Anatomy and Physiology Answer Key

B there must be a system within the heart muscle

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Unformatted text preview: t operate at a lower pressure than the systemic circuit to prevent fluid accumulation in the lungs. The systemic circuit must also develop enough pressure to enable blood flow to increase to the muscles when required and to maintain kidney filtration rates without compromising blood supply to the brain. (b) The left ventricle is thicker to enable the left side of the heart to develop higher pressure. There is no such requirement of the right side, which pumps only to through the lower pressure pulmonary circuit. 7. B: venules D: capillaries You are recording expansion and recoil of the artery that occurs with each contraction of the left ventricle. Control of Heart Activity (page 117) 1. (a) Sinoatrial node: Initiates the cardiac cycle through the spontaneous generation of action potentials. (b) Atrioventricular node: Delays the impulse. (c) Bundle of His: Distributes the action potentials over the ventricles (resulting in ventricular contraction). 2. Delaying the impulse at the AVN allows time for atrial contraction to finish before the ventricles contract. 3. (a) Cardiac output 70 cm3 X 70 beats per min. = 4900 cm3 = 4.9 L. Biozone International 2009 Photocopying Prohibited Anatomy and Physiology 4. Aorta Right atrium 2. (b) Trained endurance athletes achieve a high cardiac output primarily through having a very high stroke volume: the heart pumps a lot of blood with each beat. For any given level of exercise, their heart rates are relatively low. 20 The Cardiac Cycle (page 119) 1. (a) QRS complex (b) T 2. During the period of electrical recovery the heart muscle cannot contract. This ensures that the heart has an enforced rest and will not fatigue, nor accumulate lactic acid (as occurs in working skeletal muscle). 3. changing controllable factors. (b) Controllable risk factors often occur together because some tend to be causative for others, or at least always associated, e.g. obesity greatly increases the risk of high blood lipids and high blood pressure: all factors increase the risk of CVD. (c) Those with several risk...
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This document was uploaded on 01/28/2014.

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