1. Cardiovascular Physiology
“The Heart as a Pump”

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Hemodynamics
Hemodynamics is the process of keeping blood continually circulating while varying the amount of blood to regions that need more or less.
Ex: digestion and exercise
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Blood Distribution
Under normal condition blood resides mainly in the veins and venules.
Changes in activity can cause a shunting of blood to where it is needed.
Ex: digestion, exercise, SAT tests
The spleen acts a reservoir of blood
Hypovolemic shock is caused by sudden, drastic drop in blood pressure
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4. Conduction System of the Heart
Specialized tissues in the heart initiate and conduct impulses through the heart.
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Conduction Pathway
Sinoatrial (SA) node (AKA “pacemaker”) initiates contractions in the heart. This node is at the junction of the right atrium and the coronary sinus, hence its name.
The impulse travels through the interatrial bundles and causes atrial contraction.
A slowed impulse reaches the atrioventricular (AV) node via the internodal bundles.
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Conduction Pathway
The impulse is accelerated as it passes to the AV bundle (bundle of His).
The impulse then reaches the Purkinje fibers causing ventricular contractions.
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Pacemakers
Although the SA node can maintain intrinsic rhythm it is also influenced by autonomic impulses and hormones.
If needed, the AV node or Purkinje fibers take over.
Artificial pacemakers keep the heart beating at a minimum rate.
A normal resting heart rate is around 75 bpm.
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ECG or EKG
Electrocardiogram is a diagnostic tool that monitors the electrical activity of the heart.
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ECG Waves
P wave- depolarization of the atria (atrial contraction)
QRS complex- ventricular depolarization (ventricular contraction)
T wave- represents repolarization of the ventricles
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Abnormal Heart Rates
Dysrythmia/arrythmia- abnormal heart beat
Bradycardia-abnormally slow heart rate, <50
Tachycardia- unusually fast heart rate, can be caused by stimulants, caffeine, stress
Fibrillation- arrythmis in which heart begins to quiver, potentially fatal
Asystole- no heart beat, flatline
Digitalis causes cells to retain Calcium which strengthen beats, also it slows down the number of signals from SA node thus giving less chance for abnormal beats.
Digitalis is medicine made from the foxglove plant used to strengthen the heart beat and control irregular rhythms.
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Cardiac Cycle
Systole-contraction part of the heartbeat.
Diastole- relaxation part of the heartbeat.
Normal blood pressure 120/80
Hypertension-High blood pressure
Atrial Contractions- occurs simultaneously, cuspid valves open and ventricles relax
Ventricular Contractions-occur simultaneously as semilunar valves open
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Cardiac Cycle
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Heart Sounds
The sound of the heart beat is usually described as “lub-dub.”
The lub part is caused by closing of the cuspid valves.
The dub is caused by the closing of the semilunar valves.
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