Consider the following statements about the blood vessels and their layers:
(i) Both arteries and veins consist of three distinct layers of tissues. (ii) The tunica intima is the middle layer consisting of smooth muscle and elastic fibres. (iii) The tunica media is comparatively thinner in the veins than in the arteries. (iv) The outermost layer, tunica externa, is made of fibrous connective tissue with collagen fibres.
Explanation: Statement (ii) is incorrect because the tunica intima is the innermost endothelial layer. The tunica media forms the middle muscular layer. Statements (i), (iii), and (iv) are correct.
Question 12 of 100
📘 CLASS XI
Read the statements regarding the regulation of cardiac activity:
(i) Normal activities of the human heart are regulated intrinsically, making it myogenic. (ii) A special neural centre in the cerebellum moderates cardiac functions. (iii) Sympathetic neural signals can increase the rate of heartbeat, strength of contraction, and cardiac output. (iv) Parasympathetic neural signals decrease the heartbeat rate and speed of action potential conduction.
Explanation: Statement (ii) is incorrect because the cardiac regulatory centre is located in the medulla oblongata, not the cerebellum. Statements (i), (iii), and (iv) are correct.
Question 13 of 100
📘 CLASS XI
Examine the statements regarding Erythroblastosis Fetalis:
(i) It is caused by an Rh incompatibility mismatch between an Rh-negative mother and an Rh-positive foetus. (ii) During the first pregnancy, maternal and foetal blood are usually well separated by the placenta. (iii) During subsequent pregnancies, maternal Rh antibodies may enter the foetal circulation and destroy foetal RBCs. (iv) This condition can be prevented by administering anti-Rh antibodies to the mother immediately before the delivery of the first child.
Explanation: Statement (iv) is incorrect because anti-Rh antibodies are administered immediately after the delivery of the first Rh-positive child to prevent sensitization. Statements (i), (ii), and (iii) are correct.
Question 14 of 100
📘 CLASS XI
Read the statements regarding the circulatory pathways of different vertebrates:
(i) Fishes have a two-chambered heart with single circulation, pumping deoxygenated blood to the gills. (ii) Amphibians and reptiles (including crocodiles) possess a three-chambered heart with incomplete double circulation. (iii) Crocodiles, birds, and mammals have a four-chambered heart with complete double circulation. (iv) Ventricles in a four-chambered heart pump out oxygenated and deoxygenated blood separately without mixing.
Explanation: Statement (ii) is incorrect because crocodiles are an exception among reptiles and possess a four-chambered heart with complete double circulation. Statements (i), (iii), and (iv) are correct.
Question 15 of 100
📘 CLASS XI
Consider the following statements regarding blood disorders and physiological markers:
(i) Hypertension (high blood pressure) is defined as repeated checks showing a blood pressure of 140/90 mm Hg or higher. (ii) In 120/80 mm Hg blood pressure, 120 represents systolic (pumping) pressure and 80 represents diastolic (resting) pressure. (iii) Coronary Artery Disease (CAD) makes the lumen of arteries wider due to calcium, fat, and cholesterol deposits. (iv) Angina pectoris occurs when insufficient oxygen reaches the heart muscles, causing acute chest pain.
Explanation: Statement (iii) is incorrect because calcium, fat, cholesterol, and fibrous tissue deposits narrow the arterial lumen in Coronary Artery Disease. Statements (i), (ii), and (iv) are correct.
Question 16 of 100
📘 CLASS XI
Analyze these statements regarding Heart Failure, Heart Attack, and Cardiac Arrest:
(i) Heart failure is the state of the heart when it is not pumping blood effectively enough to meet the needs of the body. (ii) Heart failure is exactly the same clinical condition as cardiac arrest and heart attack. (iii) Cardiac arrest refers to the clinical event when the heart stops beating completely. (iv) A heart attack occurs when the heart muscle is suddenly damaged by an inadequate blood supply.
Explanation: Statement (ii) is incorrect because heart failure, heart attack, and cardiac arrest are distinct clinical conditions. Heart failure is ineffective pumping, cardiac arrest is cessation of heartbeat, and heart attack results from inadequate blood supply to the heart muscle. Statements (i), (iii), and (iv) are correct.
Question 17 of 100
📘 CLASS XI
Study the statements regarding the human heart's structural positioning and protection:
(i) The heart is a mesodermally derived organ situated in the thoracic cavity, between the two lungs. (ii) It is tilted slightly to the right side of the chest. (iii) It is protected by a double-walled membranous bag called the pericardium, which encloses the pericardial fluid. (iv) A thin muscular wall called the inter-atrial septum separates the right and left ventricles.
Explanation: Statement (ii) is incorrect because the heart is tilted slightly to the left. Statement (iv) is incorrect because the inter-atrial septum separates the atria, whereas the inter-ventricular septum separates the ventricles. Statements (i) and (iii) are correct.
Question 18 of 100
📘 CLASS XI
Check the following statements regarding blood volume calculations during the cardiac cycle:
(i) During a cardiac cycle, each ventricle pumps out approximately 70 mL of blood, known as the stroke volume. (ii) Stroke volume multiplied by heart rate gives the cardiac output. (iii) In a healthy individual, the cardiac output averages about 5000 mL or 5 litres per minute. (iv) The human body lacks the ability to alter either the stroke volume or the heart rate.
Explanation: Statement (iv) is incorrect because both stroke volume and heart rate can be altered according to the physiological needs of the body. Statements (i), (ii), and (iii) are correct.
Question 19 of 100
📘 CLASS XI
Read the statements below regarding the sounds produced during the cardiac cycle:
(i) The first heart sound is 'dub' and is associated with the closure of semilunar valves. (ii) The second heart sound is 'lub' and is associated with the closure of the tricuspid and bicuspid valves. (iii) Heart sounds are of high clinical diagnostic significance. (iv) Both heart sounds can be easily heard through a stethoscope.
Explanation: Statements (i) and (ii) are incorrect because the first heart sound is 'lub' due to closure of the atrioventricular valves, while the second heart sound is 'dub' due to closure of the semilunar valves. Statements (iii) and (iv) are correct.
Question 20 of 100
📘 CLASS XI
Read the following statements regarding Blood Group Rh compatibility:
(i) The Rh antigen is similar to one present in Rhesus monkeys and is observed on the surface of RBCs in nearly 80 per cent of humans. (ii) An Rh-negative person, if exposed to Rh-positive blood, will form specific antibodies against Rh antigens. (iii) Rh group matching is not required for blood transfusions if ABO matching is already done. (iv) Majority of human beings are Rh-negative.
Explanation: Statements (iii) and (iv) are incorrect because Rh matching is essential before blood transfusion, and nearly 80% of humans are Rh-positive. Statements (i) and (ii) are correct.
