Hemodynamics and Distribution of blood in the systemic circulation Physiology of circulation (Hemodynamics) Circulation is a continuous circuit through which the same amount of blood flow through each subdivision of circulatory system is maintained by the heart. In a resting animal about 25% of the blood volume is in the central circulation (pulmonary and coronary circulation) and […]

Pulse in animals Pulse in animals is a wave of expansion and elongation followed by recoiling of the arterial walls and due to the forceful entry of the blood from the aorta during each heart beat. It originates from aorta spreads throughout arterial system and disappears at the arterioles. Systolic rush of blood into aorta

Electrocardiography or ECG in animals Electrocardiography (ECG) is the recording of the electrical changes occurring during the process of depolarization and repolarization of the heart. The instrument, the electrocardiograph is used to take the recording known as elctrocardiogram. Einthoven (1908) first recorded ECG using bipolar leads. The depolarisation and repolarisation of cardiac muscle generate electrical

Vasodilator chemicals and hormones in animals Vasodilator chemicals Nitro-glycerin Halothane Nikethamide Caffeine Camphor Nitrates Vasodilator Hormones Glucagon Insulin Thyroxine Serotonin Histamine PGE2 Prostacyclin VIP Substance P  Vasoconstrictor Hormones Vasopressin PGF2µ Thromboxane A2 Leukotriene D4 Angiotensin II Endothelin

Coronary circulation in animals Coronary circulation in animals starts as coronary orifices in the aorta and supplies the blood to the heart muscles through right and left coronary arteries. These orifices are in free communication with aorta both during systole and diastole. The main coronary artery branches into right and left coronary arteries. The left

Metabolism and energetics of working myocardial cells in animals Cardiac muscle requires a continuous supply of oxygen and therefore myocardial cells under normal conditions, utilise aerobic metabolic system that provides a constant supply of high energy phosphate for mechanical and chemical working of the heart. The major fuel required for cardiac metabolism is free fatty

Chemical regulation of the heart in animals Cations Na+ and K+ ions favour diastole, whereas Ca++ ion favours systole. Sudden infusion of the Ca++ ions into the heart causes calcium rigor or systolic arrest. Catecholamines Epinephrine and norepinephrine are the neurotransmitters of sympathetic division, acts on β1 receptors and exerts positive chronotropic (atria and ventricles) and inotropic effects on heart. β1 receptors are found

Nervous Regulation of Heart rate in animals Sympathetic and parasympathetic divisions of ANS play a key role in the regulation of heart rate. The nerves regulate to a larger extent the rate rather than the force of contraction either directly or indirectly. The two atria are especially well supplied with large number of both sympathetic and

Extrinsic Regulation of Heart in animals Heart regulates its cardiac output based on the functional blood requirement of different parts of the body by adjusting its rate. Heart rate is directly proportional to metabolic activity, but inversely proportional to the size of the animal. Large animals have a slower heart rate than smaller ones. Athletic

Intrinsic Regulation of heart in animals Frank’s Starling Mechanism/Heterometric Regulation Regulation of the cardiac function is independent of the nervous or humoral control. This was proved by the Starling’s experiment using Starling’s heart lung preparation i.e., isolating the heart from the body so as to remove humoral and neural influences. The heart is perfused through