topic 6.3 defence against infectious disease
DESCRIPTION
Topic 6.3 Defence against infectious disease. Topic 6: Human Health and Physiology. A pathogen in an organism or virus that causes disease. Some diseases are caused by genetic defects, others by environmental stresses – not all diseases are infections. What is a pathogen?. - PowerPoint PPT PresentationTRANSCRIPT
Topic 6.3Defence against infectious disease
Topic 6: Human Health and Physiology
A pathogen in an organism or virus that causes disease.
Some diseases are caused by genetic defects, others by environmental stresses – not all
diseases are infections.
What is a pathogen? Patho = disease Gen = Producer A pathogen is an organism or virus
that causes a disease. Why aren’t viruses called
organisms?? Organisms are living things. What
are the characteristics of living things?
Characteristics of living things
Properties of life Cellular Respiration Reproduction Metabolism Homeostasis Heredity Responsiveness Growth and development
Viruses infecting living cells
Viruses are not living organisms
Viruses do not Grow Have homeostasis Metabolize
Viruses do Infect cells and use the cell to make
more viruses Cause disease in many organisms
Viruses Viruses are micro organisms
consisting of a strand of DNA or RNA surrounded by a protein coat
They enter cells and hijack the cells machinery to make more viruses.
They then burst out of the host cell, destroying or damaging it.
Other pathogens Bacteria Fungi Protozoa Animals Prions
Flip over to I-biology ppt
Antibiotics
Major medical improvement Produced by fungi and bacteria Work on bacteria but… Cannot be used on viruses antibiotics block specific metabolic pathways found in bacteria, but not
eukaryotic cells because viruses reproduce using the host cell (eukaryotic) metabolic pathways,
they are unaffected by antibiotics antibiotics have produced great benefits world-wide in the control of bacterial
diseases Staphylococcus infections controlled STD's, such as gonorrhea and syphilis controlled
antibiotic resistance has evolved in bacterial populations
6.3.3 Outline the role of skin and mucous membranes in defence against pathogens
Skin Unbroken skin
provides a fantastic barrier against pathogens trying to enter the body
Sebum (oil) waterproofing You do not need to
learn the parts of this diagram.
Mucous Membranes (and other non-specific immunity)
Lungs – Mucous membranes and cilia
Stomach – Acid
Urethra – mucus membranes + urine is sterile
Eyes – tears contain lysozymes
Vagina – mucous membranes and acid
Anus – mucous membranes
Anywhere on the body that is not protected by skin has its own method of protection.
Infection! This occurs if pathogens do get
inside the body. The proteins on the surface of a
pathogen are immediately recognised as “foreign”.
Phagocytes (a type of leucocytes) will ingest the pathogen by phagocytosis.
Phagocytosis
Phagocytes Phagocytes are
found in the blood and in body tissues such as the lungs.
After phagocytes engulf pathogens, they destroy them with digestive enzymes found in lysosomes.
Phagocytosis
damage to tissues allows invasion across 1st line of defense microbes successfully invade body fluids or tissues damaged cells release histamine and other chemicals
initiating inflammation
phagocytes attracted to site by chemotaxis toward histamine phagocytes recognize microbes as foreign by antigen
recognition variety of phagocytic cells: neutrophils (small phagocytic
& macrophages (large phagocytic)
phagocytes endocytotically engulf microbes,which are digested by enzymes held in lysosomes digested microbe fragments are displayed on cell
membrane phagocytes with microbe fragments displayed =
antigen-presenting cells
antigens and antibodies
antigen: a molecule recognized as foreign by the immune system; it elicits an immune response; usually a foreign protien
antibody: =immunoglobulin a globular glycoprotein recognizes an antigen by its complementary shape and charge thus allowing it to attach to the antigen specifically marking it for attack by the immune system
Antibodies Also known as immunoglobulins Globular glycoproteins The heavy and light chains are
polypeptides The chains are held together by
disulphide bridges Each antiboby has 2 identical antigen
binding sites – variable regions. The order of amino acids in the variable
region determines the shape of the binding site
How Antibodies work? Some act as labels to identify
antigens for phagocytes Some work as antitoxins i.e. they block
toxins for e.g. those causing diphtheria and tetanus
Some attach to bacterial flagella making them less active and easier for phagocytes to engulf
Some cause agglutination (clumping together) of bacteria making them less likely to spread
Type Number of ag binding sites
Site of action Functions
IgG 2 BloodTissue fluidCAN CROSS PLACENTA
Increase macrophage activityAntitoxinsAgglutination
IgM 10 BloodTissue fluid
Agglutination
IgA 2 or 4 Secretions (saliva, tears, small intestine, vaginal, prostate, nasal, breast milk)
Stop bacteria adhering to host cellsPrevents bacteria forming colonies on mucous membranes
IgE 2 Tissues Activate mast cells HISTAMINEWorm response
Lymphocyte with antigens
Blood types
Where do antibodies come from?= Lymphocytes
Produce antibodies B-cells mature in bone marrow then
concentrate in lymph nodes and spleen
T-cells mature in thymus B and T cells mature then circulate in
the blood and lymph Circulation ensures they come into
contact with pathogens and each other
White Blood cellsWBC (Lymphocytes) are made in the bone marrow.
The cells divide and mature into 2 types:
T Lymphocytes B Lymphocytes
Develop in the thymus gland Develop in the bone marrow lymph nodes
Plasma ɞ cells have a different shape receptor on its membrane. There are about 10 million kinds in your body at any one time! Each can detect any antigen of a pathogen. Once activated they divide very fast (clone) and start to secrete specific antibodies. Antibodies slowly removed from blood and lymph. Memory ɞ cells remember antigens and can turn into Plasma ɞ if re-infected.
The Humoral (Antibody) ResponseThe Cell-Mediated ResopnseForeign, mutant or infected cells are identified as ‘non-self’ by surface antigens.T helper cell recognises antigens andalerts the other T cells.Killer (Cytotoxic) cells attack with perforinor nitric oxide. T memory cells rememberthe antigen for a later attack.T suppressor cells switch off T and B cellsafter attack over.
HIV HIV is a virus that specifically attacks
the T lymphocytes. This means the number of
lymphocytes decreases. Less antibodies are made. Predict the consequences…
