Page 3 of 54) Select the correct statement about the heart valves. A) The mitral
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Page 3 of 54) Select the correct statement about the heart valves. A) The mitral valve separates the right atrium from the right ventricle B) The AV valves are supported by chordae tendineae so that regurgitation of blood into the atria during ventricular contraction does not occur C) Aortic and pulmonary valves control the flow of blood into the heart D) The tricuspid valve divides the left atrium from the left ventricle 55) Muscle tone is A) a state of sustained B) the condition of a C) the feeling of well-being following exercise D) the ability of a muscle to efficiently cause skeletal movements 56) Myoglobin A) produces the end plate potential B) breaks down glycogen C) stores oxygen in muscle cells D) is a protein involved in the direct phosphorylation of ADP 57) Which of the following is true about veins? A) Up to 35% of total body blood is in venous circulation at any given time. B) Venous valves are formed from the tunica media. C) Veins are called capacitance vessels or blood reservoirs. D) Veins have a small lumen in relation to the thickness of the vessel wall. 58) During vigorous exercise, there may be insufficient oxygen available to completely break down pyruvic acid for energy. As a result, the pyruvic acid is converted to A) a strong base B) lactic acid C) stearic acid D) hydrochloric acid 59) Which of the events below does not occur when the semilunar valves are open? A) AV valves are closed. B) Ventricles are in systole. C) Blood enters pulmonary arteries and the aorta. D) Ventricles are in diastole. 60) The left ventricular wall of the heart is thicker than the right wall in order to A) pump blood with greater pressure B) expand the thoracic cage during diastole C) pump blood through a smaller valve D) accommodate a greater volume of blood 61) Norepinephrine acts on the heart by A) causing a decrease in stroke volume B) blocking the action of calcium C) decreasing heart contractilit D) causing threshold to be reached more quicklyExplanation / Answer
54.(B). During ventricular systole (Contraction) the pressure in the ventricles rises above that in the atria and the valves snap shut, preventing backward flow of blood. The valves are prevented from opening upwards into the atria by tendinous cords, called chordae tendineae, which extend from the inferior surface of the cusps to little projection of mycardium into the ventricles, covered with endothelium, called papillary muscles.
55. (D). Muscle tone is a sustained, partial muscle contraction that allows posture to be maintained without fatiguing the muscles involved. For instance, keeping the head upright requires constant activity of the muscles of the neck and shoulders. Therefore, the answer is the ability of a muscle to efficiently cause skeletal movements.
56. (C). Myoglobin is a specialised oxygen-binding substance, which is similar to the haemoglobin to the of red blood cells and stores oxygen within the muscle.
57. (C). Veins are called capacitance vessels because they are distensible, and therefore have the capacity to hold a large proportion of the body's blood.
58. (B). During vigorous exercise,there may be insufficient oxygen available to completely breakdown pyruvic acid for energy. As a result, the pyruvic acid is converted into Lactic acid.
59. (D). During the semilunar valves are open the AV valves are closed, ventricles are in systole and blood enters pulmonary arteries and the aorta. Therefore, the answer would be, Ventricles are in diastole.
60. Norepinephrine also known as noradrenaline comes under the category of catecholamine that works in the brain and the body like a hormone or a neurotransmitter. Therefore, the answer would be causing threshold to be reached more quickly.
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