Cardiovascular and Nervous System

Simple squamous epithelium forms inner lining of lung alveoli.

The tricuspid valve or right atrioventricular valve is present on the right dorsal side of the mammalian heart in between the right atrium and the right ventricle. The function of the valve is to ensure that blood flows from the right atrium to the right ventricle by closing an prevented back flow during ventricle systole.

It is the pressure, which is exerted on the walls of the various arteries around the body in between heart beats when the heart is relaxed. Its normal range in adults is 60 to 80 mm Hg.

 The total volume of blood in healthy individual is 5 litres

 Pulse pressure is the difference between systolic and diastolic pressure.

ECG (Electrocardiogram) records the electrical activity of the heart over time, specifically the potential difference (voltage changes) of the cardiac muscle. This is detected through electrodes placed on the skin. It does not directly record rate, volume, or diseases.

ECG is used to detect various cardiac conditions including heart attacks (myocardial infarction), heart blocks (conduction abnormalities), and coronary thrombosis (clot in coronary arteries). All of these conditions produce characteristic changes in the ECG pattern.

The mediastinum is the central compartment of the thoracic cavity. It contains all organs of the thoracic cavity, except the lungs.

Angiogenesis is the term used to indicate the growth of new blood vessels.It is a normal and vital process in growth and development, as well as in wound healing.

Pulse pressure is the arithmetic difference between systolic pressure (peak pressure during heart contraction) and diastolic pressure (minimum pressure between beats). Normal pulse pressure is typically 30-50 mmHg. It reflects the force generated by the heart and arterial elasticity. Options A, B, and C describe individual components but not the definition of pulse pressure itself.

Purkinje fibres are specialized cardiac muscle fibers located in the ventricles that form the terminal part of the conduction system. They rapidly transmit electrical impulses from the AV bundle to the ventricular myocardium, ensuring coordinated ventricular contraction.

The SA node (sinoatrial node) is the heart's natural pacemaker, located in the right atrium. It spontaneously generates electrical impulses that initiate each heartbeat. These impulses then spread to the AV node, Bundle of His, and Purkinje fibres to coordinate the cardiac cycle.

The human cardiac cycle consists of one complete heartbeat (systole + diastole) and takes approximately 0.8 seconds at a normal resting heart rate of about 75 beats per minute (60/75 = 0.8 sec). 0.5s would mean 120 bpm (too fast), while 1.0-1.2s would mean only 50-60 bpm (unusually slow for a healthy adult at rest).

When the stress subsides, the parasympathetic nervous system of the body produces opposite effects of sympathetic nervous system. It conserves energy as it calms an individual by decreasing heart rate, lowering blood sugar, and so forth.