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Chapter

BIOL 273 - Unit 6- Immune System

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Department
Biology
Course Code
BIOL 273
Professor
Vivian Dayeh

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Unit 6The Immune SystemThe primary job of our immune system is to recognize self from nonself and rally defenses when neededImmunitythe bodys ability to protect itself from itself as well as from viruses bacteria and other diseasecausing entities The immune system consists of the lymphoid tissues of the body the immune cells and chemicals that coordinate and execute immune functionsIt is heavily dependent on celltocell communication particularly local communication by cytokines and contactdependent signalingKey Features Specificity and MemoryThe immune systems 3 major responses o To recognize and remove abnormal self cellscreated when normal cell growth and development go wrong ie Cancer o To remove dead or damaged cellsas well as old red blood cells through the use of macrophages o To protect the body from diseasecausing invaders pathogensmicroorganisms that are pathogens include bacteria viruses fungi and onecelled protozoapathogens also include multicellular parasites ie Hookworms and tapewormsimmunogens are substances that trigger the bodys immune response like pollen chemicals etcantigens are substances which trigger the immune response and call react with products of the responseIncorrect Response if mechanisms for distinguishing self from nonself fail and the immune system attacks the bodys normal cells results in autoimmune disease ie Diabetes mellitusOveractive Reponses conditions in which the immune system creates a response that is out of proportion to the threat posed by the antigen ie Allergies Lack of Response when a component of the immune system fails to work properly an immunodeficiency disease arises o Primary immunodeficiency a family of genetically inherited disorders that range from mild to severe o Acquired immunodeficiency occur as a result of infection and drug or radiation therapy acquired immunodeficiency syndrome AIDS is caused by the human immunodeficiency virus HIVPathogensCan be ingested through contaminated food or water inhaled introduced by biting insects and through contact with the skin etcBacteria Viruses Structure Cells usually surrounded by cell wall Not cells nucleic acid core with protein coat some are encased in a capsule for sometimes have an envelope of phospholipid additional protection and protein made from the hosts cell membrane Living Conditions Most can survive and reproduce Parasitic must have a host cell to outside a host as well as they have the reproducereplicateright environmental conditions pH temperature required nutrients etc Susceptibility to drugs Most can be killed or inhibited by Cannot be killed with antibiotics some can be antibiotics inhibited with antiviral drugs which target specific viral stages of replication The replication cycle of a virus begins upon entering the host cell 1 To cross the host cells membrane the virus binds to membrane receptors triggering endocytosis of the entire virus particle 2 Or the virus envelop fuses with the host cell membrane allowing the virus to enter the cytoplasm 3 Once inside the virus nucleic acid takes over and starts initiating the production of new viral DNA or RNA as well as new viral proteins they assemble into additional virus particles that are released from the host cell to infect other cellsTo leave the cell a virus has one of two options 1 The virus causes the host cell to rupture releasing virus particles into the ECF 2 Virus particles surround themselves with a layer of host cell membrane and then bud off from the surface of the host cellVirus can also kill a cell by disrupting the cells metabolismSome virus only replicate sporadically whereas others incorporate their DNA into the host cells DNAlike HIV and oncogeniccancer viruses The Immune ResponseThere are two lines of defense for the body 1 Physical and chemical barriers they try first to keep pathogens out of the bodys internal environmentEpitheliumthe protective barrier of skin and mucous membranes is the bodys first line of defenseGlandular secretions salivary glands and the glands in airways secrete mucous and immunoglobulins to trap and disable inhaled or ingested pathogensStomach acidity the low pH of the stomach helps destroy swallowed pathogens 2 The immune response is broken down into 4 steps I Detection and identification of the foreign substance II Communication with other immune cells to rally an organized response III Recruitment of assistance and coordination of the response among all participants IV Destruction or suppression of the invaderCytokinesprotein messengers released by one cell that affect the growth or activity of another cellAntibodiesproteins secreted by certain immune cellsbind antigens and make them more visible to the immune systemThere are two categories of the human immune response 1 Nonspecific innate immunityInnate immunity is present from birth and is the bodys nonspecific immune response to invasionThe membrane receptors have broad specificity and allow some immune cells to respond to molecular signals that are both unique and common to pathogenic microorganisms Inflammation apparent on the skin as a red warm swollen area a reaction of cytokinemediated innate immunity the balance of colloid osmotic and hydrostatic pressures is disrupted Histamine release in response makes capillary walls leakier and allows proteins to escape from the plasma into the interstitial fluid
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