Blood circulates around the body through three kinds of blood vessel: veins, arteries and capillaries the heart pumps the blood through the blood vessels to enable food and oxygen to get to all the cells in the body.
Arteries carry blood away from the heart and to the body cells they divide into smaller vessels called arterioles.
Arterioles divide into microscopic vessels called capillaries.
Capillaries join up to form veins.
Veins return the blood to the heart.
Arteries have a thick wall with an outer layer of fibrous muscle and a thick layer of elastic tissue and smooth muscle there is then a thin layer of folded endothelial tissue when the ventricles contract, blood enters the arteries at high pressure which stretches the endothelium and the elastic walls. When the ventricles relax the artery wall keeps the blood pressure up, if the blood pressure drops too much between heartbeats organs such as the kidneys would not function,
Arterioles are tiny branches of arteries that lead to the capillaries they regulate blood flow by constricting and dilating this is done by the control of the sympathetic nervous system. Arterioles are the main regulators of blood pressure and blood flow.
Capillaries are tiny blood vessels their walls are only a cell thick which enables materials such as oxygen, water, salts, and carbon dioxideto exchange between the contents of the capillaries and the tissue surrounding them. There are capillaries in most organs and tissues in the body the capillaries are supplied with blood by arterioles and drained by venules.
A venule is a small blood vessel which allows deoxygenated blood to return from the capillary bed to a larger vein.
Veins consist of 3 layers of tissue that are thin and less elastic than arteries, veins have valves that help blood to return to the heart and prevent it from flowing backwards, blood flow though veins is helped by muscle contraction for example when a muscle contracts it bulges and presses on the walls of the veins which pushes blood to the vein when the muscle relaxes the valve closes this helps the blood return to the heart.
references
cgp handout arteries and veins
cgp handout the heart and blood vessels
http://www.youtube.com/watch?v=PgI80Ue-AMo
Thursday, 23 April 2009
Monday, 20 April 2009
The Roles of the Nervous System
The diaphragm is supplied with spinal nerves from segments c3 c4 and c5 the intercostals muscles are supplied by the thoracic spinal nerves t1 to t12 the nerves of the diaphragm lead from the brain stem and down the spine they run back to neurones in the medulla oblongata which are known as the respiratory centres. These in turn are connected to a second respiratory centre in the pons which enables automatic breathing, there are two recognised centres in the pons the pneumotaxic and the apneustic centres, these two areas are also involved in automatic breathing, if we consciously hold our breath then these centres would override it by the cerebella cortex, the cerebella cortex has a direct line to the respiratory muscles through the relevant neurones.
Built into the pons is a standard rate of breathing this is variable, there are connections between the pons and medulla, in the aortic arch there are sensors which detect the oxygen and carbon dioxide concentration of blood.
references
cgp respiratory system handout
The Respiratory System
Respiration is essential to human life; it provides oxygen and the energy which keeps us alive
The respiratory system supplies the blood with oxygen the blood then carries oxygen to all parts of the body, the respiratory system takes oxygen in through breathing (pulmonary ventilation) we inhale oxygen and exhale carbon dioxide through the nose (diffusion of gases) this process takes place between 15 and 25 times each minute.
Oxygen is inhaled through the nose and to the pharynx where the air is then passed through the larynx and to the trachea the bronchus then leads away from the trachea and to the lungs, this single bronchus splits into smaller bronchi which are narrow airways which make up the lungs known as the bronchial tree these supply air to a single lobe and then again to tertiary bronchioles which each supply a single part of that lobe. These tertiary bronchioles lead to the alveoli.
Alveoli is a thin walled sac with a moist inner surface that allows gases to be exchanged between the air and blood. Alveoli in a cluster look like a bunch of grapes there are lots of them so there is a greater surface area for the gas exchange to take place. We breath in around 21% of oxygen but we only breath out around 16% the remaining 5% passes through the walls of the alveoli through the thin walls and capillaries and into the blood. At the same time carbon dioxide passes in the opposite direction.
The respiratory system and exercise
In the short term the body has a number of responses to exercise such as:
Tidal volume increases
Breathing rate increases and becomes deeper and more regular
Heart beat increases supplying the demand for O2 in the working muscles
Gaseous exchange in the alveoli increases
The more muscles contract the more energy they use, to replace the energy the body needs to do more aerobic respiration, it needs to take more oxygen and breathe out more carbon dioxide. The body does this by increasing the breathing rate; this is a physiological adaptation that helps the body cope with exercise.
During exercise carbon dioxide levels rise these decrease the Ph levels in blood, there are receptors in the medulla, aortic bodies and carotid bodies called chemo receptors these detect changes in the ph of blood, if they detect and increase or decrease they send a signal to the medulla to send more frequent nerve impulses to the intercostals muscles and diaphragm, this then increases the rate and depth of breathing. Gaseous exchange then takes place co2 levels drop and extra o2 is supplies for the muscles.
references
cgp powerpoint respiratory handout
www.youtube.com
cgp handout physiological adaptations
The respiratory system supplies the blood with oxygen the blood then carries oxygen to all parts of the body, the respiratory system takes oxygen in through breathing (pulmonary ventilation) we inhale oxygen and exhale carbon dioxide through the nose (diffusion of gases) this process takes place between 15 and 25 times each minute.
Oxygen is inhaled through the nose and to the pharynx where the air is then passed through the larynx and to the trachea the bronchus then leads away from the trachea and to the lungs, this single bronchus splits into smaller bronchi which are narrow airways which make up the lungs known as the bronchial tree these supply air to a single lobe and then again to tertiary bronchioles which each supply a single part of that lobe. These tertiary bronchioles lead to the alveoli.
Alveoli is a thin walled sac with a moist inner surface that allows gases to be exchanged between the air and blood. Alveoli in a cluster look like a bunch of grapes there are lots of them so there is a greater surface area for the gas exchange to take place. We breath in around 21% of oxygen but we only breath out around 16% the remaining 5% passes through the walls of the alveoli through the thin walls and capillaries and into the blood. At the same time carbon dioxide passes in the opposite direction.
The respiratory system and exercise
In the short term the body has a number of responses to exercise such as:
Tidal volume increases
Breathing rate increases and becomes deeper and more regular
Heart beat increases supplying the demand for O2 in the working muscles
Gaseous exchange in the alveoli increases
The more muscles contract the more energy they use, to replace the energy the body needs to do more aerobic respiration, it needs to take more oxygen and breathe out more carbon dioxide. The body does this by increasing the breathing rate; this is a physiological adaptation that helps the body cope with exercise.
During exercise carbon dioxide levels rise these decrease the Ph levels in blood, there are receptors in the medulla, aortic bodies and carotid bodies called chemo receptors these detect changes in the ph of blood, if they detect and increase or decrease they send a signal to the medulla to send more frequent nerve impulses to the intercostals muscles and diaphragm, this then increases the rate and depth of breathing. Gaseous exchange then takes place co2 levels drop and extra o2 is supplies for the muscles.
references
cgp powerpoint respiratory handout
www.youtube.com
cgp handout physiological adaptations
Friday, 3 April 2009
Plasma and Red Blood cells
Plasmablood is a specialised tissue consisting of several types of cell suspended in a fluid called plasma.
the cellular constituents consist of Red blood cells, white blood cells and platelets.
plasma is a clear liquid which is made up of mainly water, sugar, fat, protein and salt solution it carries the red blood cells white blood cells and platelets around the body. 55% of our bloods volume is made up of plasma about 95% of it consists of water. plasma allows blood to navigate fast moving substances in solution and slow thicker substances in suspension. as the heart pumps blood to cells throughout the body plasma brings the nourishment to them and removes any waste products.
proteins make up 6-8% of the blood they are equally divided between serum globulins and serum albumin, serum albumin is made in the liver and it binds small molecules for transport through the blood and helps maintain the osmotic pressure of the blood.
other proteins are the serum globulins, alpha globulins the proteins which transport thyroxin and retinol, beta gobulins is the iron transporting protein to be transfered.
gamma gobulins are the main antibodies which become more abundent following infections and immunisations.
red blood cells
Red blood cells are made in the red bone marrow such as the vertebrae, cranial bone ends of the femur and humerus bone and live for around 120 days they are biconcave in shape and are very flexible with an ability to twist and bend through blood vessels they are only 1/12.000 of an inch in size. The blood contains 25 trillion red blood cells and has to replace them at around 3 million per second.
The reason they are known as red blood cells is because of a substance called haemoglobin, haemoglobin consists of protein and iron pigments and when combined with oxygen their colour becomes bright scarlet. Red blood cells assist with the transportation of oxygen, each molecule binds four oxygen molecules where ox haemoglobin forms. (Hb + 402= Hb08) the oxygen molecules are then carried to individual cells and released in the body tissue. Carbon dioxide then diffuses from the tissue into the red blood cells it then combines with water to form carbonic acid this is a slow reaction but if enzyme carbonic anhydrase is present it is a quicker process.
references
cgp blood powerpoint handout
www.texasheartinstitute.org/HIC/anatomy/blood.cfm
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