Biology 3 Marks Question

The formed elements of the blood are

• Red blood cells (Erythrocytes)
• White blood cells (Leucocytes)
• Blood platelets (Thrombocytes)

1. Functions of red blood cells: RBCs are oxygen carriers. They contain haemoglobin which is the respiratory pigment. Haemoglobin combines with oxygen to form oxyhaemoglobin which carries oxygen to regions of lower oxygen concentration in the body.
2. Functions of white blood cells: Neutrophils perform a defense mechanism against bacteria called phagocytosis.Lymphocytes produce antibodies which kill or neutralise germs.
3. Functions of blood platelets: Blood platelets help in blood coagulation.

• The sino-atrial node generates the action potential and produces the 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.
• Because of the property of originating a cardiac impulse, the sino-atrial node is called the pacemaker of the heart.

	Blood		Lymph
1.	Blood is red liquid connective tissue.	1.	Lymph is a white tissue fluid
2.	. It flows through blood vessels—arteries, veins and capillaries.	2.	It flows in the lymph vessels.
3.	It contains haemoglobin, red blood cells, white blood cells and platelets.	3.	It contains white blood cells called lymphocytes.
4.	It transports gases and other nutrients in the body	4.	Exchange of gases and nutrients between the blood and the cells occurs through the lymph.

	Blood		Lymph
1.	Blood is a red-coloured fluid that contains RBCs.	1.	Lymph is a colorless fluid that lacks RBCs.
2.	It contains plasma, RBCs, WBCs, and platelets. It also contains proteins.	2.	It contains plasma and lesser number of WBCs and platelets. It lacks proteins.
3.	Blood transports nutrients and oxygen from one organ to another.	3.	Lymph plays a role in the defensive system of the body. It is a part of the immune system.

Connective tissues have cells scattered throughout an extra-cellular matrix. They connect different body systems. Blood is considered as a type of connective tissue because of two reasons.

1. Like the other connective tissues, blood is mesodermal in origin.
2. It connects the body systems, transports oxygen and nutrients to all the parts of the body, and removes the waste products. Blood has an extra-cellular matrix called plasma, with red blood cells, white blood cells, and platelets floating in it.

	Systole		Diastole
1.	It is the contraction of the heart chambers to drive blood into the aorta and the pulmonary artery.	1.	It is the relaxation of the heart chambers between two contractions. During diastole, the chambers are filled with blood.
2.	Systole decreases the volume of the heart chambers and forces the blood out of them.	2.	Diastole brings the heart chambers back into their original sizes to receive more blood.

1. Erythrocytes: They are also known as Red Blood Cells (RBC). They are the most abundant of all the cells in blood. A healthy adult man has, on an average, 5 millions to 5.5 millions of RBCs mm of blood. RBCs are formed in the red bone marrow in the adults. RBCs are devoid of nucleus in most of the mammals and are biconcave in shape. They have a red coloured, iron containing complex protein called haemoglobin, hence the colour and name of these cells. A healthy individual has 12-16gms of haemoglobin in every 100ml of blood. These molecules play a significant role in transport of respiratory gases. RBCs have an average life span of 120 days after which they are destroyed in the spleen. Hence, spleen is also known as the graveyard of RBCS.
2. Leucocytes: They are also known as White Blood Cells (WBC) as they are colourless due to the lack of haemoglobin. They are nucleated and are relatively lesser in number which averages 6000-8000mm of blood. Leucocytes are generally short lived There are two main categories of WBCs:

1. Granulocytes, e.g., neutrophils, eosinophils and basophils
2. Agranulocytes. e.g., Lymphocytes and monocytes.

• Neutrophils are the most abundant cells (60-65 percent of the total WBCs and basophils are the least 10.5-1 percent) among them. Neutrophils and monocytes (6-8 percent) 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 percent) resist infections and are also associated with allergic reactions.
• Lymphocytes (20-25 percent) are of two major types - 'B' and T forms. Both B and T lymphocytes are responsible for immune responses of the body.

3. Structure of Heart: The heart is a muscular organ. It consists four chambers which are as follows:

• Right Auricle.
• Left Auricle.
• Right Ventricle.
• Left Ventricle.

Apart from these four chambers the heart consists valves at junctions of auricles and ventricles and at junctions of right ventricle and pulmonary artery. These valves allow unidirectional flow of blood.

When atherosclerosis happens in coronary artery; it diminishes the blood supply to the cardiac muscles: This condition is known as coronary artery disease (CAD). Long term repercussions of coronary artery disease include damage to the heart muscle and can also end up in myocardial infarction.

1. A- antigen A and anti b-antibodies.
2. B- antigen B, and anti-a-antibodies.
3. O- no antigen and both anti-a and anti-b antibodies.

• Rh-antigen is present on the surface of erythrocytes in about 80–85% of the human beings.
• The individuals who possess this antigen are called Rh-positive and those who do not have it are called Rh-negative.
• An Rh-negative person, when exposed to Rh-positive blood, develops anti-Rh-antibodies.
• If a pregnant women who is Rh-negative, bears an Rh-positive foetus, will develop anti-Rh-antibodies during the first delivery, when the foetal blood comes in contact with her blood.
• These antibodies linger in the blood for sufficiently longer periods.
• If she carries a second foetus, that is Rh-positive, the anti-Rh-antibodies in her blood enter the foetal circulation and cause damage to the foetal RBCs that could become fatal.
• This condition is called erythroblastosis foetalis.

• The action potential generated by the sino-atrial node is first conducted to the atria and then to the ventricles through atrioventricular node (AV node) and atrioventricular bundle (AV bundle) passing through the atrioventricular septum (AV septum).
• On entering the top of the interventricular septum, the AV bundle divides into two branches, the left and the right bundle branches.
• These bundle branches give rise to minute fibres, called Purkinje fibres, which conduct the impulse throughout the ventricular wall to initiate ventricular systole.

S.No.	Right ventricle	Left ventricle
(i)	Right ventricle is smaller than the left ventricle.	Left ventricle is comparatively larger than the right ventricle.
(ii)	Moderator band is present.	Moderator band lacks.
(iii)	Columnae carneae thicker, but less intricate.	Columnae carneae narrower, but more intricate.
(iv)	Receives and pushes deoxygenated blood.	Receives and pumps oxygenated blood.
(v)	Crescent-shaped.	Biconvex in shape.
(vi)	The wall of right ventricle is thinner than left ventricle.	The wall of it is thicker than right ventricle

1. The normal blood pressure is 120/80mm Hg; in this 120mm Hg is the systolic pressure and 80mm Hg is the diastolic pressure.
2. Hypertension is the term used when repeated checks of blood pressure of an individual show 140/90mm Hg or higher.
3. Kidneys and Brain.

The mammals have no renal portal system due to the following facts:

1. It is an evolutionary trend that fishes and amphibians have well-developed renal portal system, while, in reptiles and birds this system gets reduced. Finally in mammals it ultimately disappears.
2. The heart of mammals is four-chambered, due to which there is a total separation of oxygenated and deoxygenated blood.
3. Posterior portion of the body gets oxygenated blood from the heart and after oxidation process, etc., the blood does not contain so much impurities that it should go to the kidneys for filtration.

Rh Incompatibility of Foetus and Mother: A special case of Rh incompatibility (mismatching) has been observed between the Rh -ve blood of a pregnant mother with Rh +ve blood of the foetus. Rh antigens of the foetus do not get exposed to the Rh -ve blood of the mother in the first pregnancy as the two bloods are well separated by the placenta. However, during the delivery of the first child, there is a possibility of exposure of the maternal blood to small amounts of the Rh +ve blood from the foetus. In such cases, the mother starts preparing antibodies against Rh in her blood. In case of her subsequent pregnancies, the Rh antibodies from the mother (Rh-ve) can leak into the blood of the foetus (Rh ve) and destroy the foetal RBCs. This could be fatal to the foetus or could cause severe anaemia and jaundice to the baby. This condition is called erythroblastosis foetalis. This can be avoided by administering anti-Rh antibodies to the mother immediately after the delivery of the first child.

The birds and mammals have evolutionary advancement as far as structure of heart is concerned. They need more oxygen to live in terrestrial habitat. In these animals, the blood received by left and right auricles is oxygenated and deoxygenated respectively. It passes towards the left and right ventricles and thus no oxygenated and deoxygenated blood is mixed. The ventricles pump oxygenated deoxygenated blood without mixing. Thus, two separate circulatory pathways are found thus this type of blood circulation is called as double circulation, which include systemic and pulmonary circulation.

Differences between plasma and serum are:

	Plasma	Serum
(i)	It is the fluid minus blood corpuscles.	It is liquid minus clotting elements.
(ii)	It is faint yellow in colour.	It is pale yellow.
(iii)	It has fibrinogen and other clootting materials.	It dose not have fibrinogen and other clotting materials.
(iv)	It takes part in blood clotting.	It dose not take part in blood clotting.

1. The blood recieving chambers of the heart are left and right atrium.
2. The blood pumping chambers of the heart are left and right ventricles.

• At the start of the ventricular diastole the semilunar valves close, producing the second heart sound dupp.
• The atria are also in their diastole (joint diastole) for a brief period, before they start their systole.
• During this phase, blood continues to flow into the atria from the major veins.
• Blood also flows from the atria into the respective ventricles, through the open AV valves.

No, all cardiac chambers cannot experience systole simultaneously.

• Atrial systole occurs first, since the sinoatrial node (SA node) that initiates the cardiac impulse is in direct contact with atrial muscles and the impulse is first discharged to atria.
• The impulse is transmitted from the atrial muscles to the ventricular muscles through atrioventricular node and AV-bundle.
• The impulse passes slowly across the AV-node and hence, ventricular systole begins after the atrial systole is completed.

Normal activities of the heart are regulated intrinsically, Les, auto regulated by specialised muscles (nodal tissue), hence the heart is called myogenic. A special neural centre in the medulla oblongata can moderate the cardiac function through autonomic nervous system (ANS). Neural signals through the sympathetic nerves (part of ANS) can increase the rate of heart beat, the strength of ventricular contraction and thereby the cardiac output. On the other hand, parasympathetic neural signals (another component of ANS) decrease the rate of heart beat, speed of conduction of action potential and thereby the cardiac output. Adrenal medullary hormones can also increase the cardiac output.

Hypertension is elevated blood pressure.Normal blood pressure in an adult is 120/ 80mmHg. The pressure on the higher side is called systolic blood pressure, while that on the lower side is called diastolic blood pressure. If blood pressure consistently shows 140/ 90mmHg or more in successive readings, then the person can be diagnosed to be suffering from hypertension. Hypertension can have serious long term repercussions because it can give rise to coronary artery disease, damage to kidneys, liver, retina and brain.

S. No	Single circulation	Double circulation
(a)	It is the process in which the heart of an animal receives and pumps either oxygenated or deoxygenated blood.	It is the process in which the heart of an animal receives and pumps oxygenated and deoxygenated blood through two separate pathways, without any mixing up.
(b)	Heart is two-chambered with a single atriumand a single ventricle.e.g. fish.	Heart is four-chambered ventricles. e.g. mammals and birds.

Heart failure: It is the state of heart when it does not pump blood effectively enough to meet the need of the body. Congestion of lungs is one of the main symptoms of this disease. Heart failure is not the same as cardiac arrest (when the heart stops beating) or a heart attack (when the heart muscle is suddenly damaged by inadequate blood supply).

Structure of an artery:

• An artery consists of a three-layered wall enclosing a narrow lumen.
• Tunica externa is the outermost or external layer that is made of fibrous connective tissue with collagen fibres.
• Tunica media is the middle layer composed of smooth muscles and elastic fibres.
• Tunica interna is the innermost layer, made of squamous endothelium.

Differences:

• The tunica media is thicker in arteries than in vein.
• The lumen is narrow in the artery and is broader in the vein.

2. The patient should be given medicine because in case of certain infections, WBCs may not be enough to fight the infection.

Explanation:
Certain pathogens may be too harmful to be overcome by WBCs alone. Additionally, WBCs take time to fight the infection and a quick spread of infection can prove disastrous for the patient. The role of medicine is to limit the infection to a level so that the WBCs can do their job. It is always better to prevent a disease than to cure a disease. Personal hygiene is e very important in preventing many diseases. Bathing daily and maintaining personal cleanliness can prevent most of the skin diseases. Trimming nails and washing hands can prevent germs from entering our body along with food and water. Maintaining cleanliness around us can prevent many water borne diseases.

1. Electrocardiograph is the instrument.
2. Three electrical leads connect the patient to the instrument, one to each of the wrists and one to the left ankle.

1. Atrial systole:

• As the cardiac impulse from the SA node reaches E the atrial musculature, both the atria contract simultaneously.
• The blood flow to the respective ventricles increases by about 30 percent.

2. Ventricular systole:

• The atria undergo diastole.
• The ventricular systole increases the ventricular pressure that causes closure of the bicuspid and tricuspid valves.
• As the pressure increases further, the semilunai valves guarding the pulmonary artery and the aorta are forced open.
• Blood enters the pulmonary artery from the right ventricle and aorta from the left ventricle.

3. Ventricular diastole:

• The ventricles start relaxing.
• Since, the pressure in the ventricles decreases the semilunar valves close preventing the backflow of blood into the ventricles.

• An electrocardiogram is the graphic record of the electrical potential differences produced by the cardiac muscles during a cardiac cycle.
• The P wave represents the depolarisation of atria, which leads to atrial systole.
• The QRS complex represents the depolarisation of the ventricles that leads to ventricular systole.

Atherosclerosis or Coronary Artery Disease (CAD): It refers to the deposition of fatty substances specially cholesterol and triglycerides in the tunica interna and smooth muscles of medium sized and large arteries which results in plaque formation, which deform the arterial wall. Gradually these plaques grow and as a result, the lumen of the artery decreases and the flow of the blood is reduced. In extreme cases these plaques may block the artery completely. This may result in heart attack or stroke.

• The cardiac impulse arises from the SA node located in the wall of the right atrium.
• The impulse first spreads through the atrial musculature, causing the atrial systole.
• Then it passes through AV node and AV bundle to the ventricles to initiate ventricular systole, before which the atrial systole is completed; hence atrial systole always precedes ventricular systole.

It is an electronic device, which regularly sends a small amount of electrical charge for maintaining the rhythmicity of the heart. It is implanted subcutaneously in the upper thoracic region having a connection with the heart.The artificial pacemaker is called a life-saving instrument because, it stimulates the heart electrically at regular intervals to maintain its beats. Thus, it replaces the SA node as the originator of the cardiac impulse. It is to be noted that some pacemakers stimulate the heart at a fixed rate, others sense when the natural heart rate falls below a predetermined value and then stimulates the heart.

1. Blood pressure is the pressure exerted on the walls of the blood vessels by the pumping of blood into them by contraction of the left ventricle of heart.
2. A persistent high blood pressure results from narrow arterial lumen and reduced elasticity of arterial walls in old age. It can cause rupturing of capillaries and is a silent killer.
3. Normal range of blood pressure in human is 120/80mmHg, while, high blood pressure may occur if continuous readings come to be 140/90mmHg or slightly above this.
4. Sumit was concerned about his grandfather's health. He is intelligent, and good observer. He has the ability to apply subject knowledge to real practical situations.

Layers in arteries:

• Tunica Intima: This is the inner lining and is composed of squamous endothelium.
• Tunica media: This is the middle layer and is composed of smooth muscles and elastic fibres.
• Tunica externa: This is the external layer and is composed of collagen fibres.

Functional significance of lymphatic system:

1. It collects interstitial fluid from tissues.
2. It plays special role in immunity building and memory generation.
3. It transports many important nutrients and hormones.
4. Fat is only absorbed through the lymph from small intestine. Thus, lymphatic system plays an important role in absorption of fat.

Hypertension (High blood pressure): It is the common disease affecting heart and blood vessels. A blood pressure of 120/ 80 is considered normal, but the increase in blood pressure beyond 140mmHg (systolic) and 90mmHg (diastolic) is called high blood pressure (hypertension). High blood pressure can harm heart, brain, kidneys and eyes. Hypertension can be due to mental stress, tobacco smoking, and intake of diet having high cholesterol.