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.

Cardiac output and its importance

Cardiac output is the volume of blood pumped by the heart in a minute. At rest this is about 5 litres in one minute and during exercise cardiac output can increase up to 30 litres in one minute. Heart rate is the number of beats per minute and the stroke volume is the amount of blood pumped out of the heart with each beat. Increasing either one of these will increase cardiac output.

Cardiac output is dependant on the amount of blood returning to the right side of the heart. During exercise the blood returning increases so the cardiac output increases. This is caused by the myocardium being stretched which causes it to contract with greater force. It changes the sodium and potassium balance in the heart which increases the myocardial temperature which changes the heart rate.

My cardiac output is: 80x80=6400 which is 6.4 litres a minute.

Every ones cardiac output is different this could be due to do with someones height, weight, age and the demands of the individuals body.

If someone has a low cardiac output they may be prone to low blood pressure, fainting as you are not getting enough oxygen to the brain and you are not getting rid of the carbon dioxide out of your body.

Cardiac output should be taken at different times of the day dependant of what you are doing and you will get a better reading of your cardiac output by doing this.

Electrical activity of the heart during a heart beat

The heart is a natural pacemaker which regulates the rate of our hearts. It is in the upper portion of the right atrium. Each spark travels across a specialised electrical pathway and stimulates the muscle wall of the four chambers of the heart to contract. The atria is first stimulated and emptied and the two ventricles are electrically stimulated. Adrenaline is like an accelerator in a car it causes the sinus node to increase the number of sparks per minute which increases the heart rate. The heart normally beats around 72 times per minute and the sinus node speeds up during exertion, stress, fever or if our body needs an extra boost of blood supply.

The electrical activity within our heart can be recorded on a ECG (electrocardiogram).

Structure of the heart and the cardiac cycle

The heart is a muscular pump that pushes blood around the body. It is behind the breastbone and between the ribs and it is made up of cardiac muscle. It is a muscular cone shaped organ which is about the size of a clenched fist.

It is divided into sections. Right and left sections which are also divided into upper and lower compartments which are the atria and ventricles.

The heart structure has three layers. Epicardium which is a thin outer layer which gives the hearts surface a smooth, slippery texture. Endocardium is the smooth inner lining of the heart and it is continuous with the large blood vessels which the heart is connected too. Myocardium is the biggest part of the heart is responsible for pumping blood. The myocardium is made of strong cardiac muscle fibres which are connected by electrical synapses which allow muscle action potentials to spread from fibre to fibre.

The upper chambers (the atria) receive blood that is returning to the heart. The lower chambers (the ventricles) eject blood into your arteries to your lungs. The average human heart beats about 72 beats per minute and weighs around 9-11oz in females and 11-12oz in males.

Blood flows from the heart in one direction from the Atria to the ventricles. Blood is prevented from flowing backwards by the triscupid, mitral, aortic and pulmonary valves.

The function of the right side of the heart is to collect deoxygenated blood into the right atrium from the body and pump it through the right ventricle into the lungs so that carbon dioxide can be dropped off and oxygen can be picked up.

The left side collects oxygenated blood from the lungs into the left atrium. From the left atrium the blood moves to the left ventricle which pumps it out to the body via the aorta.

The cardiac cycle is what happens when the heart beats. There are two phases, the diastole phase where the heart ventricles are relaxed and the heart fills with blood and the systole phase where the ventricles contract and pumps blood to the arteries. In the diastole phase the atrioventricular valves are open. Deoxygenated blood flows into the right atrium. The open atrioventricular valves allow blood to pass through to the ventricles. The sino atrial (sa) node contracts triggering the atria to contract. The right atrium empties its contents into the right ventricle. The tricuspid valve prevents the blood from flowing back into the right atrium.

During the systole phase, the right ventricle receives impulses and contracts. The atrioventricular valves close and the semi lunar valves open. The deoxygenated blood is pumped into the pulmonary artery. The pulmonary valve prevents the blood from flowing back into the right ventricle. The pulmonary artery carries blood to the lungs. The blood picks up oxygen and is returned to the left atrium.

In the next diastole period the semi lunar valves close and the atrioventricular valves open. Blood from the pulmonary veins fills the left atrium. The sa node contracts again and the left atrium empties into the left ventricle.

In the next systole period the atrioventricular valves close and the semi lunar valves open. The left ventricle receives impulses and contracts. Oxygenated blood is pumped into the aorta. The aorta branches out to provide oxygenated blood to all parts of the body. The oxygen depleted blood is returned to the heart. One cardiac cycle is completed when the heart fills with blood and is then pumped from the heart. The heart beat sounds we hear are the closing of the valves, so this shows us how quickly our hearts are working inside of us.

The structure of arteries, veins ad capillaries and their function

There are three main types of blood vessels these are veins, arteries and capillaries. Their main job is to transport blood around the body.

Arteries

The walls of arteries contain smooth muscle fibre that contract and relax under the instructions of the sympathetic nervous system. The functions of arteries are, they transport blood away from the heart, they carry oxygenated blood and they transport blood under higher pressure more than veins. Arteries also don't have valves (except for the semi-lunar of the pulmonary artery and the aorta.)

Capillaries

Capillaries are extremely narrow blood vessels. They are around 5-20 micro-metres in diameter. Capillary walls are only one cell thick this is because of the contents of the capillary and the surrounding tissues. Capillaries are supplied with blood by arterioles and they are drained by venules. Their function is to not only transport blood but to supply tissues with components and also removes waste from the surrounding cells.

Veins

The walls of veins have three layers of tissue that are thinner than arteries. Veins include valves that aid the return of blood to the heart by preventing blood from flowing in reverse, this is important as it prevents waste materials returning to the bodies tissues. The job of veins is to get blood from the tissues and return deoxgenated blood back to the heart.

Structure of red blood cells

Red blood cells are the most common cells found in blood. There are about 5 million red blood cells in each cubic millimeter of blood or approximately 250 million red blood cells in every drop of blood.
They contain hemoglobin which gives them their colour of red.
These cells are produced by bone marrow and have a life spam of 3-4 months.
Red blood cells are about 7.8 micrometers in diameter, they are biconcave in shape. They have a very large surface area to help with gaseous exchange. They are very flexible which allows them to bend and bounce back to their original shape. This is handy when they have to squeeze through the tiny capillary alleyways between cells in the tissues.
Red blood cells in humans don't have a nucleus this leaves more space to carry gases instead they have hemoglobin which is a molecule composed of protein and iron. Hemoglobin carries oxygen and holds onto it until it reaches areas of the body which are low in concentration and then releases it to diffuse in local tissues.
Red blood cells also carry part of the carbon dioxide waste from the cells and is transmitted through plasma as soluble carbonates.

The components of plasma and their function

Plasma is the liquid component of blood, in which the red blood cells, white blood cells and platelets are suspended. It contributes more than half of the bloods volumes and consists mostly of water that contains dissolved salts and proteins.
Proteins in plasma include antibodies which defends our bodies from viruses and clotting factors which controls bleeding.
Plasmas have other functions, it acts as a reservoir, it absorbs the excess water from our bodies tissues and when the body tissues need additional water it gets it from the plasma. Plasma also prevents our blood vessels from collapsing and clogging and it helps maintain our blood pressure and circulation throughout the body. This also regulates our body temperature by carrying heat generated in core body tissues through areas that lose heat more rapidly.
Red blood cells make up about 40% of blood volume, they contain hemoglobin which gives the red colour and it carries oxygen from the lungs and delivers it to the body tissues. Oxygen is used to produce energy that the body needs which leaves carbon dioxide to be rid of. Red blood cells carry the carbon dioxide back to the lungs to then get rid of it by breathing it out. If you have low red blood cells then fatigue will kick in and you will become more tired. When you have too many red blood cells your blood becomes thick and can cause clotting which increases the risk of heart attacks and strokes.
We have a lot less white blood cells than red with the ratio of about 1 to every 600-700 red blood cells. White blood cells main function is to defend our bodies against infection. There are five main types of white blood cells. Neutrophilis helps protect our bodies against infections by killing bacteria and fungi. Lymphocytes protect against viral infections and can detect and destroy some cancer cells. Monocytes ingest dead or damaged cells. Eosinophils kills parasites, destroys cancer cells and are involved in allergic responses along with basophils. White blood cells act like an army, when a white cell finds an infection it releases a substance to attract more white blood cells.
Platelets are particles which are smaller than red and white blood cells. The ratio of platelets is 1 to every 20 red blood cells. They are like a plug, they gather at a bleeding site and they clump together to help seal a blood vessel. They also release a substance that help promote further clotting. When platelet numbers are low, bruising and abnormal bleeding becomes more likely. When there are too many platelets, blood clots excessively which would cause a stroke or heart attack.

Role of the nervous system in generating breathing rhythm

The nervous system controls the flow of air going in and out of our lungs. The nervous system ensures that the unconscious breathing process is carried out in a regular pattern and rate. The autonomic nervous system is a controlling system in the brain.

The diaphragm is supplied with spinal nerves these lead from the brain stem from the spine. These nerves run back to collections of neurones in the medulla oblongata known as the respiratory centres. These are in turn connected to a second respiratory centre in the pons. The interplay between the cells of the two respiratory centres enables automatic breathing, the neurones are both stimulatory (telling us to breathe in and contract) and inhibitory (telling us to breathe out and relax). The respiratory centres transmits regular impulses to the diaphragm intercostal muscles to cause us to inhale and sends signals to the respiratory centre to cause us to exhale. Ventilation is under voluntary control from the cortex.

Conscious actions can control the rhythm of the respiratory system. Such conscious alterations of the respiratory system is done by holding or controlling the breathe.

The cerebral cortex has a main role to play, it sends signals to the rib muscles and diaphragm to override the respiratory centre signals and makes us gasp for breathe. When we do hold our breath and don't exhale our blood builds up of dangerous amounts of carbon dioxide.

Structure of the respiratory system

Air normally enters via the nostrils. it goes to the nasal passages which serve as a filter and it warms up the air before it reaches the lungs. The hairs in the nostrils prevent any foreign objects from entering. The mucus and cilia collect dust, bacteria and other particles in the air. The nose has three jobs, it warms, filters and moistens the air before it reaches the lungs. Air then travels from the nasal passage to the pharynx (throat) it leaves the pharynx and passes to the larynx. The voice box (larynx) has vocal chords which are two pairs of membranes that are stretched on the inside of the larynx. When air is breathed out the vocal chords vibrate. We can control the vibrations of vocal chords which enables us to speak. After the larynx the air goes to the trachea. This is a tube which is 12cm long and 2.5cm wide. It is opened by rings of cartilage within its walls. It is also covered with mucus membrane like the nasal passages. Cilia moves the mucus to the pharynx after that they leave the air passages and are swallowed. About the center of the chest the trachea divides into two cartilage-ringed tubes called bronchi. These are also lined with ciliated cells. The bronchi enters the lungs and they spread into tree like branches into smaller tubes called bronchial tubes, The bronchial tubes divide then divide again, their walls become thinner and have less cartilage eventually they become a small group of tubes called bronchioles. At the end of each bronchiole is a tiny chamber which looks like a bunch of grapes. Each one of these contain cup shaped cavities called alveoli. They are thin, moist and surrounded by capillaries. Gas exchange of oxygen and CO2 takes place in the alveoli. Oxygen from the inhaled air diffuses through the walls of the alveoli and capillaries into the red blood cells. The oxygen is then carried by the blood to the body tissues. CO2 is produced by the body's metabolism which returns to the lung via blood, it then diffuses across the capillary and alveolar walls into the air and is removed from your body by breathing out.

The lung on the left side of your body is slightly smaller than the one on the right which leaves room for your heart. Your lungs are also protected by a rib cage which is made up of 12 sets of ribs. Beneath your lungs is your diaphragm which is a domed shaped muscle that works with your lungs to allow you to breath in and out air. When you breathe in your diaphragm tightens and moves downwards, this increases the space in your chest cavity for your lungs to expand. The intercostal muscles between your ribs also help enlarge your chest cavity. They contract to pull your rib cage both upwards and outwards when you breath in.