The human heart is important to maintain life through circulating blood around the body. Continuous flow provides oxygen, nutrients, and hormones to tissues and removes waste products. The heart functions within an exquisite, at the same time miracle-like, interplay of electrical impulses, mechanical contractions, and the various physiological processes. This is a comprehensive review of cardiac physiology, including how the heart works, what is involved, and the way it attempts to function optimally.
Anatomy of the Heart
- Without the study of anatomy, there is no chance of giving comprehensive information about cardiac physiology. The heart is that muscular organ approximately the fist’s size; it is situated inside the chest cavity. It has four chambers in total, divided among those chambers as shown below:
- Two atria above: deoxygenated blood from all body systems goes into the right atrium via the superior and inferior vena cava, while the left goes into the left via the pulmonary veins of the lungs.
- Lower two chambers (ventricles): This is through pumping deoxygenated blood to the lungs for further oxygenation. On the left is the ventricle, where deoxygenated blood to every part of the body passes before it undergoes oxygenation as pumped by this side via the aorta.
There are four valves of the heart: tricuspid, pulmonary, mitral, and aortic. They ensure that blood flows only one way and does not go back. A thick wall of muscle inside the heart acts as a septum between the right and left sides, meaning oxygenated blood and deoxygenated blood never intermix.
Electrical System of the Heart
- It controls the heartbeat and coordinates the contraction timing between the atria and ventricles. The electrical impulse starts in the sinoatrial (SA) node, often referred to as the pacemaker of the heart.
- Sinoatrial (SA) Node: The SA node is located in the right atrium wall. These nodes produce impulses at the rate of 60-100 times per minute, which is increased or decreased according to the body’s needs, and this is called sinus rhythm. These impulses cause the contraction of the atria and pump blood into the ventricles.
- AV Node: The impulse travels to the AV node that is found where the atria and ventricles meet. Here, it acts like a gatekeeper, slowing down the signal so the ventricles are fully pumped with blood when they contract.
Bundle of His and Purkinje Fibers:
From the AV node, the impulse moves through the bundle of his that splits to both left and right branches, in which the impulse then leads to the ventricles. The impulse then further disperses within the ventricles through Purkinje fibers, leading to its contraction.
- The cardiac cycle are the events occurring with every heartbeat of pumping of blood both to the lungs and other body parts
- Diastole: It is the relaxation phase. During diastole, the atria and ventricles relax, and the heart fills up with blood. The atria contract a little to push any remaining blood into the ventricles. At the end of diastole, the ventricles are filled with blood and ready to contract.
- Systole: It is the contraction phase. An electrical impulse coming from the SA node causes a contraction of ventricles that pumps blood into the pulmonary artery & aorta. The right ventricle pumps blood to the lungs for oxygenation, while the left ventricle pumps oxygen-rich blood to the whole body.
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Cardiac Output and Regulation
- Cardiac output is the volume of blood the heart pumps per minute. It is determined by two main factors:
- Heart Rate: The number of heart beats per minute, regulated by the autonomic nervous system. The sympathetic nervous system increases heart rate, and the parasympathetic nervous system decreases it.
- Stroke Volume: The volume of blood ejected from the left ventricle in one contraction. Normal stroke volume is 60-70 ml/min. It is determined by three major factors:
- Preload: The stretch of the heart muscle before the contraction, mainly determined by venous return.
- Contractility: The force of the contraction of the heart, increased by sympathetic stimulation and other drugs.
- Afterload: The amount of resistance that ventricles must generate in order to push the blood out; it depends on factors like blood pressure.
- CO = HR × SV
- Normally at rest, cardiac output is 5 L/min
Significance of Cardiac Physiology
Thus, knowledge of cardiac physiology is important so that all the symptoms of heart diseases are identified and cardiovascular health is maintained. Hypertension, heart failure, arrhythmias, and coronary artery disease are just a few of the diseases that manifest with the normal functioning of the heart, leading to major complications. Understanding the lifestyle, like diet, exercise, and managing stress, really goes a long way in cardiac health.
For example, high blood pressure elevates the workload of the heart and, with time, makes the heart muscle bulkier and less efficient—a condition called left ventricular hypertrophy—which increases the risk of heart failure and arrhythmias.
Conclusion
The heart is an amazing product of biology, which has systems of electrical impulses, muscle contractions, and circulatory pathways that work in a harmony that is nothing but astounding. Whether one is a student of medicine or an interested observer in how the human body works, to understand the complexities of cardiac physiology means knowing how we maintain life and health.
