Animal Physiology (2) Flashcards
What is the primary line of defence? State the components and explain how it is adapted to defend against pathogens
The first line of defence against infectious disease are the surface barriers that prevent the entry of pathogens into the body
Skin
Protects external structures when intact as a continuous layer (outer body areas)
Consists of a dry, thick and tough region composed predominantly of dead surface cells
Contains biochemical defence agents (sebaceous glands secrete chemicals and enzymes which inhibit microbial growth on skin)
The skin also secretes lactic acid and fatty acids to lower the pH (skin pH is roughly ~ 5.6 – 6.4 depending on body region)
-Microbiome of non harmful bacteria which are competitive
Mucous Membranes
Protects internal structures (i.e. externally accessible cavities and tubes – such as the trachea, oesophagus and urethra)
Consists of a thin region of living surface cells that release fluids to wash away pathogens (mucus, saliva, tears, etc.)
Contains biochemical defence agents (secretions contain lysozyme which can destroy cell walls and cause cell lysis)
Mucous membranes may be ciliated to aid in the removal of pathogens (along with physical actions such as coughing / sneezing)
Define clotting and explain its purpose
Clotting (haemostasis) is the mechanism by which broken blood vessels are repaired when damaged
Clotting functions to prevent blood loss from the body and limit pathogenic access to the bloodstream when the skin is broken
Outline blood clotting
When a blood vessel is damaged inactive platelets are exposed to collagen fibres causing the platelets to become active and form a plug at the wound.
Clotting factors cause platelets to become sticky and adhere to the damaged region to form a solid plug
These factors also initiate localised vasoconstriction to reduce blood flow through the damaged region
Additionally, clotting factors trigger the conversion of the inactive prothrombin into the activated enzyme thrombin
Thrombin in turn catalyses the conversion of the soluble plasma protein fibrinogen into an insolube fibrous form called fibrin
The fibrin strands form a mesh of fibres around the platelet plug and traps blood cells to form a temporary clot
When the damaged region is completely repaired, an enzyme (plasmin) is activated to dissolve the clot
Distinguish between type I and type II diabetes
Type I
-Early onset in childhood
-Inability to produce sufficient insulin
-Genetic predisposition / autoimune
-Requires daily injections of insulin or beta cell transplant
Type II
-late onset in adulthood
-Inability to respond to insulin
-Lfe style factors and dietary factors
-Requires weight loss, diet and possible medication but not insulin injections.
Explain homeostasis using blood sugar control as an example (9 marks)
maintaining the environment between narrow limits/
example such as pH or oxygen and CO2 conc or body temp/
involves negative feedback/
deviation from limit triggers correction mechanism/
controlled by nervous and endocrine system/
blood sugar above normal stimulates insulin release/
insulin secreted by beta-cells in the pancreas/
insulin lowers blood sugar/
by converting to glycogen/
blood sugar below normal stimulates glucagon release/
glucagon released by alpha cells of pancreas/
glycogen converted to glucose/
raises blood sugar/
Outline why antibiotics are effective against bacteria but not viruses
Antibiotics block metabolic pathways specific to bacteria/
Viruses do not have thier own metabolic pathways and use eukryotic hosts metabolism
Discuss the cause, transmission and social implications of AIDS
AIDS is caused by HIV/
Penetrates T lymphocytes/
Reverse transcriptases enables DNA to be produced/
from Viral RNA/
number of lymphocytes reduce over years/
results in lower immunity/
other opportunistic infections develop
HIV transmitted through blood, sexual contact/ placenta/ breastfeeding/
certain minorities do not have receptors for HIV and are immune/
Use of condoms and latex barriers reduces risk of transmission /
expensive treatment/
discrimination against victims/
comment on religion and beliefs/
Key properties of innate immunity
It does not differentiate between different types of pathogens (non-specific)
It responds to an infection the same way every time (non-adaptive)
Outline phagocytosis
Phagocytic leukocytes circulate in the blood and move into the body tissue (extravasation) in response to infection
Damaged tissues release chemicals (e.g. histamine) which draw white blood cells to the site of infection (via chemotaxis)
Pathogens are engulfed when cellular extensions (pseudopodia) surround the pathogen and then fuse to form an internal vesicle
The vesicle is then fused to a lysosome (forming a phagolysosome) and the pathogen is digested
Pathogen fragments (antigens) may be presented on the surface of the phagocyte in order to stimulate the third line of defence
Properties of third line of defence
It can differentiate between particular pathogens and target a response that is specific to a given pathogen
It can respond rapidly upon re-exposure to a specific pathogen, preventing symptoms from developing (immunological memory)
What are B lymphocytes?
B lymphocytes (B cells) are antibody-producing cells that recognise and target a particular pathogen fragment (antigen)
What are Helper T lymphocytes?
Helper T lymphocytes (TH cells) are regulator cells that release chemicals (cytokines) to activate specific B lymphocytes
Outline the production of antibodies upon infection
When phagocytic leukocytes engulf a pathogen, some will present the digested fragments (antigens) on their surface
These antigen-presenting cells (dendritic cells) migrate to the lymph nodes and activate specific helper T lymphocytes
The helper T cells then release cytokines to activate the particular B cell capable of producing antibodies specific to the antigen
The activated B cell will divide and differentiate to form short-lived plasma cells that produce high amounts of specific antibody
Antibodies will target their specific antigen, enhancing the capacity of the immune system to recognise and destroy the pathogen
A small proportion of activated B cell (and activated TH cell) will develop into memory cells to provide long-lasting immunity
Define antibody and antigen providing characteristics for each
Antigen: An antigen is a substance that the body recognises as foreign and that will elicit an immune response
Antibody: An antibody is a protein produced by B lymphocytes (and plasma cells) that is specific to a given antigen
Antibodies are made of 4 polypeptide chains that are joined together by disulphide bonds to form Y-shaped molecules
The ends of the arms are where the antigen binds – these areas are called the variable regions and differ between antibodies
The rest of the molecule is constant across all antibodies and serves as a recognition site for the immune system (opsonisation)
Each type of antibody recognises a unique antigen, making antigen-antibody interactions specific (like enzymes and substrates)
Explain why and how antibiotics are used for treating bacterial infections in humans
Antibiotics are compounds that kill or inhibit the growth of microbes (specifically bacteria) by targeting prokaryotic metabolism. Metabolic features that may be targeted by antibiotics include key enzymes, 70S ribosomes and components of the cell wall
Because eukaryotic cells do not possess these features, antibiotics will target the pathogenic bacteria and not the infected host
Antibiotics may either kill the invading bacteria (bactericidal) or suppress its potential to reproduce (bacteriostatic)
Outline Flory and Chains work
Working with another scientist (Ernst Chain) and a team of researchers, Florey tested penicillin on infected mice
Eight mice were injected with hemolytic streptococci and four of these mice were subsequently injected with doses of penicillin
The untreated mice died of bacterial infection while those treated with penicillin all survived – demonstrating its antibiotic potential
Outline the effects of HIV
HIV specifically targets the helper T lymphocytes which regulate the adaptive immune system
Following infection, the virus undergoes a period of inactivity (clinical latency) during which infected helper T cells reproduce
Eventually, the virus becomes active again and begins to spread, destroying the T lymphocytes in the process (lysogenic cycle)
With a reduction in the number of helper T cells, antibodies are unable to be produced, resulting in a lowered immunity
The body becomes susceptible to opportunistic infections, eventually resulting in death if the condition is not managed