Cardiac output or minute volume in animals Cardiac output or minute volume in animals is the volume of blood ejected by either the left or the right ventricles into the greater vessels, the aorta or pulmonary artery in a minute. Cardiac Output (L/min) → Stroke Volume × Pulse Rate In most animals, the cardiac output […]

Stroke volume The definite volume of blood pumped into the aorta / pulmonary trunk by each ventricular contraction (left / right) is referred to as stroke or pulse volume or the systolic discharge. If the stroke volume is expressed based on body weight it is known as stroke index. A portion of the blood is

Cardiac sounds Cardiac sounds are the distinct sounds produced during systole (S1) and diastole (S2) of the cardiac cycle, which can be recorded by the phonocardiogram. The first heart sound “lub”, is systolic sound indicates the firm closure of AV valves, occur during ventricular systole. It is associated with the vibration of the valves (valvular

Pressure and volume changes in atrium and ventricle Pressure changes in the atria The intraatrial pressure records three major positive waves- ‘a’ wave: Results from atrial systole. Atrial systole causes an increase in the atrial pressure resulting in the opening of the AV valves and blood flows into the ventricles. ‘c’ wave: It results due to bulging

Cardiac cycle Cardiac cycle is defined as sequence of events such as pressure and volume changes, cardiac sounds and changes in the electrical potential occurring during the period between two successive ventricular contractions. It is characterised by one complete contraction (systole) and relaxation (diastole) and indicates a complete heart beat. These periods are not equal in duration, when heart

Properties of myocardium of animals Rhythmicity The cardiac muscles have an inherent ability to generate their own impulses spontaneously at regular intervals known as rhythmicity without the influence of nerves and hormones,. This property can be demonstrated by coronary perfusion of the isolated mammalian heart using Ringer’s solution. Contractility Contraction of cardiac muscle differs from other

Action potential in cardiac muscle Cardiac muscle has an inherent property of generating its own action potentials rhythmically, independent of nerve stimulation. This occurs in the peacemaker cells of the S.A. node, which depolarizes faster than any other parts of the heart. The onset of action potential in cardiac muscle is slower but prolonged than

Electro chemical changes during action potential in heart Spike potential (over shoot) Spike potential (over shoot) is the steep change in the negativity of the cell from – 90 mV to more positivity of + 40 mV in the membrane potential due to rapid increase in the permeability of the Na+ ions to the interior of the cell.

Channels system of cell membrane of heart Na – K leakage channels and Voltage gated Na channels and K channels are the Channels system of cell membrane of heart. Na – K leakage channels These channels are 100 times more permeable to K+ ions than Na+ ions and are exceedingly important in determining the level of normal

Events of action Potential in heart The action potential is caused by a sequence of changes or events occurring in the membrane permeability to Na+ and K+ ions. When an excitable cell is stimulated the cell membrane permits the inflow of Na+ ions into the cell to generate the action potential. Action potential is the rapid changes in