response to exercise 4.2.2

• muscles are made of protein fibres
• muscles need energy from respiration to contract, when you exercise, some of your muscles contract more frequently than normal so you need more energy, then energy comes from increased respiration
• your breathing rate and breath volume increase to get more oxygen into the blood and your heart rate increases to get more oxygenated blood round the body faster, this removes CO2 more quickly at the same time
• carbon dioxide levels increase when you exercise and it needs to be removed so muscles can work effectively
• glycogen is a carbohydrate form of glucose stored in muscles, so your blood sugar is not too high
• glycogen is converted rapidly back to glucose during exercise to be used for energy
• really vigorous exercise can cause the muscles to respire anaerobically which is not good because lactic acid can build up in the muscles which gets painful
• long periods of exercise can cause muscle fatigue - the muscles get tired and stop contracting efficiently
• muscle contractions contract harder and faster to move faster
• glycogen stores break down into glucose to use for energy and anaerobic and aerobic respiration
• heart rate increases to pump more oxygenated blood around the body
• arteries supplying muscles with blood widen so the muscles can get more blood with oxygen and glucose
• breathing rate increases to get rid of more CO2 and get more oxygen
• the depth of breathing increases to increase oxygen capacity
• adrenaline increases before you begin the exercise, this causes the heartrate to increase right before the exercise, before this the heartrate and breath are at a steady level
• during the exercise, the heart rate increases gradually, with a quick increase at the start, as the breathing increases, so does the heartrate until it reaches maximum level, because you need more oxygen for aerobic respiration and there is more carbon dioxide to remove
• in recovery, the heart rate decreases quickly, whereas the breathing rate decreases slower to get the oxygen levels back to normal
• an oxygen debt is the amount of extra oxygen your body needs to react with the build up of lactic acid and remove it from the cells, oxygen reacts with lactic acid to form harmless CO2 and water
• the pulse and breathing rate stay high whilst there are high levels of lactic acid and CO2
• an unfit person would produce more lactic acid therefore they would need more oxygen to break down this lactic acid, the lungs are less efficient so it takes longer to pay off the oxygen debt
• as a result of long term exercise, the volume of the heart at rest increases to pump more blood so there is more oxygen and glucose and so more aerobic respiration
• as a result of long term exercise, the volume of blood pumped by each heart beat increases so there is more oxygen and glucose pumped to muscles
• as a result of long term exercise, the resting pulse decreases so there is less strain on the heart because it isnt working as hard
• as a result of long term exercise, the maximum lung volume increases to take in more oxygen with each breath and to get rid of more CO2
• as a result of long term exercise, the resting breathing rate decreases so there is less strain on the lungs
• anaerobic respiration causes a build up of lactic acid and creates an oxygen debt
• the blood that enters the muscles can also transport the lactic acid to the liver where the lactic acid is converted back to glucose