The systolic phase is the first phase of the heartbeat. It starts with the heart contracting and can be detected with a stethoscope. The systolic phase begins when the first sound is detected, from a downward deflection of the heart’s wall, leading to increased pressure in the ventricles. The chamber then fills up with blood until it reaches its maximum volume. This phase occurs during systole and lasts for about six seconds before it ends, which causes cardiac relaxation and the diastolic phase to occur next. After systole, the heart relaxes and ejects blood into the venous circulation.
Heart anatomy:
The heart is divided into left and right chambers by stiff connective tissue sheets called the septum. The left and right chambers are also separated by a wall called the interventricular septum, which also forms heart valves. The heart ventricles that contract to pump blood out are categorised as those below and above the aortic arch. The four heart chambers can hold different amounts of blood depending on the body’s condition. The amount of blood it can hold can be weighted per volume (mL/L).
Functioning of heart and terms related to it:
- The rate of blood flow increases automatically to meet the body’s needs. This process is known as cardiac output (CO). The cardiac output is increased by a hormone called adrenaline, which can double CO in 20 seconds.
When one is in a stressful situation and adrenaline levels increase, the heart beats faster. This can help save a life when one experiences an emergency by increasing the oxygen supply to muscles and brain cells.
- When there are problems such as heart diseases, the heartbeat rate can speed up and slow down. When the heartbeat goes faster and is more forceful, this is known as tachycardia.
The opposite is when the heartbeat is weaker, and there are pauses between beating movements. This is known as bradycardia. The next step in studying the heart’s beating is how quickly it beats in pulses per minute (PPM).
- The pulses produced by each beating occur every few seconds. This is typically heard when a doctor listens to the heartbeat using a stethoscope. The pulses produced are due to blood being pushed out of the heart into the arteries and veins in each cardiac cycle. The time it takes for one PPM is known as heart rate (HR).
- Heart rates can vary during a person’s day and be influenced by nervousness, exercise, drugs, alcohol, caffeine, and smoking. They can also be influenced by emotions such as anger or stress.
The Cardiac cycle:
The cardiac cycle begins in the systole when ventricles are filled with blood. The cycle then switches to diastole, where the ventricles relax and fill up again with blood. The heart pumps blood from the left atrium into the left ventricle and from the right atrium into the right ventricle. The cardiac cycle consists of the following phases:
Systole:
The systolic phase is the first phase of the heartbeat. Systole is also known as ventricular contraction when ventricles contract to pump blood out. The interventricular septum separates the right and left ventricles.
The function of these two chambers is to pump blood out into the body. They can also be divided into the atria and ventricles. Atria are the filling chambers that receive blood via venous circulation, and then pump it into the ventricles. Heartbeats are produced by cardiac muscle cells in the heart’s walls.
The first phase begins with the contraction of myocardial muscles in both ventricles, leading to the downward deflection of heart walls and increased pressure. The systolic phase continues when ventricles contract to pump blood out of the heart. When left and the right ventricles contract, it is known as the ejection phase and forces blood into the aorta via the tricuspid and mitral valve. This leads to the closure of both valves.
Diastole:
The diastolic phase begins when ventricles relax and fill back up with blood. The relaxation allows the lungs to fill with air after a period of exhalation known as the respiratory cycle, which is caused by the contraction of muscles in the chest wall that leads to a rise in pressure within them. The heart is also relaxed during this phase, allowing the blood to accumulate in the chambers known as atria. However, it is only a short period, as systole will start soon.
The diastolic phase continues when ventricles relax and fill back up with blood. The relaxation allows the lungs to fill with air after a period of expiration, which leads to a rise in pressure within them. During this phase, the heart is also relaxed, allowing the blood to accumulate in the atria. However, it is only a short period, as systole will start soon after again.
Conclusion:
The heart is the main pump of the body. The heart’s function is to pump blood by rapid contraction and relaxation. The heart can be divided into four chambers: the atria and ventricles. The atria are filled with blood after it passes through the right and left pulmonary veins; it once passes through arteries. During systole, both ventricles contract and pump out blood into the aorta. During diastole, ventricles again relax and are filled with blood and have the highest pressure.