BIO UNIT 4 AOS 1

Consequence based approach

 

Which action produces the most good and the least harm?

The action that leads to the best overall outcome to the most people (minimising negative effects) regardless of whether the act is right or wrong.

Duty and/or rules based approach

 

Which action follows the rules/duty regardless of the consequences?

People have an obligation to follow rules/laws/moral duties regardless of the consequences.

Virtue based approach

 

Which action would a good person follow?

Need to consider the virtues/moral character of the person carrying out the action.

Virtue based approach example

Batman could have chosen to kill the joker early in the movie, however he has to decide what kind of person does he want to be. Using virtues based Ethics, the question that needs to be asked is does Batman want to be the person that killed the joker or not?

Duty and/or rules based approach example

If a person is a computer programmer and they know that a bomb is going to be set off that will kill a large number of people, they can choose to hack the system and prevent millions of people dying. However, this is against the law and a breach of professional standards (rules/morals) of computer programmers, therefore if following this approach they cannot hack and stop the bomb.

integrity

actions involving truth and trustworthiness.

beneficence

actions resulting in positive outcomes and minimising harm.

non-maleficence

**** avoiding actions that cause harm.

respect

considering autonomy.

justice

actions involving equality.

a disease is a

change that impairs the functioning of an individual

infectious diseases are

diseases caused by pathogens

what does the immune system do

it fights diseases

Antigens (antibody-generator)

• Unique molecules (e.g. proteins, carbohydrate, lipid, nucleic acid)

• Can be self or non-self

‘self’

• Your own healthy cells/material

• ‘Non-self’

refers to cells/material from an invader or your own cancerous or infected cells

• Our immune system can differentiate

self antigens on our own cells (and not destroy them) from non-self antigens (initiating an immune response).

allergens

are antigens that trigger an allergic reaction

MHC - major histocompatibility complex

-group of proteins found on the surface of virtually all mammalian cells

two types: MHCI and MHCII

MHC function

they allow immune cells to differentiate between self and non-self antigens

MHC I found on

all body cells (except red blood cells)

MHC II found on

some immune cells (macrophages, dendritic cells, b cells)

pathogen

is the causative agent of a disease

what do pathogens do

• they elicit an immune response as they contain , are covered in, or secrete antigens that are recognised as non-self by the immune system.

prions are

proteins with an abnormal shape

prions impact on normal protein

-through contact causes a normal protein to change to a prion

are prions easy to destroy

no they are hard to destroy

prion function

-destroy neural tissue leading to holes (spongy) causing degenerative neurological diseases (e.g. kuru and cjd in humans, scrapie in sheep)

viruses structure

DNA or RNA and protein coat (capsid) and some have envelope or surface proteins

some viruses have

envelope or surface proteins

Viruses are

host specific, obligate intracellular parasites

Some viruses (eg influenza) change their

surface antigens through antigenic drift or antigenic shift

bacteria

-unicellular prokaryotes

-one circular chromosome (DNA)

-many plasmids (small circular DNA)

-various adaptations (i.e. slime layer, flagella)

-reproduce rapidly by binary fission (asexual)

-some are pathogenic

virus features

(non cellular, not living, don’t have ribosomes, need the host cell to replicate their nucleic acid and protein coats)

non cellular pathogens

prions, viruses

can non cellular pathogens replicate themselves

no, prions replicate by touching other proteins, viruses cant replicate outside host

virus host specific meaning

infects only one type of organism, however sometimes they can go thru mutations and switch from one host to another

antibiotics what r they used to treat and what do they attack

-are used to treat bacterial infections

-most antibiotics attack the cell wall

fungi

-unicellular or multicellular

-eukaryotic

-yeast, molds (e.g. ringworm)

fungal infection treatment

-antifungals are used

parasites

-organisms that live on or inside another organism and obtain nourishment from it, usually causing harm

-they can be single-cellular-protozoa (e.g. giardia), or multicellular worms (e.g. hookworm) or arthropods (e.g. ticks)

-cellular pathogens, like bacteria and parasites, are

living organisms composed of cells that can reproduce and grow on their own

-non-cellular pathogens, like viruses and prions,

are not made of cells and require a host cell to replicate

transmission of pathogens

-physical contact

-sexual contact

-food and water

-droplet or airborne

-carrying vector

-injecting vector

barriers are

the first line of defence (physical and chemical)

barriers function

-they prevent pathogens from entering or becoming established in the host

-physical barriers function

prevent entry of pathogens

-chemical barriers function

destroy or inhibit growth of pathogens

-microbiota barriers

prevent colonisation or growth of pathogenic microorganisms

physical barriers in animals

-intact skin and body tracts (covered in tightly packed epithelial cells)

-mucous membranes (trap and wash away bacteria)

-cilia/hair (trap and sweep away pathogens)

chemical barriers in animals

-natural secretions

• enzymes (eg lysozyme in tears)

• acids (eg stomach acid)

• surfactants (eg in lungs)

physical barriers in plants

-intact waxy cuticle

-think bark

-hairs

-galls

chemical barriers in plants

-toxics (eg defensins)

-repellents (eg citronella)

-antibacterial/antifungal agents (eg oils)

-enzymes (eg chitinases)

first-line defenses work

non-specifically and are always active

innate immune response comprises:

first line of defence: barriers

second line of defence: cells, components, and inflammation

innate immunity is

non-specific, rapid and has no memory of prior infections. i.e. it responds the same way every time it encounters a pathogen

non-specific describes a component of the immune system that

responds the same way to all pathogens

innate immunity rapidness

rapid compared to the first time you have an adaptive immune response, it acts immediately when pathogen enters tissue

(white blood cells) of innate immunity NNMMDE

neutrophils, macrophages, dendritic cells, mast cells, eosinophils, NK cells,

macrophages and dendritic cells

– are also known as antigen-presenting cells

neutrophils:

main phagocytic cell at the site of inflammation. their job is to destroy pathogens through phagocytosis and degranulation (release of antimicrobial substances)

macrophages:

also engulf and destroy pathogens (phagocytosis) but are found in smaller numbers. they are important in releasing cytokines (chemicals that signal more immune cells to leave the bloodstream and enter the tissue) and they move to the lymph nodes to perform antigen presentation

cytokines-

chemical released by immune cells that have an effect on other cells

phagocytes examples DMN

macrophages, dendritic cells, neurophils,

dendritic cells

also engulf and destroy pathogens but are found in even smaller numbers. they are the main antigen presenting cell, so also move to the lymph nodes

steps in phagocytosis:

1. the phagocyte will recognise the pathogen

2. it will extend part of its cell membrane to surround the pathogen

3. the pathogen will become contained in a vacuole called a phagosome

4. a lysosome containing digestive enzymes (lysozymes) will fuse with the phagosome to create a phagolysosome

5. the pathogen will be destroyed

6. macrophages and dendritic cells can then present parts of the digested pathogen on their MCHII to T helper cells

mast cells:

found in connective tissue release histamines which cause vasodilation during inflammatory response (and in allergic reactions)and increased permeability of blood vessels(leaky) → allows entry and exit of immune cells

eosinophils:

contain granules in their cytoplasm which release enzymes that kill or inactivate pathogens, particularly parasites (also important in allergic reactions)

natural killer cells:

identify and destroy virus infected cells and cancer cells without requiring prior exposure (innate). nk cells detect changes in cell surface molecules (eg absence of MHC class I). they induce apoptosis of the cell

viruses are obligate intracellular pathogens

→ must enter host cells to be replicated.

NK induce apoptosis through

release granules which are cytotoxic → causes target cell to undergo apoptosis

inflammatory response

• Pathogens breach barriers (eg enter through a cut in the skin)

• Macrophages phagocytose pathogens and together with damaged cells release cytokines to attract immune cells from the blood stream

• Mast cells release histamines which cause blood vessels to dilate and become leaky. Allowing entry of immune cells and fluids (such as complement) into infected tissue.

• Neutrophils phagocytose pathogens and release antimicrobial compounds (defensin) to kill pathogen

• Formation of pus

• Platelets release clotting factors to form a clot (prevents blood loss and forms scab)

why is site of inflammation hot, red and swollen?

looks red because blood vessels have dilated, more red blood cells coming to area

1. hot because blood carries body temp

   Swelling occurs when blood vessels become more leaky, allowing fluid and immune cells to move into the infected tissue

cytokines:

chemical released by immune cells that have an effect on other cells

interferons:

cytokines produced by virus infected cells. they protect neighbouring uninfected cells from viral infection, by causing activation of antiviral genes that inhibit viral replication.

why dont interferons always work against virruses

-a lot of viruses have evolved to have anti interferon abilities

components of innate immunity

complement proteins, cytokines, interferons

complement proteins

: a group of plasma proteins that are activated in a cascade and are rapid responders in innate immunity:

complement proteins function

-coat bacteria and other pathogens which makes it more attractive to phagocytes and enhances phagocytosis

-promote inflammation

-create membrane attack complexes (MAC) which form holes in bacterial membranes causing their lysis

phagocytes

neutrophils, macrophages, dendritic cells,

structure of the lymphatic system

• lymph

• lymphatic vessels

• primary lymphoid organs

• secondary lymphoid organs

• lymph

(the fluid from tissue that drains into lymphatic vessels

• primary lymphoid organs

(thymus, bone marrow)

• secondary lymphoid organs

(lymph nodes, tonsils, spleen)

lymph vessels

run throughout the body and carry lymph

lymph draining

lymph drains one way (due to valves) from tissue to the lymph nodes and then back into the circulatory system

role of primary lymphoid organs

• allow lymphoid stem cells to proliferate, differentiate, and mature

• all immune cells are created in

bone marrow (stem cells located in bone marrow) and then move to the blood and secondary lymphoid tissue to mature

• b cell maturation occurs in

the bone marrow

• t cell maturation occurs

in the thymus

primary lymphoid organs

organs of the immune system where lymphocytes are formed and mature

primary lymphoid organs contain

either b cells or t cells

primary lymphoid organs other info

-no contact w antigens

-undergo atrophy w age

atrophy -

decrease in size with age

role of secondary lymphoid tissue in immunity

allow lymphoid cells to become functional

secondary lymphoid tissue meaning

organs of the immune system which maintain mature naive lymphocytes and initiate an adaptive immune response

main site of antigen presentation

• lymph nodes are

significance immune cells are close to each other in the lymph node

• this maximises the chances of encounters between pathogens/antigen and immune cells

lymph carries what to where

pathogens (or antigen presenting cells that have engulfed pathogens) to lymph nodes

once pathogens or (APCS which have engulfed pathogens arrive at lymph nodes)

• resident dendritic cells and macrophage engulf pathogens that arrive and present antigen to helper T cells

• APCs which engulfed pathogens in tissue also present antigen to helper T cells (TH)