LQB185 Chapter Notes - Chapter 20: The Heart Beats, Stroke Volume, Systolic Geometry
20.4 The Cardiac Cycle
➢ The cycle includes everything that
happens with one heartbeat
➢ Pressure and Volume Changes during the
Cardiac Cycle
- Atria and ventricles alternatively
contract and relax, high pressure to
low pressure.
- Each ventricle expels same volume
of blood per beat.
➢ Atrial Systole
- During atrial systole, the atria are
contracting while the ventricles are relaxed.
➢ Ventricular Systole
- During ventricular systole, the ventricles are contracting while the
atria are relaxed in atrial diastole
➢ Relaxation Period
- During this period, the atria and the ventricles are both relaxed.
The heart beats faster and faster making the relaxation period
shorter and shorter.
➢ Heart Sounds
- Auscultation (act of listening)
- 4 sounds with you able to hear 2.
20.5 Cardiac Output
➢ Volume of blood ejected from the left ventricle into the aorta each
minute.
➢ Cardiac Output= the stroke volume (SV) of blood ejected by the
ventricle during each contraction x by
the heart rate.
➢ Cardiac Reserve: Maximum CO-CO at
rest
➢ Regulation of Stroke Volume
- At rest SV is 50-60% of the end-diastolic volume.
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