Topic 1: Lifestyle, Health and Risk Flashcards
1.1 Why do many animals have a heart and circulation system?
Substances, such as glucose, oxygen, water and carbon dioxide are required for metabolic reactions. While substances can be transported easily in unicellular organisms (diffusing fast enough across a short distance to meet the organism’s requirements), diffusion would be too slow for the large distances found in multicellular organisms. These organisms rely on a mass transport system to move substances efficiently over long distances by mass flow: all the particles in a liquid move in one direction through tubes due to differences in pressure.
1.1 How does an open circulatory system work?
Blood circulates in large open spaces. A simple heart pumps blood out into cavities surrounding the animal’s organs, where substances can diffuse between the blood and cells. When the heart muscle relaxes, blood is drawn back into the heart through small, valved openings.
1.1 Why do larger, more active animals have a closed circulatory system?
Blood vessels allow a higher pressure to be generated, as the blood is forced along narrow tubes rather than flowing into large cavities. This allows the blood to travel faster, making it more efficient at delivering substances around the body.
1.1 How does a single circulatory system work?
In fish, for example: The heart pumps deoxygenated blood to the gills, where gaseous exchange takes place with the surrounding water. The oxygenated blood leaves the gills and flows around the rest of the body before returning to the heart. So the blood flows through the heart once for each complete circuit of the body.
1.1 How does a double circulatory system work?
The right side of the heart pumps deoxygenated blood to the lungs where it receives oxygen, returning to the heart to be pumped a second time by the left side. It goes out to the rest of the body, returning to the right side as deoxygenated blood once again.
1.2 Describe the structure and bonding of water.
Because the shared negative hydrogen electrons are pulled towards the oxygen atom, the other side of each hydrogen atom is left with a slight positive charge. The unshared negative electrons on the oxygen atom give it a slight negative charge. Water is therefore a dipolar molecule, and the slightly negatively-charged oxygen atoms attract the slightly positively-charged hydrogen atoms of other water molecules (hydrogen bonding).
1.2 Why is water a good transporting substance?
Water is a solvent, allowing substances to dissolve in solution, and thereby enabling biological reactions to occur in solution. Ionic substances dissolve easily in water: the slightly positive end will be attracted to the negative ion and the slightly negative end attracted to a positive ion, resulting in water molecules surrounding each ion.
Cohesion is the attraction between molecules of the same type. Water’s dipole nature, and the hydrogen bonds between molecules allows it to be very cohesive, transporting substances in a continuous column for mass flow.
The specific heat capacity of water is very high because a large amount of energy is required to break the strong hydrogen bonds. Because water warms up and cools down slowly, organism can avoid rapid changes in their internal temperature.
1.3 How does the structure of an artery relate to its function?
Arteries carry blood from the heart to the rest of the body. They have a narrow lumen, thick walls with a lot of muscle, collagen and elastic fibres, but no valves. During systole, blood is forced into the arteries and their elastic walls stretch to accommodate the blood. The thick artery walls can withstand the high pressure generated as the blood is forced against the walls. During diastole, the elasticity of the artery wall causes them to recoil behind the blood and help push it forward.
1.3 How does the structure of a capillary relate to its function?
Blood flows more slowly in the capillaries due to their narrow lumen and the resulting friction between the blood and capillary wall. This slower steady flow allows gas exchange to take place between the blood and the surrounding cells, with the one-cell-think wall speeding up diffusion. The network of capillaries increase the surface area for exchange, allowing rapid diffusion.
1.3 How does the structure of a vein relate to its function?
Veins take blood back to the heart. They have a wide lumen, with little muscle, collagen and elastic fibres as the blood is under relatively low pressure. Blood flow is assisted by the contraction of surrounding body muscles, and backflow is prevented by semilunar valves within the veins.
1.4 i) Describe the first phase in the cardiac cycle?
Phase 1: Atrial Systole (and Ventricular Diastole)
The ventricles are relaxed, with the semilunar valves closed and atrioventricular valves open already. The atria contract, decreasing the volume and increasing the pressure inside the chambers. This pushes the blood into the ventricles, where there’s a slight increase in ventricular pressure and chamber volume as they receive the ejected blood from the contracting atria.
1.4 i) Describe the second phase in the cardiac cycle?
Phase 2: Ventricular Systole (and Atrial Diastole)
Before this, the semilunar valves are closed and the atrioventricular valves open. The atria relax, and the ventricles contract, decreasing their volume and increasing their pressure. Because the pressure is lower in the aorta (left) and pulmonary artery (right), the semilunar valves are forced open and blood is pushed into these arteries, leaving the heart. The blood is also lower in the atria then the ventricles, forcing the atrioventricular valves to shut and prevent any backflow.
1.4 i) Describe the last phase in the cardiac cycle?
Phase 3: Cardiac Diastole
Before this, the semilunar valves are open and the atrioventricular valves are closed. The atria and ventricles both relax. The higher pressure in the pulmonary artery and aorta closes the semilunar valves to prevent backflow into the ventricles. Blood returns to the heart, with the higher pressure in the vena cava (right) and pulmonary vein (left) allowing the atria to fill again. In turn this starts to increase the pressure of the atria, with a lower pressure in the relaxed ventricles resulting in the atrioventricular valves to open. This allows blood to flow passively into the ventricles, causing a decrease in pressure in the atria and an increase in the ventricles.
1.4 ii) How does the thickness of each heart structure relate to its function?
The ventricles have thicker walls than the atria, because they have to push blood out of the heart whereas the atria just need to push blood a short distance into the ventricles. The left ventricle has thicker, more muscular walls than the right, because it needs to contract more powerfully to pump blood all the way round the body, whereas the ride side only to needs to get to the more nearby lungs.
1.5 What is atherosclerosis?
Atherosclerosis is a disease process where plaques or atheromas (fatty deposits) can either block an artery and harden it or increase its chance of being blocked by a blood clot.
1.5 What events lead to atherosclerosis?
The inner lining of the artery, the endothelium, is usually smooth and unbroken. When it becomes damaged, an inflammatory response is triggered. White blood cells accumulate chemicals in the blood, particularly cholesterol, causing a fatty deposit to build up (an atheroma). Calcium salts and fibrous tissue also build up at the site over time, resulting in a hard plaque. The artery will harden and the lumen will become narrower as results, which can lead to a rise in blood pressure.
1.5 Why do only arteries get atherosclerosis?
The fast flowing blood in the arteries is under significant pressure, so there is a higher risk of damage to the endothelium (in comparison to the much lower pressure in the veins).
1.6 How can atherosclerosis and thrombosis play a role in cardiovascular disease?
An atheroma can rupture the endothelium of an artery, damaging the wall and leaving a rough surface. This can trigger thrombosis, allowing a blood clot to form at the site. This blood clot can completely block the artery, or it can become dislodged and block a blood vessel elsewhere. The blood flow to tissues supplied bu the blocked artery will be restricted, so less oxygen will reach those tissues. Heart attack, stroke and deep vein thrombosis are three forms of cardiovascular disease that can be caused by blood clots preventing oxygen to be reached to these tissues.
1.6 How does a blood clot form?
A protein called thromboplastin is released from the damaged blood vessel. Thromboplastin, along with Vitamin K and calcium ions, triggers the conversion of prothrombin (a soluble protein) into thrombin (an enzyme). Thrombin then catalyses the conversion of fibrinogen (a soluble protein) to fibrin (solid insoluble fibres). The fibrin fibres tangle together and form a mesh in which platelets and red blood cells get trapped - this is the blood clot.
1.7 How can high blood pressure increase the risk of CVD?
High blood pressure increases the risk of damage to the artery walls, which increases the risk of atherosclerosis, which increases the risk of blood clot formation - this in turn can lead to CVD.
1.7 How can diet and exercise impact the the risk of CVD?
- A lack of exercise can increase blood pressure.
- A diet high in salt increases the risk of high blood pressure.
- A diet high in saturated fat increases blood cholesterol level, which increases atheroma formation. This increases the risk of blood clot formation, which in turn increases the risk of CVD.
1.7 How can smoking increase the risk of CVD?
- Nicotine makes platelets sticky, which increases the chance of blood clots forming.
- Carbon monoxide combines with haemoglobin, which reduces the amount of oxygen transported in the blood. This results in less oxygen reaching tissues.
- Smoking decreases the amount of antioxidants in the blood, which serve to protect cells against damage. This increases the rick of cell damage in artery walls, which increases the rick of atheroma formation.
1.7 How can factors beyond your control effect the rick of CVD?
- Some people inherit certain alleles that make them more susceptible to high blood pressure or high blood cholesterol.
- Plaque can build up over time, so the risk of developing CVD increases with age.
- Men are more likely to suffer from CVD than pre-menopausal women.
1.8 Define correlation and causation.
There is a correlation between two variables when a change in one is accompanied by a change in the other (Two variables are positively correlated when an increase in one is accompanied with an increase in another. If the values of one value decrease while the other increases, there is a negative correlation). Two variables are causally linked when a change in one is responsible for a change in the other (Remember than a correlation between two variables doesn’t necessarily mean that the variables are causally linked).
1.8 How do you analyse and interpret data?
When analyzing and interpreting data, describe the results, calculate the change and draw conclusions. Be aware of any conflicting evidence that may require further assessment, and be able to comment of the validity and reliability of the date.
