Circulation and Gas Exchange GCSE

passes air down to the bronchi.

bones that help to protect the lungs

contracts and relaxes to expand the volume of the lungs.

contracts and relaxes to expand the volume of the lungs, located at the bottom of it.

passes air from the trachea to the bronchioles

passes air from the bronchi to the alveoli

where gas exchange with blood takes place

they make up a continuous envelope around the lungs, forming an airtight seal. It also produces pleural fluid. This makes the pressure inside the thorax and lungs decrease to draw in air

contracts and relaxes to expand the volume of the lungs, located at the bottom of it

contracts and expands to allow air ventilation.

acts as lubrication so that the surface of the lungs don’t stick to the ribs (inside of the chest wall). It is between both of the membranes - the pleural cavity.

Thorax: chest, which includes the ribcage enclosing the heart and lungs Ribs: bones that help protect the lungs Intercostal muscles: two sets of antagonistic muscles lying between the ribs. Diaphragm: a shallow dome shape Trachea: windpipe leading form the nose and mouth to the bronchi, it is made of lots of cartilage rings shaped like the letter ‘C’ Bronchi: two tubes, one entering each lung, walls contain cartilage Bronchioles: narrow tubes that provide small air passages leading from the bronchi to the alveoli Alveoli: microscopic air sacs where gas exchange takes place Pleural membranes: two thin, moist membranes that make up a continuous envelope around the lungs, forming an airtight seal

• Ventilation - the movement of air into and out of the lungs • When inhaling, the external (outer) intercostal muscles between the ribs contract, causing the ribcage to rise/expand. At the time, the diaphragm muscle contracts and changes shape to become flatter. • These two movements cause the volume of the ribcage to increase. The consequent decrease in pressure causes air to flow into the lungs from the atmosphere via the trachea • Exhalation involves the reversal of the changes above (this would mean a contraction of the outer rib muscles) but if forced exhalation was involved, the internal rib muscles would contract as well.

• They have a large surface area to maximise absorption • It is one cell thick • It has a good supply of blood to absorb oxygen • It is moist (it dissolves the gas and makes it easier to go across) • Not alveoli but still good knowledge: ventilation keeps oxygen levels high and CO2 levels low • Capillary walls are also 1 cell thick • Short diffusion distance meaning total of two cells two diffuse through

• Emphysema: Alveoli become damaged and lose their elasticity. Smoking causes inflammation and irritation in the airways leading to the release of enzymes that break down this lung tissue. This weakens the walls of the alveoli, the SA for has exchange is reduced and they expel air worse. This leads to a difficulty in breathing, shortness of breath, feeling breathlessness and tiredness. It also makes the alveoli worse at expelling air. • Lung cancer: harmful chemicals and carcinogens enter the lung by smoking. These can damage DNA and lead to the uncontrolled growth of abnormal cells. These cells can form tumors in the lungs, obstructing the airways and reducing lung function. It is often diagnosed at late stages making it hard to treat effectively. • Bronchitis/smoker’s cough: tar is a sticky substance that is present in cigarette smoke. It has detrimental effects on the cilia in the trachea. Cilia are tiny hair-like structures that line the respiratory tract and play an important role in clearing mucus, dust particles and other substances. When exposed to tar, the cilia become coated and immobilized, reducing their ability to remove the harmful particles. This leads to an accumulation of mucus, debris and toxins in the airways, resulting in a chronic cough and an increased susceptibility to respiratory infections like bronchitis and a reduced lung function. • Cardiovascular diseases (e.g. coronary heart disease): Nicotine is found in cigarettes. When nicotine is inhaled through smoking or other forms of tobacco use, it enters the bloodstream and reaches the brain. It stimulates the release of neurotransmitters like dopamine and serotonin. It also constricts blood vessels, raising blood pressure and increases heart rate, putting extra strain on the cardiovascular system. The increased blood pressure can damage the walls of the coronary arteries leading to atherosclerosis. Blockages of the blood vessels can lead to heart attack. During CHD: aka heart attack. The coronary arteries become blocked due to the build-up of plaque (atherosclerosis). Blood supply to the area is reduced/stops. The heart doesn’t receive enough oxygen and it begins to respire aerobically, releasing lactic acid, eventually the20heart muscles dies so the heart doesn’t beat in sync. Smoking raises blood pressure and it makes clots more likely to form. • Carbon monoxide binds to haemoglobin → reduces oxygen transport → increases CHD risk.

• Make someone sit completely relaxed for five minutes. Then they count the number of breaths they rake in one minute, recording their results. They repeat this until they get a steady value for ‘resting rate’. • Then make the person carry out vigorous exercise such as running on the spot for 5 minutes. Immediately after they finish the exercise, they sit down and record the breathing rate as before. They then continue to record the breaths per minute until they return to their normal resting rate. • Repeat it 3 times to make sure that there are no anomalies. • Some notes: ○ Resting pulse rate before exercising is taken so you can compare. ○ The effect of exercise on your pulse rate: muscles work harder so more energy and oxygen is needed so more respiration for energy in the muscle cells so more oxygen is needed to be delivered to the respiring muscles so more breaths (frequency) and deeper breather are taken. ○ The reason your heart rate doesn’t return to its resting rate immediately after stopping exercise is due to the oxygen debt (lactic acid that has been built up and needs to be removed by breathing oxygen)

• Red blood cells • White blood cells • Platelets • Plasma

• It is mainly made up of water (the liquid part of the blood. It is a pale yellow liquid that carries everything that needs to be transported in your body. • It carries blood cell (red and white blood cells and platelets) around the body as well as dissolved substances (nutrients/digested foods, hormones, CO2, Urea and any other waste). It also distributes heat

• To carry oxygen around the body • Its adaptations are: ○ Flexible ○ Have no nucleus so there is more space for haemoglobin which associates (attaches) itself with oxygen so it transport more oxygen ○ It is biconcave (shape) so it does gas exchange more effectively with oxygen ○ It has a high SA:VOL ratio so there is a larger area for diffusion to occur ○ Their thin shape makes diffusion distance to the centre of the cell shorter

• Phagocytes ○ Digest and destroy bacteria and other microorganisms that have infected our bodies by phagocytosis ○ Phagocytes detect things that are ‘foreign; to the body e.g. pathogens. They then engulf the pathogens and digest them. They are non-specific meaning that they attack anything that shouldn’t be there. They do it using this: 1. The pseudopodia of the cell surrounds the bacterium 2. The bacterium is enclosed in a vacuole 3. Digestive enzymes destroy the bacterium • Lymphocytes ○ Produce antibodies to destroy microorganisms, some lymphocytes persist in our blood after infection and give us immunity to specific diseases • All cells have chemical ‘markers’ on their surface which are referred to as ‘antigens’. Your immune system uses these as a way of recognising pathogens as these will have different antigens on their surfaces than your own cells. • When your immune system detects a foreign antigen, it produces specialised proteins called ‘antibodies’ that will bind to that antigen and mark it out for destruction to any other white blood cells. Antibodies are described as being ‘complementary’. This means that each type of antibody will bind to only one type of antigen. Each antibody carries a number of binding sites which are specific in shape to the antigen to which it binds. Because different pathogens have different antigens on their surface this means that your immune system must produce separate antibodies for each different pathogen. • Each lymphocyte has a specific receptor on its surface. This receptor is similar in shape to a particular antigen. When an antigen binds to this receptor, it actives the lymphocyte. This causes the lymphocyte to divide repeatedly by mitosis. Most of the cells produced as the lymphocyte divides become plasma cells - these cells immediately start rapidly producing antibodies to fight the infection. A small number of cells produced become memory cells. These cells remain in the blood for many years. If the body gets re-infected with the same pathogen, these cells can be quickly alerted to divide and start producing antibodies so that the pathogen can be killed before you start to feel anything. This is known as immunity.

• Result in the manufacture of memory cells • Vaccines contain weakened, inactivated or part of pathogens • They stimulate the primary immune response without causing disease • This leads to the production of memory cells, so if the person gets it later, then the secondary response is triggered so the microbe can be destroyed quicker. • Primary response = first time you have the microbe. It releases low amounts of antibodies into the blood that react to the microbe. It also takes longer to be released. • Secondary response = other times you get the microbe. Much faster than the primary response, releases a lot of antibodies into the blood. Reacts quicker. (Sooner, faster and greater quantity)

• Damage to blood vessels like capillaries cause platelets to be activated • They form a plug at the site of injury. It also triggers a chain of chemical reactions which causes proteins dissolved in the plasma (fibrinogen, a soluble protein) to form insoluble fibres called fibrin • The fibrin forms a fibrous mesh that strengthens the platelet plug

• The side with the thicker wall is the left side of the heart. • On the right side of the heart, blood enters via the vena cava into the right atrium. It passes the tricuspid (atrio-ventricular valves) to reach the right ventricle. It then passes through the semi lunar valves to the pulmonary artery to go to the lungs. It returns via the pulmonary vein into the left atrium. It goes through the bicuspid into the left ventricle and it gets pumped through the semi lunar valves into the aorta. The valves prevent the backflow of blood by ensuring a one-way flow.

• Blood enters the heart from the vena cava, however it cannot pass into the ventricles because the ventricular valves (tricuspid and bicuspid) are closed. • The walls of the atria start to contract and this increases the blood pressure in the atria and that forces the atrio-ventricular valves to open and let blood pass through into the ventricle to even out the pressure • When the ventricles are full, they start to contract and this increases the pressure in the ventricles, which closes the atrio-ventricular valves and stops blood returning to the atria. • The ventricles continue to contract and the pressure continues to rise. This forces the semi-lunar valves at the base of the aorta and the pulmonary artery to open. Blood is then ejected into these two arteries. • As the ventricle empties, the pressure in it decreases so the higher pressure in the aorta and pulmonary artery cause the semi-lunar valves to close. Then the cycle begins again.