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
(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
(c) Those with several risk...
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This document was uploaded on 01/28/2014.
- Winter '13