygenated blood. There is optimum utilization of oxygen because of this type of system. 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 (a) Blood contains RBCs and hence can transport gases. Lymph doesn t contain RBCs and cannot transport gases. Lymph mainly contains WBCs and play a role in the immune system of the body. (b) The Open Circulatory System is a system in which fluid (called hemolymph) in a cavity called the hemocoel bathes the organs directly with oxygen and nutrients and there is no distinction between blood and interstitial fluid; this combined fluid is called hemolymph or haemolymph. The cardiovascular systems of humans are closed, meaning that the blood never leaves the network of blood vessels. (c) Systole is the contraction of heart muscle and diastole is the dilatation of the heart muscle. (d) Each peak in the ECG is identified with a letter from P to T that corresponds to a specific electrical activity of the heart. The P-wave represents the electrical excitation (or depolarisation) of the atria, which leads to the contraction of both the atria. The QRS complex represents the depolarisation of the ventricles, which initiates the ventricular contraction. The contraction starts shortly after Q and marks the beginning of the systole. The T-wave represents the return of the ventricles from excited to normal state (repolarisation). The end of the T-wave marks the end of systole. 8. Describe the evolutionary change in the pattern of heart among the vertebrates. As is clear from the following diagram the heart of fish has two chambers. This means there is no separate circulation for oxygenated and deoxygenated blood. There is separation of two chambers in the atrium of amphibians. This has further

4 evolved to partial separation of ventricle as well in reptiles. Finally in birds there is complete separation of oxygenated and deoxygenated blood circulation with advent of four chambers in the heart. Mammal heart is the most developed having the most efficient double circulatory system. 9. Why do we call our heart myogenic? Cardiac muscles are capable of generating their own contraction. This type of contraction is called myogenic contractions. That is why heart is called myogenic. 10. Sino-atrial node is called the pacemaker of our heart. Why? Sino-atrial node is a bundle of nerves which initiates the conduction of heart beat. So, this is also called the pacemaker of our heart. 11. What is the significance of atrio-ventricular node and atrio-ventricular bundle in the functioning of heart? AV Node and atrio-ventricular bundles are responsible for conduction of cardiac beat cycle to further parts of heart. 12. Define a cardiac cycle and the cardiac output. Cardiac Cycle:

5 To begin with, all the four chambers of heart are in a relaxed state, i.e., they are in joint diastole. As the tricuspid and bicuspid valves are open, blood from the pulmonary veins and vena cava flows into the left and the right ventricle respectively through the left and right atria. The semilunar valves are closed at this stage. The SAN now generates an action potential which stimulates both the atria to undergo a simultaneous contraction the atrial systole. This increases the flow of blood into the ventricles by about 30 per cent. The action potential is conducted to the ventricular side by the AVN and AV bundle from where the bundle of HIS transmits it through the entire ventricular musculature. This causes the ventricular muscles to contract, (ventricular systole), the atria undergoes relaxation (diastole), coinciding with the ventricular systole. Ventricular systole increases the ventricular pressure causing the closure of tricuspid and bicuspid valves due to attempted backflow of blood into the atria. As the ventricular pressure increases further, the semilunar valves guarding the pulmonary artery (right side) and the aorta (left side) are forced open, allowing the blood in the ventricles to flow through these vessels into the circulatory pathways. The ventricles now relax (ventricular diastole) and the ventricular pressure falls causing the closure of semilunar valves which prevents the backflow of blood into the ventricles. As the ventricular pressure declines further, the tricuspid and bicuspid valves are pushed open by the pressure in the atria exerted by the blood which was being emptied into them by the veins. The blood now once again moves freely to the ventricles. The ventricles and atria are now again in a relaxed (joint diastole) state, as earlier. Soon the SAN generates a new action potential and the events described above are repeated in that sequence and the process continues. This sequential event in the heart which is cyclically repeated is called the cardiac cycle and it consists of systole and diastole of both the atria and ventricles. Cardiac Output: The heart beats 72 times per minute, i.e., that many cardiac cycles are performed per minute. From this it could be deduced that the duration of a cardiac cycle is 0.8 seconds. During a cardiac cycle, each ventricle pumps out approximately 70 ml of blood which is called the stroke volume. The stroke volume multiplied by the heart rate (no. of beats per min.) gives the cardiac output. Therefore, the cardiac output can be defined as the volume of blood pumped out by each ventricle per minute and averages 5000 ml or 5 litres in a healthy individual. 13. Explain heart sounds. The heart sounds are the noises (sound) generated by the beating heart and the resultant flow of blood through it. This is also called a heartbeat. In cardiac auscultation, an examiner uses a stethoscope to listen for these sounds, the

6 heartbeat sounds like bassdrum, which provide important information about the condition of the heart. In healthy adults, there are two normal heart sounds often described as a lub and a dub (or dup), that occur in sequence with each heart beat. These are the first heart sound (S1) and second heart sound (S2), produced by the closing of the AV valves and semilunar valves respectively. In addition to these normal sounds, a variety of other sounds may be present including heart murmurs, adventitious sounds, and gallop rhythms S3 and S Draw a standard ECG and explain the different segments in it. The P-wave represents the electrical excitation (or depolarisation) of the atria, which leads to the contraction of both the atria. The QRS complex represents the depolarisation of the ventricles, which initiates the ventricular contraction. The contraction starts shortly after Q and marks the beginning of the systole. The T-wave represents the return of the ventricles from excited to normal state (repolarisation). The end of the T-wave marks the end of systole. Obviously, by counting the number of QRS complexes that occur in a given time period, one can determine the heart beat 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 a great clinical significance.