Health And Disease

Question 1

Define disease

Answer 1

A departure from good health caused by a malfunction of the mind or body

Question 2

Define parasite

Answer 2

An organism that lives in or on another living thing, taking nutrition from their host. They do not always cause disease.

Question 3

Define pathogen

Answer 3

An organism that causes disease that takes over the host cell’s DNA

Question 4

Causes, means of transmission and global impact of malaria

Answer 4

Eukaryotic parasite from genus Plasmodium (most widespread is a Plasmodium falciparum)

Spread by unsterilised needles, placenta and a vector, the female Anopheles mosquito, proboscis penetrates blood vessel, saliva contains parasite in infective stage, parasite invades liver to multiply then passes into blood, enter erythrocytes and feeds on haemoglobin

Kills 3m people each year. Mainly tropical regions. Most sub-Saharan Africa.

Question 5

Causes, means of transport and global impact of AIDS/HIV

Answer 5

Human immunodeficiency virus. Once active, attacks and destroys T helper cells in immune system, ability to resist infection is reduced, can contract a range of opportunistic infections. AIDS stands for acquired immune deficiency syndrome

Transmitted by body fluid exchanged: unprotected sex, sharing needles, across placenta or during child birth, breast feeding.

30m died by end of 2005. 2006 spread in China and Russia. Spread is pandemic. Most infected in sub-Saharan Africa.

Question 6

Causes, means of transmission and global impact of tuberculosis

Answer 6

Bacteria, Mycobacterium tuberculosis and M. bovis. Usually found in the lungs, can affect many body parts though.

Transmitted by droplet infection, talking, laughing, coughing, sneezing. Mainly when overcrowded, poor ventilation, poor health or diet, homelessness. Also in milk/ meat of cattle in some places.

30% of world’s population may be infected, but in many it’s controlled by immune system. 1.6m died in 2005. Most common in sub-Saharan Africa and South-East Asia. Rising in Eastern Europe. Some strains are resistant to drugs.

Question 7

Define immune response

Answer 7

response to an antigen, involving lymphocytes and the production of antibodies

Question 8

Define antigen

Answer 8

Molecules that stimulate an immune response

Question 9

Define antibody

Answer 9

Protein molecules that can bind to antigens (leading to agglutination or neutralisation)

Question 10

Describe the primary defences against pathogens and parasites

Answer 10

Skin
dead cells slough off, taking bacteria with it.
Physical barrier, prevents entry
Chemical barrier, antimocrobial, and can lower pH
Keratin in cells can’t be easily digested by pathogens
Sebum lowers pH and inhibits pathogen growth
Sweat contains lysozymes, digest bacterial cell walls

Mucous membranes
So, the airways, lungs and digestive systems are protected by mucous membranes. goblet cells, mucous traps pathogens, cilia waft mucus to top of trachea to be swallowed, pathogens killed by acidity of stomach acid.

The eyes are protected by antibodies in the tear fluid The wax in the ear canal traps pathogens
The conditions around the vagina are relatively acidic

Question 11

Structure and mode of action of phagocytes

Answer 11

Multilobed nucleus (neutrophils), allows flexibility, passage through capillary endothelium. Many lysosomes, many mitochondria. Macrophages larger, made in bone marrow and settle in organs eg lymph nodes.

Phagocyte recognises antigens on pathogen
Pathogen attachs to phagocyte by antibody and surface receptor
Pathogen engulfed by infolding of phagocyte membrane
Lysosomes release lysins into the phagosome (a vacuole with the pathogen trapped inside)
Harmless products of digestion are absorbed
Pathogen antigen presentation on cell surface membrane

Question 12

The structure of antibodies

Answer 12

Four polypeptide chains held together by disulfide bridges
Y-shaped
A constant region, which is the same in all antibodies. This enables the antibody to attach to the phagocytic cells and helps the process of phagocytosis
A variable region which has a specific shape and differs from one type of antibody to the next. It ensures that the antigen can attach only to the correct antigen complementary shape to antigen shape.
Hinge regions, which allow a certain degree of flexibility. They allow the branches to move further apart to allow attachment to more than one antigen

Question 13

Mode of action of antibodies

Answer 13

Neutralisation
Antibodies cover binding sites on pathogen
Prevent binding/ entry to host cell
Can bind to toxins (antitoxin)

Agglutination
Bind together many pathogens
Too large to enter host cell
Increase likelihood of being consumed by macrophages/monocyte/neutrophils (phagocytes)

Question 14

Mode of action of T-lymphocytes

Answer 14

Phagocytes activate T-lymphocytes
Receptors on T cell bind with antigen presented on macrophage
Clonal selection- activates
Clonal expansion- divides to produce clones, which differentiate

Cytotoxic killer T cells, attaches to infected cells, secrete toxic substances (hydrogen peroxide) into cell, kill pathogens inside.

Helper T cells stimulate activity of killer T cells and B cells by releasing interleukins

Suppressor T cells switch off lymphocyte response when infection clears

Memory T cells remain in circulation and can respond quickly if same pathogen enters body again

Question 15

Mode of action of B lymphocytes

Answer 15

Activated by helper T cells cytokines, and pathogen antibody binding
Colonial expansion, then clones differentiate into
Plasma cells -flow around blood, making and releasing antibodies
B memory cells- remain in body for many years, act as immunological memory

Question 16

What cells manufacture antibodies?

Answer 16

Plasma cells (from the clonal expansion of B lymphocytes)

Question 17

Compare and contrast the primary and secondary responses

Answer 17

Primary response
When the infecting agent is first detected, the immune system starts to produce antibodies, but it takes a few days before the number of antibodies in the blood rises to a level that can fight the infection
Pathogen enters for first time
Slow speed of response
B and T cells activated
Symptoms
Secondary immune response
The immune system recognises the pathogen if the body is infected again, so the immune system can swing into action more quickly.
The production of antibodies rises sooner and reaches a higher concentration.
Pathogen enters for second time
Fast speed of response
Memory cells activated
No symptoms

Question 18

Compare and contrast active, passive, natural and artificial immunity

Answer 18

Active-immune system makes its own antibodies, exposed to antigen, takes a while for protection, long term protection, memory cells produced

Passive- given antibodies made by another organism, no exposure to antigen, immediate protection, short term protection, memory cells aren’t produced

Natural- catching the disease or receiving antibodies from mother through placenta and breast milk

Artificial- vaccination with antigens/ injection of antibodies

Question 19

Explain how vaccination can control disease

Answer 19

Provide immunity to all those at risk
Herd vaccination- provide immunity for most of population at risk, once enough immune disease can’t spread.
Ring vaccination- vaccinate those in immediate vicinity of new case, villages towns etc.

Can inject/ give orally…live microorganism, harmless version of pathogenic organism, dead pathogen, antigens, harmless toxin.

Question 20

Discuss responses of governments an other organisations to the threats of new strains of influenza

Answer 20

Vaccinate those at risk to prevent pandemics, the elderly, AIDS sufferers, others at risk.
Strains of flu change each year, researchers estimate the strain that’s most likely to spread.

Question 21

Outline possible new sources of medicines

Answer 21

Natural compounds found in plants, animals, produced by microorganisms.
Traditional medicines
Self medicating animals (birds line nest with medicinal leaves protect chicks from mites).
A small proportion of organisms have been investigated so far. Lots of potential sources.
Need to maintain biodiversity so species don’t die out before we have a chance to study them.

Question 22

Describe the effects of smoking on the mammalian gas exchange system

Answer 22

Chronic bronchitis
Inflammation of lungs, smoke damages cilia so goblet cells produce more mucus, which accumulates, so more coughing. Microorganisms multiply in mucus, cause infections leading to inflammation (decreases gas exchange)

Emphysema
Smoke trapped in alveoli, causes inflammation, more phagocytes which produce enzymes that break down elastin in alveoli, alveolar walls destroyed, reduced surface area (decreases gas exchange rate) so wheezing, shortness of breath, faster breathing rate. (Chronic obstructive pulmonary disease, permanent airflow reduction)

Lung cancer
Smoke contains carcinogens, DNA mutations of lung cells, uncontrolled cell growth, malignant tumour formation, blocking air flow, shortness of breath, uses lots of nutrients to grow causing weight loss.

Question 23

Define health

Answer 23

A state of mental, physical and social wellbeing

Question 24

Describe the effects of nicotine in tobacco smoke on the cardiovascular system

Answer 24

Causes release of adrenaline, can cause constriction of arteriole and raise blood pressure
Makes platelets sticky, increasing risk of blood clots, if in coronary arteries it could cause a heart attack

Question 25

Describe the effects of carbon monoxide in tobacco smoke on the cardiovascular system

Answer 25

Haemoglobin has a higher affinity for CO than for O2. Carbon monoxide combines with haemoglobin to form carboxyhaemoglobin, which is very stable. This reduces the oxygen carrying capacity of the blood. Smokers feel this when they exercise. The body will detect lower levels of oxygen and the heart rate will rise. Increases risk of stroke as oxygen to brain is limited.

Question 26

Atherosclerosis

Answer 26

CO damages artery endothelium, also high blood pressure and excess salt adds to damage.

Phagocytes repair damage, encourage smooth muscle growth and fatty acid deposition (including cholesterol from LDLs) high blood pressure increases cholesterol deposition. Deposits (atheromas) also include fibres, dead blood cells and platelets.

Atheromas build up under the endothelium in artery wall. May break through inner lining of artery. Atheromas form plaques, which stick out of artery lumen.

Leaves artery wall rougher and less flexible. Reduces the artery lumen size, reducing blood flow.

Question 27

Coronary heart disease

Answer 27

Lumen of coronary artery narrowed by plaques, reduces blood flow to heart muscles which receive less oxygen for respiration. Leads to CHD, which takes 3 forms
Angina- chest pain may extend to left arm or neck
Heart attack- death of part of heart muscle
Heart failure- heart can’t pump

Question 28

Stroke

Answer 28

Death of a part of brain tissue, caused by loss of blood flow to parts of the brain. Two causes include:
Blood clot (thrombosis) floating around in blood blocking a small artery that leads to a part of the brain
Artery bursting (haemorrhage) that leads to a part of the brain

Question 29

Evaluate epidemiological and experimental evidence linking cigarette smoking to disease and early death

Answer 29

Epidemiological
A regular smoker is three times more likely to die prematurely than a non smoker
50% of regular smokers are likely to die of a smoking related disease
25% of smokers die of lung cancer
The chance of developing lung cancer reduces as soon as a person stops smoking

It is not easy to link smoking with cardiovascular diseases because there are so many other factors that can contribute to cardio-vascular disease.

Experimental
In the 1960s
Some dogs were made to breathe smoke from unfiltered cigarettes. They developed changes in their lungs that were similar to those of Chronic Obstructive Pulmonary Disease. They also developed early signs of lung cancer
Some dogs were made to breathe smoke from filtered cigarettes. These doges remained healthier, but their lungs still showed early signs of lung cancer
Ethical issues, can we extrapolate evidence from dogs

Question 30

Who is at most at risk of infection

Answer 30

Pregnant women’s foetus (undeveloped immune system)
Patients HIV positive, chemotherapy
Health workers
Those with chronic diseases (heart disease)?