SBI4U (AP Biology) - Homeostasis Summary/Test Review
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Course
Biology
Institution
12th Grade
This test review + free Quizlet summarizes the key concepts of homeostasis, as covered by the AP Biology/Ontario Grade 12 Biology curriculum. It deals with the immune, nervous, endocrine, and excretory system in 15 pages of detail!!
Homeostasis - Unit Test Review (Quizlet here and here)
Chapter 43 (Immune System)
1. Innate Immunity
Innate Immunity: A rapid, broad response to pathogens - innate defenses include:
a. Barrier Defenses - Skin, mucus membranes (which trap and expel
pathogens), and body fluids (whose low pH kills microbes)
b. Internal Defenses - Phagocytic cells, natural killer cells (which kill abnormal
cells), antimicrobial/interferon proteins (which interfere with pathogen
reproduction), and inflammatory response
Phagocytic Cells: Cells that recognize certain pathogens using Toll-like receptors,
before engulfing and destroying them (phagocytosis!) These include:
a. Neutrophils - small cells that circulate in blood
b. Macrophages - larger cells that stay in organs/tissues or travel
c. Dendrites - tissue cells that can present antigens
d. Eosinophils - tissue cells that destroy parasites
Inflammatory Response: A response that occurs upon infection or injury, often
characterized by pain, swelling, and a fever, which involves:
a. Mast cells release histamine, causing blood vessels to dilate/become more
permeable, and macrophages signal neutrophils to the injury
b. Neutrophils and antimicrobial proteins enter the tissue, and digest/kill any
pathogens
c. As the tissue heals, pus (dead white blood cells, pathogens, and cell debris)
may accumulate
2. Adaptive Immunity
Adaptive Immunity: A slower immune response that is activated after the innate
response, which targets traits specific to certain pathogens - adaptive responses
depend on lymphocytes (white blood cells) and include:
a. Humoral Response - Plasma B-cells (lymphocytes from the bone marrow)
release antibodies into the bloodstream, which bind to antigens
(pathogens) and mark them for destruction by neutrophils and
macrophages in a process called opsonization
, b. Cell-Mediated Response - Cytotoxic T-cells (from the thymus) recognize the
antigens displayed by pathogen-infected cells, and secrete proteins to
trigger apoptosis (cell suicide)
Structure of an antibody (the site on an antigen that binds to an antibody is THE EPITOPE)
3. Immune Response
a. A macrophage (or dendritic cell) ingests an antigen, before displaying
antigen fragments on its surface along with a class II MHC molecule,
becoming an antigen-presenting cell
b. A helper T-cell with a respective antigen receptor binds to the antigen-MHC
complex: the macrophage releases interleukin-I, stimulating the helper
T-cell to release interleukin-II
c. This stimulates the proliferation of cytotoxic T-cells and activates B-cells,
which differentiate into plasma B-cells - both of which can recognize and
attack the specific antigen
d. Memory helper T, cytotoxic T, and B cells are made, which last for decades
and can be used as a template to make their respective cells in case the
antigen comes back, making a secondary immune response much stronger
(and faster) than the first
Active Immunity: Immunity that develops when a pathogen invades the body (or
through vaccination), eliciting an immune response from the body
Passive Immunity: Immediate, short-term immunity conferred through the transfer
of antibodies, either from a mother to her baby or through the injection of
monoclonal antibodies (antibodies grown from a single clone of B cells specific to
one epitope)
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