BIOLOGY Write the short note.

1. Heart transplant is the replacement of severely damaged heart by normal heart from brain-dead or recently dead donor,
2. Heart transplant is necessary in case of patients with end-stage heart disease and severe coronary arterial disease.

1. Silent heart attack is a type of heart attack that lacks the general symptoms of classic heart attack like extreme chest pain, hypertension, shortness of breath, sweating and dizziness.
2. Symptoms of silent heart attack are so mild that a person often confuses it for regular « discomfort and thereby ignores it.
3. Men are more affected by silent heart attack than women.

1. Angiography is an X-ray imaging of the cardiac blood vessels to locate the position of blockages.
2. Depending upon the degree of blockage, remedial procedures like angioplasty or by¬pass surgery are performed.
3. In angioplasty a stent is inserted at the site of blockage to restore the blood supply while in by-pass surgery, the atherosclerotic region is by-passed with part of vein or artery taken from any other suitable part of the body, like hands or legs.

1. Electrocardiogram or ECG is the graphic v record of electrical variations produced by the heart during one heartbeat or cardiac cycle.
2. ECG is taken with the help of an instrument called electrocardiograph or ECG machine. Electrocardiograph records the action potentials generated by the heart muscles.
3. The electrical activity of heart is represented in the form of a graph plotted with time on X-axis against voltage displacement on Y-axis.
4. A normal ECG is a graph having series of ridges and furrows. There are waves such as P-wave, QRS complex and T-wave.
5. P-wave is a small upwards wave representing impulse generated by SA node. P-wave is caused by atrial depolarization that results in atrial contraction.
6. QRS-complex wave begins as a downward deflection, continues as a large upright triangular wave and ends’ as a downward wave.
7. QRS-complex wave represents spreading of impulse from SA node to AV node, then to bundle of His and Purkinje fibres. It causes ventricular depolarization resulting in ventricular contraction.
8. T-wave is a broad upward wave which represents ventricular repolarization resulting in ventricular relaxation.
9. Functions of ECG are mainly for diagnosis and also for prognosis. It is useful to detect abnormal functioning of heart as in coronary artery diseases, heart block, angina pectoris, tachycardia, ischemic heart disease, myocardial infarction, cardiac arrest, etc.

1. Atherosclerosis is the deposition of fatty substances and cholesterol on the inner lining of eateries.
2. This deposition results in the formation of atherosclerotic plaque.
3. It results in the decrease of the lumen of the blood vessels causing increasing resistance for the blood to flow which in turn results in the hypertension.
4. Atherosclerosis of the coronary arteries results in decrease in the blood flow to the heart muscles.
5. Due to such condition, coronary heart disease is caused.

1. Heart failure is caused due to progressive weakening of the heart muscle. This results in the failure of the heart to pump the blood effectively.
2. Hypertension increase the after load on the heart leading to significant enlargement of the heart.
3. This finally results in heart failure.
4. Factors responsible for heart failure are advanced age, malnutrition, chronic infections, toxins, severe anaemia or hyperthyroidism, etc.
5. Any problem leading to degeneration of heart muscle, may result in heart failure.

1. Angina pectoris is the pain in the chest. It results from a reduction in blood supply to cardiac muscle due to narrowed and hardened coronary arteries.
2. Atherosclerosis and arteriosclerosis can cause this problem. Basically, the coronary arteries are affected during angina pectoris.
3. It causes heaviness and severe pain in the chest. The pain can also be felt at the neck, lower jaw, left arm and left shoulder.
4. Angina pectoris often occurs during exertion, when the heart demands more oxygen and narrowed blood vessels cannot supply. It disappears with rest.

1. Coronary artery disease is a condition caused due to problems like atherosclerosis.
2. In this disease, coronary arteries are narrowed due to deposition of fatty substances.
3. Due to this the blood flow to the heart is reduced.
4. In coronary heart disease, the heart muscle is damaged because of an inadequate amount of blood due to obstruction of its blood supply.
5. The symptoms of CAD depend upon the degree of obstruction.
6. Symptoms are mild chest pain or angina pectoris.
7. In severe cases it results in heart attack known as myocardial infarction.

1. In a normal healthy person the blood pressure values are 120 mm Hg (systolic)/ 80 mm Hg (diastolic).
2. When the blood pressure is persistently more than 140 mm Hg systolic pressure and 90 mm Hg diastolic arterial blood pressure then it is said to be hypertension or high blood pressure.
3. Excessively high blood pressure is very dangerous as high blood pressure of about 220/120 mm Hg may cause rupturing of blood vessels.
4. Rupture of eye blood vessels can lead to blindness.
5. If blood vessels of kidney are affected then nephritis is caused.
6. Hemorrhage occurring in the brain can lead to stroke or paralysis. Therefore, hypertension is commonly called silent killer. It may be present for years with no distinct symptoms.
7. The factors causing hypertension are arteriosclerosis (reduction of elasticity of blood vessels), atherosclerosis (deposition, of cholesterol inside the blood vessels wall), obesity, physical or emotional stress, alcoholism, smoking, cholesterol rich diet, increased secretion of renin, epinephrine or aldosterone, etc.

1. Blood pressure is the pressure exerted by the flowing blood on the walls of arteries.
2. Blood pressure described in two terms viz. systolic blood pressure and diastolic blood pressure. Systolic blood pressure is the maximum pressure of blood when heart undergoes ventricular systole. It is responsible for flow of blood in the arteries. Normal systolic pressure is 120 mm Hg.
3. Diastolic blood pressure is the minimum pressure of blood when heart undergoes diastole. Normal diastolic pressure is 80 mm Hg.
4. Blood pressure is represented as 120/80 mm Hg for a normal human being.

1. Pacemaker is the region in tile heart which initiates the beating.
2. The natural pacemaker of the heart is sinoatrial node (SA node).
3. The pacemaker is autorhythmic, it is able to repeatedly and rhythmically generate impulses.
4. SA node is responsible for initiation of cardiac excitation. Therefore, it is called a pacemaker.

1. A pressure wave that travels through the arteries after each ventricular systole is called a pulse.
2. The pulse can be felt in any artery that lies near the surface of the body.
3. The radial artery at the wrist is most commonly used to feel the pulse.
4. The pulse rate per minute indicates the heart rate. Since each heartbeat generates one pulse in the arteries, the pulse rate is same as that of heart rate, i.e. 72 times per minute.

1. The rhythmic contraction and relaxation of the heart is called heartbeat.
2. Each heartbeat includes one systole and one diastole. During systole the heart contracts and during diastole it relaxes.
3. The rate with which the heart beats is called heart rate. The normal heart rate is 72 beats per minute.
4. Tachycardia means faster heart rate of about more than 100 beats per minute.
5. Bradycardia means slower heart rate that is below 60 beats per minute.

1. Erythrocytes or red blood corpuscles. They are circular, biconcave, enucleated cells.
2. The RBC size : 7 pm in diameter and 2.5 pm in thickness.
3. The RBC count : 5.1 to 5.8 million RBCs/ cu mm of blood in an adult male and 4.3 to 5.2 million/cu mm in an adult female.
4. The average life span of RBC : 120 days.
5. RBCs are formed by the process of erythropoiesis. In foetus, RBC formation takes place in liver and spleen whereas in adults it occurs in red bone marrow.
6. The old and worn out RBCs are destroyed in liver and spleen.
7. Polycythemia is an increase in number of RBCs while erythrocytopenia is decrease in their (RBCs) number.

1. Transport of oxygen from lungs to tissues and carbon dioxide from tissues to lungs with the help of haemoglobin.
2. Maintenance of blood pH as haemoglobin acts as a buffer.
3. Maintenance of the viscosity of blood.

(1) Artificial ventilation is the artificial respiration. It is the method of inducing breathing in a person when natural respiration has ceased or is faltering. If used properly and quickly, it can prevent death due to drowning, choking, suffocation, electric shock, etc.
(2) The process involves two main steps:
a. Establishing and maintaining an open air passage from the upper respiratory tract to the lungs.
b. Force inspiration and expiration as in mouth to mouth respiration or by mechanical means like ventilator.
(3) A ventilator is a machine that supports breathing and is used during surgery, treatment for serious lung diseases or other conditions when normal breathing fails.

(1) Respiration is under dual control, i.e. nervous and chemical. Normal breathing is an involuntary process. Steady state of respiration is controlled by neurons located in the pons and medulla and are known as the respiratory centres. They regulate the rate and depth of breathing.
(2) These centres are divided into three groups : dorsal group of neurons in the medulla (inspiratory centre), ventro-lateral group of neurons in medulla (inspiratory and expiratory centre) and pneumotaxic centre located in the pons and apneustic centre which is antagonistic in action to pneumotaxic centre.
(3) During inspiration, when the lungs expand to a critical point, the stretch receptors are stimulated and impulses are sent along the vagus nerves to the expiratory centre. It then sends out inhibitory impulses to the inspiratory centre.
(4) The inspiratory muscles relax and expiration follows. As the air leaves but, the lungs are deflated and the stretch receptors are no longer stimulated. Thus, the inspiratory centre is no longer inhibited and a new respiration begins. These events are called the Hering – Breuer reflex. The Hering – Breuer reflex controls the depth and rhythm of respiration. It also prevents the lungs from inflating to the point of bursting.
(5) The respiratory centre has connections with the cerebral cortex that means we can voluntarily change our pattern of breathing. Voluntary control is protective because it enables us to prevent water or irritating gases from entering the lungs.

1. Carbon monoxide poisoning is caused when carbon monoxide is combined with haemoglobin.
2. Haemoglobin is said to have 250 times more affinity for carbon monoxide than that for the oxygen.
3. Therefore, haemoglobin with carbon monoxide forms a stable compound, the carboxyhemoglobin.
4. Due to the formation of carboxyhaemoglobin, the haemoglobin no longer carries oxygen to the cells and tissues. Tissues then suffer from oxygen starvation. This leads to asphyxiation and in extreme cases it leads to death.
5. Carbon monoxide poisoning occurs in closed rooms with incompletely burning substances such as stove burners or furnaces and garages having running automobile engines.
6. Person suffering from carbon monoxide poisoning has to be administered with oxygen-carbon dioxide mixture, so that high levels of CO₂ makes carbon monoxide dissociated from haemoglobin.