Topic 1

Question 1

Why have a heart and circulation?

Answer 1

The heart and circulation have one primary purpose to move substances around the body.In very small organisms such as unicellular creatures where diffusion distances are short, substances such as oxygen, carbon dioxide and digestive products move around the organism by diffusion.

Question 2

What is diffusion

Answer 2

Diffusion is the movement of molecules or ions from a region of a higher concentration to a region of a low concentration by relatively slow movement of molecules.

In unicellular creatures diffusion is usually fast enough to meet the organisms requirements.

Question 3

Heart and circulation in complex organisms

Answer 3

Most complex multicellular organisms are too large for diffusion to substances around their bodies quickly enough. These organisms rely on a mass transport system to move substances efficiently over a long distance by mass flow. All the particles in a liquid move in one direction through tubes due to the difference in pressure.

Question 4

What do animals have to move move vital substances around their body?

Answer 4

Animals usually have blood to carry vital substances around their bodies and a heart to pump it instead of relying on diffusion, in other words they have a Circulatory system

Question 5

Open circulatory system

Answer 5

In insects and some other animal groups, blood circulates in large open spaces.A simple heart pumps blood out to the cavities surrounding the animals organs. Substances can diffuse between the blood and cells. When the heart muscle relaxes, blood is drawn from the cavity back into the heart through small, valved openings along its length.

Question 6

Closed circulatory system

Answer 6

Many animals, including all verbrates, have a closed circulatory system in which blood is enclosed within tubes ( blood vessels). This generates higher blood pressures as blood is forced along fairly narrow channels instead of flowing into large cavities. This means that the blood travels faster and so the blood system is more efficient at delivering substances around the body.

Question 7

How blood travels in close circulatory system

Answer 7

1. The blood that leaves the heart is under pressure and flows along arteries and then arterioles (small arteries) to capillaries.
2. These are extremely large number of capillaries. These come into contact with most the cells in the body where substances are exchanged between the blood and cells.
3. After passing along the capillaries, the blood returns to the heart by the means of venules (small veins) and then veins.
4. Valves ensure that blood flows in one direction.

Animals with close circulatory system are generally larger in size and often more active than those with open systems.

Question 8

Single Circulatory system

Answer 8

Animals with a closed circulatory system have either single circulation or double circulation. Fish for example, have single circulation.

1. The heart pumps deoxygentated blood to the gills.
2. Gaseous exchange takes place in the gills; there’s a diffusion of carbon dioxide from the blood into to the water that surrounds the gills and a diffusion of oxygen from the water into to the blood within the gills.
3. The blood leaving the gills then flows round the rest of the body before eventually returning to the heart.

Note that the blood flows through the heart once for each complete circuit of the body.

Question 9

Double circulatory system

Answer 9

Birds and mammals have double circulation:

1. The right ventricle of the heart pumps deoxygentated blood to the lungs where it receives oxygen.
2. The oxygenated blood then returns to the heart to be pumped a second time (by the left ventricle) out to the rest of the body.

This means that blood flows through the heart twice for each complete circuit of the body.The heart gives the blood returning from the lungs an extra boost which reduces the time it takes for blood to circulate round the whole body.This allows birds and mammals to have a high metabolic rate, as oxygen and food substances required for metabolic processes can be delivered more rapidly to cells and meet the needs of the organism.

Question 10

How does circulation work?

Answer 10

The transport medium
In the circulatory system a liquid and all the particles it contains are transported in one direction due to the difference in pressure in a process known as mass flow.

Question 11

What is the transport medium in animals

Answer 11

In animals the transport medium is usually blood. The fluid plasma, is mainly water and contains dissolved substances such as digested food molecules, (e.g. glucose), oxygen and carbon dioxide.Proteins, amino acids, salts, enzymes, hormones, antibodies and urea ( the waste product from the break down of proteins) are just some of the other substances transported in the plasma.

Cells are also carried in the blood: red blood cells, white blood cells and platelets.

Question 12

What other vital role does blood play apart from transport of dissolved substances and cells?

Answer 12

Blood is important not only in the transport of dissolved substances and cells, it also plays a vital role in the regulation of body temperature, transferring energy around the body.

Question 13

Properties of water that make it an ideal transport medium:

Answer 13

• Water is a liquid at room temperature while most other small molecules, such as co2 and o2, are gases.
• Water is a polar molecule it has unevenly distributed electrical charge. The two hydrogens are pushed towards each other forming a V-shaped molecule. The hydrogen end of the molecules is slightly positive and the oxygen end is slightly negative beacuse the electrons are more concentrated at that end.
• Water is said to be a dipole it is this polarity that accounts for many of its biological important properties.
• The slightly positively charged end of the water molecule is attracted to the slightly negative ends of the surrounding water molecules. This hydrogen bonding holds the water molecules together and results in many of water including being liquid at room temperature.

Water also has solvent and thermal properties that make it an ideal transport medium

Question 14

Solvent Properties of water

Answer 14

• Many chemicals dissolve easily in water due to their dipole nature allowing vital biochemical reactions to occur in the cytoplasm of cells.Free to move around in an aqueous environment, the chemicals can often react with water itself being involved in the reaction (hydrolysis and condensation reactions) . The dissolved substances can also be transported around organisms, in animals via the blood and lymph systems and in plants via the xylem and phloem.
• Ionic substances such as sodium chloride dissolve easily in water as the negative cl- ions are attracted to the positive ends of the water molecules while the positive Na+ ions are attracted to the negative ends of the surrounding water molecules. The chloride and sodium ions are hydrated in aqueous solution, they become surrounded by water molecules.
• Polar molecules also dissolve easily in water. Their polar groups, for example the -OH group in sugars or the amine group, -NH2, in amino acids become surrounded by water and go into the solution. Such polar molecules are hydrophilic ( Water attracting)
• Non- polar, hydrophobic substances, such as lipids, do not dissolve easily in water. To enable transport in the blood, lipids combine with proteins to form lipoproteins.

Question 15

Thermal properties of water

Answer 15

The specific heat capacity of water the amount of energy joules required to raise the temperature of 1cm^3 of water by 1°C is very high. This is because in water a large input of energy is required to break the hydrogen bonds. A large input of energy only causes a small increase in temperature, so water warms up and cools down slowly.This is useful for organisms, helping them to avoid rapid changes in their internal temperature and enabling them to maintain a steady temperature even when the temperature in their surroundings varies considerably. This also means that the bodies of water in which aquatic organisms live do not change temperature rapidly.

Water also has a high boiling point because there are so many hydrogen bonds and a lot of them is needed to break them all.

Question 16

The structure of blood vessels

Answer 16

-The walls of both arteries and veins contain collagen, a tough fibrous protein, which makes them strong and durable.
- They contain elastic fibres that allow them to stretch and recoil.
-Smooth muscles cells in the walls allows them to constrict and dilate.

Question 17

The structure of Arteries, veins and capillaries

Answer 17

Arteries:

• narrow lumen
  -thicker walls
• more collagen smooth muscle and elastic fibres
• no valves

Veins:
- wide lumen
- thinner walls
- less collagen smooth muscle and fewer elastic fibres
- valves

Question 18

Structure of Capillaries

Answer 18

The Capillaries that join the smaller arteries (arterioles) and smaller veins (venules ) are very narrow, with walls that are only one cell thick.

These features can directly relate to the function of blood vessels.

Question 19

How does blood move through vessels ?

Answer 19

Every time the heart contracts ( systole), blood is forced into arteries and their elastic walls stretch to accommodate the blood.The thick artery walls can withstand the high blood pressure generated as blood is forced against the walls.

During diastole (relaxation of the heart) , the elasticity of the artery walls causes them to recoil the blood, helping to push the blood forward and smoothing blood flow. The blood moves along the length of the artery as each section in series stretches and recoils in this way.The pulsing flow of flow through arteries can be felt anywhere an artery passes over a bone close to the skin.

By the time the blood reaches the smaller arteries and capillaries there is a steady flow of blood.Blood flows more slowly in the capillaries due to their narrow lumen causing more of the blood to be slowed down by friction against the capillary wall. This slower steady flow allows exchange between the blood and the surrounding cells through the one-cell thick capillary walls. The network of capillaries that lies close to every cell ensures that there is a rapid diffusion between the blood and the surrounding cells.

The heart has less direct on the flow of blood through veins. Blood flows steadily and without pulses in veins where it is under relatively low pressure. In the veins blood flow is assisted by the contraction of skeletal muscles during the movement of limbs and breathing. Low pressure developed in the thorax ( chest cavity) when breathing in also helps draw blood into the heart from the veins. Backflow is prevented by the semilunar valves within the veins.

Question 20

How is the heart muscle supplied with blood?

Answer 20

Two vessels called coronary arteries , a network of capillaries, and two coronary veins.

Question 21

How the heart works?

Answer 21

The Chambers of the heart alternately contract (systole) and relax (diastole) in a rhythmic cycle.

One complete sequence of filling and pumping is called cardiac cycle or heartbeat.

Question 22

The cardiac cycle

Answer 22

Phase 1 : Atrial Systole
Blood returns to the heart due to the action of skeletal and muscles involved in breathing as you move and breathe. Blood under low pressure flows into the left and right atriafrom the pulmonary veins and vena cava. As the atria fill the increasing pressure of blood against the atrioventicular valves pushes them open and blood begins to leak into the ventricles. The atria contract forcing more blood into the ventricles. This contraction of the atria is known as atrial systole.

Phase 2: Ventricular systole
The ventricles contract from the base of the heart upwards increasing the pressure in the ventricles. The pressure forces open the semilunar valves and pushes blood up and out of the pulmonary arteries aorta. The pressure of blood against the atrioventricular valves closes them and prevents blood flowing backwards into the atria.

Phase 3: Cardiac diastole
The atria and ventricles then relax during cardiac diastole. Blood under higher pressure in the pulmonary arteries and aorta is drawn from the ventricles, closing the semilunar valves and preventing further backflow into the ventricles. The coronary arteries fill during diastole. Low pressure in the atria helps draw blood into the heart from the veins.

Question 23

What is atherosclerosis?

Answer 23

Atherosclerosis is the the disease process that leads to coronary heart disease and strokes. In Atherosclerosis fatty deposits can either block an artery directly or increase its chance of being blocked by a blood clot (thrombosis). The blood supply can be blocked completely if it is not restored the affected cells are permanently damaged.

In coronary arteries this results in a heart attack ( myocardial infraction).

In the arteries leading to the brain it results in a stroke. The blood supply to the brain is restricted or blocked causes damaged or death in the cells in the brain.

Narrowing of the coronary arteries in the legs can result in tissue death or gangrene ( decay).

An artery can burst where blood builds up behind an artery that has been narrowed as a result of Atherosclerosis.

Question 24

What happens in Atherosclerosis?

Answer 24

1. The endothelium , a delicate layer of cells that lines the inside of an artery and separates the blood that flows along the artery from the muscular wall becomes damaged and dysfunctional for some reason. This endothelium damage can result from high blood pressure , which puts extra strain on the layer of cells, or it might occur due to some of the toxins in cigarette smoke in the bloodstream.
2. Once the inner lining of the artery is breached there is an inflammatory response. White blood Cells leave the blood vessel and move into the artery wall. These cells accumulate chemicals from the blood, particularly cholesterol. A fatty deposit builds up, called an atheroma.
3. Calcium salts and fibrous tissue also build up at the site, resulting in a hard swelling called a plaque on the inner wall of the artery. The build-up of fibrous tissue means that the artery wall loses some of its elasticity; in other words, it hardens.
4. Plaques cause the lumen of the artery to become narrower.This makes it more difficult for the heart to pump blood around the body and can lead to a rise in blood pressure.Now there is a dangerous positive feedback building up. Plaques lead to raised blood pressure and raised blood pressure makes it more likely that further plaques will form, as damage to the endothelial tissue in other areas becomes more likely.

Question 25

Why do only arteries get Atherosclerosis?

Answer 25

The fast- flowing blood in arteries is under high pressure so there is a significant chance of damage to the walls. The low pressure in veins means that there is a less risk of damage to the walls.

Question 26

Why does blood clot in arteries?

Answer 26

**Blood clotting** Rapid blood clotting is vital when a blood vessel is damaged. The blood clot seals the break in the blood vessel and limits blood loss and prevents entry of pathogens through any open wounds. When **platelets**, a type of blood cell without a nucleus, come into contact with the damaged vessel wall they change from flattened discs to spheres with long thin projections. Their cell surfaces change, causing them to stick to the exposed collagen in the wall and to each other to form a temporary platelet plug. They also release substances that activate more platelets. The direct contact of blood with collagen within the damaged blood vessel wall also triggers a complex series of chemical changes in the blood. A **cascade** of changes results in the formation of a blood clot.

Question 27

The steps to clotting cascade:

Answer 27

1. Platelets and damaged tissue release a protein called **thromboplastin**. 2. Thromboplastin activates an enzyme which catalyses the conversion of the protein **prothrombin** into an enzyme called **thrombin**. A number of other protein factors such as vitamin K and calcium ions must be present in the blood plasma for this conversion to happen. 3. Thrombin then catalyses the conversion of the soluble plasma protein **fibrinogen** into the insoluble protein **fibrin**. 4. A mesh of fibrin forms that taps Platelets and more red blood cells forming a clot.

Question 28

What happens inside arteries to cause blood clotting

Answer 28

Usually blood does not clot inside blood vessels. It is very smooth and has substances on its surface that repel platelets. However, if there is atherosclerosis and the endothelium is damaged the platelets come into contact with the damaged blood vessel and any exposed collagen. The clotting cascade will be triggered within the vessel resulting in a clot.

Question 29

The consequences of atherosclerosis:

Answer 29

*Coronary heart disease*: Narrowing of the coronary arteries limits the amount of oxygen-rich blood reaching the heart of muscle. The result may be a chest pain called **angina**.Angina is usually experienced during exertion when the cardiac muscle is working harder and needs to respire more. Because the heart muscle lacks oxygen, it is forced to respire **anaerobically**. It is thought that this results in chemical changes which trigger pain.Usually these symptoms will ease with rest. If a fatty plaque in the coronary arteries ruptures, collagen is exposed which leads to rapid clot formation. The blood supply to the heart may be blocked completely. The heart muscle supplied by these arteries does not receive any blood, so it is said to be **ischaemic** (without blood). If the affected muscle cells are starved of oxygen for long they will be permanently damaged. This is what we call a heart attack or **myocardial infarction**. If the zone of dead cells occupies only small area of tissue the heart attack is less likely to prove fatal. **Stroke** If the supply if blood to the brain is briefly interrupted then a mini-stroke might occur. A mini-stroke has all the symptoms of a full stroke but the effects last for only a short period, and full recovery can happen quite quickly. However, a mini-stroke is a warning of problems with blood supply to the brain the could result in a full stroke later. If a blood clot blocks one of the arteries leading to the brain, a full **stroke** will result. If brain cells are starved of oxygen for more than a few minutes they will be permanently damaged, and it could be fatal.

Question 30

Symptoms of cardiovascular disease: **Coronary heart disease** and **stroke**

Answer 30

**Coronary heart disease** -Shortness of breath and angina are the first signs. - The main symptom of angina is intense pain, ache or a feeling of constriction and discomfort in the chest, or in the left arm or shoulder. - Other symptoms are similar to severe indigestion and include a feeling of heaviness, tightness, pain , burning and pressure usually behind the breastbone, but sometimes in the jaw arm or neck. Women may not have chest pain but experience unusual fatigue, shortness of breath and indigestion- like symptoms. - Sometimes coronary heart disease causes the heart to beat irregularly. This is known as **arrhythmia** and can itself lead to heart failure. Arrhythmia can be important in the diagnosis of coronary heart disease. **Stroke** The effects of a stroke will depend on the type of stroke where in the brain the stroke has occurred and the extent of the damage. The more extensive the damage, the more severe and the lower the chance of recovery. These are the symptoms: - numbness - dizziness - confusion - slurred speech - blurred or lost of vision, often only in one eye - visible signs for example: paralysis on one side of the body, a dropping arm , or an eyelid . The right side of the brain controls the left side of the body and vice versa, so paralysis occurs on the opposite side of the stroke.

Question 31

What are aneurysms?

Answer 31

If part of an artery has narrowed and become less flexible, blood can build behind it. The artery bulges as it fills with blood and an **aneurysm** forms.

Question 32

Estimating risks in cardiovascular disease

Answer 32

Risk is defined as the probability of occurrence of some unwanted event or outcome.

Question 33

Perception of risk

Answer 33

People will overestimate the risk of something happening if the risk is: - involuntary ( not under their control) - not natural - unfamiliar - dreaded - unfair - very small If you look at this list you'd house be able to see why people may greatly overestimate some risks ( such as the chances of contracting vCJD from blood transfusions) while underestimating driving over the speed limit.

Question 34

Risk factors for cardiovascular disease Cohort and case- control studies

Answer 34

**Cohort studies** Cohort studies follow a large group of people over time to see who develops the disease. At the start of the study none of the participants have the disease. Researchers are interested in what happens to them in the future.During the study people's exposure to suspected risk factors and whether they develop the disease is recorded so any correlations between the risk factors and disease development cab be identified. It make take a long time for the condition to develop and be very expensive. **Case- control studies** A group of people with the disease (cases) are compared with a control group of individuals who do not have the disease. Information is collected about the risk factors that they have been exposed to in the past, allowing factors that may have contributed to be identified.

Question 35

Risk factors for cardiovascular disease ( CVD)

Answer 35

Your chances of having coronary heart disease or stroke is increased by several inter-related risk factors, the majority of which is common to both conditions. These include: - high blood pressure - obesity - blood cholesterol and other dietary factors - smoking - inactivity - genetic inheritance Some you can control, while others you cannot.

Question 36

What is considered one of the most common factors in the development of cardiovascular diesease?

Answer 36

Elevated blood pressure is known as **hypertension** is considered to be one of the most common factors in the development of cardiovascular disease. High blood pressure increases the likelihood of atherosclerosis occurring.

Question 37

What is blood pressure?

Answer 37

Blood pressure is a measure of the hydrostatic force of the blood against the walls of a blood Vessel. You should remember that blood pressure is higher in arteries and capillaries than in veins. The pressure in an artery is highest during the phase of the cardiac cycle when the ventricles have contracted and forced blood into the arteries. This is the **systolic pressure**. Pressure is at its lowest in the artery when the ventricles are relaxed. This is the **diastolic pressure**.

Question 38

Measuring blood pressure:

Answer 38

Measuring blood pressure: A **sphygmomanometer** is the traditional device used to measure blood pressure. It consists of an inflatable cuff that is wrapped around the upper arm, and a manometer, or gauge, that measures pressure.When the cuff is inflated the blood flow through the artery in the upper arm is stopped. As the pressure in the cuff is released the blood starts to flow through the artery. This flow of blood can be heard using a stethoscope positioned on the artery below the cuff. A pressure reading is taken when the blood first starts to spurt through the artery that has been closed. This is the systolic pressure. A second reading is taken when the pressure falls to the point where no sound can be heard and it equals the lowest pressure in the artery. This is the diastolic pressure.

Question 39

The units for blood pressure:

Answer 39

The SI units ( International system of units) for pressure are kilopascals but it'd is still traditional to use millimetres of Mercury, **mmhg**. The numbers refer to the number of millimetres the pressure will raise a column of mercury. Blood pressure is reported as two number one over each other for example: 140/85. This means a systolic pressure of 140mmHg and a diastolic pressure of 85mmHg. For an average healthy person you would expect a systolic pressure of between 100-140 mmHg and a diastolic pressure of 60-90 mmHg. For example for 140/85 systolic pressure, the maximum blood → 140 pressure when the heart contracts diastolic pressure, the blood pressure → 85 when the heart is relaxed

Question 40

What determines you blood pressure?

Answer 40

Contact between the blood and the walls of the blood vessels causes friction and this impedes the flow of blood. The aterioles and capillaries offer a greater total surface area than ateries, resisting flow more, slowing the blood down and causing the blood pressure to fall. Notice that the greatest drop in pressure occurs in the arterioles. The flucations in pressure are caused by the contraction and relaxation of the heart. As blood is expelled from the heart, pressure is higher. During diastole, elastic recoil of the blood vessels maintains the pressure and keeps the blood flowing. High blood pressure: If the smooth muscles in the walls of an artery or ateriole contract, the vessel constrict, making the lumen narrower and increasing resistance. In turn, your blood pressure is raised. Low blood pressure: If the smooth muscles relax the lumen is dilated, so peripheral resistance is reduced and blood pressure falls. Any factor that cause arteries or aterioles to constrict can lead to elevated blood pressure Such factors include: natural loss of elasticity with age, release of hormones such as adrenaline and a high salt diet. High blood pressure can lead to atherosclerosis.

Question 41

Tissue fluid and oedema

Answer 41

One sign of high blood pressure is **oedema** – fluid building up in the tissues and causing swelling. Oedema may be associated with kidney or liver disease, or with restricted body movement. At the aterial end of the capillary, blood is under pressure. This forces fluid and small molecules normally found in the plasma put through the tiny gaps between the cells in the capillary wall into the intercellular space, forming **tissue fluid** also know as interstitial fluid. Blood cells and larger plasma proteins stay inside the capillary; their larger size prevents them from passing through the gaps in the capillary wall. The tissue fluid drains into a network of lymph capillaries which returns the fluid to the blood via a lymph vessel which empties into the vena cava. If blood pressure rises above normal more fluid may be forced out of the capillary. Fluid accumulates within the tissues causing oedema. **See page 29 for the diagram of the capillary bed!**

Question 42

Where do we get energy from in our diet?

Answer 42

**Carbohydrates**, **lipids**( often called fats and oils) and **proteins** are constituents of our food that contain energy. Alcohol can also provide energy.

Question 43

What is the general formula for carbohydrates?

Answer 43

**Cx(H2O)n**

Question 44

What are monosaccharides, disaccharides and polysaccharides?

Answer 44

Sugars are either**monosaccharides**, single sugar units or**disaccharides**, in which two single sugar units have combined in a condensation reaction. Long straight or branched chains of sugar units form **polysaccharides**.

Question 45

Simple molecules join together in different ways to produce many of the large important biological molecules:

Answer 45

Polymers, such as polysaccharides, protein and nucleic acids are made by linking identical or similar subunits, called monomers, to form straight of branched chains. Lipids are another group of biological molecules also constructed by joining smaller molecules together, though they are not polymers since they are not chains of monomers. Large biological molecules have features that are well suited to their functions. In each case the small molecules join together in a condensation reaction, so called because a water molecule is release when the two molecules combine in the reaction. **Condensation** reactions are common in the formation of complex molecules . Addition of water in a **hydrolysis** reaction spilts the molecule.

Question 46

What are monosaccharides?

Answer 46

Monosaccharides are single sugar units with a general formula (CH2Ol)n, where n is the number of carbon atoms. Monosaccharides have between three and seven carbon atoms, but the most is six. For example the Monosaccharides **glucose**, **galactose** and **fructose** all contain six carbon atoms and are know as **hexose** sugars.

Question 47

What are hexose sugar molecules?

Answer 47

A hexose sugar molecule has a ring structure formed by five carbons and an oxygen atom; the sixth projects above and below the ring. The carbon atoms are numbered, starting with 1 on the extreme right of the molecule. The side branches project above or below the rings, and their position determines the type of sugar molecule and its properties. Monosaccharides provide a rapid source of energy. They are readily absorbed and require little or,in the case of glucose, no change before being used in cellular respiration. Glucose and fructose are found naturally in fruit, vegetables and honey) they are both used extensively in cakes, biscuits and other prepared foods.

Question 48

Glucose:

Answer 48

Glucose is important as the main sugar used by all cells in respiration.Starch and glycogen are polymers made of glucose subunits joined together. When starch or glycogen is digested glucose is produced. This can be absorbed and transported into the bloodstream to cells.