Evaluate the conditions necessary for effective gaseous exchange

The main function of the respiratory system is gaseous exchange. This is the process of oxygen and carbon dioxide moving between the lungs and blood.

Diffusion occurs when molecules move from an area of high concentration to an area of low concentration, this occurs during gaseous exchange, as blood in the capillaries which surround the alveoli has lower concentration compared to the air in the alveoli which has just been inhaled.

The alveoli and capillary walls are only one cell thick to allow gases to diffuse across them. It is the same for carbon dioxide. The blood in the surrounding capillaries has a higher concentration of CO2 than the air you have just inhaled and this CO2 which has already travelled around the body is ready to become a waste product. Whereas CO2 diffuses the other way, from the capillaries, into the alveoli where it can be exhaled.

' The air we breath contains approximately 21% oxygen and 0.04% CO2. When we exhale there is approximately 17% oxygen and 3% CO2.' This shows a decrease in oxygen levels as it is used in producing energy and increases the CO2 due to it being a waste product of energy production.

The effects of smoking on the body system

When you inhale a cigarette it goes from your mouth down your throat past your pharynx and your trachea into the bronchioles and into the lungs. The inhaled cigarettes have tar in them which is sticky and brown and it can cause damage to your body.

It can cause damage to your teeth, mouth and gums as well as ulcers of the digestive system. The carbon monoxide binds with hemoglobin and takes over the oxygen carried by the blood. So with there being less oxygen in the blood cells your heart has to pump more so the body gets the amount of oxygen which is needed.

Hydrogen cyanide prevents the lungs from cleaning themselves and the cilia becomes damaged, harmful chemicals collect in the lungs. Other chemicals in smoke are highly reactive chemicals that can damage heart muscles and blood vessels. Cigarettes also include dangerous metals which many are known to cause cancer. The tar in cigarettes can cause cancer of the esophagus and throat. Smoking increases stomach acids which can lead to ulcers and higher rates of pancreatic cancer. Carcinogen from cigarettes are excreted in your urine which can cause bladder cancer and high blood pressure from smoking can cause damage to your kidneys.

Fertility is compromised, in female smokers it can affect the reproductive system and they are also high risk of getting cervical cancer and men tend to have lower sperm count because of the damaged blood vessels in the penis.

Smokers immune systems are vulnerable and they are very prone to minor infections such as chest infection.

The relationship between smoking and coronary heart disease

When the blood is pumped through the heart, the nicotine from the cigarettes also builds up in the blood stream.

Smoking is possibly the highest risk factor for coronary heart disease. The toxins will float around within the blood which causes the hardening of the arteries which puts people at greater risk for having a heart attack or heart failure.

Smoking affects the blood which increases the risk of cardiovascular disease. It is found that smokers have higher levels of fibrinogen which can cause blood clots, increased blood viscosity and lower levels of oxygenated blood, this is because carbon monoxide attaches itself to the hemoglobin more easily than it can to oxygen.

One in eight cardiovascular deaths were attributable to smoking, if you have already had a heart attack, quitting smoking reduces the risk of having a fatal heart attack by 25 per cent.

Women who smoke and use contraceptive pills increase the risk of coronary heart disease by several times.

Smoking and lung cancer

Lung cancer usually starts in the lining of the bronchi, but can also begin in areas such as the trachea, bronchioles or the alveoli.

Lung cancer is when cells become abnormal and grow out of control, they form a clump which is called a tumour. Lung cancer develops in your airways however it can grow inside the lung and can even spread to outside the lung. If it spreads outside the lung it becomes incurable.

The more cigarettes you smoke the more at risk you become of getting lung cancer. It can take many years to develop, the main age group for this disease is 55-65 years old.

The cancer is located and it starts with affecting the first few layers of cells, then the cancer is located in the lungs and the tissues surrounding them are normal. The cancer then spreads from the lungs and affects the lymph nodes near the lungs, then the cancer spreads to other organs which surrounds the lungs such as the diaphragm and the chest walls, the cancer can then spread to all other parts of the body.

Cancer can develop in the lungs in two ways. It can start in the lungs which is called primary lung cancer or it can spread to the lungs from other parts of the body. If it does start from other parts of the body and spread to the lungs it is known as secondary or metastatic lung cancer.

Cancerous tumours are made up of cells, these cells can break away from the primary cancer and travel through the blood stream or the lymphatic system to other parts of the body.

The tar from cigarettes sticks to the cilia which lines the airways in the lungs. The cilia normally cleans out any dirt but when you smoke a cigarette and the tar sticks to it, it cant do its job properly so dirt stays in the lungs and causes problems. Mucus also piles up and overtime the cilia dies and the lungs are exposed to more dangerous substances.

The relationship between diet, blood pressure, blood cholesterol and circulatory disease

If you have a poor diet which is high in saturated fats it can cause high blood cholesterol. Cholesterol is a type of fat called lipid which is made by the body. It is essential we have some of this for good health. It is found in every cell in the body however too much of it does cause high cholesterol levels in the blood which can increase the risk of high blood pressure.

High blood pressure makes your heart work harder to pump the blood around the body. Over a period of time this will damage your heart. The increased pressure can also damage the walls of your arteries, resulting in a blockage or causing the artery to split. Both of these situations can cause a stroke. High blood pressure produces hardly any symptoms, so it may go unnoticed until it causes something serious such as a stroke or a heart attack.

High blood cholesterol also damages and roughs up the artery walls which is easy for free floating fatty acids to attach to which causes atheroma. Cholesterol damages by blocking the blood vessels of the circulatory system. As cholesterol enters the blood it clings to the walls of the blood vessels such as arteries. If the blood vessels block completely it can cause an heart attack. Once the plaque has completely blocked the vessel, oxygen rich blood is no longer able to reach the heart, the heart quickly becomes starved of oxygen and thye heart muscle cells begin to die. This is what causes you to have a heart attack.

Changes of artery structure associated with circulatory disease

Coronary artery disease is the most common type of heart disease. This happens when the arteries that supply blood to the heart become hardened and narrowed. This is because of cholesterol build up called plaque which builds up on the inner walls of the arteries. The plaque build up is a clot, this travels around the body and is formed in another location in the body which is called an embolism. An arterial embolism could be caused by more than one clot, they can get stuck in the artery and block blood flow. As more and more plaque builds up the less blood can flow through the arteries (as shown in the picture) so the heart cant get enough blood or oxygen it needs to supply the body. This can lead to angina or a heart attack. Coronary artery disease can also weaken the heart which could lead to heart failure or changes in the normal beating rhythm of the heart, this is called atherosclerosis.

Process of redistributing blood during exercise

When you exercise blood flow is redistributed, less blood goes to all your major organs except for the heart and brain and more blood flows to the muscles and skin. Arteries dilate during exercise in the working muscle and blood flow increases through the capillaries. The increases flow of blood to the muscles increase the exchanges of oxygen. The nervous system prepares the body for exercise by passing hormones which signals the dilation of the blood vessels in the heart and working muscles these systems act more efficiently to redistribute blood. Blood redistribution takes a few minutes. If you suddenly stopped exercising it can leave you light headed due to the reduction of pumping action from the leg muscles to return blood to the heart and if you suddenly start exercising it can leave you breathless and strain any muscle which is not prepared to do exercise. The amount of capillaries in working muscles increases however the blood becomes thinner to ensure it flows better through the capillaries. Thinning the blood flow through these more water and dissolved proteins are added to the plasma volume. So the plasma volume is increased and the concentration of red blood cells decreases.

The mechanisms for regulating ventilation and pulse rates

Homeostasis is the maintenance of a constant internal environment within the body. This includes:
Control of the water balance of the blood.
Control of blood sugar levels.
Control of body temperature.
Control of blood urea level.
Each of these internal controls is maintained by separate mechanisms. All mechanisms for homeostasis have specific sensors which are able to detect the value of the factor which is being monitored and any differences from the norm are corrected so the norm is more or less maintained and stable at all times.
When something like the temperature outside drops our bodies homeostasis mechanism makes adjustments which produces more body heat for us. Muscular activity and shivering help to generate heat which keeps our body temperature at a constant level.
Regulating ventilation is controlled by the neurons in the medulla. Our breathing rates are normally maintained at a constant level involuntary by the medulla. The rate of our breathing depends on the medulla to detect the pH level in our blood. By detecting the pH level the medulla determines how much carbon dioxide is in our blood. If we have high pH levels the medulla becomes stimulated and our breathing rate will increase and when the pH level is low our breathing rate will become slower due to the decrease in nervous stimulation. The medulla controls your heart rate. A healthy pulse rate reading is between 60- 100 beats per minute. It can be felt in any place that allows an artery to be compressed against the bone such as in your neck, on your wrist or behind your knee. High heart rate risk factors are being overweight, high blood pressure, high cholesterol, fatty diet, diabetes, smoking and depression and this could result in having a heart attack. The heart rate is controlled by the balance of stimulation coming from the sympathetic and parasympathetic branches of the autonomic nervous system. The nerves then meet together in the right atrium which is the sino-atrial node. Parasympathetic stimulation slows down the rate and sympathetic increases the rate.
When exercising the body needs more oxygen and the muscles produce more carbon dioxide. The chemoreceptors in the carotid artery in the neck, recognise the changes in gases after the blood travels through the aorta in the chest which will increase the heart rate. When the heart rate increases more blood is pumped into the arteries resulting in an increase in blood pressure. This is detected by the baroreceptors which are located in certain arteries, they send impulses to the control centre ( the medulla oblongata) which interprets the message and sends impulses to the cardiovascular system. This slows the pulse and decreases the blood pressure.