The cardiovascular system is composed of three main parts: the heart, the blood vessels and the blood. Its function is to deliver oxygen and nutrients and excrete waste products from all the cells of the body.
The heart The heart is about the size of a closed fist, and shaped like a cone. It is located behind the sternum and ribs, slightly to the left of the centre of the chest. It is made up of four chambers, two upper atria and two lower ventricles.
Structure The heart is divided into four chambers: The two chambers at the top are called atria The two lower chambers are called ventricles Blood travels from the atria to the ventricles. They are separated by valves, (atrioventricular valves), to ensure that blood flows in one direction only.
Cardiac muscle The chambers are surrounded by a wall of muscle, called the myocardium. This muscle is specific to the heart and is termed cardiac muscle. Cardiac muscle: Is involuntary and contracts automatically Has interwoven muscle fibres Contains many mitochondria. The walls of the ventricles are more muscular than the atria since more force is required to pump blood out of the heart to the lungs and body.
Structure The heart can also be divided into left and right halves. Each side has a different role / function: The left side is responsible for circulating blood (rich in oxygen) around the whole body The right side is responsible for pumping blood (low in oxygen) to the lungs to collect more oxygen
Blood vessels The blood and blood vessels are responsible for carrying blood and nutrients around the body. There are 3 types of blood vessels: arteries, veins and capillaries. The arteries carry blood away from the heart to the working muscles and other parts of the body where oxygen and nutrients are required. The arteries branch off and progressively become smaller vessels known as arterioles.
Blood vessels These arterioles then join even smaller vessels known as capillaries where diffusion takes place. The capillaries are the essential link between arteries and veins; they are tiny vessels with semi permeable membranes allowing oxygen and nutrients to be delivered to the tissues and waste products such as carbon dioxide and water to be removed.
Blood vessels Following diffusion the blood moves from the capillaries into venules (small veins); these then join together to form larger veins as the blood is moved back towards the heart. Because the pressure of the blood in the veins is low they have valves to prevent back flow which helps the blood to travel in the right direction.
Blood Vessels ArteriesVeinsCapillaries Vessel wallThick & muscularThinVery thin (one cell thick only) DiameterSmallLargeVery small ValvesNoYesNo PressureHighVery lowLow BloodOxygenated*De-oxygenated*Both Blood flowAway from heartTowards heartFrom artery to vein FunctionCarry nutrients and oxygen to working tissues Carry waste products including carbon dioxide away from working tissues Allow diffusion of nutrients, oxygen and carbon dioxide between blood and working tissues
Blood Vessels The pulmonary artery and vein are the exception. The pulmonary artery carries deoxygenated blood away from the heart to the lungs and the pulmonary vein carries the freshly oxygenated blood from the lungs back to the heart. Arterioles and venules are small extensions of the arteries and veins which distribute blood from the arteries to the capillaries and back to the veins.
The Blood Functions: Transport oxygen from the tissues Return carbon dioxide from the tissues to the lungs Carry waste products from the tissues to the liver and kidneys to be broken down/excreted Distribute hormones Carry essential nutrients
The blood Characteristics: Thick and more viscous than water Temperature 30oc Volume, 4-6 litres (typical man/woman)
The blood ComponentDescription / function PlasmaStraw coloured liquid, mainly water Carries nutrients Red blood cellsKnown as erythrocytes Contain haemoglobin which carries oxygen Produced in bone marrow Typically 40-45% of total blood volume White blood cellsKnown as leucocytes Fight infections Produced in bone marrow Fewer in number than red blood cells PlateletsThrombocytes Control bleeding after injury Help in process of blood clotting and repairing damaged tissues
Short term effects of exercise on the cardiovascular system Exercise has the following short term effects on the cardiovascular system: There is an increase in heart rate at the onset of exercise. This is due to the release of the hormone adrenalin. Adrenalin prepares the body for action by stimulating the respiratory and circulatory systems. It is often associated with nerves, butterflies, rapid breathing, and sweating palms
Short term effects of exercise on the cardiovascular system There is an increase in stroke volume (the amount of blood pumped out of the heart per beat). Because there is an increase in both heart rate and stroke volume cardiac output (the amount of blood pumped by the heart per minute) also increases. (Cardiac output (Q) = SV x HR)
Short term effects of exercise on the cardiovascular system The working muscles’ demand for oxygen means that blood is redirected away from areas which need it less. For example, when cycling blood may be redirected from the gut to the legs The body's temperature increases as does the temperature of the blood. To cope with this increase in temperature more blood is shunted to the skin surface to help it cool. Sweating cools you by evaporation Blood pressure increases at the onset of exercise
Long term effects of exercise on the cardiovascular system Exercise has the following long term on the cardiovascular system: The heart muscle will also increase in size (cardiac hypertrophy), particularly that of the left ventricle leading to a more forceful contraction. More blood is pumped per beat (stroke volume) and therefore per minute (cardiac output) Resting HR decreases (bradycardia), but SV increases so the same amount of blood is pumped out per beat at rest
Long term effects of exercise on the cardiovascular system There is an increase in the size and number of blood vessels feeding the muscles and lungs After endurance training (low intensity, long duration) the quantity and quality of the blood improves. More red blood cells are produced. This means that more oxygen can be transported to and used by the muscles Blood pressure is decreased in individuals with hypertension. All of these effects only occur if regular exercise is maintained. If the exercise is stopped for a period of time then the training effects will be lost.
COMPARISON OF BLOOD VESSELS ArteryVeinExplain differences Structure: Vessel wallThick & muscularThin The artery wall allows constriction when the muscle contracts, which increases blood flow ValvesNoneYes Veins have little muscle in the walls to change shape, so movement of blood is supported by pocket valves which prevent the backflow of blood
COMPARISON OF BLOOD VESSELS Function: Blood flow Away from heart, oxygenated blood Towards the heart, de- oxygenated blood The exceptions are the pulmonary artery, carrying deoxygenated blood from the heart to the lungs, and the pulmonary vein, carrying oxygenated blood from the lungs to the heart Pressure High pressure Low pressure Pressure is highest in the arteries due to the elastic nature of the vessel wall, the movement if blood is much slower in the veins TransportOxygen to working muscles Carbon dioxide away from working muscles Arteries transport oxygen to the capillaries where gaseous exchange can take place, and as a result carbon dioxide enters capillaries as oxygen enters the muscle, this is then passed on to the veins where it is transported back to the lungs for re-oxygenation
Capillary walls are composed of a single cell. They are very thin and allow oxygen and carbon dioxide to squeeze through. A membrane which allows gases to pass through can be termed semi-permeable. The main function of capillaries is for gaseous exchange. This process is efficient owing to a dense capillary network surrounding the muscle.
Circulation The vascular system has two pathways of circulation, the pulmonary circulation (to the lungs) and the systemic circulation (to the body).
The Double Circulatory System Humans have a double circulatory system where blood passes through the heart twice. The route around the body of blood leaving the left and right sides of the heart are different. These routes or systems, are referred to as pulmonary circulation and systemic circulation.
Pulmonary Circulation Transport of blood between heart and lungs Blood, low in oxygen, is transported to the lungs where it becomes oxygen rich, then returns to the heart
Systemic Circulation Transport of blood from the heart to the rest of the body and vice versa Blood rich in oxygen is distributed from the heart to the rest of the body and working tissues to deliver oxygen. Blood then returns to the heart, oxygen poor
Vasodilation & Vasoconstriction Vasodilation (definition) = the increase in the internal diameter of blood vessels that is caused by relaxation of smooth muscle within the wall of the vessels, thus causing an increase in blood flow. The opposite effect is Vasoconstriction. The opposite effect is vasoconstriction, when blood vessels dilate, the blood flow is increased due to a decrease in vascular resistance. Vasodilation
Venous Return Blood returning to the right side of the heart The heart can only pump as much blood out as it receives, so cardiac output is dependent upon venous return The process is aided by a muscle pump, as the muscle contracts, the veins are compressed slightly and squeeze blood back towards the heart
Blood flow through the heart and lungs Deoxygenated blood is returned from the muscles and the rest of the body via the superior and inferior vena cava into the right atrium. It then passes into the right ventricle and from here it is pumped into the pulmonary artery where it travels to the lungs. It is in the lungs that pulmonary diffusion occurs; the blood is removed of its waste produces and enriched with oxygen.
The blood is then returned to the heart via the pulmonary vein into the left atrium. It is then pumped into the left ventricle and from here into the aorta where the oxygenated blood is then delivered the working muscles.
Within the heart there are a number of valves which ensure that the blood can only flow in one direction. Valves are found between atria and ventricles (atrio-ventricular valves) and between ventricles and the main vessels transporting blood away from the heart (semi- lunar valves). The blood flow pushes the valve open and it is then closed by connective tissue called chordae tendineae.
The Cardiac Cycle The heart muscle needs to contract in order to eject blood from the heart and be transported around the body. How the heart works. Cardiac muscle contractions are initiated by an impulse from a pacemaker, called the sino-atrial node (SAN) within the right atrium wall. The contraction spreads throughout the walls of the atria and through branched fibres within the ventricle walls. The cardiac cycle refers to the sequence of events occurring as this impulse spreads through the heart. One complete contraction / cycle of the heart is one heartbeat The cycle usually lasts for about 0.8 seconds, and occurs about 72 times per minute.
Atrial diastole Atria fill with blood Atrioventricular valves closed Ventricular diastole Pressure builds in atria Valves pushed open Ventricles begin to fill with blood Semi-lunar valves closed
Stages of the cardiac cycle Atrial systole Atria walls contract Remaining blood forced into ventricles Semi-lunar valves closed Ventricular systole Ventricle walls contract Atrio-ventricular valves closed Blood forced into circulatory system Semi-lunar valves pushed open Heart Sounds The closing of the valves within the heart and the circulatory system are responsible for the ‘lub-dup’ sounds of the heart.
Heart Rate, Stroke Volume and Cardiac Output Heart rate The number of times the heart beats per minute Stroke Volume The amount of blood ejected from the heart every time it beats Typically about 70-80cm 3 at rest
Heart Rate, Stroke Volume and Cardiac Output Cardiac Output The volume of blood ejected from the left ventricle in one minute Typically about 5000cm 3 at rest Can be determined from knowing an individuals heart rate and stroke volume: Cardiac Output= Stroke Volume x Heart Rate Q= SV x HR
Heart rate is controlled through the nervous system, originating in the brain. Heart rate can speed up or slow down in response to feedback For example, during exercise, the heart rate speeds up to ensure a greater supply of blood and oxygen to the working tissues. However, when blood pressure rises, there is a need to slow down the heart rate (and subsequent blood flow rate).
Blood Pressure The force exerted by the blood against the walls of the blood vessels Factors affecting blood pressure: Cardiac output Resistance Measurements of blood pressure are taken as systolic pressure (when the heart is contracting) over diastolic pressure (when the heart is relaxing). A typical reading for resting blood pressure is 120 / 80 mmHg
Vasomotor Control Vessels constrict and dilate in order to control blood flow around the body The vasomotor and venomotor control centre in the brain sends signals via the nervous system in response to the body’s demands, for vessels to either increase or decrease the flow of blood.
Pulse Rate When the heart contracts, a wave of pressure is generated through the vessels and there is a slight dilation of the arteries. This can be felt at various sites in the body Most common sites: Carotid artery Radial artery Brachial artery
Factors affecting blood pressure Blood pressure is taken to give an indication of general health. There are a number of factors which affect blood pressure: exercise - blood pressure increases when you exercise. This is because the heart is working harder to supply your muscles with more oxygen. Regular exercise helps to lower resting blood pressure and prevent cardio-vascualr disease. diet - high levels of fat and salt cause the arteries to stiffen or clog up. This clogging leads to an incresae in blood pressure. age - blood pressure increases as you grow older. This is because the arteries lose their elasticity and do not expand so much when blood is pumped through them. stress and tension - increases blood pressure. This is because hormones are released into the bloodstream when the body becomes stressed or anxious. smoking - cigarette smoking increases blood pressure because nicotine reduces the efficiency of the capillaries.
Structure and route of air to lungs NoseAir enters here and is filtered by tiny hairs and warmed PharynxBoth food and air pass through the pharynx Food is then directed into the oesophagus LarynxCommonly known as voice box Opening covered by epiglottis (a flap of cartilage) which prevents food entering here TracheaWindpipe, about 10cm long, supported by rings of cartilage Contains cells which remove foreign particles from the air BronchiRight and left branches, which further divide into bronchioles BronchiolesFurther divide into smaller pathways, leading to alvoli AlveoliSmall air filled sacs Large surface are Thin walls Surrounded by capillaries LungsThe bronchi extend into the lungs 2 cone shaped organs separated by the heart Surrounded by a protective membrane
Mechanics of breathing An average adult will inhale and exhale approximately 12 to 15 breaths per minute. For air to be drawn into the lungs, the pressure of the air within the lungs must be lower than that in the atmosphere. The greater the difference in pressure, the faster air can be drawn into the lungs. The pressure difference is created by altering the size of the thoracic cavity.
Inspiration When an individual breathes in it is referred to as inspiration. During inspiration the intercostal muscles contract pulling the ribs upwards and outwards at the same time as the diaphragm contracts and flattens. These combined actions increase the area inside the lungs meaning that air is then drawn into the lungs until the pressure inside the lungs is equal to the atmospheric pressure.
Expiration When an individual breathes out it is known as expiration. During expiration the intercostal muscles relax lowering the rib cage to its resting position. The diaphragm also relaxes (moving upwards). This causes the area inside the lungs to decrease, increasing the pressure inside. This greater pressure forces the air out of the body until the pressure is equal to that of the atmosphere.
Gaseous Exchange Oxygen passes into the body and carbon dioxide leaves the body through the process of gaseous exchange. Movement of oxygen and carbon dioxide occurs from a high concentration to a low concentration, known as diffusion. The amount of each gas which moves is controlled through a semi-permeable membrane
Gas exchange at the lungs There is a high concentration of oxygen in the lungs as we breathe in, and a low concentration in the capillaries surrounding the alveoli. There is a high concentration of carbon dioxide in the blood and capillaries then in the alveoli air from breathing in Two way process As oxygen diffuses into the capillaries to be delivered to the tissues, carbon dioxide diffuses into the alveoli to be expired The capillary wall is thin to allow efficient gaseous exchange The alveoli have a large surface are to allow optimal exchange of gases
Transport of Oxygen and Carbon Dioxide Oxygen combines with haemoglobin in the red blood cells to form oxy-haemoglobin In the lungs, where there is little carbon dioxide haemoglobin is said to be 100% saturated with oxygen When large amounts of carbon dioxide are present, the saturation of haemoglobin with oxygen is reduced, enabling oxygen to disassociate (unload) and feed the working tissues At the site of the tissues, most oxygen has been unloaded Most carbon dioxide is transported in the form of bicarbonate ion, and some combines with haemoglobin to form carbaminohaemoglobin
Gas exchange at the muscles and tissues Oxygen is rich in the capillary blood, and low in the muscle cell. Oxygen can disassociate from haemoglobin and pass across the capillary wall into the muscle cytoplasm Oxygen forms with myoglobin Carbon dioxide produced in the muscle passes into the capillary and can be transported to the lungs in the veins
Respiratory volumes There are a number of measures or capacities that can be taken of the amount of air moving into and out of the lungs: Lung volume / capacityDefinitionApproximate normal values Tidal volume (TV)The amount of air inspired / expired per breath 500ml Inspiratory reserve volume (IRV) The amount of air forcibly inspired above tidal volume 3300ml Expiratory reserve volume (ERV) The amount of air forcibly expired above tidal volume 1000 – 1200ml Residual volume (RV)The lungs never completely empty, and the air that is left after a maximum exhalation is the residual volume. 1200ml Vital capacity (VC)Vital capacity is the maximum amount of air that you can breathe out after breathing in as deeply as you can. IRV + TV + ERV 5500ml Total lung capacityVC + RVUp to 8000ml Minute ventilationThe volume of air inspired / expired per minute. Minute volume = TV x RR 7500ml Respiratory rate (RR)How many breaths you take per minute Average is 12-15
Short term effects When you take part in sport or exercise the body places a number of demands on the oxygen transport systems, these demands are also referred to as the short term effects of exercise: even before you start to exercise your body releases the hormone adrenalin. It prepares you for action by stimulating the respiratory and circulatory systems. It is often associated with nerves, butterflies in your tummy, rapid breathing, a quickened heart rate, sweating palms and sometimes it even makes people feel sick. during exercise the working muscles need more oxygen. This process is referred to as internal or cell respiration and as a result the levels of carbon dioxide (CO2) in the blood start to rise.
Short term effects increased levels of CO2 in the blood are detected by the brain. The brain then sends a message to the lungs to breathe faster and deeper in order to expel the CO2 and so the respiratory rate increases. Levels of CO2 dictate the rate of breathing of the body during exercise. the process of gas exchange in the lungs speeds up as a result of the increase in the rate of breathing. More CO2 is absorbed out of the blood and more oxygen is drawn in. in order to cope with the working muscles demand for more oxygen, the brain sends a message to the heart to speed up.
Short term effects as a response to this message, the heart rate increases. More blood is pumped with each beat of the heart to provide more oxygen to the working muscles and so the stroke volume increases. If stroke volume and heart rate both increase then so too does cardiac Output. increased cardiac output means that more blood and therefore oxygen is being pumped each minute to the working muscles, and more carbon dioxide is being carried away. the arteries and arterioles dilate in order to accommodate the increased flow of blood. Dilation of the blood vessels also keeps blood pressure low.
Short term effects muscles can receive up to three times the resting amount of oxygen. Blood flow can be increased up to 30 times the resting rate. The working muscles therefore can receive up to 90 times the resting amount of oxygen. the working muscles demand for oxygen means that blood is redirected away from areas which need it less. For example, when cycling blood may be redirected from the gut to the legs. the body's temperature increases as does the temperature of the blood. To cope with this increase in temperature more blood is shunted to the skin surface where it cools. Sweating cools you be evaporation.
Short term effectsEffects / Changes Heart rate Increases Stroke volume Increase Cardiac output Increases Body temperature Increase Blood flow Re-distribution to working tissues Blood pressure Aerobic exercise – increase in systolic pressure Anaerobic exercise – increase in both systolic and diastolic pressure Breathing rate Increase Tidal volume Increase Inspiratory reserve volume Decrease Expiratory reserve volume Slight decrease Residual volumeSlight increase Vital capacitySlight decrease
Short term effectsEffects / Changes Total lung capacitySlight decrease Respiratory musclesIncreased rate of contraction Oxygen disassociationIncrease Carbon dioxide productionIncrease
Long Term Exercise has the following long term effects on the respiratory system: The intercostal muscles become stronger helping to make the respiratory system more efficient The lungs get bigger, increasing their capacity to draw in oxygen There is an increase in the rate at which carbon dioxide is drawn out of the lungs and oxygen is drawn in Vital capacity increases The combined respiratory and circulatory systems become more efficient There is an increase in capillary density surrounding the alveoli thus improving gaseous exchange All of these effects only occur if regular exercise is maintained. If the exercise is stopped for a period of time then the training effects will be lost.
BODY SYSTEMLONG TERM EFFECTS OF EXERCISE MUSCULAR1.muscles develop a bigger blood vessel network. This feeds more blood (oxygen and energy) to the muscle 2.muscles adapt to using more oxygen. They can therefore work more efficiently and for a longer time 3.increased muscle tone and maybe a reduction in body fat RESPIRATORY1.the muscles used for breathing become stronger 2.the lungs get bigger, increasing their capacity to draw in oxygen 3.an increase in the rate at which carbon-dioxide is drawn out of the lungs and oxygen is drawn in CIRCULATORY1.the heart becomes larger and stronger. More blood is pumped per beat (stroke volume) and therefore per minute (cardiac output) 2.each heartbeat pumps more blood, so your resting heart rate falls, while the same amount of blood is pumped 3.there is an increase in the size and number of blood vessels feeding the muscles 4.after endurance training (low intensity, long duration) the quantity and quality of the blood improves. More red blood cells are produced. This means that more oxygen can be transported to and used by the muscles CARDIO-VASCULAR1.the combined respiratory and circulatory systems become more efficient. They take more oxygen and carbon dioxide to and fro, and they do it more quickly.
Cardio-Respiratory FunctionAdaptations Heart Cardiac hypertrophy Increased size of ventricles & walls Heart rate Decreased maximum heart rate Bradycardia (decreased resting heart rate) Stroke volumeIncreased Blood pressureDecreased BloodIncreased haemoglobin levels Blood vessels Increased capillary density surrounding muscles and lungs Stronger muscle in vessel walls Gaseous exchange Increased alveoli Increased strength of respiratory muscles Lung VolumesIncreased tidal volume