IMPORTANT TERMS:
Arterial Pulse: Wave of distension experienced in the arteries as a result of ventricular systole.
v Atrio-Ventricular Node (AV node):
Specialised muscle fibres present in the interatrial septum that conducts
cardiac impulse from SA node to bundles of His.
v Bicuspid Valve (Mitral Valve):
A valve consisting of two flaps between left atrium and left ventricle in the
heart.
v Blood Pressure (BP): The
pressure exerted by the blood against the walls of arteries. BP of a normal
person at rest is 120/80 mm of Hg, ie., systolic pressure=120; diastolic
pressure=80.
v Cardiac Cycle:
Rhythmic contraction and relaxation of cardiac chambers in a specific manner
during one heart beat.
v Closed Circulatory System:
The circulatory system in which the blood flows through heart and blood
vessels.
v Diastole:
Relaxation of cardiac chamber.
v Electrocardiogram (ECG):
A graphic record of the electric current produced by the excitation of cardiac
muscles.
v Haemocoel: Body
cavity containing blood.
v Interstitial Fluid: The
fluid that occurs in the spaces between the cells of a tissue.
v Joint Diastole:
Relaxation of cardiac chambers- both atria and ventricles together.
v Lymph: Transparent
fluid derived from blood containing lymphocytes but low in protein.
v Myogenic Heart: The
heart in which cardiac impulse originates in cardiac muscle fibres as in
vertebrates.
v Neurogenic Heart:
The heart in which cardiac impulse originates by specialized nerve fibres as in
invertebrates.
v Open Circulatory System:
The circulatory system in which the blood flows through open spaces (lacunae)
and channels (sinuses).
v Pacemaker:
The structure that initiates the cardiac impulse, eg. SA node.
v Pericardium: A
double walled membranous sac that encloses the heart.
v Pulmonary Circulation:
The flow of deoxygenated blood from right ventricle to the lungs and the
oxygenated blood from the lungs to the atrium back.
v Semilunar Valves: The
valves containing three flaps present at the base of pulmonary artery and aorta
in the heart.
v Sinoatrial Node (SA Node):
Also called pacemaker. It is present in the right atrium and initiates cardiac
impulse.
v Sinus Venosus: A
chamber present before the right auricle to collect deoxygenated blood in the
hearts of fishes and amphibians.
v Systemic Circulation:
The flow of oxygenated blood from the left ventricle to all parts of the body
(except lungs) and flow of deoxygenated blood from all parts of the body to the
right atrium.
v Systole:
Contraction of cardiac chambers.
v Tricuspid Valve:
A valve consisting of three flaps present between right atrium and right
ventricle.
v Vagus Nerve:
A nerve from parasympathetic system that slows down the heart rate.
ADDITIONAL INFORMATION:
v Cardiology:
Study of heart and its functions.
v Heart Skeleton:
Ring of connective tissues in the heart muscle (myocardium) act as cardiac
skeleton.
v Cardioscope:
An instrument fitted with lens and light for examining the inside of the heart.
v Cardiomegaly:
Enlargement of heart.
v Myocardial Ischaemia:
Deficient blood supply to heart muscle, causes angina pectoris.
v Angiography:
A non surgical technique of determining the arrangement of blood or lymphatic
vessels by X-rays after injecting radio-opaque material. Angiography of the
arteries supplying the heart is termed as coronary
angiography.
v Varicose Vein:
When the walls of a vein become weak, blood collects in it and distends it so
much that the valve flaps cannot meet to check reverse flow of blood. Blood
collects in the weakened vein, which is then called a varicose vein. Generally
found in lower limb.
v Haemotoma:
Blood collected in the tissues outside the blood vessels, a common skin bruise
due to blow.
v Haemorrhage:
Loss of blood from injured blood vessels.
v Haemodialysis: Removal
of waste products from the blood in an artificial kidney.
v Blue Baby:
A baby with a blue tinge to the skin due to insufficient oxygenation of the
blood. It indicates a congenital heart or lung defect.
v Brachycardia:
Decreased heart beat than the normal.
v Tachycardia: Increased
heart beat than the normal.
v HDL (High Density Lipoproteins):
These are called ‘good lipoproteins’.
Their high level in the blood may help reduce the risk of coronary heart
disesase.
v LDL (Low Density Lipoproteins):
These are called ‘bad lipoproteins’. Their high level in the blood increases
the risk of coronary heart diseases.
v Stroke:
A thrombosis in the blood vessels in the brain.
v Haemorrhoids:
These are varicose veins in the walls of rectum. They develop due to pressure
as in constipation and pregnancy.
v Coronary Thrombosis:
Formation of clot in the coronary artery. It generally occurs in the left
anterior descending artery.
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