Topic 1 Flashcards
What is health?
A state of complete physical, mental and social well-being and not merely the absence of disease or infirmity
What are the types of factors that contribute to poor health?
Controllable factors - Lifestyle choices
Uncontrollable factors - Inherited conditions
What are the main components of a circulatory system?
Circulatory systems need a pump, vessels, and a transport medium.
What does the pump do?
The pump (the heart) contracts to put pressure on the transport medium. The pressure generates movement of the fluid and transport by mass flow
what do the vessels do?
They keep the fluid at high pressure, so it can move greater distances (more important in larger organisms)
What does the transport medium do?
This (very often water) transports substances by dissolving them and moving them by mass flow.
How are substances moved around small organisms?
Diffusion
How are substances moved around large, complex organisms?
Mass transport systems using mass flow
What is the purpose of mass transport systems?
To carry raw materials from specialised exchange organs to body cells and to remove metabolic waste (Carbon Dioxide)
What is an open Circulatory System?
Blood circulates around the body into open spaces where substances diffuse into the cells and the blood is pulled back out
What is a closed circulatory system?
In a closed circulatory system, blood is fully enclosed within blood vessels at all times.
What are the benefits of a closed system?
They ensure a higher pressure than open systems. allowing:
- Faster delivery of nutrients and removal of waste
- Maintaining concentration gradients
- Higher metabolic rate
- Size of organism to be larger
What is a double circulatory system?
In a double system, the blood goes through the heart twice for every circuit of the body. Mammals and birds have a double system
What are the benefits of a double system?
The pressure delivering blood to body tissues can be higher than that delivering blood to the exchange surface (lungs), enabling a higher metabolic rate
What is a single circulatory system?
A system where the blood goes through the heart once for every circuit of the body. Fish have a single circulatory systems.
What are the benefits of a single system?
There is lower pressure, so gill capillaries are not damaged
What happens when the blood leaves the heart?
- Blood leaves the heart
- Arteries
- Arterioles
- Capillaries
How does blood get back to the heart?
- Venules
- Veins
- Back to the heart
How does our circulatory systems work?
The arteries transport oxygenated blood form the heart at high pressure
Near organs/cells, these arteries branch into arterioles, which branch into capillaries
Gas exchange occurs by diffusion between the capillaries and body cells in both directions
The capillaries join together into venules and then veins, and the deoxygenated blood is transported back into the heart.
How does the blood move through the arteries?
Every time the heart contracts, the blood is forced into the arteries, and their elastic walls stretch to accommodate the blood
During relaxation of the heart, the elasticity of the artery walls causes them to recoil behind the blood, helping to push the blood forward
The blood moves along the length of the artery as each section in series stretches and recoils
This produces a pulse
How does blood move through capillaries?
Blood flows more slowly in the capillaries due to their narrow lumens, causing more of the blood to be slowed down by friction against the capillary wall
This allows exchange between the blood and the surrounding cells through one cell thick capillary walls
How does blood move through veins?
The heart affects the flow of blood less in veins. Blood flows steadily and without pulses in veins where it is under relatively low pressure
In the veins, the contraction of skeletal muscles assists blood flow during the movement of limbs and breathing
Low pressure developed in the thorax (chest cavity) when breathing in also helps draw blood back into the heart
Valves prevent backflow
What is the structure of Water?
- Polar Molecule - has an unevenly distributed electrical charge
- Bent shape - non-linear molecule
- Dipole
What properties does water have due to hydrogen bonds?
- High Melting and boiling points
- High specific heat capacity
- High latent heat of vaporisation
- Cohesion and adhesion
- Lower density on freezing
Why is water a good solvent?
Due to its dipole nature, water can act as a solvent for ions and polar molecules
Why do water’s solvent properties allow it to do?
- Act as a transport medium (dissolving important substances)
- Act as a medium for biochemical reactions (dissolving the substrates and products)
- Act as a habitat (allowing aquatic organisms to exchange substances with their environment)
how are hydrophobic substances, such as lipids, transported in blood?
To enable transport in blood, lipids combine with proteins to form lipoproteins
What is specific heat capacity?
The amount of energy required to increase the temperature of 1kg of a substances by 1 degrees Celsius
Why is a high Specific Heat Capacity beneficial for water?
It can absorb large amounts of energy before its temperature raises a significant amount. This allows organisms to avoid rapid changes in their internal temperature and maintain a steady temperature
This also means bodies of water where aquatic organisms live don’t change temperature rapidly
What is latent heat?
The energy absorbed or released during a change of state (hidden energy)
What is the latent heat of vaporisation of water?
Water has a high latent heat of vaporisation, so absorbs a large amount of heat energy while changing from water to a vapour
What does cohesion mean?
Cohesion refers to the tendency of (water) molecules to stick to each other
What does adhesion mean?
Adhesion refers to the tendency of (water) molecules to stick to other things
How much water is in blood?
Plasma is the part of the blood which contains water
How much of the body is made up of Water?
60-70%
What is the cardiac cycle?
The cardiac cycle is one complete heartbeat
What are the three stages of the cardiac cycle?
Diastole, atrial systole, and ventricular systole
What happens during cardiac diastole?
The heart muscle relaxes and the atria fill with blood. Elastic recoil of the atrial walls generates low pressure in the atria, helping draw blood into the heart (0.4s)
What happens during atrial systole?
As the atria fill with blood, pressure increases, the atrioventricular valves are forced open, and blood flows into the relaxing ventricles. The two atria contract simultaneously, forcing the remaining blood into the ventricles (0.1s)
What happens during ventricular systole?
After a slight delay, the ventricles contract, increasing pressure and forcing the atrioventricular valves to close
Blood is forced into the pulmonary arteries/aorta, the semilunar valves are open, and the cycle repeats (0.3s)
Why do the muscles in the heart chambers contract?
Contraction of the muscles decreases the volume of the chambers to increase pressure, which is what makes the blood flow
What causes the ‘lub’ and ‘dub’ of the heartbeat?
The atrioventricular valves closing due to the high pressure in the ventricles causes the ‘lub’
The closing of the semilunar valves as the ventricles relax causes the ‘dub’
How do the valves open and close?
The valves do not open and close by any muscular effort of their own. The cusps are simply pushed open and closed by changes in blood pressure that occur as the heart chambers contract and relax
What does the artery do?
Carries blood from the heart to the rest of the body
What are the properties of arteries?
- Narrow Lumen
- More collagen and smooth muscle
- Thicker walled, muscular and have elastic tissue in walls to cope with high pressure flow of blood
- Folded endothelium to allow it to expand and cope with high pressure flow of blood
- No valves
What do veins do?
Take blood back to the heart
What are the properties of veins?
- Wider lumen than arteries
- Thinner walls
- Less collagen and smooth muscle
- Valves to prevent back flow
- Less elastic tissue than arteries because the blood is under lower pressure
- Contraction of skeletal muscles due to breathing or movement of limbs helps blood flow through the veins
What do capillaries do?
Site of metabolic exchange - between cells and capillaries
What are the properties of capillaries?
- Smallest
- Networks of capillaries in tissue increase the surface area for exchange
- Walls are one cell thick which speeds up diffusion of substances into and out of cells
What does the muscle and elastic tissue do?
Withstands high pressure without damage, and has elastic recoil to maintain pressure on blood
What does the folded endothelium do?
Allows expansion and stretch without damage
What does a narrow lumen without valves do?
Maintains blood at high pressure and faster flow
Why do veins have thinner walls than arteries?
This allows skeletal muscle movement and low heart pressure to draw blood towards the heart
Why do veins have valves?
To prevent backflow of blood
What is the function of collagen in vessel walls?
Collagen is a tough fibrous protein which makes vessel walls more durable
What is the function of smooth muscle in vessels?
Muscle allows vessels to constrict and dilate
What does the aorta do?
Carries blood from the left ventricle to the rest of the body
What does the pulmonary artery do?
Carries blood from the right ventricle to the lungs
What does the pulmonary veins do?
Carries blood into the heart from the lungs
What does the right ventricle do?
Pumps blood to the lungs
What does the tricuspid valve do?
Has 3 flaps of tissue and prevents backflow of blood
What do the heartstrings do?
Hold valves in place
What does the right atrium do?
Receives blood from the body and pumps it into the right ventricle
What does the Superior Vena Cava do?
Carries blood from the upper half of the body into the right atrium
What does the inferior vena cava do?
Carries blood from the lower half of the body into the right atrium
What does the septum do?
A wall of tissue separating the left and right side of the heart
What does the left atrium do?
Receives blood from the lungs and pumps it into the left ventricle
What does the bicuspid valve do?
Has 2 flaps of tissue and prevents the backflow of blood
What does the semilunar valve do?
Prevents backflow of blood into left and right ventricles
What does the left ventricle do?
Receives blood from the left atrium and pumps it into the body
Why is the left side of the heart thicker than the right?
It needs to pump blood at a higher pressure to the rest of the body
Where is the heart situated?
Between the two lungs and above the diaphragm, enclosed by the pericardium
What is the pericardium?
The pericardium is a thin sac that surrounds your heart. It protects and lubricates your heart and keeps it in place within your chest. It stops the heart from over expansion
What are the walls of the heart made of?
Cardiac muscle, aka myocardium, which is only found in the heart. This never tires but can’t tolerate a lack of O2
What is the name of the arteries which supply the walls of the heart with blood?
Coronary arteries
What is risk?
The probability of occurrence of some unwanted event or outcome, usually in the context of hazards
What are the different types of risk factor?
- Age
- Heredity
- Physical environment
- Social environment
- Lifestyle and behaviour choices
When will people overestimate the risk of something happening?
If the risk is:
- Involuntary
- Not natural
- Unfamiliar
- Dreaded
- Unfair
- Very small
What is correlation?
There is a correlation between two variables when a change in one variable is accompanied by a change in the other one
What is causation?
Two variables are casually linked when a change in one is (definitively) responsible for a change in the other
What is a null hypothesis?
When it is assumed for the sake of argument that there will be no difference between an experimental group and a control group, then this hypothesis is tested using statistical analysis
What is an epidemiologist?
A scientist who studies patterns in the occurrence of disease and looks for correlations between a disease and specific risk factors
What is a cohort study?
A study which follows a large group of people over time to see who develops the disease and who doesn’t
These types of studies are prospective - no participants have the disease at the start
People’s exposure to suspected risk factors and whether they develop the disease is recorded, so correlations between risk factors and disease development can be identified. These studies can be very expensive
What is a case-control study?
A retrospective study where a group of people with a disease (cases) are compared with a control group of individuals who don’t have the disease (controls). Information is collected about the risk factors they have been exposed to in the past, allowing factors that may have contributed to the development of the disease to be identified
What should the control group be like?
It should be representative of the population from which the case group was drawn
Sometimes controls are individually matched to cases so that known risk factors (e.g. age/sex) are similar in each case control pair. This allows the potential role of unknown risk factors to be investigated
It is important not to match any variables which could potentially turn out to be risk factors
What are the features of a good study?
- Clear aim
- Representative sample
- Repetition
- Controlled variables
- Controls
What does clear aim mean in terms of studies?
A well designed study should have a clear stated hypothesis/aim. The design of the study must be appropriate to the hypothesis/aim and produce results that are valid and reliable
What is selection bias?
Selection bias occurs when those who participate in a study aren’t representative of the target population
How can you ensure a study is representative?
Differences between those asked to take part in a study and those who respond should be considered before generalising findings to the target population. Non participants can differ in important respects from participants. The proportion of individuals who drop out of a study after it has begun should be kept to a minimum (especially in cohort studies)
Characteristics of remaining participants should be monitored to ensure they are still representative of the target population
What does valid mean?
Data is valid if it measures what it is supposed to be measuring
How can you ensure measurements are valid?
Choose appropriate methods of measurement (e.g. using a blood pressure monitor to take blood pressure measurements)
What does reliable mean?
A reliable method produces measurements that are repeatable and reproducible. The method will give similar results when used at different times, or by different people
How can you ensure the method is reliable?
The method should be consistently applied. The same type of equipment and same procedure should be used every time a measurement is made. Any variable that could affect the measurement should be controlled or taken into account
How can sample size affect reliability?
A sample must be large enough to produce results that could not have occurred by chance. With larger samples, more accurate estimates for the wider population can be calculated in both cohort and case-control studies
It is difficult to control variables when carrying out a human study. However, it is possible to match case and control groups on variables known to correlate with the disease being studied. Explain this experimental technique using an example.
In a study of blood pressure and development of CVD, a group with low blood pressure is compared with a group with higher blood pressure. The data shows that the group with lower blood pressure has less CVD
However, if the average age of this group is less than the high blood pressure group, the difference in CVD development may be due to age, not blood pressure
Matching case and control groups on variables known to correlate with the disease being studied will ensure that only the factor under investigation is influencing the outcome
What is HDL cholesterol?
High density lipoprotein, often called ‘good’ cholesterol, because it picks up excess cholesterol and transports it back to the liver, where it is made into bile salts and later excreted
What is LDL cholesterol?
Low density lipoprotein, or ‘bad’ cholesterol. LDLs transport cholesterol to cells, where it is needed to maintain membrane fluidity
What is an atheroma?
The build up of fatty deposits, mainly LDL cholesterol, which forms within the endothelium of an artery
What is the process of events leading to atherosclerosis?
- The endothelium becomes damaged (perhaps due to high blood pressure or because of cigarette toxins in the bloodstream). This causes an inflammatory response
- Once the inner lining of the artery is breached, there is an inflammatory response. White blood cells move into the artery wall, accumulating chemicals from the blood, particularly cholesterol. A fatty deposit/atheroma builds up
- Calcium salts and fibrous tissue also build up, causing the atheroma to harden and form a plaque. The build up of fibrous tissue causes the artery wall to lose some of its elasticity
- The blood vessel is now much narrower, increasing blood pressure, which could cause another atheroma. This is positive feedback in effect
What is positive feedback?
The enhancing or amplification of an effect by its own influence on the process which gives rise to it
How can you lower cholesterol with diet?
- Choose healthier fats, and limit both total and saturated fats
- Limit foods with cholesterol
- Eat plenty of soluble fibre
- Eat lots of fruit and veg
- Eat fish high in omega-3 fatty acids
- Limit salt and alcohol
What is the process of blood clotting?
- Damage to a blood vessel exposes collagen fibres
- Collagen fibres activate platelets, which change shape. Long, thin projections allow them to stick to the collagen and other platelets, forming a platelet plug
- Thromboplastin, a protein, is produced by platelets and damaged cells
- Thromboplastin activates a series of enzymes which, in the presence of Vitamin K and calcium ions, cause the protein prothrombin to be converted into the enzyme thrombin
- Thrombin catalyses the conversion of soluble fibrinogen into insoluble fibrin
- When many fibrin molecules are formed they can polymerise, creating a mesh of fibrin which traps more platelets and red blood cells, forming a clot and effectively sealing the wound
What happens to the clot when it is no longer needed?
Your body dissolves it
Why is blood clotting due to atherosclerosis problematic?
It blocks up an already restricted artery and restricts blood flow
What is coronary heart disease?
When your heart’s blood supply is blocked or interrupted by a build up of fatty substances in the coronary arteries
What are the symptoms of coronary heart disease?
- Chest pain (angina)
- Shortness of breath
- Pain throughout the body
- Feeling faint
- Feeling sick (nausea)
What is angina and how is it caused?
Chest pain caused by not enough oxygen-rich blood reaching the heart muscle (could be caused by atherosclerosis)
It is usually experienced during exertion, when the cardiac muscle needs to respire more. Since it lacks oxygen, it respires anaerobically. It is thought that this results in chemical changes which trigger pain (but the detailed mechanism is unknown)
how can coronary heart disease lead to a heart attack?
- If a fatty plaque in the coronary arteries ruptures, collagen is exposed, leading to rapid clot formation and perhaps blocking blood supply to the heart completely
- The heart muscle will become ischaemic (without blood). If the affected muscle cells go without oxygen for too long, they will be permanently damaged. This is called a heart attack/ myocardial infraction
- If the zone of dead cells only occupies a small area of tissue, the heart attack is less likely to prove fatal
What are the symptoms of a stroke?
- Sudden weakness or numbness of the face, arm and leg, usually on one side of the body
- Difficulty talking or understanding speech
- Dimness or loss of vision on one eye
- Unexplained dizziness and unsteadiness
- Falls
- Sudden severe headache
What causes a stroke?
If a blood clot blocks an artery 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 can prove fatal
What is a mini-stroke?
If the supply of blood to the brain is only briefly interrupted, a mini-stroke may occur. A mini stroke has all the symptoms of a full stroke, but the effects last for only a short period of time, and full recovery can be relatively quick
What is a mini stroke a sign of?
It is a warning of problems with the blood supply to the brain that could cause a full stroke in the future
What is blood pressure?
Blood pressure is the pressure exerted by circulating blood upon the walls of blood vessels.
How does blood pressure change throughout the circulatory system?
As peripheral resistance increases with greater total surface area, the flow of blood slows, causing pressure to fall
What is systolic pressure?
Pressure in an artery during ventricular systole
What is diastolic pressure?
Pressure in an artery during diastole
What is peripheral resistance?
Contact between blood and blood vessel walls causes friction, impeding flow of blood. This is peripheral resistance
How can the diameter of blood vessels affect blood pressure?
The diameter of a blood vessel is changed by smooth muscle (controlled by nerves and hormones) in the vessel walls. When the muscle contracts, blood pressure is raised. When the muscle relaxes, the blood pressure is reduced
How do elastic fibres maintain blood pressure?
Elastic fibres in blood vessel walls allow stretching during systole (which we feel as a pulse), and recoil during diastole. This maintains hydrostatic force of blood
How does the heart affect pressure in the arteries?
Fluctuations in pressure in the arteries are caused by 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 pressure and blood flow
What is heart rate and stroke volume?
Heart rate is the number of beats per minute. Stroke volume is the amount of blood pumped by the left ventricle during systole
What is a sphygmomanometer/ sphygmometer?
A device used to measure blood pressure. It is composed of an inflatable cuff to restrict blood flow, and a mercury or mechanical manometer to measure pressure
What are the units used to measure blood pressure?
mmHg, which refers to the number of mm the pressure will raise a column of mercury
What is a healthy blood pressure?
A healthy blood pressure is a systolic pressure between 100-140 mmHg, and a diastolic pressure between 60-90 mmHg
What is hypertension?
High blood pressure
What factors can lead to elevated blood pressure?
- High salt diet
- Natural loss of elasticity with age
- Release of hormones such as adrenaline
- Atherosclerosis
How can high blood pressure be treated?
- ACE inhibitors relax blood vessels
- Beta-blockers lower the pulse, making the heart beat less with force
- Calcium channel blockers dilate the arteries
- Diuretics - flush the water and salt from the body
(ABCD)
What is oedema?
Fluid building up in tissues and causing swelling
What is tissue fluid?
At the arterial end of a capillary bed, blood is under pressure. This forces fluid and small molecules from the blood into the tissues via the tiny gaps between the cells of the capillary walls, forming tissue fluid. Blood cells and large plasma proteins are too big to pass through and remain within the capillaries
What happens to tissue fluid if blood pressure increases?
Usually, tissue fluid passes back into capillaries and lymph capillaries (which eventually drain into the vena cava via a lymph vessel). If the blood pressure rises above normal, more fluid may be forced out of the capillaries, causing oedema
How is tissue fluid produced in a capillary bed?
Excess fluid formed is drained away through the lymphatic system
How can oedema be treated?
Mild oedema usually goes away on its own, particularly if the affected limb is raised higher than the heart. Most severe oedema may be treated with drugs that help your body expel excess fluid in the form of urine (diuretics). One of the most common diuretics is furosemide
What are the risk factors of CVD?
- High blood pressure
- Obesity
- Blood cholesterol levels
- Dietary factors (e.g. salt, vitamins, free radicals)
- Smoking
- Inactivity
- Genetic inheritance
What are free radicals?
Atoms with unpaired electrons. They are highly reactive and can damage cell components such as enzymes and genetic material
This type of damage is linked to some cancers, heart disease and premature ageing
How can vitamins protect against radical damage?
Some vitamins such as vitamin C, beta-carotene, and vitamin E provide hydrogen atoms that stabilise radicals by pairing up with unpaired electrons
What are antioxidants?
Compounds that protect cells from the damage caused by oxidation (loss of electrons)
Which study showed a link between antioxidants and heart disease?
The MONICA study showed that high levels of antioxidants seemed to protect against heart disease
Why is too much sodium harmful to the heart?
Sodium can increase blood pressure, since it holds excess fluids in the body, creating an added stress to your heart
How is smoking related to heart disease?
- Reduces levels of HDLs
- Toxins in smoke can damage endothelium lining of blood vessels if they get into the bloodstream
- Nicotine increases stickiness of platelets, increasing risk of blood clots, especially in the coronary arteries
