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Edexcel Categories Archives: Topic 1: Lifestyle, Health and Risk

Blood vessels

BLOOD VESSELS

  • When muscles relax, the lumen widens thus decreasing B.P
  • There is no pulse and pressure is low.
  • Valves prevent backflow.

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Reducing Risk

REDUCING RISK

A person’s risk of developing coronary heart disease can be reduced by:

DIET

  • should be energy balanced
  • reduced cholesterol, saturated fats and salt
  • more polyunsaturated fats, including omega-3 fatty acids found in oily fish
  • more fruit and vegetables containing soluble fibre and antioxidants
  • include food with added sterols and stanols (saturated plant compounds which reduce cholesterol)

EXERCISE

  • A person who is physically active is much more likely to survive a heart attack or stroke.

STOP SMOKING

  • After stopping, the risk of CHD is almost halved after one year.

CONTROLLING BLOOD PRESSURE

  • Can be achieved by changes in lifestyle and diet,
  • Drugs such as antihypertensive and blockers can be used.

 

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Cholestrol

CHOLESTROL

Insoluble cholesterol combines with proteins to form soluble lipoproteins so that it can be carried in the bloodstream.

Eating both monounsaturated and polyunsaturated fats reduces the level of LDLs in the blood.

 

 

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Lipids

LIPIDS

Lipids contain the elements carbon, hydrogen and oxygen. They are insoluble in water but soluble in organic solvents (ethanol).

They provide twice as much energy as carbohydrates and supply the body with essential fatty acids. Vitamins are often found dissolved in lipids.

The most common type we eat and use as energy storage is triglycerides: made up of 3 fatty acids joined to 1 glycerol:

 

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Energy + Diet

ENERGY BUDGET + DIET

Carbohydrates, proteins, lipids and alcohol all contain energy: used to be measured in calories; the SI unit is the Joule.

  • Average person requires 8,000-10,000 kilojoules per day.

Dietary Reference Values encourage balanced & healthy diets and indicate the amount of energy derived from different foods.

The basal metabolic rate (BMR) varies between individuals.

  • BMR is higher in males and people who are younger, heavier or more active.

The body mass index (BMI) doesn’t have an exact correlation to each individuals fat levels thus it isn’t very accurate.

  • Normal range is around 20. Less than this is underweight and over 30, obese.

Waist – to – hip ratio is a better measure of obesity b/c has a continuous positive correlation against diseased groups.

Larger W – T – H ratio = more likely to get a heart attack

Obesity

20% of the population are obese – excess dietary fat and inactivity are likely causes.

Obesity increases the risk of cardiovascular disease, Type II diabetes, raises B.P and raises lipid levels.

 

 

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Tissue Fluid

TISSUE FLUID

 

How is Tissue Fluid formed?

  1. At the start of the capillary bed, the arteriole end, there’s high pressure due to the contraction of the ventricle
  2. This pressure is called hydrostatic pressure and it forces fluid out of the capillaries into the spaces around the capillary wall, forming tissue fluid (consists of plasma with dissolved nutrients and oxygen – others are too big to be pushed out)
  3. As the fluid leaves the blood, there’s a lower pressure at the end of the capillary bed near the venules.
  4. The fluid surrounds body cells, so that gaseous and nutrients exchange can occur by diffusion

 

How does fluid return to the blood?

  1. Not only does the hydrostatic pressure force the fluid out, but the tissue fluid itself has some hydrostatic pressure, which will push fluid back into capillaries
  2. The water concentration of the blood (in the vessel) is lower than that of tissue fluid.
  3. This means water re-enters into the capillaries from the tissue fluid at the venous end (where there is a low conc. of water) by osmosis.

Lymph:

Not all the tissue fluid returns to the blood capillaries. There’s excess that is drained away into the lymphatic system. 20% of the tissue fluid returns to the circulation via the lymph system.

Oedema

If B.P increases (hypertension) more fluid is forced out. The fluid accumulates in the tissues causing oedema. This is a sign of hypertension.

 

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Blood Pressure

BLOOD PRESSURE 

Blood pressure is higher in arteries and capillaries than in veins.

Systolic blood pressure is highest and occurs when the ventricles contract (ventricular systole)

Diastolic blood pressure is at its lowest in the arteries when the ventricles relax (diastole)

Any factor which causes arteries or arterioles to constrict will lead to hypertension. These include:

  • Loss of elasticity with age
  • Atherosclerosis
  • Adrenaline
  • High salt diet.

A larger surface area means that peripheral resistance is greater thus blood pressure drops (veins)

A smaller surface area means that peripheral resistance is less thus blood pressure increases.

 

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Studies

STUDIES

Epidemiologist – studies patterns in the occurrence of diseases

Cohort studies – follows a group of people over time to see who develops the risk and who doesn’t

Case-control studies – people with the disease are compared to people without

  • Controls should be representative of the population from which the case group was drawn from

Features of a good study

  • Clear aim
  • Representative sample – otherwise selected bias occurs
  • Consider people who are asked to do the study with people who respond (e.g. unemployed people may agree to day-time interviews but they may be [physically unhealthier than employed people who are working thus cannot do the interview)
  • Proportion who drop out should be kept to a minimum so that the remaining are still representative of target population
  • Valid + reliable results
  • Control variables or else may influence outcome
  • Repeatability + reproducibility
  • Same method used
  • Large sample

 

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