life sciences

Heartbeat and Cardiac Cycle

• Heartbeat sounds: 'lub-dup'
  • 'Lub': Closing of AV valves; louder and longer
  • 'Dup': Closing of semilunar valves; shorter and sharper
• Cardiac cycle: Events in one heartbeat, lasting about 0.8 seconds and occurs at ~70 beats/min.
• Phases: Systole (muscle contraction, increased pressure), Diastole (muscle relaxation, decreased pressure).
• Stroke volume: Each ventricle pumps ~70ml of blood/beat.

Heart Valves

• Two sets of valves:
  • Atrioventricular (AV) valves: Tricuspid (right side) and Mitral (left side) allow blood flow from atria to ventricles.
  • Semilunar valves: Pulmonary and Aortic, prevent backflow into ventricles.

Blood Flow through the Heart

• Right side (low pressure): Deoxygenated blood from body via superior/inferior vena cavae to right atrium, then to right ventricle, and pumped to lungs through pulmonary artery.
• Left side (high pressure): Oxygenated blood from lungs via pulmonary veins to left atrium, then to left ventricle, and pumped to body through aorta.

Double Circulatory System

• Ensures efficient oxygen delivery: Pulmonary circulation (to lungs) and systemic circulation (to body).
• Blood passes through the heart twice per complete circuit.

Effects of Heart Blockage and Structure

• Blockage in coronary arteries can cause myocardial infarction (heart attack) due to oxygen deprivation of heart muscle.
• Heart structure: Four chambers, muscular walls (myocardium), and valves ensure unidirectional blood flow.

Characteristics of Circulatory Systems

• Circulatory systems transport gases, nutrients, and wastes; consist of blood, vessels, and heart.
• Types: Open (invertebrates) and closed (vertebrates, including humans). A closed system allows for fast, high-pressure blood flow.