Health and Disease
OCR AS Biology
Unit 2
Module 2: Food and Health
Learning Outcomes
• Discuss what is meant by the terms
health and disease
• Define and discuss the meanings of
the terms parasite and pathogen
What is health?
• “health is more than just the absence
of disease”
– What is meant by health?
– What is meant by disease?
• Health
– absence of disease
• Disease
– disorder of a systems normal functions
What is health?
• You have been given 6 case studies
• In your groups
– discuss the health of each individual
– Rank them from 1 – 6
• 1 healthiest
• 6 unhealthiest
– Remember you must be able to give
reasons for your choices
Definitions
• Health
– A state of complete physical, mental and
social well-being, which is more than just
the absence of disease.
• Disease
– A problem with mind or body leading to a
departure from good health.
Good Health
• Free from disease
• Able to carry out mental and physical
tasks expected by society
• Well fed, balanced diet
• Housing and sanitation
• Happy and positive outlook
• Well integrated into society
The Health Triangle
• Physical health means the health of
the body
• Mental health means the health of the
mind.
• Social health means forming good
relationships.
The Health Triangle
Physical
Social
Mental
• If you take any of these away - the
triangle collapses
What is health?
• In your groups
– Go back to the original 6 case studies
– Have your opinions changes
– Rank them from 1 – 6
• 1 healthiest
• 6 unhealthiest
– Remember you must be able to give
reasons for your choices
Disease
• There are nine broad overlapping
categories of disease (see handout)
• Diseases can also be grouped into
– Single cause e.g. malaria
– Multifactorial e.g. heart disease
Disease
• Acute
– Sudden rapid changes and lasting for a
short time
• Chronic
– Long term – debilitating
– Develops slowly and persists
pathogen
• Infectious diseases are diseases caused by
pathogens.
• A pathogen
– is defined as an organism which causes disease
– Lives by taking nutrition from the host
– May cause damage to the host
• Disease transmission is the transfer of a
pathogen from infected to uninfected
people
Parasite
• A parasite is defined as
– Organisms that live in or on another living
things
– Benefit at the hosts expense
– Can be
• Internal parasite e.g. tapeworm
• External parasite e.g. head louse
Infectious Disease
• Organisms that can cause infectious
disease include
–
–
–
–
Bacteria e.g. cholera and TB
Fungi e.g. athlete’s foot and ringworm
Virus e.g. cold, influenza and AIDS
Protoctista e.g. amoeboid dysentery,
malaria
Learning Outcomes
• Describe the causes and means of
transmission of malaria, AIDS/HIV and
TB (symptoms not required)
• Describe the global impact of malaria,
AIDS/HIV and TB
Infectious diseases
• A pathogen can:
–
–
–
–
Gain entry to the host
Colonize the tissues of the host
Resist the defences of the host
Cause damage to host tissues
Transmission
• The most common forms of transmission are
– By means of a vector
– By physical contact
– By droplet infection
• Malaria and tuberculosis
– Pathogens invade cells and spread through the
tissues
• HIV
– Virus can lie dormant in T lymphocytes
– Weakens the immune system to opportunistic
infections (AIDS)
Malaria
• Causative organism
– Protoctista
– genus Plasmodium
– P. falciparum is the
most widespread
• Methods of transmission
– insect vector
– Female Anopheles
mosquito
– See diagram
• Global distribution
– Widely distributed
through the tropics and
sub tropics
– Annual incidence
• 300 million
– Annual mortality
worldwide
• 1.5 – 1.7 million
Malaria
• Global impact
– Increasing drug
resistance by
Plasmodium
– 40% of world’s
population live in
malarial areas
– Difficulty in developing a
vaccine
– Increase in epidemics as
environmental and
climatic changes favour
mosquitoes
– Mosquitoes are
developing resistance to
insecticides
• Control measures
– Use sleeping nets to
prevent mosquitoes
biting at night
– Use of drugs to fight of
Plasmodium
– Reduce mosquito
populations
• drain marshes and
swamps
• destroy mosquito larva –
oil or insecticide on
water, use carnivorous
fish
TB (tuberculosis)
• Causative organism
– Mycobacterium
tuberculosis
– Mycobacterium
bovis
• Methods of transmission
– inhalation of droplets
from infected person
– via infected milk
• Global distribution
– Worldwide in developing
countries and among
migrants and inner cities
in developed countries
– 8.8 million new cases
every year
– 1.5 million deaths
TB (tuberculosis)
• Global impact
– Some strains are resistant
to drugs (1950’s)
– AIDS pandemic
– Poor housing and rising
homelessness
– Breakdown of TB control
programmes
• Control measures
– Contact tracing,
• through testing for
bacteria and screening
for symptoms
– 2005 – BCG vaccine
ruled ineffective
– DOTS (directly observed
short course treatment)
– Long course of
antibiotics
HIV/AIDS
• Causative organism
– Human
Immunodeficiency Virus
• Methods of transmission
– Body fluids, esp. semen,
vaginal fluids and blood
– Sexual intercourse,
– shared needles,
– child birth, breast
feeding
– Infected blood products
• Global distribution
– World wide
– Highest prevalence in subSaharan Africa and Southeast Asia
HIV/AIDS
• Global impact
– 39.5 million people living
with HIV
– 2006
• 4.9 million new cases
• 2.9 million deaths from
AIDS
– Affects the affluent and
the impoverished
– TB is an associated
opportunistic infection
• Control measures
– Use of condoms
– Health education (safe
sex)
– Screening of blood
donations
– Heat treatment of blood
products to kill viruses
– Needle exchange
schemes
– Contact tracing
Immunity
Module 2: Food and Health
Health and Disease
Learning Outcomes
• Define the terms immune response,
antigen and antibody.
• Describe the primary defences against
pathogens and parasites (including
skin and mucous membranes) and
outline their importance.
• Describe, with the aid of diagrams and
photographs, the structure and mode
of action of phagocytes.
Definitions
• Immune response
– Specific response to a pathogen
– Involves the action of lymphocytes and the
production of antibodies
• Antibodies
– Protein molecules produced and released in
response to a antigen
• Antigen
– Foreign molecule – protein or glycoprotein
– Provokes an immune response
Primary Defences
• The body’s primary defences attempt
to stop pathogens from entering body
tissues
• This includes
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–
–
–
The skin (epidermis)
Mucous membranes
Eyes protected with tears
Ear canal lined with wax
Epidermis
• The outer layer of the epidermis is a
layer of dead cells which contain the
fibrous protein keratin.
• These cells are produced in the
process keratinisation – the cells dry
out and the cytoplasm is replaced
with keratin.
• This layer of cells acts as a barrier
Mucous membranes
• Mucous membranes protect surfaces which
are at risk of infection
• Mucus is secreted by the epithelial linings of
airways, digestive system and reproductive
systems
• In the airways ciliated cells move mucus up
to the mouths where it can be swallowed
• In the stomach, hydrochloric acid kills most
pathogens that we ingest.
Secondary Defences
• Non-specific immune response
– Phagocytes
• Specific Immune response
– B and T lymphocytes
– Antibody production
Phagocytosis
• Phagocytes engulf and digest pathogenic
cells
• Neutrophils
– found in the blood and body tissues
– Collect at an area of infection
• Macrophages
– Travel in blood as monocytes
– settle into the lymph nodes where they develop
– Stimulates production of T lymphocytes
Phagocyte - photographs
Neutrophil
Macrophage
Macrophage
engulfing
tuberculosis
bacterium
Stages in phagocytosis
• Pathogens are recognised by antigens on
their surface
• Phagocyte moves towards pathogen and
receptors on the cell surface membrane
attach to antigens on the pathogen
• Phagocyte engulfs the pathogen creating a
phagosome
• Lysosomes fuse with the phagosome
releasing digestive enzymes
• End products absorbed into the cytoplasm.
Phagocytosis Animations
• http://www.microbelibrary.org/images
/tterry/anim/phago053.html
Stages of Phagocytosis
Learning Outcomes
• Describe the structure and mode of action
of T lymphocytes and B lymphocytes,
including the significance of cell signalling
and the role of memory cells.
• Describe, with the aid of diagrams, the
structure of antibodies.
• Outline the mode of action of antibodies,
with reference to the neutralisation and
agglutination of pathogens.
Immune Response
• Immune response is the activation of
lymphocytes in the blood to help fight
disease
– T- Lymphocytes
• Produced in bone marrow
• Mature in the Thymus
– B-Lymphocytes
• Produced and matures in bone marrow
Immune response
• Pathogen enters body
• Clonal selection
– Antigens bind to complementary
glycoproteins on B and T lymphocytes
– This stimulate the immune response
• Clonal expansion
– B and T lymphocytes divide by mitosis
T-lymphocytes
• T lymphocytes divide into 3 types of cell
– T helper cells (Th)
• Release cytokines
– stimulate B cells to develop
– Stimulate phagocytosis (cell signalling)
– T killer cells (Tk)
• Attack and kill infected body cells
– T memory cells (Tm)
B lymphocytes
• B lymphocytes develop into two types
of cell
– Plasma cells (P)
• Flow in blood
• Manufacture and release antibodies
– B memory cells (Bm)
• Immunological memory
– Remain in blood for a number of years
– Stimulate the production of plasma cells quickly
upon reinfection by same pathogen.
Cell signalling in immune
response
• Identification of pathogens
• Sending distress signals
• Antigen presentation
• Instructions
– Communication using cytokines
Stages in immune response
• Infection and reproduction of
pathogen
• Presentation of antigens
• Clonal selection
• Clonal expansion
• Differentiation (proliferation)
• Action – antibody production
Antibodies
• Proteins a.k.a. immunoglobulins
• Specific shape complementary to that
of an antigen
• Antibody shape
– 4 polypeptide chains held together by
disulphide bridges
– Variable region
• 2 binding sites specific to an antigen
– Hinge regions allow flexibility
Antibody structure
Mode of action of antibodies
• Neutralisation
– Antibodies bind to toxins neutralising their
effects
– Antibodies combine to viruses and
prevent them from entering the cell.
• Agglutination
– Pathogen clump together
• Too large to enter host cells
• Helps phagocyte to engulf and digest
pathogens
Learning outcome
• Compare and contrast the primary
and secondary immune responses.
Primary Immune response
• Production of plasma cells
• Antibodies produced to combat
infection
• Takes a few days for number of antibodies in blood to rise
Secondary immune response
• B memory cells circulate in blood
• Rapidly produce plasma cells upon
reinfection
• Plasma cells produce antibodies
• Rapid response
Primary and secondary immune
response
Learning Outcomes
• Compare and contrast active, passive,
natural and artificial immunity.
• Explain how vaccination can control
disease.
• Discuss the responses of governments
and other organisations to the threat
of new strains of influenza each year
Immunity
• Natural immunity
– gained as part of normal life processes
• Artificial immunity
– Gained by deliberate exposure to antibodies or
antigens
• Active immunity
– Results from stimulation of immune response
• Passive immunity
– Introduction of antibodies
– Short lived
Immunity
Immunity
Active
Passive
Natural
Long term immunity
Infected by the disease
inducing an immune
response
Takes time
Immediate protection
Antibodies from mother
-Across placenta
-In colostrum (breast milk)
Short term immunity
Artificial
Long term immunity
Immunisation or vaccination
Takes time
Immediate protection
Injected with antibodies
e.g. tetanus injections
Short term immunity
Vaccination
• Vaccine
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–
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Preparation of antigen
Injected or given by mouth
Stimulates primary immune response
Boosters given to stimulate secondary
immune response
Antigenic material
• Living attenuated micro-organisms
– Can not cause symptoms
– Multiply
– E.g. TB, poliomyelitis
• Dead micro-organisms
– Harmless but induce immunity
– E.g. typhoid, cholera
• Preparation of antigens
– E.g. hepatitis B vaccine
• Harmless toxin
– E.g. tetanus vaccine
Control of disease
• Vaccinations can be used to control
disease by providing immunity to all
those at risk
• Herd immunity
– Use a vaccine to provide immunity to all
of the population at risk
• Ring immunity
– Vaccinate everyone in surrounding area
to prevent transmission of disease
Influenza
• Viral disease of the respiratory system
• Associated with
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–
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–
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Fever
Sore throat
Headache
Muscle pains
Weakness
• Can lead to pneumonia
• Can be fatal
• New strains arise by mutations (some
virulent)
vaccination programmes
• Epidemic
– Disease suddenly spreads rapidly to infect
many people
• Pandemic
– Large scale outbreak of a disease
• Governments research and try to
predict which strains of flu are going to
appear each year
Vaccination programmes in UK
• All people aged over 65
• Young people with asthma
• People who work in high-risk categories
such as medical professionals
• The strains of flu used in the
immunisation programme change each
year.
Learning Outcomes
• Outline possible new sources of
medicines, with reference to
microorganisms and plants and the
need to maintain biodiversity.
New Medicines
• Why do we need new medicines
– Pathogens become resistant to existing
drugs e.g. antibiotics
– New disease emerge
– New vaccines needed e.g. HIV
– Existing vaccines can be improved
Discovery of New Medicines
• By accident
– E.g. Alexander Fleming and the discovery
of penicillin
• Traditional medicine
• Anaesthetics
• Observation of wildlife
• Modern research
Natural medicines
• Discovery of natural drugs has concentrated
on tropical plants due to the great diversity
of species in tropical rainforests
• Examples
– Madagascan periwinkle – anticancer
– Sweet wormwood – antimalarial
• It is important that plant species do not
become extinct before we can discover
their value.
Smoking and Disease
Module 2: Food and Health
Health and Disease
Learning Outcome
• Describe the effects of smoking on the
mammalian gas exchange system,
with reference to the symptoms of
chronic bronchitis, emphysema
(chronic obstructive pulmonary
disease) and lung cancer.
Smoking - Intro
• WHO considers smoking to be an
epidemic
• Cigarette smoke contains
– Tar – a group of chemicals including
carcinogens
– Carbon monoxide
– nicotine
Reasons to give up
smoking
Short term effects of Tar
• Tar settles in linings of airways and
alveoli
– Inceases diffusion distance of gases
– Chemicals can cause an allergic reaction
• Lumen of airway narrows restricting air flow.
– Paralyses cilia
– Mucus secreting cells enlarge – produce
more mucus
– Increase risk of infection
Long term effects of tar
• Smokers cough
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–
–
–
Irritation of airways
Damages lining of airways and alveoli
Lining replaced by scar tissue
Smooth muscles thickens, lumen narrows
and airflow is permanently restricted.
Diseases linked with smoking
• Chronic Obstructive Pulmonary
disease
– Combination of diseases that includes
• Asthma
• Chronic bronchitis
• emphysema
Chronic Obstructive Pulmonary
Disease
Chronic Bronchitis
• Inflamed lining
• Smooth muscle
layer thickens
• Goblet cells and
mucus glands
secrete more
mucus
• Damage to cilia
• Symptoms
–
–
–
–
Shortness of breath
Wheezing
Persistent cough
Increase risk of lung
infection
Emphysema
• Loss of elasticity of
alveoli
• Alveoli burst
• Air spaces are
larger reducing
surface area for gas
exchange
• Symptoms
– Shortness of breath
– Difficulty exhaling
– Blood less well
oxygenated
– fatigue
Lung Cancer
• Cigarette smoke contains
carcinogenic compounds including
benzopyrene
– Carcinogens enter cells of lung tissue
– Mutation affects the gene controlling cell
division
– Uncontrolled cell division leads to a
tumour
– Bronchi become blocked by cancerous
growths
Symptoms of lung cancer
• persistent cough
• Coughing up blood
• Weight loss
• Pain in chest
Learning Outcomes
• Describe the effects of nicotine and
carbon monoxide in tobacco smoke
on the cardiovascular system with
reference to the course of events that
lead to atherosclerosis, coronary heart
disease and stroke.
Nicotine and carbon monoxide
• Nicotine and carbon monoxide pass
from the lungs into the circulation
• Changes occur that can lead to
– Atherosclerosis
– Coronary heart disease
– stroke
Nicotine
• Addictive drug
• stimulant
• Releases adrenaline which increases
heart rate and blood pressure
• Stimulates decrease in blood flow to
extremities
• Increases chance of blood clots
• Makes platelets sticky
Carbon monoxide
• Enters red blood cells and combines
with haemoglobin to form
carboxyhaemoglobin
• Reduces oxygen carrying capacity of
the blood
• Damages linings of arteries
Cardiovascular disease
• Multifactorial
– There is a number of risk factors
– Of which smoking is just one
• Degenerative disease of the heart and
circulatory systems
• 20% death worldwide
• Up to 50% developed countries
Atherosclerosis
• Atherosclerosis
– Accumulation of fatty material
(atheroma) in artery walls, reducing flow
of blood to the tissues
– Reduces the size of the lumen
– Reduces blood flow
Definitions
• Atheroma
– Contains cholesterol, fibres, dead muscle
cells and platelets
• Plaques
– Build up of atheroma
– Make arteries less elastic and reduce the
flow of blood
atherosclerosis
Stages in development of
Atherosclerosis
• Damage to endothelium of arteries
• invasion of phagocytes to repair damage
• Secretions from phagocytes stimulate
growth of smooth muscle and the
accumulation of cholesterol
• Atheroma builds up
• Atheroma forms plaque
• Size of lumen reduced, Blood flow reduced
Stages in atherosclerosis
Thrombosis
• Blood flow past the plaque is not
smooth which increases the risk of
blood clotting.
• Thrombus
– Blood clot in artery which stops flow
– May dislodge and be carried in the blood
Coronary heart Disease
• Lumen of coronary arteries narrowed
by plaque
• Reduces the blood flow to heart
muscles
• 3 forms
– Angina
– Heart attack / myocardial infarction
– Heart failure
Stroke
• Death of part of the brain
• Can be sudden
• Two causes
– Thrombus
• Blood clot blocks a narrow artery in the brain
– Haemorrhage
• an artery leading to the brain burst
• Aneurysm = weakness in wall of artery
Learning Outcomes
• Evaluate the epidemiological and
experimental evidence linking
cigarette smoking to disease and early
death.
Epidemiology
• The study of the distribution of diseases
in order to find a means of preventing
and controlling it.
• Epidemiological studies
– Identify links between disease and risk
factors
– Identifies which countries / age range /
gender may be at greater risk.
Epidemiological studies
• Information gained can be used to:
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–
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Target funding
Target research
Target screening
Target education and advice
Predict future incidences of the disease
Smoking and diseae
• 1950’s doctors first noticed a
correlation between lung cancer and
smoking.
• About half of smokers die of smoking
related diseases
• Smokers are three times more likely to
die in middle age than non-smokers
Linking smoking to lung cancer
• if stop smoking the risk of lung cancer
decreases
• Smokers 18 times more likely to
develop lung cancer than non
smokers
• 25% smokers die due to lung cancer
Linking smoking to lung diseases
• 98% emphysema sufferers are smokers
• 20% smokers suffer emphysema
• smokers twice as likely to die from
pneumonia and influenza
• COPD is rare in non smokers
Linking smoking to CVD
• This is less evident as CVD are
multifactorial
• However, substances in cigarette
smoke can influence the
cardiovascular system and likely to
enhance atherosclerosis
IMPORTANT POINT
All conclusions drawn by
epidemiological data show
an association and not a
causal link.
Experimental Evidence - Dogs
• Dogs exposed to unfiltered smoke
developed changes similar to COPD
and early signs of lung cancer.
• Dogs smoking filtered cigarette smoke
developed changes which can lead
to lung cancer
Experimental evidence - Tar
• Chemical analysis of tar shows that it
contains known carcinogens
• When painted onto the bare skin in
rats the tar caused cancer in the skin
cells.