cardiovascular system

• The components of the cardiovascular system and their functions are described at the end of this lecture.
• The characteristic of cardiac muscle cells are discussed in this lecture.
• The basic ECG is explained in this lecture.
• The cardiac cycles are discussed in this lecture.
• Factors affecting cardiac output are described in this lecture.
• The compensatory mechanism involves CVS is discussed in this lecture.
• The role of blood vessel in maintaining BP is discussed in this lecture.
• The basic lymphatic system is discussed in this lecture.
• The heart is the first organ to appear during fetal development: at ~3 weeks development.
• The heart will beat over 3 million time over your lifetime.
• Heart cells are not replaced: The same cells support it’s activity throughout your life.
• The heart is the biological pump that distributes blood from high regions to low regions.
• The arrangement of endothelial cells that overlap each other at both ends and the existence of valves intermittently along the lymphatic vessels permit only one way direction of flow of the lymph.
• Lymph from the upper quadrant, which includes the head region, neck and arms, drains into the right lymphatic duct following the right subclavian veins in the systemic circulations.
• The other function of the lymphatic system is the absorption of nutrients from the GI tract, such as fat absorption by the lacteals.
• The lymphatic system consists of a network of vessels and nodes that transport lymph, a fluid that contains infection-fighting white blood cells.
• Lymph from the lower quadrant, such as legs, drains into the thoracic duct before entering systemic circulations through the left subclavian veins.
• The lymphatic system also has an immune effect by the lymphocytes.
• Blood vessels are passageways that distribute the blood and control pressure and distribution.
• Blood is the mobile component of CVS that transports oxygen, nutrients, hormones, and removes CO2 and waste products.
• The heart is responsible for maintaining adequate circulation of oxygenated blood around the vascular network of the body, maintaining tissues supply of oxygen adequately at all time without fail.
• The heart is situated in the chest cavity (mediastinum), behind the sternum in a position of anterio-posteriorly with the apex pointed obliquely to the left.
• The heart is encapsulated by a tough double membrane, called the pericardium.
• The wall of the heart is primarily composed of a thick muscle tissues called myocardium.
• The inner surface of the cardiac chambers that is in contact with blood is lined by a thin connective tissue sheet called endocardium, whereas the outermost layer of the heart, that in contact with the pericardium is called epicardium.
• The heart is divided into right and left halves by a central wall, called the septum.
• Each half of the heart is comprised of 2 chambers called an atrium and a ventricle.
• In between the atriums and ventricles in each halves, there are atrio-ventricular valves which permits blood flow from the atrium to the ventricle but not from the ventricle to the atrium.
• Typical ECG normalities are: P wave, QRS complex, and T wave.
• The repolarization phase of the action potential generation from the SA node is the recovery phase of the cells’ resting membrane potential where Ca2+ channels start to close off and opening of K+ channel begins.
• Electrocardiogram (ECG) is a tool to evaluate the electrical activity of the heart, where current generation within the myocardium can be traced by electrodes attached in specific part of the body (3 limb leads and 12 chest leads).
• A cardiac cycle consists of a complete atrial and ventricular contractions and relaxations, and is described as the event associated with one heart beat process.
• Cardiac contraction is called systole, whereas cardiac relaxation is called diastole.
• P wave in ECG corresponds to the current flows during atrial depolarization.
• Electrocardiogram (ECG) is used to determine possible conducting pathway abnormality, cause of chest pain, and detection of damage of certain region of the heart.
• The plateau phase of the action potential generation from the SA node is a phase where depolarization (positivity) is maintained despite of low Na+ influx, due to the opening of Ca2+ channels resulting with an increased of Ca2+ delivery from the sarcoplasmic reticulum into the cytoplasm.
• The action potential generation from the SA node begins with a depolarization phase, where the resting membrane potential is disrupted with an influx of Na+ into the cells from a massive opening of voltage gated Na+ channel, increasing the positivity of the cells’ electrical charge.
• Electrical events of the cardiac muscle cells are governed by the action potential generation from the SA node, which spreads along the conducting system and to the contractile cardiac muscle cells, causing the generation of action potential in the cardiac muscle cells.
• The cardiac muscle has a long refractory period, meaning the second action potential cannot be generated until complete muscle relaxation is accomplished.
• QRS complex in ECG visualizes the rapid ventricular depolarization.