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Unformatted text preview: s in the vena cavae and atrium
(venous return). The accelerator centre responds by
sympathetic stimulation of the heart (via the cardiac
nerve and release of norepinephrine) bringing about
increased rate and force of heart contraction. Tricuspid 6. (a) Increased arterial flow (in aorta and carotid
(b) Stretch receptors in carotid sinus and aorta detect
an increase in arterial flow and send afferent
impulses to the inhibitory centre in the medulla.
The inhibitory centre mediates a decrease in
heart rate via the vagus nerve (the carotid and
aortic reflexes). There is a subsequent decrease
in cardiac output and arterial blood pressure. 7. (a) and (b) any of the following in any order:
– Aortic pressure receptors (baroreceptors) in
the wall of the aortic arch respond to increased
arterial blood flow in the aorta.
– Carotid baroreceptors in the carotid sinus
respond to increased arterial flow in the carotid
– Baroreceptors in the vena cava and the right
atrium respond to increased venous return
(mediates an increase in heart rate - the
Bainbridge reflex). 8. (a) Individuals have different tolerances to the
same level of a substance (also depends on
their previous intakes of other substances such
as coffee). Different body mass will affect the
(b) Controls should drink an energy drink that does
not contain guarana. Bicuspid Semi-lunar
ventricle Valves prevent the blood from flowing the wrong
way through the heart and help regulate filling of the
chambers. 3. (a) The heart has its own coronary blood supply
to meet the high oxygen demands of the heart
(b) There must be a system within the heart muscle
itself to return deoxygenated blood and waste
products of metabolism back to the right atrium. 4. If blood flow to a particular part of the heart is
restricted or blocked (because of blocked blood
vessel), the part of the heart muscle supplied by that
vessel will die, leading to a heart attack or infarction. 5. A: arterioles
C: arterioles 6. (a) The pulmonary circuit mus...
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This document was uploaded on 01/28/2014.
- Winter '13