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GCSE Physical Education The Circulatory System At the end of this topic you should know the following… The role and components of the circulatory system; The structure of the heart; How the circulatory system works; Definitions of… Heart rate, stroke volume, cardiac output; The roles and characteristics of the 3 types of blood vessels; The functions of blood cells; How the circulatory system is affected by exercise. The Circulatory System Components are… 1 The heart 2 Blood vessels 3 Blood Major functions include… 1 Transport of 0² & CO² to & from the muscles 2 Temperature regulation 3 Preventing infection The Heart 1. 2. 3. 4. 5. The heart is a special type of muscle called…? Why is it special? What is its main job? Why is the heart often described as a ‘double pump’. Approximately how big do you think the heart is? Answers 1. 2. 3. 4. 5. Cardiac muscle Because it never tires Pump blood around the body There are 2 circuits, the pulmonary and the systemic Size of a fist The Structure of the Heart Labelling of the Heart; The Circulatory System Using diagram of heart on previous slide describe the flow of blood through the circulatory system. Deoxygenated blood from the body enters the right atrium via the vena cava. Following its journey through the body, the blood has now collected a number of waste products including CO². From the atrium the blood is now forced into the right ventricle through the tricuspid valve Blood is then forced up into the pulmonary artery which leads to the lungs Here blood picks up O² and deposits CO² The newly oxygenated blood is then forced back to the heart through the pulmonary vein into the left atrium. Blood is then forced into the left ventricle through the bicuspid valve and then into the aorta to supply oxygenated blood to all parts of the body. Blood vessels Blood vessels are needed to transport blood around the body Arteries: carries oxygenated blood away from the heart to the organs & muscles Veins: carry de-oxygenated blood back to the heart. This blood carries excess CO² Capillaries: the smallest blood vessels. Lie close to the muscle allowing O² & CO² to pass to & from the blood & the muscles. Blood Vessels Vessels Arteries Characteristics Capillaries Veins Connective tissue and smooth muscle (elastic) Blood travels under high pressure Oxygenated blood away from the heart Linked to arterioles Have pulses & thick walls One cell thick Allow gaseous exchange Linked to arterioles and venules Smooth muscle (non-elastic) Blood travels under low pressure Deoxygenated blood to the heart Thinner walls Linked to venules Blood pressure Blood Pressure Pressure under which the blood travels as it is ejected from the left ventricle Blood vessel constriction increases BP; dilation reduces BP 1. DIASTOLE: Heart is relaxed, BP is reduced 2. SYSTOLE: Heart contracts, BP is increased BP during aerobic exercise; Systolic BP increases in direct proportion to increased exercise intensity Diastolic BP changes little if any during endurance exercise, regardless of intensity Muscles help squeeze the blood through the veins back to the heart. Note how valves work together. Blood – what is it?? Blood accounts for __8__% of total body weight. It is made up of cells & platelets, which are suspended in plasma. There are 3 parts to the blood: 1. Red & White Blood cells 2. Platelets 3. Plasma Blood cells, Platelets & Plasma; Red blood cells (erythrocytes) are extremely small and give the blood its red colour. A typical adult has about 4.8 to 5.4 million red blood cells. The main function of these cells is to transport O² & CO² around the body Oxygen is transported via a chemical called Haemoglobin White blood cells (leukocytes) have the function of protecting the body from bacteria, viruses, infections & foreign bodies Platelets (thrombocytes) are small cell fragments which help blood clotting Plasma is mainly made up of water, but also includes waste, hormones, glycogen and nutrients. Heart Rate Heart rate defines as …….. ‘The number of times the heart beats per minute’ RHR averages 60 to 80 beats per minute (bpm); can range from 28 bpm to above 100 bpm. HR tends to decrease with age and with increased cardiovascular fitness. Therefore resting heart rate is often used to indicate a person’s fitness levels. HR is also affected by environmental conditions such as altitude and temperature Stroke volume Stroke Volume defines as .... ‘The amount of blood pumped out of the heart by each ventricle during 1 beat/contraction’ SV increases with increasing rates of work. It also influences aerobic endurance capacity when working maximally. Stroke Volume Increases During Exercise Frank Starling mechanism—more blood in the ventricle causes it to stretch more and contract with more force. Cardiac output Cardiac Output is defined as ..… ‘The amount of blood pumped out of the heart by each ventricle in one minute.’ Resting value of cardiac output (Q) is approximately 5.0 L/min. Q increases directly with increasing exercise intensity to between 20 to 40 L/min. Value of increase varies with body size and fitness level How can you calculate the Cardiac Output? Q = HR x SV When exercise intensity exceeds 40% to 60% of maximum, further increases in Q are more a result of increases in HR than SV. CHANGES IN HR, SV, AND Q The Heart in Action Heart Rate [beats per minute] Stroke Volume [mls per beat] Cardiac Output [litres per minute] Homer Flanders 100 65 90 70 Complete the table [remember there are 1000ml in a litre!]