Search for Better Health Notes

Biology notes
The search for better health
Discuss the difficulties of defining the terms ‘health’ and ‘disease’ - Disease is any condition that impairs normal living processes and is recognised by the presence of specific symptoms - Many diseases are best understood as a disturbance of homeostasis - Health is a state of complete physical, mental and social well-being and not merely the absence of disease or infirmity - ‘Health’ and ‘disease’ are not always easy terms to define - For example, someone with HIV may be ‘healthy’ if symptoms of disease AIDS have not appeared Outline how the function of genes, mitosis, cell differentiation and specialisation assist in the maintenance of health - Degree to which an organism is healthy depends on whether or not its cells are functioning properly and how well the body can repair of a malfunction/imbalance - Growth of tissue and healing of tissues are dependent on protein metabolism - Protein metabolism is controlled by genes - Important chat genes causing this metabolism have not been altered by mutations - Mitosis is cell division that will allow normal growth and repair - If processes controlling mitosis go wrong, cancer may occur - Cancer occurs when cells divide rapidly and do not carry out cell differentiation and specialisation properly - Cell specialisation allows cells to develop the structure to best perform specific functions - Cell differentiation is the normal process by which a less specialised cell develops or matures to possess a more distinct form and function Distinguish between infectious and non-infectious disease - Infectious diseases can be caused by prions, bacteria, viruses, protozoans, fungi or macroscopic parasitic animals - Infectious diseases can be spread from one organism to another by direct or indirect transmission - Non-infectious diseases cannot be spread rom one organism to another - Non-infectious disease can be caused by genetic factors, environmental factors, diet or physiological malfunction Explain why cleanliness in food, water and personal hygiene practices assist in control of disease - Control of disease caused by organisms include: - ways of preventing contamination of food and water through: - proper sanitation - proper food handling - personal hygiene - water treatment processes - ways to prevent decomposition and spoilage of food - ways to prevent transmission of disease and infection by using: - disinfectants - sterilisations and antiseptics - minimising contact with food and water - crowded conditions, poor sanitation and untreated sewage increase the spread of disease

Identify the conditions under which an organism is described as a pathogen - A pathogen is any organism living in or on another organism that is capable of causing disease - If a pathogen is to cause a disease, it must: - have enough virulence (number of particular pathogen needed to cause disease). A virulent pathogen will only need to be present in small numbers to cause the disease - enter the host through a certain part of the body or survive on the body without being destroyed by the body’s natural acidity and mucus - escape from one host to another - survive transmission from one host to another. Some pathogens can only be transmitted by direct contact because they cannot survive long outside the host - Pathogens cause disease symptoms in a number of ways: - large numbers of pathogens present are too many for the host tissue to function normally - the pathogens actually destroy cells or tissues - bacteria produce poisons called toxins - the pathogen may not directly harm the host but an excessive immune response by the host may damage tissue Describe the contribution of Pasteur and Koch to our understanding of infectious disease Pasteur - Pasteur and Koch stimulated the search for microbes as causes of disease - Among other things, Pasteur discovered that microbes such as bacteria can cause disease - With his famous swan-neck flask experiment, he demonstrated that bacteria and mould cannot generate spontaneously

Koch - Koch showed that bacteria were the cause of a disease called anthrax in horses, cows, sheep and humans - He also demonstrated that bacteria were the cause of tuberculosis in humans - Koch designed rules of procedure for showing that a particular micro-organism is the cause of a particular disease - Rules of procedure are called Koch’s postulates - Koch’s postulate are: 1. It must be shown that the micro-organism believed to be the cause of the disease is always present in the diseased organism 2. The micro-organism must be isolated and grown in a pure culture - a culture containing only that micro-organism 3. Micro-organisms from pure culture, when injected into a health organism, must produce the disease 4. Micro-organisms are isolated from experimental organisms, grown in pure culture and compared with the micro-organisms in original culture and shown to be identical

Distinguish between prions, viruses, bacteria, protozoans, fungi and macro-parasites and name one example of a disease caused by each type of pathogen Type of pathogen Prion Some distinguishing features - Defective form of a protein molecule - Does not contain DNA or RNA - Mostly attacks brain or nerve cells - Non-cellular - Contains DNA, RNA and protein coat - Requires a living host cell to replicate - Procaryotic cell - Divides quickly and/or produces toxins - Eucaryotic cell with cell wall - May have a complex life cycle - Eucaryotic cell with cell wall - Spreads via spores or rapid division - Some infect external skin and nails, while other enter the host’s body - Eucaryotic cells - multicellular organism - Mostly arthropods or worms

Virus

Bacteria Protozoan Fungi

Macro-parasites

Prions: - Newly discovered infectious agents that consist only of protein - Prion hypothesis states that certain diseases are caused not by known pathogens but by a protein that has adopted an abnormal disease-producing form - Prion diseases are both infectious and hereditary - Examples include: - Scrapie in sheep - Mad Cow Disease (bovine spongiform encephalopathy/BSE) Viruses: - Consists of a nucleic acid (DNA/RNA) core surrounded by a protein coat - Have genetic code and can replicate - Viruses invade cells and insert their genetic code into the host cell’s genetic code Example of virus Hepatitis B Herpes simplex 1 and 2 Human Immuno Deficiency Virus (HIV) Disease caused by the virus Viral liver infection Cold sores and genital herpes Acquired Immune Deficiency Syndrome (AIDS)

Bacteria: - Tiny procaryotic cells - Can cause disease by: - secreting toxins - invading cells - forming bacterial colonies that disrupt normal cell function Examples of bacteria Enterobacteria Bacterial leaf spot Disease caused by bacteria Salmonella disease and gastroenteritis Causes rotting of leaves and stems in snapdragons

Protozoans: - One-celled organisms, larger than bacteria, with DNA organised in a nucleus Example of protozoan Entamoeba: an amoeba protozoan Giardia: a flagellate protozoan Plasmodium: a sporozoan protozoan Disease caused by the protozoan Amoebic dysentery Diarrhoea Malaria

Fungi: - Simple organisms, similar to plants but without chlorophyll - Examples are yeasts and moulds Examples of fungus Candida Tinea Botrytis cinerea Disease caused by fungus Thrush and mucous membrane infection Ringworm and athlete’s foot Grey, furry growth on grapes, passionfruit and lettuce

Macro-parasites: - Multicellular parasites such as roundworms, tapeworms and flukes and arthropods such as ticks, mites and fleas - Example: - Blood fluke in humans causes a disease called schistosomiasis. The disease causes the body to become weak and more susceptible to other diseases. Symptoms include coughing, rashes, body pains, severe dysentery and anaemia Identify the role of antibiotics in the management of infectious disease - Antibiotics are compounds that kill or inhibit bacterial pathogens - For example, penicillin is made from a fungus (Penicillium mould) - Antibiotics serve mainly as a treatment but in some extreme situations, such as burns victims, may be used to prevent infection - Rarely used for infectious diseases that are caused by non-bacterial pathogens - There are reports of antibiotics being abused by being used in farming practices as a preventative, with possible consequences of increasing resistant strains - When taking antibiotics, the full course should be taken to avoid more resistant members or a population surviving and developing more resistant strains

Identify defence barriers to prevent entry of pathogens in humans: skin, mucous membranes, cilia, chemical barriers and other body secretions Skin: - Skin is a mechanical barrier - Unbroken skin protects other tissues, and collects and holds pathogens Mucous membranes: - Mucous membranes occur along the alimentary canal - Mucus traps pathogens - The respiratory surfaces and urogenital surfaces are also lined with mucous membranes Cilia: - Motile cilia are found in lining of trachea - Cilia beat in one direction to sweep mucus containing trapped pathogens and small particles out of the lungs - Coughing also helps remove materials and pathogens from the lungs Chemical barriers: - Chemicals such as lysosomes found in body fluids and secretions inhibit pathogens - pH of body fluids may also inhibit some pathogens - For example, acid pH on the skin discourages growth of many microbes and acidity of the stomach destroys many macro-organisms Other body secretions: - Oil glands on skin secrete fatty acids that inhibit the growth of some bacteria and fungi - Saliva and tears also contain substances that may inhibit or destroy pathogens Identify antigens as molecules that trigger the immune response - The term antigen is used for any substance that is usually foreign to an organism’s own body - Antigens are protein molecules that trigger an immune response, often because of the production of specific antibodies - Each pathogen has its own antigen Explain why organ transplants should trigger an immune response - Antigen-antibody responses result in rejection of transplanted tissue - That is, the transplanted tissue fails to live and become part of the organism - This is because the transplant tissue is identified by the body to contain a foreign antigen and this triggers an immune response Identify defence adaptations, including inflammation response, phagocytosis, lymph system and cell death to seal off pathogens - If foreign substances or micro-organisms get past the first line of defence, the below response is triggered Inflammation response: - Inflammation of tissue is designed to isolate and destroy foreign particles and prepares tissue for healing - Dilation of blood vessels occurs, increasing blood flow and raising temperature of the tissue Phagocytosis: - Phagocytes are cells that engulf and destroy micro-organisms - Phagocytosis is important as the body’s immediate defence against infection - Phagocytosis is carried out by: - some white blood cells - scavenger cells that remove foreign particles - macrophages

Lymph system: - Plays a major role in fighting disease at the second line of defence and the third line of defence - Lymph system drains intercellular fluid back into the blood - At second line of defence the lymph nodes filter out foreign bodies such as harmful bacteria and cell debris - The lymph nodes are found in the armpits, neck and groin and their enlargement is often a sign of infection Cell death to seal of the pathogen: - After phagocytes have destroyed an antigen, they die - They form a region that contains dead cells and phagocytes - This thick layer of dead cells seals off the pathogen in a structure like a cyst - This prevents the entry of nutrients to the pathogen, thereby killing it Identify the components of the immune response: antibodies, T cells and B cells - T cells, B cells and antibodies are components of the body’s main immune response - These responses help the body to build up resistance and fight long-term infection Antibodies: - Are proteins found in blood plasma and other body fluids that can combine with and help to neutralise an antigen - They are highly specific for the antigen that stimulated their synthesis and release - An antibody can react with the antigen in a number of ways: - The antibody combines with the antigen to cover its active site so it has no effect on the body - The antibody may dissolve parts of the cell walls of bacteria, destroying them - The antibody neutralises the toxins produced by the antigen - The antibody may cause bacteria to clump together, making the bacteria less active and more easily taken up by the lymph system - The antibody may make the antigen more susceptible to phagocytosis T cells: - Some white blood cells are phagocytes - Some are non-phagocytic cells called lymphocytes - These lymphocytes are receptor cells for antigens - T cells and B cells are two different types of lymphocytes - Stem cell of the bone marrow is the precursor of all lymphocytes - Those lymphocytes that continue their development in the bone marrow are called B cells - Those immature lymphocytes that migrate to the thymus from bone marrow develop into T cells - T cells are lymphocytes that destroy antigens themselves - They do not produce antibody-producing plasma cells - When antigen enters body, T cells secrete substances that either: - directly destroy the antigen; or - stimulate the activity of phagocytes - T cells are responsible for cellular immunity - T cells are produced in the thymus - The thymus is a gland situated under the sternum - T lymphocytes are constantly circulating through the blood to the lymph nodes and spleen and then back to the blood

B cells: - Are lymphocytes that are stimulated to produce plasma cells - Presence of antigen molecules stimulates the lymphocyte cells which begin to divide and produce more lymphocyte cells and specialised cells called plasma cells, which make antibodies - B cells accumulate in the spleen and lymph nodes and do not circulate Describe and explain the immune response in the human body in terms of interaction between B and T lymphocytes, the mechanisms that allow interaction between B and T lymphocytes and the range of T lymphocyte types and the difference in their roles - T cells influence and help B cells - Two mechanisms have been proposed to explain the cooperation between T cells and B cells in antibody formation The mechanisms that allow interaction between B and T lymphocytes Mechanism 1: - The T cell produces a soluble factor after interaction with an antigen - The B cell reacts with the soluble factor and the specific antigen to become a functional antibodyproducing cell Mechanism 2: - This is based on cell contact between the T cell and the B cell - The close contact comes about because of interaction with the antigen - This contact allows the T cell to signal the B cell to become a functional antibody-producing cell The range of T lymphocytes and the difference in their roles: - Exposure to an antigen makes the particular responding T cell differentiate into a range of T lymphocytes - These include: - Killer T cells, which secrete substances that destroy antigens directly, enhance the activity of macrophages and inhibit replication of viruses - Helper T cells, which enhance antibody production by B cells - Chronic infection with HIV leads to a decrease in the number and function of T4+ cells (T-helper cells) - Suppressor T cells, which help to turn off the immune response after an infection has been controlled - Memory T cells, which retain the ability to recognise the original invading antigen so that a subsequent invasion can be dealt with quickly Outline the way in which vaccinations prevent infection - Artificial acquired immunity is called immunisation - Vaccinations are used in immunisation programs - Vaccination involves the injecting or ingesting into the body of antigens from living, dead, weakened or non-virulent strains of micro-organisms - It stimulates a person’s own immune system to develop resistance - For example, to immunise against polio, Sabin polio vaccine is given to humans - The vaccine is a live, non-virulent strain of the polio virus - When it is taken, it brings about a specific immune response - Subsequent exposure to the same antigen will then result in an antibody-antigen response and the antigen is destroyed

Outline the reasons for the suppression of the immune response in organ transplant patients - Transplantation brings about an antigen-antibody response because the tissue proteins of one individual are not the same as those of another (except for identical twins or closely inbred strains) - T cells are the main cell type responsible for the rejection of transplanted organs - For this reason, transplant patients are given powerful drugs that suppress the immune response in order to help the transplant tissue to live and become part of their body - These substances have a number of side effects, such as diabetes and renal impairment, and leave recipient susceptible to infection - Therefore, antibiotics are given to transplant patients Identify and describe the main features of epidemiology using lung cancer as an example - Epidemiology has been called the ‘science of prevention’ - It is based on the systematic and ongoing collection, collation, analysis and interpretation of data - Epidemiologists study how often diseases occur in different groups or people and ask why - Their work can support vaccination programs for controlling infectious diseases, but commonly it relates to risk factors for non-infectious disease, such as cancer - Leonardo Simonella, co-ordinator of the Lung Cancer Project for the NSW Cancer Council, cites an example of some of the limitations of epidemiology - In the past there were some epidemiological studies that found a protective effect associated with beta-carotene - However, investigators found that beta-carotene increased the risk of mortality for patients who were at risk of developing lung cancer Identify causes of non-infectious disease using an example from each of the following categories: inherited disease, nutritional deficiencies and environmental diseases Inherited diseases: - Diseases caused by genetic factors inherited from parents include Down’s syndrome, haemophilia and muscular dystrophy - Down’s syndrome has been shown to be caused by an additional chromosome 21 - Individuals with the disease usually suffer mild to moderate mental retardation and have poor muscle tone - Their appearance is characterised by almond shape to the eyes, shorter limbs and protruding tongue - They experience a higher risk for congenital heart defects, gastroesophageal reflux disease, recurrent ear infections and thyroid dysfunctions - Down’s syndrome is more common in babies born to older mothers and it is believed to be linked to mistakes in gamete production Nutritional deficiencies: - These can lead to obesity, and malnutrition diseases such as scurvy or night blindness that are caused by protein or vitamin deficiencies - Inadequate or imbalanced diets have a role in diseases such as arthritis, heart and circulatory problems, kidney, liver or gall bladder disease - Nutritional deficiencies resulting from anorexia nervosa and bulimia can be fatal

Environmental diseases: - Diseases are sometimes associated with factors in the environment that include high stress levels, noise, overcrowding, drugs and pollutants - Chemicals in environment have been shown to cause diseases such as cancer - Chemicals include nicotine, asbestos, mercury and food additives - Cancer-causing substances are called carcinogens - Carcinogens may get in the nucleus of the cell and combine with the cell’s DNA, making it abnormal - Some diseases are combinations of factors - For example, some cancers can be a combination of a predisposed genetic condition and environmental factors Discuss the role of quarantine in preventing the spread of disease and plants and animals into Australia or across regions of Australia - Australia’s isolation has served to prevent the introduction of some plant and animal diseases - This protection would not have continued without quarantine services at entry points into Australia - Quarantine regulations have prevented the entry of foot and mouth disease, which has the potential to devastate the livestock industry - Within Australia, some areas are free from certain diseases such as the bunchy top virus in bananas - Movement of plant material, such as fruit and plant stock, across regions of Australia has been restricted by quarantine laws to prevent the spread of the disease - Quarantine regulations now apply to importations and customs at airports and shipping terminals - North Head in Sydney served as a quarantine station from 1828 until 1984 - North Head quarantine station helped to prevent the entry of plague, cholera, typhus fever, typhoid fever, yellow fever, smallpox and leprosy - Before quarantine, many plant and animal pests in Australia were deliberately introduced without a consideration for their potential environmental impact - Problems with rabbits, foxes, feral pigs and camels have resulted - Some organisms were accidentally introduced before quarantine, or irrespective of quarantine, such as rats, lantana and marine organisms in ballast water - Quarantine works well for diseases that have a relatively short incubation such as SARS but are less effective in diseases such as AIDS with a long incubation period Explain how one of the following strategies has controlled and/or prevented disease: public health programs, pesticides or genetic engineering to produce disease-resistant plants and animals Public health programs: - Public education programs, such as the ‘slip, slop, slap’ campaign designed to prevent skin cancer, raise public awareness - The ‘grim reaper’ campaign was used to warn of the risks involved in contracting AIDS - The childhood immunisation program, run by the Commonwealth Department of Health and Aged Care, includes a public health program Pesticides: - Use of pesticides helps control insect-borne diseases such as malaria - Mosquitoes are vectors of malaria, yellow fever, dengue fever and lymphatic filariasis - Initially DDT was used, but there is now an increased awareness of the risk of chemical pesticide use and there are strict guidelines governing the pesticide used and the manner of its use - Some pesticides target the mosquito larvae

- They can be either biological (toxins from bacteria) or chemical products, such as insect growth regulators or surface films - They are applied directly to water sources that hold mosquito eggs or larvae - Adult mosquitoes can be killed by pesticides in hand-held sprayers, in truck-mounted sprayers or by using aerial spraying Genetic engineering to produce resistant plants and animals: - Tobacco mosaic virus causes the leaves of some important crop plants, such as tomatoes, to wither and die. Scientists have now incorporated a virus-resistant gene into tomatoes - Genetic engineering has now been used to produce transgenic plants (cotton, soybean and potato) that contain the gene from a naturally occurring insecticide taken from a soil bacterium (Bt). The plant can now kill its own pests