Cardiac Cycle

Cardiac Cycle

 

Introduction

The human heart is a muscular organ that is about the size of a fist. Pumps blood through a set of connections between arteries and veins, known as the cardiovascular system. It includes systemic and pulmonary circulation.

The cardiovascular cycle is a period that begins from the narrowing of the atria and ends at ventricular rest.

Two words are very important in the heart cycle

• Systolic (the contraction phase)

• Diastolic (the relaxation phase)

The Human Heart and the Cardiac Cycle

The heart is a powerful organ that pumps blood from the heart to the body through the circulatory system. The heart is a pumping organ. The triangular section, is slightly wider slightly tilted to the right, and the lower half is slightly tilted to the left. The heart wall is made up of 3 layers endocardium, myocardium, and epicardium. The heart is a closed envelope of two layers called pericardial membranes (pericardium). There is a protective cover on the outer side of the heart called the pericardial membrane. Between the two membranes, there is the presence of a fluid known as pericardial fluid.

The human heart is divided into four chambers. The two upper chambers are the auricles (atria) and the lower chambers are called the ventricles.

Right Auricle (Atrium)

The right auricle has holes for the superior vena cava, the inferior vena cava, and the coronary sinus. Oxygen-free blood from the veins of the head, neck, and upper extremities enters the right auricles through the superior vena cava and from the rest of the body and lower organs through the inferior vena cava. Coronary sinus, auricle blood that passes through the right ventricle through the tricuspid valve.

• Right Ventricle: Protected by a semilunar valve.
• Left Auricle: This chamber receives four pulmonary arteries. The left auricle drains its blood into the left ventricle with a bicuspid valve.
• Left Ventricle: This blood is returned to the heart through the coronary arteries that form the coronary sinus.
• Cardiac Cycle Classes: The heart cycle consists of six stages;

Diastole Combined

When all chambers in the atria and ventricles are in a relaxed state. Blood flows from the vena cava to the atria and from the atria to the ventricles. Atria is filled with blood from the upper vena cava and the inferior vena cava. The left atria occupy the pulmonary arteries of the lungs from the left and right sides, both ventricles filled with blood in their tricuspid and bicuspid areas.

Atrial Systole

When atrial fibrillation is present. During diastole concentration 70 to 80 per cent of the blood will flow from the atria to the ventricles only 20 to 30 per cent will remain in the atria to release this blood, the atria will use some energy. This contraction is caused by the shortening phase of the atria known as the arterial system as the SA node transmits its impulses; the atherosclerosis stage occurs.

Ventricular Systole

When ventricular contracting begins, it is called ventricular systole or ventricular contraction segment. In ventricular contraction, pressure from the SA node will be transferred to the AV node to further transmit it to the Purkinje fibre and its office bundle which begins to contract in the event of pressure starting or rising in the ventricle via the tricuspid. and bicuspid valves are closed so that, there is no back blood flow. As these walls close there is a noise that will be the sound of its ‘rub’.

Complete ventricular

When the ventricles are in full swing. As ventricular pressure begins blood will flow to the walls of the semolina open and blood from the ventricles will flow to its different parts from the right ventricle to the aorta of the lungs and to the left through the aorta arch. Now the semilunar walls are open, the ventricles are incomplete in the narrowing phase and blood flow from the pentacles to the pulmonary aorta to the aorta arch.

The onset of Ventricular Diastole

After the systolic phase, the ventricles enter the resting phase. As ventricular relaxation begins the semilunar walls close so that there is no blood flow from the pulmonary aorta and aortic arch. This produces a sound called ‘dub’, the first sound produced during a call. wall loss and second-generation during wall closure which means when semilunar valves are closed.

Complete ventricular diastole

When the chambers or ventricles are fully relaxed, the semilunar walls are closed while the tricuspid or bicuspid walls are open. There is a flow of blood from our atria to their ventricles and a diastolic joint occurs when all the chambers are filled with blood again.

This is our heart rate of 0.8 seconds, the normal blood flow throughout the cycle.

Guarding Your Heart

Ribs protect the heart from shock and injury, thus allowing the heart to beat faster without any form of external pressure.

The heart is also protected by the pericardium, which is filled with fluid to prevent collisions within the chest.

Duration of Cardiac Cycle

For the average person, the heart rate is 72 beats/minute. Therefore, the length of a single cardiac cycle can be calculated as follows:

1/72 beats / minute = .0139 minutes / beat

With a heart rate of 72 beats/minute, the length of each heart rate will be 0.8 seconds.

The lengths of the different stages of the heart cycle are given below:

Atrial systole: lasts about 0.1 seconds
Ventricular systole: lasts about 0.3 seconds
Atrial diastole: lasts about 0.7 seconds
Ventricular diastole: lasts for about 0.5 seconds

 

The heart cycle is the work of the human heart from the beginning of the heartbeat to the beginning of the next. It consists of two phases: one when the heart muscle relaxes and fills with blood, called diastole, followed by a period of tight contraction and pumping of blood, called asystole. After the excision is made, the heart quickly relaxes and expands to receive more blood from the lungs and other body systems, before resuming the flow of blood to the lungs and systems. A normally functioning heart must be fully extended before it can pump properly again. Assuming a healthy heart with a normal rate of 70 to 75 beats per minute, each heart cycle, or heart rate, takes about 0.8 seconds to complete the cycle.

FAQ’s

Q. What are the different stages of the heart cycle?

Ans: Different stages of the heart cycle include:

• Atrial diastole
• Atrial systole
• Isovolumic contraction
• Ventricular discharge
• Isovolumic relaxation
• Ventricular filling

What happens during the systole?

Systole is a time when the coronary arteries contract causing blood to flow to the aorta and pulmonary trunk.

What is diastole?

Diastole is part of the cardiovascular cycle when the heart replenishes blood and after it is released during the systolic phase.

Q. What are the major symptoms of diastolic dysfunction?

Ans: Major symptoms of diastolic dysfunction include:

• Shortness of breath
• Weaknesses
• Dizziness
• Nausea
• Lack of food
• Cough or shortness of breath