Cardiovascular and Nervous System

Purkinje fibres lie in the deepest layer of the endocardium and supply the papillary muscles. Hence, the apex of the heart contracts first, followed by the papillary muscles.

It is the pacemaker of the heart as it sets the rhythm of the heart.

This is the correct sequence.

It has a thicker myocardium than the right ventricle or both the atriums as it has to push oxygenated blood to longer distances to all the body parts and also through more blood vessels.

Stroke volume is the volume of the blood ejected by each ventricle at each contraction whereas the pulse rate is the number of heart beats per minute.

Tricuspid valves are present in between right atrium and right ventricle.

The bicuspid valve (also called the mitral valve) is located between the left atrium and left ventricle. It prevents backflow of blood from the left ventricle to the left atrium when the ventricle contracts. The tricuspid valve is between the right atrium and right ventricle. Atria are separated from each other by the interatrial septum, not a valve.

Mitral (or bicuspid) valve in mammals guards the opening between left atrium and left ventricle.

Echocardiography is routinely used in the diagnosis, management and follow up of patients with any suspected or known heart diseases. In this technique, pulses of ultrasonic waves are emitted towards the organ and reflected waves are analysed. Recording of echoes and changes in the acoustic impedence provides information about the movement of wall of the heart, valves and the septum.

The ability of junctional tissue of the heart to generate its own impulses without external stimulation is called autorhythmicity. This is due to a small percentage of muscle cells called autorhythmic cells that are specialised to generate and conduct action potentials and make up the conduction system of the heart.

An electrocardiogram, also called an EKG or ECG is a simple test that detects and records the electrical activity of the heart. It is recorded using an active or exploring electrode and an indifferent electrode at zero potential or by using two active electrodes as in bipolar recording. It is also used in detecting functional abnormalities of heart like heart blocks, arrhythmias and myocardial infarction.

The lower two chambers are called ventricles. They can pump blood from the heart to the body.

It is a decrease in pulse rate below 60 beats/minutes. At this rate, the heart is not able to pump enough oxygen rich blood to our body during normal activity or exercise. Physiologically, it is seen in athletes and during sleep. Pathologically, it is observed in myxoedema and in heart blocks.

Myogenic heart contracts without having a message from the brain as in the pacemaker. In the human heart, contraction is initiated by a special modified heart muscle known as sinoatrial node. Since the heart beat is initiated by the SA node and the impulse of contraction originates in the heart itself, the human heart is termed myogenic. The heart of vertebrates and molluscs are also myogenic.

Sino atrial node is a specialised cardiac tissue present at the junction of superior vena cava and right atrium. It generates the maximum number of impulses (70 to 80 per minute) and sets the pace for the heart. Hence, it is called pacemaker of the heart. The cardiac impulse originates at the SA node.