The study of electrical signals in the heart muscles is Electrocardiography (ECG). The potentials generated in the fibers of heart muscles produces ECG waveforms. ECG deals with depolarization and repolarization of heart muscles. ECG signals get generated due to contraction of atria and ventricles. An electrocardiograph is the recorded ECG signal that appears on the screen.
Cross Section of Heart
The heart has four chambers namely two lower and two upper chambers. Atrium forms the upper chambers and ventricles form the lower chambers. We again classify these as left atrium, right atrium, left ventricle and right ventricle. The heart has three layers namely pericardium which is the outer layer of the heart. It helps to protect the heart from friction.
The middle layer is myocardium. Some short cylindrical fibers join together to form this layer. It acts as the primary muscle of the heart. The innermost layer is endocardium that makes the blood to flow smoothly. The heart has four important valves named as
Tricuspid Valve or Right Atria Ventricular Valve
This valve located at the midway between the right atrium, and right ventricle is to prevent the blood from flowing back from the right ventricle to the right atrium.
Bicuspid or Left Atria Ventricular Valve
This valve helps to prevent the blood from flowing back to the left atrium from the left ventricle. The valve is in between the left atrium and left ventricle.
The shape of the valve has three cusps. It presents in the right ventricle, to stop the blood from flowing back to the right ventricle.
It presents between left ventricle and aorta to stop the blood flowing back to the left ventricle.
Next essential parts of the heart are the blood vessels. The tubes that carry the blood to various parts of the body is the blood vessels. They are hollow tubes. We classify these tubes as arteries and veins. Arteries are thick-walled blood vessels. Arteries carry the oxygenated/pure blood away from the heart to other parts of the body. Veins are thin-walled blood vessels, and they carry impure blood to the heart from other parts of the body. Capillaries are the smallest blood vessels to carry the blood flowing through the body. In pulmonary circulation, heart pumps blood to the lungs for purification. The purified blood flows through pulmonary veins to the left atrium. In the systemic circulation, heart pumps blood from the left atrium to the left ventricle. From the left ventricle, blood flows to other parts of the body through aortas.
Origin of Cardiac Heart Potential
In our heart, we have Sino Atrial node that initiates heart activity. SA node generates heart impulses at the normal heart rate. The generated impulses travel through right and left atria. We have another node named Atria-ventricular node (AV node). AV node results in a delay to carry the impulses to the ventricles. The maximum delay time is 0.12 seconds
The recording of heart sound is Phonocardiography. The recorded graph is phonocardiograph. Auscultation is the technique of listening sounds generated from organs and blood vessels. Heart sounds occur due to the sudden closure of valves and vibration in the blood inside the heart. Murmurs occur due to improper closure of valves and when blood flows backward. There are four heart sounds.
- First Heart Sound: Occurs due to the sudden closing of the mitral and tricuspid valve.
- Second Heart Sound: Occurs due to the closure of semilunar valves
- Third Heart Sound: Occurs when the ventricle relaxes
- Fourth Heart Sound: Occurs due to fast blood flow into ventricles.