The process of gaseous exchange at the lungs and the muscles and the effect of exercise on this process.
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Task 3 - The process of gaseous exchange at the lungs and the muscles and the effect of exercise on this process. Once the air has passed through the airways and reached the alveoli the process of gaseous exchange will begin. The oxygen must go into the capillaries by passing through the alveoli and capillary walls and the carbon dioxide must go into the alveoli by passing through the capillary walls and the alveoli walls to then be expired from the lungs. These gases move by diffusion; which is the movement of gaseous particles along a partial pressure gradient. http://www.schools.sandwell.net/menzies/subjects/biology/ks3/images/alveoli.png The blood supply going around the alveoli is constant, so that oxygen and carbon dioxide can be continuously moving in and out of the capillaries. Because the blood is moving quickly past the alveoli it means that one same red blood cell is never staying at the same point so the movement of gases can be constant; as deoxygenated blood is constantly coming through the gradient of oxygen will go from high in the alveoli to low in the deoxygenated blood so that the concentration gradient is very good so oxygen will diffuse more quickly.
the gradient into the muscles as they have a low partial pressure of oxygen but as the partial pressure in the muscles reaches around 40mm Hg the gradient from blood to muscle tissue will be much more equal so no oxygen will be able to pass down the partial pressure gradient which is required for diffusion to take place. Obviously during gaseous exchange at the muscles the carbon dioxide which is formed during muscular contractions must be taken away by the blood. 10% of the total carbon dioxide taken form the muscles is just carried by dissolving into the plasma. Another 20% is carried away by the red blood cells by combining with the carbon dioxide to form carbaminohaemoglobin (binds to the iron atoms) and the remaining 70% is carried in the form of bicarbonate ions. This is when the carbon dioxide combines with the water to form the plasma to form carbonic acid (H2CO3); this is then broken down by an the enzyme carbon anhydrase (which is found in the red blood cells) leaving one free hydrogen atom and a bicarbonate ion (HCO3) This remaining free hydrogen atom can then be used to bind with the oxyhaemoglobin and thus displacing the oxygen atom (due to their contrasting places in the reactivity series)
The temperature receptors within the body can recognise that heat is being produced as a result of exercise and can then do various things to aid the body, such as increasing the electrical impulses travelling to the muscles in use, bring the blood vessels closer to the surface of the skin to release more heat and also make the body sweat in order to cool down. The stretch receptors in the lungs will also be used to detect any increase in lung volume as a result of exercise; the brain can then use this information to regulate the contractions happening at the diaphragm and intercostals so that the lungs are not over stretched. It does this by initiating expiration when the lungs become over stretched; it is called the Hering-Breur Reflex. The main result of all these sensory detections is that the lungs can work efficiently so that the muscles are getting enough oxygen for the production of ATP as energy and also so that carbon dioxide and acidity levels in the muscles/blood don't rise too high. This means the muscles can keep exercising effectively as any lack of oxygen or increase in carbon dioxide/acidic substances would cause the muscles to stop working and cramp up which would obviously restrict our ability to exercise.
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