topic 4 - health and disease - mr hedditch Flashcards
what is health?
the state of complete physical, mental and social
wellbeing
what is disease?
not having complete good health because of the body/mind is not able to function at its maximum efficiency
what does acute and chronic mean?
acute - short term illness with symptoms appearing and disappearing quickly
chronic - long term illness with symptoms lasting for months and years
what is a communicable and non-communicable disease?
communicable - a disease that can spread between organisms
e.g. flu, chicken pox
non-communicable - are diseases that can’t be spread between organisms
e.g. physical (fractures), mental (depression) and inherited (cystic fibrous) diseases
what is a pathogen and the types?
a pathogen is an organism that causes a disease, these include bacteria, viruses, fungi and protoctists
how does a bacteria cause a disease?
by producing toxins, damaging cells and causing deaths of the vascular tissues (in plants)
what diseases do bacteria cause?
tuberculosis which affects humans/animals
bacterial meningitis which affects humans
ring rot affects potatoes/tomatoes
how does a virus cause a disease?
by invading the host cells to insert genetic
material into the hosts DNA. Cells make copies of the virus - they burst out of the hosts cell causing physical damage
what diseases do viruses cause?
AIDS/HIV which affects humans
Influenza which affects animals/humans
Tobacco mosaic virus which affects plants
how does a fungi cause a disease?
in animals, the microspores species in the skin send out reproductive hyphae - grows to the surface of skin and release spores
in plants - live in the vascular tissue (access nutrients).
Hyphae release extracellular enzymes - they digest surrounding tissues and cause decay - leaves shrivel/die
what diseases do fungi cause?
athlete’s foot which affect humans
ringworm which affects cattle
black sigatoka which affects banana plants
how do protoctists cause a disease?
by entering host cells and feeding on the contents of cells
what diseases do protoctists cause?
malaria which affects animal/humans
tomato/potato late blight which affects potatoes/tomatoes
what is an indirect transmission?
when a disease is transmitted from one organism to anther through a vector e.g. water, food, air, insects
wha
food and water
spores
airborne droplets
person-to-person physical
what are spores?
a spore is a unit of asexual reproduction adapted to spending a long period of time in unfavourable conditions before developing into an offspring of the plant, algae, fungi, or protozoan that created it
what is indirect transmission and e.g?
indirect transmission is when a disease is transmitted from
one organism to another via a vector
a vector is another organism that carries the pathogen from one host to another, vectors are usually insects
e.g female Anopheles mosquitoes and dutch elm disease
malaria case study?
pathogen - plasmodium falciparum
transmission - vector needed - female Anopheles mosquito
drinks infected blood, then the pathogen is passed to an
uninfected person in the mosquito’s saliva as it feeds
symptoms - fever, headache, sweats, chills and vomiting
treatment - anti-malarial drugs
prevention/control
– prevent completion of the mosquito life cycle;
– vaccination is difficult as there are many antigens (shift);
– treatment is affected by drug resistance;
– sickle cell allele gives some protection
worldwide importance -
found throughout the tropics e.g.
China, India, South America, West Indies
90% of sufferers are in Sub-Saharan Africa
global warming enhances the spread
1.5 – 3 million deaths a year
Dutch elm disease?
Dutch elm disease is caused by a member of the sac fungi
(Ascomycota), and is spread by an elm bark beetle vector
in an attempt to block the fungus from spreading farther, the tree reacts by plugging its own xylem tissue with gum. This prevents the delivery of water and minerals to the leaves, which die
roots can also die as a result of lack of sugars from the leaves as photosynthesis stops
ways to reduce spread of disease?
good personal hygiene – washing hands (esp. after using the toilet) and wearing protective clothing
using heat/radiation to sterilise surfaces and surgical equipment
disinfecting surfaces
disinfecting cuts/grazes using antiseptics like alcohol
avoiding unprotected sex (use condoms)
social factors that contribute to disease transmission?
lack of adequate shelter/homelessness
poor ventilation/overcrowding (e.g. linked to TB)
poor nutrition
poor health – individuals with
HIV/AIDS are likely to contract
other diseases
what are the two types plant defences?
passive and active
what are physical defences?
cellulose cell wall – acts as a physical barrier and
contains chemical defences
waxy cuticles on stems and the upper surface of leaves
– act as a physical barrier and prevent water collecting,
reducing the spread of water-borne pathogens
lignin – indigestible waterproofing substance found in
xylem vessels
bark - contains chemical defences
ability to close stomata when pathogens are detected through changes to cytoplasmic volume in
guard cells
callose – a large polysaccharide deposited between the cell wall and plasma membrane upon infection
callose can be used to block phloem sieve tubes and close off plasmodesmata to restrict pathogen spread
what are passive defences?
passive defences are present before infection occurs
and are aimed at preventing pathogen entry and spread
what does tyloses do and what defence is it?
swellings that block xylem vessels to restrict the spread
of pathogens - physical defence
what are chemical defences?
plants are capable of producing many different anti-microbial chemicals
some of these chemicals are present in plants all the time: • Terpenes • Phenols • Alkaloids • Hydrolytic (digestive) enzyme
how do plants detect pathogens and what does this stimulate?
plants are able to detect pathogens using receptors (proteins and glycoproteins) in their cell walls
detection of an infection stimulates the strengthening of existing physical defences:
cell walls become thicker as more cellulose fibres are laid down
callose is deposited to block phloem sieve tubes and plasmodesmata
oxidative bursts produce highly reactive oxygen molecules which damage the cells of pathogen
examples of anti-microbial chemical production when its increased?
saponins destroy the plasma membrane of fungal cells
phytoalexins inhibit the growth of pathogens like fungi
what necrosis?
infected cells are sacrificed in deliberate “cell suicide” this limits the spread of the pathogen to the rest of the plant
intracellular enzymes digest infected cells
what are primary defences?
stop pathogens entering the body
what are secondary defences?
actions of phagocytes to kill pathogens that make it past the primary defences
primary defences expulsive reflexes?
coughing and sneezing are all classed as expulsive reflexes
these are automatic responses which are the body’s attempt to expel foreign objects from the body
sneezes occur when dust or other particles irritate the nasal mucous membranes
coughing arises when the mucous membranes in the respiratory tract are irritated
