Cardiology I – A Review of Cardiovascular Anatomy and Physiology
by Cwanza A. Pinckney, M.D.
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Table of Contents
- Course Home
- Objectives
- Matching Exercise
- Introduction
- Anatomy: The Heart
- Anatomy: The Vessels
- Physiology: Introduction
- Physiology: Review of Circulation
- Physiology: The Cardiac Cycle
- Physiology: Innervation of the Heart
- Cardiac Electrophysiology: Introduction
- Cardiac Electrophysiology: Electrolytes
- Cardiac Electrophysiology: Cardiac Automaticity
- Cardiac Electrophysiology: The Cardiac Conduction System
- Cardiac Electrophysiology: Myocardial Contraction
- Sample Cases
- Case 1: Cardiac Tamponade
- Figure 1: Assessment
- Figure 2: Management
- Case 2: Cocaine Overdose
- Figure 3: Assessment
- Figure 4: Management
- Case 3: Hemorrhagic Shock
- Figure 5: Assessment
- Figure 6: Management
- Conclusion
- References
- Bibliography
Physiology: The Cardiac Cycle
The cardiac cycle is defined as the events that occur between one heart contraction and the next. This cycle is divided into two phases – relaxation and contraction. The relaxation phase of the cardiac cycle is known as diastole and is characterized by filling of the ventricles. The second part of the cardiac cycle is known as systole. During systole, the heart contracts and forces blood into the aorta and pulmonary artery.
Diastole begins with the closing of the semilunar valves and the opening of the atrioventricular valves. This allows the pressure in the ventricles to become low enough to allow blood to enter from the atria. Towards the end of diastole, the atria give a quick contraction to finish emptying blood into the ventricles. This is known as the “atrial kick” and helps to boost cardiac output. Next, the ventricles receive a stimulus to contract, which increases intraventricular pressure. This increased pressure forces the mitral and tricuspid valves to close, and opens the semilunar valves to allow blood to flow out to the pulmonary and systemic circulations. When the pressure in the pulmonary artery and aorta overcomes the pressure in the ventricles, the semilunar valves close, and the atrioventricular valves open, marking the beginning of diastole and the start of a new cardiac cycle.