Cardiovascular and Nervous System

Stroke volume is the correct term for the amount of blood ejected by the left ventricle during each heartbeat. In a healthy adult at rest, this is approximately 70-80 mL. Cardiac output is the total blood pumped per minute (stroke volume × heart rate). Ejection fraction is the percentage of blood pumped out relative to the total blood in the ventricle. 'Threshold output' is not a standard cardiac term.

The terminal sulcus is a groove in the right atrium of the heart. The terminal sulcus marks the separation of the right atrial pectinate muscle from the sinus venarum. The terminal sulcus extends from the front of the superior vena cava to the front of the inferior vena cava

The atrioventricular node, located in the wall between the right atrium and the right ventricle. Here, the impulses are delayed for about 0.1s before spreading to the walls of the ventricle.

Third heart sound is physiologic in children but pathological in adults. The four heart sound is a result of the atrial systole and vibration of the AV valves, due to blood rush during atrial systole. It is inaudible neither in adults nor in children.

The left ventricle is the pumping chamber for the systemic circulation. Because a greater blood pressure is required to pump blood through the much more extensive systemic circulation than through the pulmonary circulation, the left ventricle is larger and its walls are thicker than those of the right ventricle.

The sinoatrial (SA) node is a section of nodal tissue that is located in the upper wall of the right atrium. The SA node is also referred to as the pacemaker of the heart.

Third heart sound is physiologic in children but pathological in adults. The four heart sound is a result of the atrial systole and vibration of the AV valves, due to blood rush during atrial systole. It is inaudible neither in adults nor in children.

Lithium iodide, or LiI, is a compound of lithium and iodine. When exposed to air, it becomes yellow in colour, due to the oxidation of iodide to iodine. It is used as an electrolyte for high temperature batteries. It is also used for long life batteries as required, for example, by artificial pacemakers. The solid is used as a phosphor for neutron detection.

Blood pressure varies during sleep cycles and can fluctuate with body movements, REM sleep, and autonomic nervous system activity. While it generally decreases during sleep compared to wakefulness, it doesn't remain perfectly constant.

The cardiac cycle lasts approximately 0.8 seconds at a normal heart rate of 75 beats per minute (60 seconds ÷ 75 beats = 0.8 seconds). This duration includes systole (contraction) and diastole (relaxation) phases. At this rate, the heart completes approximately 72 cardiac cycles per minute.

A heart attack (myocardial infarction) occurs when blood flow to the heart muscle is blocked, usually by a blood clot in a coronary artery. This lack of blood supply causes heart muscle cells to die. It's not caused by bacteria, and the heart doesn't completely stop beating (that's cardiac arrest).

Chordae tendineae are fibrous cords connecting atrioventricular valve cusps to papillary muscles in the ventricles. They prevent valve inversion (prolapse) when ventricles contract, ensuring unidirectional blood flow. Without them, high ventricular pressure would force valves back into atria, causing regurgitation. They do not open valves or support the septum.

 The function of this valve is to prevent the back flow of blood into the right atrium.

Atrioventricular valves remain closed during isovolumetric contraction, ventricular ejection and isovolumetric relaxation.

Arteries have thicker walls than veins because the blood flows through the arteries at a much higher pressure. The tricuspid valve is located between the right atrium and the right ventricle.