Potential command term assessment statements Topic 6: Human Physiology 6.2 The blood system Essential Idea: The blood system continuously transports substances to cells and simultaneously collects waste products. Nature of science: Theories are regarded as uncertain—William Harvey overturned theories developed by the ancient Greek philosopher Galen on movement of blood in the body. Discuss William Harvey’s discovery of the circulation of the blood with the heart acting as the pump. Describe the separate double circulation of blood around the body. 1. Pulmonary circulation 2. Systemic circulation Identify the chambers and valves of the heart and the blood vessels connected to it in dissected hearts or in diagrams of heart structure. Identify the right and left sides of the heart in relation to structure and function. Inferior vena cava and superior vena cava Right and left atria Right and left atrioventricular valves (right is tricuspid valve and left is bicuspid or mitral valve) Right and left ventricles Semilunar valves (pulmonary semilunar valve and aortic semilunar valve) Pulmonary arteries and pulmonary veins Aorta Cardiac muscle relatively thick on left ventricle and thin on right ventricle Septum Coronary arteries Identify blood vessels as arteries, capillaries or veins from the structure of their walls. Explain the relationship between the structure and function of arteries, capillaries, and veins. Arteries convey blood at high pressure from the ventricles to the tissues of the body. Arteries have muscle cells and elastic fibres in their walls. The muscle and elastic fibres assist in maintaining blood pressure between pump cycles. Blood flows through tissues in capillaries. Capillaries have permeable walls that allow exchange of materials between cells in the tissue and the blood in the capillary. Veins collect blood at low pressure from the tissues of the body and return it to the atria of the heart. Valves in veins and the heart ensure circulation of blood by preventing backflow. Explain the cardiac cycle in terms of collecting blood, pumping blood, and the opening and closing of valves along with the pressure changes in the left atrium, left ventricle and aorta. 1. Diastole = heart relaxes and fills with blood from the vena cava and pulmonary veins while the semilunar valves prevent backflow of blood from the aorta and pulmonary arteries. 2. Atrial systole = Atria contract increasing blood pressure and pushing blood through the atrioventricular valves into the ventricles. Valves in the veins prevent a backflow of blood out of the heart. 3. Ventricular systole = Ventricles contract increasing blood pressure in the ventricles which close the atrioventricular valves and pushes blood through the semilunar valves into the aorta and pulmonary arteries. Potential command term assessment statements Outline the control of the heartbeat. Myogenic muscle contractions Heart beat initiated by a group of specialized muscle cells in the right atrium called the sinoatrial node. The sinoatrial node acts as a pacemaker. The sinoatrial node sends out an electrical signal that stimulates contraction as it is propagated through the walls of the atria and then the walls of the ventricles. The heart rate can be increased or decreased by impulses brought to the heart through two nerves from the medulla of the brain. Epinephrine increases the heart rate to prepare for vigorous physical activity. Outline the causes and consequences of occlusion of the coronary arteries. Fatty plaque occlusion or narrowing of arteries. Blood flow to the heart is restricted leading to a myocardial infarction / heart attack. Likely causes / increased risk with age: o Smoking o Lack of exercise o Obesity o High blood cholesterol (little / no link to diet) o High blood pressure (hypertension) o High blood sugar level – diabetes o Genetics risks Discuss how an understanding of the structure of the cardiovascular system has allowed the development of heart surgery. Theory of knowledge: Our current understanding is that emotions are the product of activity in the brain rather than the heart. Is knowledge based on science more valid than knowledge based on intuition?