difference between infectious and non-infectious diseases
Infectious diseases are caused by infectious agents called pathogens (like bacteria and viruses), non-infectious diseases are caused by damages or changes to the body. An infectious disease can be transmitted from on person to another, while a non-infectious disease cannot be spread through physical contact.
prions
Misfolded proteins which characterize several fatal neurodegenerative diseases in humans and many other animals. able to rearrange the structure of normal proteins
Viruses
Small infectious agent that replicates only inside the living cells of an organism
Bacteria
Microscopic, single-celled organisms that thrive in diverse environments
how can virulence be measured?
-The number of individuals the microorganisms infects -How quickly it spreads through the body -How many hosts die.
what must a organism do to cause disease?
-Enter the host -Multiply in the host tissues -Resist the host defence mechanisms -Damage the host
virulence factors
adhesion/adhesins, colonisation, life cycle changes, invasion, toxins
adhesions
-A pathogen must enter the host. To do this the pathogen must adhere (stick) to the host. -Once it is stuck to the host, it has a starting point to penetrate into the body.
adhesins
Small surface molecules which attach to specific receptors on the hosts membrane.
colonisation factors
Proteins that allow the pathogens to colonise the host’s body.
life cycle changes
Pathogen will cycle through different stages to help them survive in their host
Invasion Factors
-Proteins that allow pathogens to enter cells.-They produce proteins that disrupt host cell membranes or stimulate endocytosis.
toxins
Proteins that poison the host and cause cell damage.
endotoxins
A pathogen toxin bound to its outer cell, not free to enter the surrounding medium
exotoxins
-A pathogen produced and released by the pathogen -Damage cell membrane, interfere with signalling and impact the immune system
biofilm
A large number of bacteria congregate in one area. Pathogens can adhere in this area
ways an infectious disease can be spread
Physical contact with infected person/animal
Contact with contaminated object
Environmental sources
The lifecycle of a disease in the body can go through 7 stages if successfully treated
Exposure
Incubation Period
Prodromal Period
Acute Stage
Recovery Stage
Convalescence
Immunity
exposure
first contact with disease
incubation period
the period between infection and the appearance of symptoms of the disease (growth/ maturation) Pathogen/ parasite grows and multiplies
prodromal stage
-Slight signs & symptoms -Ex: achy/ sore/ tired -Contagious
acute stage
-Severe symptoms -Most contagious -Most affected
recovery stage
-Signs/ symptoms begin to decrease -Temperature is reduced -Feeling better
convalescence
-gradual healing after sickness or injury, (Infection is gone) -Can relapse -Need rest, sleep, healthy diet, antibiotics
immunity
-the condition in which an organism can resist disease (Body has antibodies) -Cannot catch same infection
what happens when a virus is in a cell?
it can direct the cell to produce more virus particles
wounds
Pathogens may enter the body through natural openings or via wounds and breaks in the skin
Natural active immunity
When a body is exposed to the living pathogen and produces memory cells that can counteract it.
Natural passive immunity
-When a mother is exposed to an antigen and passes the antibodies on to the foetus. -The baby does not produce memory cells so it is passive -Lasts a short time after birth.
Artificial active immunity
Injection with deactivated antigens that can cause the production of memory cells (vaccines)
vaccines
-Vaccines are produced to target a specific pathogen. -Once injected, the body reacts to produce memory cells for a period of time (6 months – 16 years) -Immunity is achieved without having to get sick.
artificial passive immunity
serums, Immunological tolerance
vector
Any agent who carries and transmits an infectious pathogen into another living organism (e.g. mosquitoes)
factors that affect immunity (1)
The portion of the population that is immune or has been immunised: -If a population already has a high level of immunity to a pathogen, then it will be more difficult for a pathogen to spread
factors that affect immunity (2)
Mobility of individuals in the affected population -If a pathogen stops people from moving easily, then it will have more trouble spreading
personal hygiene measures
These are preventative measures: -Regular hand washing reduces the spread of pathogens -Cleanliness laws -mask wearing social distancing
community level measures
Measures that are taken by the whole population to prevent the disease-Contact tracing and quarantine -School and workplace closure
homeostasis
a constant internal environment within a living organism despite internal or external changes.
metabolic
chemical processes that occur in all living organisms, which help them complete their life cycles.
anabolic
synthezing complex molecules from simpler ones (building up)
catabolic
breaking down complex molecules into simpler ones (breaking down)
stimulus-response model
when the body responds to a specific change in the environment
positive feedback
A physiological control mechanism in which a change trigger mechanisms that amplify the change e.g. blood clotting (Pushes an organism out of homeostasis)
negative feedback
A physiological control mechanism in which a change reverses a particular trend e.g. shivering (Helps the body return to homeostasis)
five types of sensory neurons
chemoreceptor, thermoreceptor, mechanoreceptor, photoreceptor, nocicereceptor
chemoreceptor
a sensory receptor that responds to chemical stimuli (Detect variation of the oxygen concentration in the arterial blood, also monitor arterial carbon dioxide and pH)
thermoreceptor
Detect any differences in temperature
mechanoreceptor
Designed to detect mechanical sensations or differences in pressure (touch).
photoreceptor
Transform light energy into action potentials that are interpreted by the brain.
nocicereceptor
Respond to damaging stimuli by sending signals to the spine and brain which result in the perception of pain
effector
a nerve fiber that terminates on a muscle or gland and stimulates contraction or secretion (last stage of a neural pathway) It is stimulates by a motor nerve that has being controlled by the brain.
muscles
Contract in response to a stimulus This will move the part of the body the muscle is connected too.
glands
Secrete hormones in response to a stimulus These hormones act as another stimulus in another part of the body
hormone
chemical messengers produced by an organism to regulate the activity of cells and organs
autocrine
Hormones that will bind to the same cell that produced them.
paracrine
Hormones that will bind to receptors of neighbouring cells.
endocrine
Hormones that travel long distance through blood to reach target cells in the body.
Down- regulation
-The process of reducing a reducing the response to a stimulus by reducing the number of receptors in a cell. -E.g: High insulin in blood is reduced by reducing the number of insulin receptors
up-regulation
-The process of increasing the response to a stimulus due to a increase number of receptors in a cell E.g: Oxytocin is released from the brain during childbirth.
parts of a neuron
function of dendrites
Receive information via synapses and deliver them to the cell body
function synapses
The connection between two neurons
function of soma
Cell Body of the neuron. Controls the metabolism and maintenance of the cell
function of axon
Nerve fibre that carries information from the soma to other nerve cells using electrical impulses
function of axon terminal
Found at the end of an axon branch and transfer information to the next neuron
function myelin sheath
Substance that surrounds the neuron. Enables efficient transmission of nerve impulses.
motor neurons
Communicate messages for the CNS, through the PNS to a muscle that needs to move. a neuron that sends an impulse to a muscle or gland, causing the muscle or gland to respond. Cell body surrounded by dendrites.
sensory neurons
Carry stimuli from the outside world, through the PNS back to the CNS Touch sensation from your hand to the brain. A neuron that picks up stimuli from the internal or external environment and converts each stimulus into a nerve impulse. Cell body to the side of the axon.
interneurons
Carry information between motor and sensory Neurons Reflexes: Touching something hot Skip the brain
action potential
what is the excretory system responsible for?
responsible for eliminating waste from the body fluids of an organism in order to maintain homeostasis.
osmoregulation
the maintenance of a constant solute and water balance
freshwater fish excretion
-In freshwater and marine habitats, animals like fish can release ammonia directly into the environment. -This is because it can be quickly diluted. -Despite their environment, marine mammals use energy to convert ammonia to urea
Terrestrial animals excretion
Terrestrial animals use energy to convert ammonia to urea or uric acid, which is less toxic. Which molecule is produced depends on habitat or evolutionary history.
birds and insect excretion
release uric acid which does not require water to be excreted. Having to carry less water for excretion means less energy is needed for flight.
osmolarity
refers to the concentration of solutes within an organism.
osmoregulatory
are organisms that expend energy to maintain a homeostatic internal solute concentration. (osmolarity is internally maintained)
osmoconformer
are organisms whose solute concentration is similar to that of the environment (maintain osmolarity according to surroundings)
osmoregulatory vs osmoconformers
three different types of adaptions for osmoregulation
Structural: physical features such as glands that secrete excess water Behavioural: changes in the way an organism behaves; animals congregating to share body heat Physiological: ability to regulate the cells or tissues within a system
transpiration
the process by which plants absorb water through the roots and then give off water vapour through the stomata in their leaves
External factors affecting transpiration
-Light: stomata open in light/ close in day. -Temperature: increase temp = increase in evaporation = increase transpiration -Humidity: increase humidity = decrease transpiration (lower diffusion gradient) -Wind: Increase wind = increase transpiration (high diffusion gradient) -Soil water: low soil water = less plant uptake = lower transpiration rate
stomata
-Stomata are tiny openings or pores in plant tissue that allow for gas exchange. -Specialized cells known as guard cells surround stomata and function to open and close stomatal pores.
vacuole
-It is surrounded by a membrane and functions to hold materials and wastes. -It also functions to maintain the proper pressure within the plant cells.
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