1. Cardiovascular System Notes
Cardiac Conduction System
Cardiac Cycle
Electrocardiogram
Heart Sounds
Blood Pressure
Heart Attack

3. What is the Cardiac Conduction System?
Heart muscle cells contract without stimulation from the nervous system in a continuous, rhythmic pattern.
Contraction is initiated by the sinoatrial (SA) node (the heart’s internal pacemaker).
SA node is located in the right atrium
Cells of the SA node can reach threshold on their own
SA node initiates one action potential after another
(~70-80 times/min)

4. Cardiac Conduction System
1. Sinoatrial (SA) node
2. Atrioventricular (AV) node
3. Atrioventricular bundle (bundle of His)
4. Bundle branches
5. Purkinje fibers

5. What is the Cardiac Cycle?
The events associated with one heartbeat.
A single cardiac cycle lasts 0.8 seconds.
Described as the contraction and relaxation of the four heart chambers.
During relaxation, chambers fill with blood (diastole).
During contraction, chambers expel blood (systole).
When the atria contract, the ventricles are relaxed (and vice versa).
The term myocardium refers to cardiac muscle tissue.

6. What is an Electrocardiogram (ECG or EKG)?
A recording of the electrical changes that occur within the myocardium as the heart contracts.
P wave depolarization of the atrial muscle cells
QRS complex depolarization of the ventricular muscle cells
T wave repolarization of the ventricular muscle cells

7. What are the Heart Sounds?
The first heart sound (lubb) occurs during ventricular contraction when the tricuspid and bicuspid valves (AV valves) close.
The second heart sound (dubb) occurs during ventricular relaxation when the pulmonary and aortic valves close.

8. What is Blood Pressure?
Blood moves through circulatory system from areas of high pressure to low pressure. (Contraction of the heart produces the pressure.)
Blood Pressure is a measurement of the force that blood exerts against the inner walls of arteries.
SYSTOLIC vs. DIASTOLIC pressure
The maximum pressure during ventricular contraction is the systolic pressure. The systolic pressure is the peak arterial pressure.
When ventricles relax (diastole) the arterial pressure drops. The lowest pressure of blood in the arteries is called the diastolic pressure.

9. Blood Pressure The systolic pressure is the top number.
The diastolic pressure is the bottom number.
ex. 120/80

10. Blood Pressure vs. Distance From Left Ventricle

11. Heart Attack Myocardial Infarction (MI)
myocardial = heart muscle tissue
infarction = tissue death due to oxygen starvation
A blood clot completely blocks a coronary artery (or one of its branches), cutting off oxygen supply to that part of the heart. This results in cardiac tissue death.