CVS

• The ultimate function of the cardiovascular system (CVS) is to keep an adequate capillary perfusion all over the body, which is essential for the maintenance of normal function of all tissues and organs of the body.
• The heart pumps blood during its contraction (systole) ejecting blood in the arterial system.
• During its relaxation (diastole), the heart acts as a suction pump withdrawing blood from the venous system.
• The arterial system's function is taking blood from the heart to the tissues.
• Capillaries have an exchange function through their thin walls, allowing exchange between plasma and tissues.
• Veins have a capacitance function, returning blood back to the heart.
• The heart is formed of two separate sides, right and left, and has four chambers: Right atrium (RA), Right ventricle (RV), Left atrium (LA), Left ventricle (LV).
• In the heart there are four valves: Atrioventricular (AV) valves between atria & ventricles: Mitral valve between the LA and LV, Tricuspid valve between the RA and RV; Semilunar valves between ventricles and vessels: Aortic valve between the LV and the aorta, Pulmonary valve between RV and pulmonary artery.
• Nodal "Pace maker" tissues in the heart include Sinoatrial node (SAN) and Atrioventricular node (AVN), which initiate the excitation wave at a regular rhythm.
• Junctional "Conductive" tissue in the heart includes His bundle, bundle branches & Purkinje fibers, which conduct the excitation wave to the rest of the heart as fast as possible.
• Muscular "contractile" tissue in the heart includes Atrial muscle & ventricular muscle, which contract and act as a pump.
• Properties of the Cardiac muscle include Excitability, Auto-rhythmicity, Conductivity, and Contractility.
• The first and most important property of the cardiac muscle is its excitability, which is common to all parts of the cardiac muscle; but in the pace maker tissue it is self-excitable.
• Automaticity means the ability to initiate its own beat, while rhythmicity means the ability to continue beating regularly i.e at a rhythm.
• Auto-rhythmicity is normally restricted to the auto-rhythmic "pace maker cells" in the SAN & AVN.
• Contractility is the ability of the cardiac muscle to respond to stimulation by contraction, which is restricted to the muscular contractile tissue namely atrial & ventricular muscle fibers.
• Pulse Rate is the number of pulsations per minute, it depends on the heart rate and the normal frequency in adults is 60 - 90 per minute.
• Arterial Blood Pressure (ABP) is the lateral pressure exerted by blood on the wall of arteries, the definitions for ABP are: Systolic ABP (SBP) is the highest pressure exerted by blood on the arterial wall during systole of the heart, Diastolic ABP (DBP) is the lowest pressure exerted by blood on the arterial wall during diastole of the heart.
• The Pulse are the pressure waves in the walls of the arterial system which are transmitted in the arterial walls towards the periphery, the pressure waves expand the arterial wall as it travels, this expansion can be palpated as arterial pulse.
• The normal ECG components are: P wave, QRS complex and T wave.
• The three ECG components are: P - wave produced by atrial depolarization, QRS - complex caused by depolarization of the ventricles, T - wave represents ventricular repolarization.
• The His - Purkinje system consists of fibers that have a fast rate of conduction (meters / sec.), while the contractile tissue has a lesser rate of conduction (cm /sec.).
• The 2nd Heart Sound (S 2) marks the end of systole and start of diastole and is due to vibrations set up by closure of semilunar valves.
• Physiologic Variations include age, sex, diurnal, sleep, emotions, exercise.
• In the nodal tissue, the rate of conduction is very slow (mm / sec).
• Normal values for arterial blood pressure are: Ideal blood pressure is 130 / 80 mmHg, Systolic pressure range is 90 – 140 mmHg, Diastolic pressure range is 60 - 90 mmHg.
• The heart acts as an electric generator, which can be conducted to the body surface and recorded by electrodes placed on the skin.
• Heart sounds are sounds caused by vibrations set in tissues around the heart due to its activity, two sounds only can be normally heard: 1st and 2nd sounds.
• The 1st Heart Sound (S 1) marks the start of systole and is due to vibrations set up by closure of A - V valves.
• All the cardiac muscle cells are conductive but at different rates, with the specialized conductive tissues having the highest conductivity.