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Physiology of the Heart
Coronary Systole Diastole
At any time the chambers of the heart can be on one of two different states.
Systole – The Cardiac muscle tissue is contracting to push blood outside the heart chamber.
Diastole – During this state, the cardiac muscle cells relax to enable the chamber to fill with blood. There is an uptick in blood pressure in the major arteries during ventricular systole and decrease during ventricular latosols. This will lead to the two numbers that are referenced when calculating the blood pressure – systolic blood pressure is the higher number, and the diastolic blood pressure is the lower number. For example, a blood pressure of 120/90 means the systolic pressure is 120, and the diastolic pressure is 90
The Cardiac Cycle
The cardiac cycle encompasses all of the events that take place during one single heartbeat. There are three different phases of the cardiac cycle: atrial systole, ventricular systole, and relaxation.
Atrial systole: In this phase of the cardiac cycle, the atria contracts and pushes blood into the ventricles. To assist in the filling, the AV valves remain open, and the semilunar valves remain closed to keep arterial blood from reentering the heart. The area is much smaller than the ventricles, so they only fill about 25% of the ventricles through this phase. The ventricles stay in diastole during this phase.
Ventricular systole. During this phase, the ventricles compress to push blood into the aorta and pulmonary trunk. The pressure of the ventricles drive the semilunar valves to open and the AV valves to shut. This system of valves enables the blood flow to from the ventricles into the parties. The cardiac muscles of the atria repolarize and enter the state of diastole during this phase.
In this phase, all four chambers of the heart are in diastole as blood pours into the heart from the veins. The ventricles swell to nearly 75% capacity during this phase and will completely fill only after the atria enter systole. The cardiac muscle cells of the ventricles repolarized during this phase to prepare for the next cycle of depolarization and contraction. Throughout this phase, the AV valves open to allow blood to move freely into the ventricles during the semilunar valves shutting to stop the regurgitation fo blood from the great arteries into the ventricles.
Blood Flow through the Heart
Deoxygenated blood returning from the body initially enters the heart from the superior and inferior vena cava. The blood goes into the right atrium and is pushed into the tricuspid valve toward the right ventricle. From the right ventricle, Then the blood is pumped throughout the pulmonary semilunar valve into the pulmonary trunk.
The pulmonary trunk brings blood into the lungs where its carbon dioxide is removed, and oxygen is absorbed back into the blood. The blood inside the lungs return to the heart via the pulmonary veins. The blood will travel through the pulmonary veins back to the heart into the left atrium.
The left atrium compresses to pump blood through the bicuspid (Mitral valve through to the left ventricle. The left ventricle pushes blood into the aortic semilunar valve through the aorta. After the blood reaches his aorta, it goes into systemic circulation into the rest of the body’s membranes and tissues until it returns to the heart via the vena cava and the cycle starts over again.
The electrocardiogram which is also the EKG or ECG is a non-invasive device that can monitor and regulate the electrical movement of the heart via the skin. The EKG creates a unique waveform that responds to the hearts electrical changes.
The first section of the wave is called the P wave, in which a small rise in voltage of approximately 0.1 mV that matches to the depolarization of the atria during atrial systole. The following section of the EKG wave is the QRS complex which creature a small dip in voltage (Q) a large voltage peak *R) and the next miniature decline in volatile (S). The QRS complex aligns with the depolarization the ventricles through the ventricular systole cycle. The atria are also repolarized during the QRS complex, however, have nearly no effect on the WKG because are much smaller than the heart ventricles.
The last section of the EKG wave is the T wave, a small peak that follows the QRS complex. The T wave expresses the ventricular repolarization during the relaxation phase of the cardiac cycle. Variations in the waveform and distance between the waves of the EKG can be used to clinically diagnose the effects of congenital heart problems, heart attacks, and electrolyte imbalances.
The sounds of normal beats are referred to as the “lubb” and “dupp” and are triggered by the blood pushing on valves of the heart. The “lubb” sound is the first in the heart beat and is the longer sound of the two. The “lubb” sound produce by closing the AV valves are the start of the ventricular systole. The “dubb” sound is shorter and sharper and is also triggered by the closing of the semilunar valves at the end of the ventricular systole. During an average heartbeat, this sounds repeat in a regular pattern of lubb-dupp-pause. If there are additional sounds such a liquid rushing, gurgling, running fluids it can indicate structural problems in the heart. The most common causes of extraneous sounds are defects with ventricular or septum, atrial or leakage in the heart valves.
The Cardiac output (CO) is the volume of blood that is pumped by the heart in one minute. The equation used to determine cardiac output is CO = Stroke Volume x Heart Rate.
Stroke volume is the quantity of blood pumped through the aorta during each ventricular systole, normally measure in milliliters. The heart is the number of heartbeat per minute. The average heart can push approximately 5 to 5.5 liter per minute rest.