gas exchange

1.diaphragm contracts and flattens 2.external intercostal muscles contract 3.internal intercostal muscles relax 4.ribcage pulled upwards and outwards 5.volume inside the thorax increases and pressure decreases 6.air rushes into the lungs

1.diaphragm relaxes and retuns to normal dome shape 2.external intercostal muscles relax 3.internal intercostal muscles contract 4.ribcage pulled inwards and downwards 5.volume inside the lungs decrease and pressure increase 6.air moves out of lungs

1.have large surface area to increase rate of diffusion 2.have thin walls which provide short diffusion distance 3.moist to dissolve gases

1.respiratory tract is lined by ciliated epithelium with goblet cells 2.the goblet cell secretes mucus which is thick and sticky to trap bacteria. 3.cilia pushes the mucus out

• during exercise rate of respiration increases, so level of co2 in blood increases 2.co2 dissolves in the plasma forming a weak acid 3.chemoreceptors in the medulla of the brain, aorta, and carotid artery detect the change in ph of blood 4.chemoreceptors send impulse to the respiratory center in the brain, which stimulates the breathing rate to increase 5.more carbon dioxide passes from the blood to the lungs to be exhaled

1.during exercise muscles run short of oxygen 2.muscles respire anaerobically resulting in the formation of lactic acid 3.lactic acid is transported to the liver

1.tar destroys the cilia and increases mucus secretion which is not swept away. bacteria in mucus causes bronchitis which blocks normal air flow causing difficulty in breathing and coughing 2.smoke damages the walls of the alveoli reducing surface area for gas exchange reducing the oxygen levels in blood this is called lung emphysema 3.tar causes lung cancer

nicotine: raises blood pressure->risk of heart attack carbon monoxide: binds to haemoglobin ->carboxyhaemoglobin so red blood cells carry less O2