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Introduction to Health and Disease

Define Health and disease: Health is physical, mental and social well being. It is more than just being free from disease.

Disease is a malfunction of the mind or body leading to a condition of poor health. Health is more than just simply the absence of disease, some may not suffering from the symptoms of a disease may have low physical fitness and may be developing a serious condition such as heart disease or lung cancer.

Categories of disease and illness

Social - Living conditions and behavior are factors in development of disease
Smoking related disease, TB

Physical - Permanent or temporary damage to the body

Changes to the mind, with or without known physical cause

Non infectious - Any disease not caused by a pathogen
Lung cancer, night blindness

Infectious - Organisms (pathogen) invade the body

Deficiency - Caused by poor diet

Degenerative - Gradual decline in a function or functions of the body

Inherited - An inherited genetic fault

Self conflicted - Damage to the body
Attempted suicide, drug abuse and lung cancer.

Reasons for collecting health statistics

Make comparisons between populations at the same time

Make comparisons between populations at different times

Find out which diseases are important

Find new, emerging diseases, such as SARS

Inform policy-making about providing resources in the health service

Find out how well government health policies are working

Investigate the spread of disease and investigate the likely causes.

Difference between standards of Health in MEDC and LEDC

LEDC

MEDC

Both the incidence of infectious disease and the mortality associated with disease have been reduced.

Living conditions are substantially better than in developing countries, which improved hygiene, sanitation and nutrition.

Successful vaccination programmes, and antibodies are readily available to cure bacterial infections.

The relative affluence of developed countries brings an increase in deaths from cardiovascular diseases, cancer and road accidents, albeit that cardiovascular disease is more prevalent amongst the poorer sections of developed countries.

Degenerative disease associated with old age are often seen.

Explain the terms

Pandemic - an outbreak of disease that occurs across the world or across continents.

Epidemic - an outbreak of disease in a population.

Endemic - this describes diseases that are always in a population.

There is a clear difference between epidemic, pandemic, and endemic. The main difference between an epidemic and a pandemic lies in the numbers of diagnosis and the size of the area involved. Epidemic is an outbreak of a certain disease that attacks a human population at about the same time. When an epidemic spreads to other areas and affects a substantial number of people, it is referred as a pandemic. An endemic is a disease that permanently exists or occurs frequently in a a particular region.
Advantages for health of the Human Genome Project are

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Diet Components of a balanced diet

	Sufficient energy for our needs provided by the macronutrients (carbohydrates, proteins and fat)
	Essential amino acids (essential means can't be made by the body, must be in the diet
	Essential fatty acids (linolenic acid and linoleic acid)
	Micronutrients - vitamins and minerals
	Water for replacing the water lost in urine, sweat, breath and faeces
	Fibre for preventing constipation

Energy and nutrient requirements of people

	Gender

 Males require more protein because their growth is greater than females during adolescence, and after that stage they have a greater mass of tissue to repair and replace.  Males requires more of the vitamin B complexes that are needed for respiration and metabolism.  Males require more calcium and phosphorus in adolescence because they develop larger bones than females during this stage of growth.

	Age

 Energy requirements increase with age, up to and including adolescence, as growth is rapid during these years and physical activity is generally at high level. These energy requirements remain almost constant up to the age of 60 years, after which they decrease as physical activity diminishes and body mass often decreases.  Protein requirements increase with age, especially around puberty. This is because additional protein is needed for the rapid growth around adolescence and thereafter, to repair and replace cells.  Calcium and phosphorus requirements are greater in the first year of life as they are laid down in the bones of infants. The rate again increases in adolescence when the second growth spurt involves relatively rapid elongation of the bones. After adolescence, the requirements remain constant.  Requirements for other minerals and vitamins increases up to the age 20 years, but thereafter remains relatively constant.

	Activity

 The more physically active a person is, the greater their energy requirement. It follows that, compared to an office worker, a manual labourer requires a greater energy intake, especially of carbohydrate food.

	Pregnancy

 Energy during the last three months of pregnancy, when fetal growth is at its greatest and the mother has this additional mass to carry around.  Protein needed to supply the growth needs of the rapidly dividing cells of the fetus.  Vitamin A, C and D, although too much vitamin A can be harmful to the fetus in the early stages of pregnancy. For this reason pregnant women are recommended to avoid liver, which is very rich in vitamin A.

	Lactation

 More calcium, phosphorus and magnesium, as these are needed by the newly born to develop their bones.  More zinc because it is present in a number of enzymes, including those involved in growth and metabolism.

Dietary reference value

	This is sets of figures relating to the requirements for energy and nutrient intake of all healthy individuals in the UK, this is sat by the department of Health in 1991.
	The three DRV are:

 Estimated Average Requirement - this is the population average  Reference Nutrient Intake - this is at the top end of the range and is enough for about 97% of the population  Lower Reference Nutrient Intake - this is at the bottom of the range and is enough for only about 2% of the population. Use of Dietary Reference value:

	Chefs and caterers to design appropriate menus for groups of people living in communities such as schools, old people's home and prisons.
	Managers to plan food supplies for large groups of people.
	Dieticians and others to assess the dietary needs of individuals, e.g. The elderly and pregnant women.
	Individuals to calculate their own dietary requirements and to maintain or improve health.
	Food manufacturers to provide appropriate nutritional information on food labels.

Describe the functions of...

	Essential amino acids - Used to synthesis protein for growth and repair of cells
	Essential fatty acids - Used to make phospholipids and fats
	Vitamin A - Used to make rhodopsin for functioning of rod cells in the eye. Used to make retinoic acid, which aids cell development and growth, especially in epithelia.
	Vitamin D - A steroid hormone that controls absorption of calcium from the gut and its deposition in bones.

Consequences of malnutrition

	Energy

 Stunting results from chronic protein-energy malnutrition, occurs in children from 2-5 years of age.  Wasting results from acute protein-energy malnutrition, occurs in individuals over 5 years of age. This is characterized by rapid weight loss in those who had near normal weight.

	Kwashiorkor

 Bloated appearance  Moon face  Apathetic

	marasmus

 Very think with wrinkled skin  Old man's face  Mentally alert

Anorexia nervosa

	Muscles waste (including heart muscles)
	Periods stop
	Blood pressure falls
	Hair becomes thin and sparse
	Hands and feet are cold
	There is increased susceptibility to infection
	There are personality changes.

Vitamin A

	Night blindness - rod cells do not make enough rhodopsin so people can not see in dim light
	xerophthalmia - the surface of cornea is scarred which leads to blindness
	Poor defence against disease such as measles.
	Dry, rough skin, as vitamin A is needed to make retinoic acid, which is needed to maintain epithelial tissues like the skin.

Vitamin D

	Rickets - occur in Children the bone become soft and grow irregularly, the joints become swollen and limbs and the chest may be distorted. Typically the legs are bow-shaped.
	Osteomalacia - occur in adults - this causes a softening of the bones, making them tender and painful, fracture of bone occur more easily. Muscle weakness as well as loss of appetite and weight.

Obesity

	Coronary heart disease - caused by increased blood pressure and blood cholesterol.
	Type II diabetes
	Cancer
	Osteoarthritis
	Rheumatoid arthritis
	Hypertension

Diet and coronary heart disease

	High level of salt - increases hypertension.
	High Blood cholesterol - contribute to the formation of plaques in the coronary arteries
	High fatty acid intake - saturated fatty acid increases the risk of CHD
	Eating dietary fibre - protect against obesity and reduce insulin levels in the blood, so reducing CHD.
	Moderate consumption of alcohol - shown by some studies to reduce the risk of CHD.
	Eating oily fish - such as mackerel and herring
	Formation of heart attack. Those who are over-weight are twice as likely to suffer from CHD than those with acceptable BMI.
	It is a Degenerative condition which involves the build-up of fatty tissue in the walls of arteries that supply heart muscles.
	If these arteries become narrowed as a result, the flow of blood decreases and the supply of nutrients and oxygen to heart muscle decreases.
	The muscle doesn't release enough energy, the heart becomes weak.
	There may be a blood clot in the coronary artery, so cutting off the supply of blood to that area completely and leading to a heart attack.

5.2 Module 2802: Human Health and Disease Preamble In addition to meeting the aims of the specification as a whole, this module is intended to develop: * an understanding of what is meant by health and disease; * an appreciation of disease in a global context and the factors that affect patterns of disease globally; * an understanding of the principles upon which preventive medicine is based; an understanding of the extent to which people can influence their health by their behaviour; * an appreciation of the role and implications of medical technology in the context of limited resources; * an understanding of how our bodies attempt to maintain good health; * a positive attitude and approach to health as being more than simply the absence of disease. Assessment Objectives See Section 3. Candidates are expected to appy knowledge, understanding and other skills gained in this module to new situations and/or to solve related problems. Recommended Prior Knowledge Candidates should have a knowledge of * Key Stage 4 Programme of Study Sc.2, 2 a - g, m, n, p, q and r; * Biology Foundation, Module 2801; * Transport, Module 2803, Component 01, sections 5.3.1 and 5.3.2. 5.2.1 Introduction to Health and Disease IT3.1, IT3.3 Recommended Prior Knowledge Candidates should have a knowledge of * Key Stage 4 Programme of Study Sc2, 2d-g,m,n,q and r; * Biology Foundation, Module 2801; * Transport, Module 2803, Component 01, sections 5.3.1 and 5.3.2. Oxford Cambridge and RSA Examinations OCR GCE Biology Specification Content 41 Content * Definitions of the terms health and disease. * Global patterns of disease distribution. Learning Outcomes Candidates should be able to: (a) discuss what is meant by the terms health and disease. (b) discuss whether health is more than simply the absence of disease. (c) explain, with one example of each, what is meant by the following categories of disease or illness: physical, mental, social, infectious, non-infectious, degenerative, inherited, self-inflicted and deficiency. (d) explain the reasons for collecting health statistics. T3.1, IT3.3 (e) describe and explain the differences between standards of health in developed and developing countries. (f) explain the terms pandemic, epidemic and endemic. (g) appreciate the significance of the Human Genome Project to human health and disease. 5.2.2 Diet C3.1a Recommended Prior Knowledge Candidates should have knowledge of * Key Stage 4 Programme of Study Sc2, 2 a and b; * Biology Foundation, Module 2801; * Transport, Module 2803, Component 01, sections 5.3.1 and 5.3.2. Content * The concept of the balanced diet. * Energy and nutrient requirements. * Essential nutrients. * The consequences of malnutrition. * Diet and coronary heart disease. Oxford Cambridge and RSA Examinations 42 Specification Content OCR GCE Biology Learning Outcomes Candidates should be able to: (a) list the components of a balanced diet. (b) discuss the energy and nutrient requirements of people with reference to gender, age, activity, pregnancy and lactation. (c) explain what is meant by the term dietary reference value (DRV) and describe how these values should be used. (The Department of Health publication Dietary Reference Values for Food Energy and Nutrients for the UK, 1991 should be consulted.) (d) describe the functions of essential amino acids, essential fatty acids and vitamins A and D in the body. (e) describe the consequences of malnutrition with reference to energy and protein deficiency, anorexia nervosa, deficiencies of vitamins A and D, and obesity. (f) discuss the possible links between diet and coronary heart disease. 3.1a 5.2.3 Gaseous Exchange and Exercise LP3.1, LP3.2, LP3.3; PS3.1, PS3.2, PS3.3 Recommended Prior Knowledge Candidates should have a knowledge of * Key Stage 4 Programme of Study Sc2, 2 d-g, m-p; * Biology Foundation, Module 2801; * Transport, Module 2803, Component 01, sections 5.3.1 and 5.3.2. Content * The gaseous exchange system. * The consequences of exercise. Oxford Cambridge and RSA Examinations OCR GCE Biology Specification Content 43 Learning Outcomes Candidates should be able to: (a) describe the distribution of alveoli and blood vessels in lung tissue. (b) describe the distribution of cartilage, ciliated epithelium, goblet cells and smooth muscle in the trachea, bronchi and bronchioles. (c) describe the functions of cartilage, cilia, goblet cells, smooth muscle and elastic fibres in the gaseous exchange system. (d) explain the meanings of the terms tidal volume and vital capacity; (e) measure their pulse rate and understand that pulse rate is a measure of heart rate. (f) explain the significance of resting pulse rate in relation to physical fitness. (g) explain the terms systolic blood pressure, diastolic blood pressure and hypertension. (h) explain the meaning of the term aerobic exercise. (i) describe the immediate effects of exercise on the body, including the concept of oxygen debt and the production of lactate by anaerobic respiration. (j) design and carry out experiments to investigate the effects of exercise on the body. (Teachers should satisfy themselves that any exercise undertaken by candidates can be done safely.) S3 (all), LP3 (all) (k) appreciate how much exercise needs to be taken for significant sustained improvement in aerobic fitness. S3 (all), LP3 (all) (l) discuss the long-term consequences of exercise on the body and the benefits of maintaining a physically fit body, relating these benefits to the concept that health is more than the absence of disease. S3 (all), LP3 (all) 5.2.4 Smoking and disease C3.2 Recommended Prior Knowledge Candidates should have knowledge of * Key Stage 4 Programme of Study Sc2, 2 c-e ,q and r; * Biology Foundation, Module, 2801; * Transport, Module 2803, Component 01, sections 5.3.1 and 5.3.2. Oxford Cambridge and RSA Examinations 44 Specification Content OCR GCE Biology Content * Effects of smoking and disease on the gaseous exchange and cardiovascular systems. * Prevention and cure. Learning Outcomes Candidates should be able to: (a) describe the effects of tar and carcinogens in tobacco smoke on the gaseous exchange system. (b) describe the symptoms of chronic bronchitis and emphysema (chronic obstructive pulmonary disease) and lung cancer. (c) evaluate the epidemiological and experimental evidence linking cigarette smoking to disease and early death. C3.2 (d) describe the effects of nicotine and carbon monoxide in tobacco smoke on the cardiovascular system with reference to atherosclerosis, coronary heart disease and strokes. (e) discuss the reasons for the global distribution of coronary heart disease. (f) discuss the difficulty in achieving a balance between prevention and cure, with reference to coronary heart disease, coronary by-pass surgery and heart transplant surgery. 5.2.5 Infectious Diseases Recommended Prior Knowledge Candidates should have knowledge of * Key Stage 4 Programme of Study Sc2, 2 a-f, m, p and q; * Biology Foundation, Module 2801; * Transport, Module 2803, Component 01, section 5.3.1. Content * Cholera, malaria, tuberculosis (TB) and AIDS. * Antibiotics. Oxford Cambridge and RSA Examinations OCR GCE Biology Specification Content 45 Learning Outcomes Candidates should be able to: (a) describe the causes and means of transmission of cholera, malaria, AIDS/HIV and TB. (Knowledge of the symptoms of these diseases is not required.) (b) assess the worldwide importance of these diseases. (c) describe the roles of social, economic and biological factors in the prevention and control of these diseases. (d) outline the role of antibiotics in the treatment of infectious disease. 5.2.6 Immunity WO3.1, WO3.2, WO3.3 Recommended Prior Knowledge Candidates should have a knowledge of * Key Stage 4 Programme of Study Sc2, 2 c and q; * Biology Foundation, Module 2801; * Transport, Module 2803, Component 01, section 5.3.1. Content * The immune system. * The role of vaccination in controlling disease. Learning Outcomes Candidates should be able to: (a) describe the origin, maturation and mode of action of phagocytes and lymphocytes. (b) explain the meaning of the term immune response. (c) distinguish between the actions of B lymphocytes and T lymphocytes in fighting infection. (d) appreciate the role of memory cells in long-term immunity. (e) relate the molecular structure of antibodies to their functions. WO3 (all) Oxford Cambridge and RSA Examinations 46 Specification Content OCR GCE Biology (f) vaccination can control disease. (g) discuss the reasons why vaccination has eradicated smallpox but not measles, TB, malaria or cholera. (h) outline the role of the immune system in allergies, with reference to asthma and hay fever.

Diet

Components of a balanced diet

Energy and nutrient requirements of people

Gender

Males require more protein because their growth is greater than females during adolescence, and after that stage they have a greater mass of tissue to repair and replace.

Males requires more of the vitamin B complexes that are needed for respiration and metabolism.

Males require more calcium and phosphorus in adolescence because they develop larger bones than females during this stage of growth.

Age

Energy requirements increase with age, up to and including adolescence, as growth is rapid during these years and physical activity is generally at high level. These energy requirements remain almost constant up to the age of 60 years, after which they decrease as physical activity diminishes and body mass often decreases.

Protein requirements increase with age, especially around puberty. This is because additional protein is needed for the rapid growth around adolescence and thereafter, to repair and replace cells.

Calcium and phosphorus requirements are greater in the first year of life as they are laid down in the bones of infants. The rate again increases in adolescence when the second growth spurt involves relatively rapid elongation of the bones. After adolescence, the requirements remain constant.

Requirements for other minerals and vitamins increases up to the age 20 years, but thereafter remains relatively constant.

Activity
The more physically active a person is, the greater their energy requirement. It follows that, compared to an office worker, a manual labourer requires a greater energy intake, especially of carbohydrate food.

Pregnancy

Energy during the last three months of pregnancy, when fetal growth is at its greatest and the mother has this additional mass to carry around.

Protein needed to supply the growth needs of the rapidly dividing cells of the fetus.

Vitamin A, C and D, although too much vitamin A can be harmful to the fetus in the early stages of pregnancy. For this reason pregnant women are recommended to avoid liver, which is very rich in vitamin A.

Lactation

More calcium, phosphorus and magnesium, as these are needed by the newly born to develop their bones.

More zinc because it is present in a number of enzymes, including those involved in growth and metabolism.

Dietary reference value

This is sets of figures relating to the requirements for energy and nutrient intake of all healthy individuals in the UK, this is sat by the department of Health in 1991.

The three DRV are:

Estimated Average Requirement - this is the population average

Reference Nutrient Intake - this is at the top end of the range and is enough for about 97% of the population

Lower Reference Nutrient Intake - this is at the bottom of the range and is enough for only about 2% of the population.

Use of Dietary Reference value:

Chefs and caterers to design appropriate menus for groups of people living in communities such as schools, old people's home and prisons.

Managers to plan food supplies for large groups of people.

Dieticians and others to assess the dietary needs of individuals, e.g. The elderly and pregnant women.

Individuals to calculate their own dietary requirements and to maintain or improve health.

Food manufacturers to provide appropriate nutritional information on food labels.

Describe the functions of...

Essential amino acids - Used to synthesis protein for growth and repair of cells

Essential fatty acids - Used to make phospholipids and fats

Vitamin A - Used to make rhodopsin for functioning of rod cells in the eye. Used to make retinoic acid, which aids cell development and growth, especially in epithelia.

Vitamin D - A steroid hormone that controls absorption of calcium from the gut and its deposition in bones.

Consequences of malnutrition

Energy

Stunting results from chronic protein-energy malnutrition, occurs in children from 2-5 years of age.

Wasting results from acute protein-energy malnutrition, occurs in individuals over 5 years of age. This is characterized by rapid weight loss in those who had near normal weight.

Kwashiorkor

Bloated appearance

Moon face

Apathetic

marasmus

Very think with wrinkled skin

Old man's face

Mentally alert

Anorexia nervosa

Muscles waste (including heart muscles)

Periods stop

Blood pressure falls

Hair becomes thin and sparse

Hands and feet are cold

There is increased susceptibility to infection

There are personality changes.

Vitamin A

Night blindness - rod cells do not make enough rhodopsin so people can not see in dim light

xerophthalmia - the surface of cornea is scarred which leads to blindness

Poor defence against disease such as measles.

Dry, rough skin, as vitamin A is needed to make retinoic acid, which is needed to maintain epithelial tissues like the skin.

Vitamin D

Rickets - occur in Children the bone become soft and grow irregularly, the joints become swollen and limbs and the chest may be distorted. Typically the legs are bow-shaped.

Osteomalacia - occur in adults - this causes a softening of the bones, making them tender and painful, fracture of bone occur more easily. Muscle weakness as well as loss of appetite and weight.

Obesity

Diet and coronary heart disease

High level of salt - increases hypertension.

High Blood cholesterol - contribute to the formation of plaques in the coronary arteries

High fatty acid intake - saturated fatty acid increases the risk of CHD

Eating dietary fibre - protect against obesity and reduce insulin levels in the blood, so reducing CHD.

Moderate consumption of alcohol - shown by some studies to reduce the risk of CHD.

Eating oily fish - such as mackerel and herring

Formation of heart attack. Those who are over-weight are twice as likely to suffer from CHD than those with acceptable BMI.

It is a Degenerative condition which involves the build-up of fatty tissue in the walls of arteries that supply heart muscles.

If these arteries become narrowed as a result, the flow of blood decreases and the supply of nutrients and oxygen to heart muscle decreases.

The muscle doesn't release enough energy, the heart becomes weak.

There may be a blood clot in the coronary artery, so cutting off the supply of blood to that area completely and leading to a heart attack.

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Revision:Ocr as biology - human health and disease

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Define Health and disease: Health is physical, mental and social well being. It is more than just being free from disease. Disease is a malfunction of the mind or body leading to a condition of poor health.

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HUMAN DISEASE AND HEALTH The human body is an amazing machine. Has the ability to repair itself, to fight off attacking microorganisms and adapt to a variety of situations. Often time microorganisms...

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Human Health & Disease | Biology | Science | Letstute

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Health can be defined as a person's physical, mental and social condition.

Good health is more than being free from disease; it is having a positive outlook on life and feeling good physically. To enjoy good health, a person needs proper shelter, nutrition, exercise, sleep and rest. Good hygiene and the access to medical and social care are also important.

Disease is a disorder or malfunction of the mind or body, which destroys good health.

Disease may have a single cause - for example, malaria or be multifactorial, such as heart disease. Diseases have characteristic symptoms, which may be physical, mental or both. Those that have a sudden onset with rapid changes, but only last for a short time are called acute, while the effects of chronic disease may continue for months or years.

There are nine main categories of disease but some diseases are more difficult to classify and fit into more than one of them.

Physical disease

These diseases involve temporary or permanent damage to the body and include all the other categories except mental disease where there is no sign of physical damage to the brain. An example would be leprosy.

Infectious disease

Pathogens are organisms living in or on our bodies, causing disease. Infectious diseases are caused by pathogens such as viruses, bacteria, fungi, protoctists, worms and insects, which can be transmitted from person to person. This may be via normal social contact - for example, chicken pox, or via food and water, sexual contact or an animal bite.

Carriers are people who can transmit the pathogen but do not have the disease symptoms.

Non-infectious diseases

These are all diseases, which are not caused by pathogens and cannot be passed on by physical contact. An example would be sickle cell anaemia.

Deficiency diseases

These are nutritional diseases caused by an inadequate or unbalanced diet. One or more essential nutrient is missing or in short supply - for example, a shortage of Vitamin C causes scurvy.

Inherited diseases

These diseases are caused by genes and can therefore be passed from parent to child. They are also sometimes called genetic diseases or disorders.

In Britain, the most common inherited disease is cystic fibrosis, which is characterised by a build-up of sticky mucus. This makes breathing difficult and can act as a breeding ground for bacteria, so sufferers need daily physiotherapy to remove the mucus.

It is caused by a recessive faulty allele and so parents may be carriers for the disease without having any symptoms. As yet, genetic diseases may be treated but not cured because we cannot replace the faulty gene (gene therapy).

The Human Genome Project involves scientists in many countries and began in 1990.
It aims to:

Determine the sequence of the bases throughout all the DNA in human cells.

Identify the estimated 1000, 000 genes formed by the bases.

Find the location of the genes on the 23 human chromosomes.

Store all this information for research.

Consider the ethical, legal and social issues arising from this information.

The findings have already had a major impact, such as the devising of diagnostic tests to see if parents are carriers for a particular disease. In the future, drugs that act against the faulty gene causing a disease may be developed, which will have fewer side effects and be more effective.

The replacement of faulty genes or gene therapy may become commonplace.

Many people are concerned about the implications of genetic testing. In many cases there may be no treatment for a disease that we can test for. There are also risks of discrimination by employers, insurance companies and others if they discover an individual has a positive test for a faulty gene.
How reliable will the test be? How will they be made available to the world's poorest nations?
Degenerative diseases

These diseases are characterised by a gradual loss of function, in one or several organs or tissues. In old age, this is often the result of the failure of the bodies repair mechanisms - for example, loss of mobility due to worn joints.

However, degenerative diseases can strike in ones youth or middle age. They may be the result of poor nutrition in childhood or due to the immune system attacking the bodies, own cells.
There are three main categories:

Diseases of skeletal, muscular and nervous tissues - for example, osteoarthritis.

Cardiovascular diseases of the circulatory system - for example, coronary heart disease.

Mental disorders

These disorders affect a person's mind, but may be accompanied by physical symptoms. Emotions, thoughts, memories and personal and social behaviour can be affected.

Some mental diseases are caused by degeneration of brain tissue - for example, Alzheimer's - a progressive deterioration in memory is followed by a general decline in all mental faculties (dementia). Other mental disorders seem to be accompanied by changes in the blood flow to the brain - for example, Schizophrenia.

Social diseases

This is a very wide category that can include almost all infectious diseases and multifactorial diseases, which are influenced by people's living conditions and their personal behaviour. For example, deficiency diseases may be the result of lack of choice of food, due to shortage of money.

Self-inflicted diseases

These diseases are caused by damage to a person's health by their own decisions and behaviour. Included in this category would be the choice to smoke or misusing drugs, sunbathing or eating a high fat diet.

Deliberate self-harm, such as attempted suicide, could also be placed here although it is often an indication of poor mental health.

An infectious disease, which is always present in a population, is called endemic.

An epidemic occurs when a disease suddenly spreads rapidly and affects many people. If a disease spreads over a continent or even the world it will be termed pandemic.

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Health can be defined as a person's physical, mental and social condition. Good health is more than being free from disease; it is having a positive outlook on life and feeling good physically. To enjoy good health, a person needs proper shelter, nutrition, exercise, sleep and rest.