THE HEART
The heart - function
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The heart is a hollow muscle
It collects blood returning in veins
It pumps blood into arteries
Direction of blood controlled by valves
Veins drain into….
Atria pump blood into…
Atrio-ventricular (biscuspid & tricuspid) valves direct
blood into …
Ventricles pump blood through …
Arterial/semi-lunar valves direct blood into…
Arteries carry blood away to the tissues.
© 2008 Paul Billiet ODWS
THE MAJOR FACTORS
CONTROLLING HEART BEAT
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The heart muscle tissue shows an inherent
contraction without connection to nerves
The heart beat is initiated and controlled at
the SINO-ATRIAL NODE (the pacemaker)
© 2008 Paul Billiet ODWS
Control of heart beat frequency
- Nervous control
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Nerve stimuli from the VAGUS NERVE will
slow the heart beat
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Stimuli from the ACCELERANS NERVE will
speed up the heart beat
© 2008 Paul Billiet ODWS
Control of heart beat frequency
- Hormonal control
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ADRENALIN in increased concentration in
the blood stream speeds up the heart beat
(direct effect)
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NORADRENALIN in the blood indirectly
causes a slowing of the heart beat
© 2008 Paul Billiet ODWS
THE CARDIAC CYCLE
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Diastole
= muscles relaxed
= low pressure in the heart
Systole
= muscles contracted
= high pressure in the heart
Sound: LUB DUB or LUP DUP
© 2008 Paul Billiet ODWS
DIASTOLE
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Atria and ventricle walls relax, pressure drops
in the ventricles
Semi-lunar valves shut, catching the
backflow from the arteries
(pressure in the ventricles < pressure in the
arteries) = DUB
Atria fill with blood returning from the veins
Blood drains into the ventricles
© 2008 Paul Billiet ODWS
SYSTOLE
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Atria muscles contract forcing blood into the
ventricles
Papillary muscles contract tensing the tendons to
the atrio-ventricular valves (bicuspid and tricuspid)
Ventricle muscles contract. Pressure increases =
LUB
Atrio-ventricular valves shut and hold the blood in
the ventricles. Pressure in the ventricles rises
Semi-lunar valves open (pressure in ventricles >
pressure in arteries)
Blood flows away from the heart
© 2008 Paul Billiet ODWS
Back to DIASTOLE
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Atria and ventricles relax (pressure in
ventricles < pressure in the arteries)
Semilunar valves shut = DUB
© 2008 Paul Billiet ODWS