health and disease

• direct spread of pathogens

  -food and water

  -spores

  -airborne droplets

  -person to person

  -blood/body fluids

  -touching contaminated surfaces
• indirect spread of pathogens

  -vectors- carry pathogen from host to host

  -normally insects

  -dutch elm disease

  -malaria
• social factors contributing to the spread of disease

  -lack of adequate shelter

  -poor ventilation

  -poor nutrition

  -poor health

  -living or working with people who have migrated from areas where a disease is more common
• transmission factors associated with developing countries

  -lack of purified water

  -inadequate education

  -poor health services

  -inadequate transport

  -lack of investment by the government
• transmission of tuberculosis

  -bacterium

  -droplet or unpasteurised milk

  -cough, weight loss, fever, appetite loss

  -1% newly infected each year

  -BCG vaccination- teenagers

  -antibiotics for months
• transmission of hiv

  -virus

  -body fluids

  -opportunistic infections

  -antiviral drugs
• transmission of malaria

  -most common in tropical climates

  -ideal for mosquitos- vectors

  -no effective vaccine

  -killing vector- prevention

  -covering skin

  -insecticides
• plant defences- passive and physical

  -waxy cuticle

  -bark trees

  -stomata

  -cellulose cell wall

  -lignin in the xylem (waterproof and indigestible)
• plant defences- passive and chemical

  -terpenes

  -phenols- natural antiseptic

  -alkaloids

  -hydrolytic (digestive) enzymes
• plant defences- active

  -callose- polysaccharide deposited between cell wall and plasma membrane upon infection- block off plasmodesmata to prevent spread

  -oxidative bursts release highly reactive oxygen molecules that damage pathogen

  -antimicrobial chemical production- saponins and phytoalexins
• plant defences- necrosis

  -cell suicide

  -intracellular enzymes digest infected cells
• plant defences- active- tyloses

  -swelling that block the xylem vessels to restrict the access of pathogens

  -also contain chemical defences such as terpenes which is toxic to pathogens
• primary defences- skin

  -waterproof physical barrier

  -outer layer (epidermis) made by layer of cells called keratinocytes

  -cells produced by mitosis at bottom of epidermis migrate to the top of the surface

  -migrating cells dry out and the cytoplasm replaced by keratin protein (keratinisation)

  -keratinised cells are dead and form and effective barrier to infection- fall off eventually
• primary defences- mucus

  -ciliated epithelium- bronchi, trachea

  -goblet cells produce mucus

  -cilia move to waft mucus

  -swallowed or coughed- stomach acid
• mucous membranes

  -exchange surfaces vulnerable to infection

  -barrier between blood and environment is reduced- rapid gas exchange

  -line all body cavities open to environment
• primary defences- blood clotting

  -platelets- fragments of cells

  -cuts and grazes provide opportunity for pathogens to enter body

  -clots prevent excess blood loss and temporarily seal wound to prevent infection
• clotting process

  -platelets release clotting factors to start process

  -mesh of protein fibrils form

  -clots dry out and form a scab- shrinks as it dries and draws sides of wounds together

  -collagen deposited under scab

  -epidermis skin cells- mitosis

  -cells differentiate

  -when new layers of skin complete, scab falls off
• expulsive reflexes

  -coughing and sneezing

  -automatic responses

  -sneezes- dust or other particles irritate nasal mucous membranes

  -coughing occurs when mucous membranes in respiratory tract are irritated
• inflammation

  -mast cells release histamine

  -capillary fenestrations become larger and more tissue fluid forms

  -neutrophils enter tissue fluid and target the source of the infection

  -more fluid- swelling- puts pressure on skin receptors- pain

  -red and heat- more blood flow to the area- vasodilation
• b- lymphocytes

  -made and mature in the bone marrow
• t- lymphocytes

  -mature in the thymus gland
• b- lymphocytes

  -tissue fluid, blood plasma, lymph- acts in fluids

  -deal with many bacteria

  -humoral pathway

  -produce antibodies
• t- lymphocytes

  -act on infected cells

  -kill body cells and typically target viral pathogens- enter cells to reproduce

  -cell mediated response
• humoral response- b-lymphocytes

  -have antibodies on surface that are complementary and act as receptors for foreign antigens
• humoral response- clonal selection

  -some b- lymphocytes don't have correct antibodies on surface for the antigen

  -only b- lymphocyte with correct specific antibody complementary to the antigen is chose and activated
• humoral response- clonal expansion

  many copies of selected b- lymphocyte are made quickly by mitosis- all cells are identical
• humoral response- differentiation

  -copies of the b- lymphocyte specialise and they can become plasma cells or b- memory cells
• plasma cells

  -short life span

  -2000 antibodies produced a second

  -large size to accommodate a large number of organelles

  -many mitochondria

  -ribosomes, rough endoplasmic reticulum, golgi apparatus- exocytosis
• b- memory cells

  -stays in blood plasma and tissue fluid

  -life span is decades

  -inactive until same antigen enters body again and is recognised

  -antibodies on surface act as a receptor for the antigen

  -upon a re encounter with antigen memory cells divide very rapidly to produce more plasma and memory cells- plasma cells produce antibodies faster and memory cells again remain in blood (second immune response)
• t- lymphocyte- cell mediated response

  -specific receptor (not antibodies) on surface

  -can detect foreign antigens- complementary shape
• cell mediated response- clonal selection

  -t- lymphocyte with a specific receptor is chosen and activated
• cell mediated response- clonal expansion

  -mitosis- copies of t- lymphocyte made
• cell mediated response- differentiation

  -t- helper cells

  -t- memory cells

  -t- regulator cells
• t- helper cells

  -recognise and detect foreign antigens

  -use cell signal molecules to direct other immune cells

  -cell signal molecules- cytokines- protein based
• t- helper cells and b- lymphocytes

  -send cytokines- develop into plasma cells for antibody production
• t- helper cells and phagocytes

  -microphages and neutrophils- increased phagocytosis
• t- helper cells and t- killer cells

  -helper cells activate the killer cells

  -kill infected body cells

  -use proteins called perforins to lyse body cells
• t- memory cells

  -provide long term immunity
• t- regulator cells

  -stop pathway at end of the immune response. also prevent autoimmunity
• delay in production of antibodies- first immune response

  -receptors on b- lymphocyte detect antigen, clonal selection and expansion etc