Electrocardiograph (ECG) :
- ECG is a graphical representation of the electrical activity of the heart during a cardiac cycle.
- Each peak in the ECG is identified with a letter from P to T that corresponds to a specific electrical activity of the heart.
- The P-wave represents the electrical excitation (or depolarization) of the atria.
- The QRS complex represents the depolarization of the ventricles.
- The ventricular contraction starts shortly after the Q and marks the beginning of the ventricular systole.
- T-wave represents the ventricular diastole (repolarisation).
DOUBLE CIRCULATION :
- Pulmonary circulation: Right ventricle (deoxygenated blood) → pulmonary artery → lungs (oxygenation) → pulmonary vein (oxygenated blood) → left atrium.
- Systemic circulation: left ventricle (oxygenated blood) → systemic aorta → body (deoxygenated) →vena cava (deoxygenated blood) → right atrium.
- Portal system: the deoxygenated blood collected from one organ by means of a vein (portal vein) entered into another organ before it is delivered to the systemic circulation.
- Hepatic portal system: the hepatic portal vein carries deoxygenated blood from the intestine to the liver before it is delivered to the systemic circulation by means of hepatic vein.
- Coronary circulation: A special blood vessel (coronary vessel) is present in our body exclusively for the circulation of blood to and from the cardiac musculature.
REGUALTION OF CARDIAC ACTIVITY :
- Rhythmicity of human heart is regulated by specialized (nodal tissues), hence the heart is called myogenic.
- A special neural centre in the medulla oblongata can regulate cardiac function moderately.
- Neural signal through sympathetic nerve can increase the heart rate and cardiac output.
- Neural signal through parasympathetic nerve can decrease the heart rate and cardiac output.
- Hormones of adrenal medulla (adrenaline) also increase the cardiac output.
DISORDERS OF CIRCULATORY SYSTEM :
Hypertension :
- Hypertension is the term for blood pressure that is higher than normal (120/80).
- 120 mm Hg is the systolic pressure and 80 mm Hg is the diastolic pressure.
- Sustained blood pressure of 140/90 or higher is said to be hypertension.
- Blood pressure is measured by sphygmomanometer.
- High blood pressure leads to heart disease and also affects vital organ like brain and kidney.
Coronary Artery Disease (CAD) :
- Often referred as atherosclerosis, affects the blood supply to the heart muscles.
- It is caused by deposition of calcium, fat, cholesterol and fibrous tissue which makes the lumen of coronary artery narrower.
Angina :
- It is also known as ‘angina pectoris’.
- Causes acute chest pain due to inadequate oxygen supply to the heart.
- It occurs due to blockade to coronary artery.
Heart failure :
- It is the state of the heart when it is not pumping blood effectively
- Cardiac arrest: the heart stops beating.
- Heart attack: heart muscle damaged suddenly by an inadequate blood supply to the heart muscles.
