Cardiac CycleBiology 2

Cardiac cycle

A complete heartbeat in which the heart chambers function in a coordinated fashion› Systole – heart chamber walls contract› Diastole- heart chamber walls relax

Systole & Diastole Pattern

Atrial systole (atria contracts) while ventricles relax called ventricular diastole

Then the ventricles contract (ventricular systole) and atria relax (atrial diastole)

Then the atria and ventricles both relax for an interval

How it works… The cusps (flaps) of the

bicuspid and tricuspid valves are anchored to the ventricle walls by fibrous “cords” called chordate tendineae, which attach to the wall by papillary muscles. This prevents the valves from being pushed up into the atria during ventricular systole

During ventricular contraction…

Blood pressure rises in the ventricles, forcing the aortic and pulmonary valves(semilunar valves) open, while closing the tricuspid and bicuspid valves (A-V valves)

This makes a lubb sound

During ventricle relaxation…

The pulmonary and aortic valves are closing, while the tricuspid and bicuspid valves open to let blood flow from the atria to the ventricles

This makes a dubb sound

Systole & Diastole

http://highered.mheducation.com/sites/0072495855/student_view0/chapter22/animation__the_cardiac_cycle__quiz_1_.html

Heart Sounds

The heart normally makes a lubb dubb sound.

A heart murmur is a deviation from this sound and is usually due to a valve’s cusp not closing entirely, allowing blood to backflow from the ventricle into the atrium

Ranges from harmless to requiring open heart surgery

Heart sounds

http://depts.washington.edu/physdx/heart/demo.html

Stethoscope – instrument to listen and measure heart sounds

ECG Electrocardiogram- recording of the

electrical charges that occur in the myocardium during a cardiac cycle› Electrodes are placed on the skin and

respond to weak electrical changes

ECG P wave- atrial systole (contraction)

› Review: What valves are closed and which are open?

QRS complex- Ventricle systole (contraction)› Review: Which valves are closed and

which are open? T wave- repolarization of the ventricles

(resting period)

Regulation of the Cardiac Cycle

Controlled by the cardiac center in the medulla oblongata

Signals the heart to increase or decrease heart rate depending on various factors› Body temperature› Muscle activity › Blood Ca2+ & K+ levels

Abnormal Heart Rhythms

Tachycardia = rapid heartbeat ( > 100 BPM)

Bradycardia = slow heartbeat ( < 60 BPM)

Fibrillation = rapid, uncoordinated unsynchronized heart rate. Atria (not serious. Ventricles (deadly)

Defibrillator Common treatment for life-

threatening cardiac arrhythmia The device shocks the heart and allows

it to re-establish its normal rhythm The device can also be used to start a

heart that has stopped

SPHYGMOMANOMETER Device used to measure blood pressure Average normal blood pressure =

120/80 Average Heart Rate = 72 http://www.sumanasinc.com/

webcontent/animations/content/bloodpressure.html