Download Note 18

South Tuen Mun Government Secondary School
Biology Revision Note 18
Health = a state of complete physical, mental and social well-being (World Health Organization)
Disease = a condition in which any body part cannot function normally, showing symptoms.
Lifestyle and health:
(i)
Diet
 Eating less  deficiency symptoms e.g. deficiency of protein  Kwashiorkor
 Eating too much
 Excess cholesterol / fat  blocking and narrowing of coronary artery  reduce transport of oxygen
and nutrients to the cardiac muscle  fail / weak to beat  stop beating  heart attack
 Excess cholesterol / fat  blocking and narrowing of artery to the brain  reduce transport of
oxygen and nutrients to brain cells  stop function  stroke
 Excess sugar  remains in the mouth  bacteria break down the sugar to release acid  acid
dissolves enamel  tooth decay
 Excess sugar / fat  excess energy intake  obese  higher risks of heart diseases, diabetes, stroke,
arthritis
 Excess salt  higher blood pressure  higher risks of heart diseases / stroke and breaking of artery
(damage to the brain and kidney)
(ii)
Exercise
 Strengthen heart muscle and intercostal muscles, diaphragm  better ventilation and circulation
 Keep bones and muscle strong and supple  reduce the risks of injuries and osteoporosis
 Promote mental and social well being
(iii)
Rest

allow the body and brain to recover physically and mentally  better alertness, judgment, reaction time
and memory + reduce the risks of depression / better mood
 allow growth hormone to work
(iv)
Personal hygiene of hair, hands, skin and mouth (oral hygiene) – reduce the chance of infection by
microorganisms and the spread of diseases
(v)
Smoking, alcohol and drug abuse
 Smoking is hazardous to health:
 diseases associated with smoking – chronic bronchitis, emphysema, asthma, heart disease and heart
attack
 miscarriage and premature birth in pregnant woman

Alcohol:
 Short term effects – judgment, physical coordination  blurred vision, slurred speech and loss of
balance  car accident  death
 Long term effects – addiction and inflammation of liver, cirrhosis, higher blood pressure, heart
disease, stroke, cancers of mouth, throat, oesophagus

Drug e.g. heroin, cannabis, MDMA, Ketamine, Methylamphetamine, cough medicine abuse  addiction
 withdrawal symptoms (e.g. nervousness, sleep problems, muscle pain)  death
 Heroin  breathing and menstrual problems, coma
 Cannabis, MDMA, Ketamine, Methylamphetamine, cough medicine  reduced concentration, slow
response
Infectious diseases
Pathogen
Bad effects
Examples
Virus (non cellular,
Act as a parasite of a host cell  destroy
Influenza, SARS, AIDS, dengue fever,
not a living thing
the cell membrane, stop the synthesis of
nucleic acid or protein  lysis of cell
measles
Bacteria


Cholera  dehydration and death
Protist
Acts as a parasite
Malaria  burst of red blood cells
Fungi
Acts as a parasite
Athlete’s foot
Worms
Acts as a parasite
Liver fluke  inflammation of liver
Acts as a parasite (food-borne disease)
Production of toxins (food poisoning)
Route of transmission
Route
Examples
Preventive measures
Droplets
Influenza, common cold,

Cover the mouth during coughing or sneezing
SARS


Wear surgical mask
Avoid crowded places
Air
Measles, tuberculosis
Good ventilation
Contaminated
water
Cholera, gastroenteritis


Drink clean water, distilled water, boiled water
Proper disposal of faeces
Contaminated food
Cholera


Proper handling of food
Cook food thoroughly
Body fluid
(through wound,
sharing of needle /
Hepatitis B, AIDS



Wear gloves when handling wounds
Cover wounds with dressing
Do not share needles / shaves


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Screen blood before blood transfusion
Stay with one healthy sex partner
Use condom during sex intercourse
Remove the breeding ground of vectors e.g.
remove or add oil to stagnant water
Kill the vectors e.g. by insecticide
Prevent contact with vectors e.g. wear
long-sleeved clothes
shaves, blood
transfusion, sex
intercourse,)
Vector (e.g.
mosquito, flies,
cockroach)
Cholera (flies, cockroach);
Denger fever & malaria
(mosquito)

Direct contact
Athlete’s foot, genital herpes



Good personal hygiene
Other preventive measures:
 Immunization programme + vaccination
 Community health – screening of infectious diseases e.g. Cervical Screening Programme; disease
surveillance; health education
Treatment of infectious diseases
 Killing bacteria by antibiotics  destroy the formation of cell wall OR inhibit synthesis of nucleic acid,
protein (bacteria cannot multiply or grow) / damage the cell membrane (lysis of bacteria)


Killing bacteria by sulpha drugs  acts as competitive inhibitors of certain enzyme in bacteria
Cocktail therapy to kill HIV (virus that causes AIDS)
Non infectious diseases
Non infectious
diseases
Causes and bad effects
Risk factors
Allergy
Overreaction of the immune system  running
nose, sneezing, itch, skin rash, swelling, shortness
of breath, loss of consciousness, death

Uncontrolled abnormal cell division in localized
region (benign tumour) OR in certain region and
spread to invade other regions through blood and
lymph (malignant tumour)  damage of tissue 
death


Cancer
Cardiovascular
diseases
High blood pressure / blocking and narrowing of
coronary artery  coronary heart disease


Family history
Chemical carcinogen e.g. tar in
cigarette, nitrosamine in salted
fish, asbestos
Radiation e.g. UV light, X ray

Virus e.g. HPV, Hepatitis B virus

Diet (excess cholesterol, fat
(trans fats, saturated fat), salt,
sugar
Smoking, alcohol
Aging, family history, obese,
diabetes, stress, lack of exercise


Diabetes
Family history (= inherited
tendency)
Allergens e.g. dust mites,
pollens, animal hair, insect
stings, certain food
Type I (insulin-dependent): defective pancreas 
less insulin secretion  excess blood glucose level
 glucose excreted in urine
Family history
Type II (non insulin-dependent) : body cells e.g.
liver cells are insensitive to insulin  excess blood
glucose level  glucose excreted in urine
Family history
Aging, obese, lack of exercise
Preventive measures – to reduce the risk of non infectious disease
 Healthy lifestyle (balanced diet, regular exercise, enough rest, good personal hygiene, do not smoke and
abuse alcohol / drugs, reduce contact of allergens and carcinogens)
 Disease surveillance e.g. data and mortality rate of cancers
 Health education (healthy lifestyle, diagnosis of non infectious disease and treatment)
Non specific body defence mechanisms
(i)
Physical barrier




(ii)
Skin is made up of a layer of dead cell that forms a physical barrier to prevent the entry of pathogens.
Hair in the nose forms a net to trap pathogens and prevent their entry into the respiratory tract.
Mucus in the nose and trachea sticks pathogens and prevent their entry into the respiratory tract.
Cilia in the trachea beats to move the sputum out of the trachea.
Chemical barrier



Oily secretion (sebum) by sebaceous gland of the skin can kill pathogens.
Gastric juice contains hydrochloric acid that can kill most pathogens.
Tear and saliva contains lysozyme that catalyses the breakdown of bacteria’s cell wall.

Vaginal fluid is acidic to inhibit the growth of pathogens.
(iii)
(iv)
Blood clotting – the formation of blood clot in the wounds, to prevent excess bleeding and the entry of
pathogens
Phagocytosis and inflammatory response

Phagocytosis is carried out by a kind of white blood cell, called phagocytes.

Phagocytosis at the wound leads to the inflammatory response
Arteriole dilate  more blood
flows to the capillary around the
wound  red and hot at the
wound
Accumulation of tissue fluid,
pathogens, phagocytes  pus
and swollen at the wound
Swollen wound  press on the
pain receptors  pain feeling
Specific body defence mechanisms
 Antigens are chemical molecules (normally protein or polysaccharides) that are found on the surface of
the cells. The antigens, if they are considered as “foreign” to a person, an immune response will be
initiated.

The cells of specific pathogen have specific antigen. The specific antigen can stimulate specific
lymphocytes to respond in two different ways: humoral immune response (HIR) or cell mediated immune
response (CMIR).
B cells are formed and matured in the bone
marrow. A pathogen has a specific antigen.
Specific antigen stimulates specific B cell to
respond. The specific plasma cell produces
specific antibody that acts on the specific
antigen. The memory cell is also specific.
The specific antibody has a shape complementary to the specific antigen. It binds with the antigen leading to
 make a hole and the pathogen cell is lysed. [lysis]
 enhance phagocytosis, more pathogen cells are engulfed and killed.


stick the cells of the pathogens into a clump, so the pathogen cannot reproduce.
neutralize the toxins of the pathogens, so the pathogens become harmless to the body.
T cells are made in bone marrow but matured
in the thymus gland. The infected cells and
cancer cells are specific. They stimulate
specific helper T cell and specific T cell to
respond. Thus the killer T cell and memory T
cell are also specific.
Primary response (first exposure to a pathogen) and secondary response (subsequent exposure to the same
specific pathogen):
The secondary response is carried out by
the specific memory B cell / T cell
formed after the first exposure. The
secondary response has a shorter latent
period, more antibody is produced at a
faster rate and the higher level of
antibody lasts longer duration to safe
guard the body.
Natural active immunity = natural secondary response of the formed memory cells after the first exposure
Vaccination (artificial active immunity) – injection of vaccine that contains a specific antigen of a pathogen
(cause a serious disease), the harmful effect of the antigen is already removed but it can stimulate the formation
of specific memory cell. The specific memory cell can be stimulated to produce the secondary response.
Types of vaccine: (i) live, weakened pathogens (e.g. measles); (ii) dead pathogens (poliomyelitis); (iii) the
specific antigen chemical molecule (whooping cough); (iv) inactivated toxins of the pathogens (tetanus)
Natural passive immunity = antibodies are obtained through natural processes e.g. through placenta, breast
feeding
Artificial passive immunity = injection of antibodies
Note : active immunity can last for a longer period of time, sometimes, it can be life-long; while passive
immunity is short-lifed.