The Heart and Circulation

• The cardiac cycle involves stages like Diastole, Atrial Systole, and Ventricular Systole
• During Diastole, cardiac muscle is relaxed and blood enters the atria and ventricles
• In Atrial Systole, the atria contract, forcing the remaining blood through the valves into the ventricles
• During Ventricular Systole, the ventricles contract, the atrioventricular valves close, and the semilunar valves are forced open
• The heart muscle is MYOGENIC, meaning it stimulates itself to contract without needing a message from the brain
• Pacemakers in the heart produce small electrical impulses that stimulate muscle contraction
• Chemoreceptors detect chemical changes like oxygen concentration, carbon dioxide levels, and blood pH, affecting heart rate
• The sympathetic nervous system, a branch of the autonomic nervous system, can increase heart rate
• Baroreceptors in the heart detect changes in blood pressure, leading to adjustments like vasodilation to regulate blood pressure
• The ventricle and aorta follow the same pattern of pressure changes during the cardiac cycle
• The left atrium receives blood full of oxygen from the lungs and pumps it into the left ventricle
• The right atrium receives blood from the body that is low in oxygen and pumps it into the right ventricle
• The right ventricle pumps blood to the lungs to pick up oxygen
• The left ventricle pumps oxygenated blood through the aorta to the body
• The tricuspid valve is located between the right atrium and right ventricle and controls the blood flow of those chambers.
• The pulmonary valve is between the right ventricle and the pulmonary artery that delivers blood to the lungs.
• The aortic valve is the valve that opens to allow blood to flow from the left ventricle to the aorta.
• The mitral valve regulates blood flow from the left atrium into the left ventricle.
• Superior Vena Cava carries blood from the head, neck, and upper limbs to the right atrium.
• Inferior Vena Cava carries blood from legs, feet and organs in the abdomen and pelvis to the right atrium.
• The pulmonary vein carries oxygenated blood from the lungs to the left atrium.
• The aorta is the largest artery in the body and carries blood from the heart to the body.
• The pulmonary artery carries deoxygenated blood from the right ventricle to the lungs
• Two advantages of double circulatory system.

  • Oxygenated and deoxygenated blood are kept separated
  • This allows the blood to be pumped at a higher pressure to the body cells so it moves faster.