science sem 1 exam
Topic 1 – Body At War
2.1 – Pathogens and Disease
Disease (infectious and non-infectious)
Disease: ⋄ Any change that impairs the function of an individual in some way
Infectious disease: They are contagious and can spread from one organism to another, Caused by a pathogen.
Non infectious diseases: Can’t be spread from one organism to another, Not caused by a pathogen.
Causes of infectious disease
Infectious diseases are caused by pathogens (cellular and non-cellular)
Pathogens (cellular and non-cellular)
Bacteria: living
» Not all Bacteria cause disease
» The are only a single cell
» Can be Rod (Bacillus), Spiral (Spirochaete) or Spherical (Coccus) shaped
» They can multiply very quickly (can divide every 20 min)
Protozoa: living
» Single celled
» Usually found in tropical and subtropical areas
» Only a few are parasitic
» Can produce a protective cyst around themselves in extreme conditions
Fungi: living
» Some Fungi are Unicellular (1 cell) while other are Multicellular (many cells)
» Not many diseases are caused by fungi
» Are usually opportunistic pathogens, require the person to be weakened by another illness first
» Can invade hair, skin and nails. Eg. Tinea
Parasites: living
» A Parasite is:
⋄ An organism that lives on or in another organism without contributing anything back to its "host"
» There are different types of Hosts:
⋄ Primary Host: Where the Parasite lives in it's adult stage.
⋄ Intermediate Host: Where the Parasite lives in it's Larval stage
» There are different types of Parasites:
⋄ Endoparasites: Live within the body
⋄ Ectoparasites: Live on the outside of the body
Prions: nonliving
» Non cellular
» Their name is comes from PRotein and infectION
» They are abnormally formed proteins
» They can convert normal proteins into new prions
» They are released when an infected cell bursts
» Prions cause Neurological (brain) diseases such as:
⋄ Kuru
Mad Cow (BSE)
Viruses: nonliving
» Non cellular
» Are just DNA or RNA within a protein coat
» Very small and can only be seen with very powerful electron microscopes
» Do not self-reproduce, feed, grow or move
» They replicate by infecting a cell and hijacking its replicating machinery and making the cell make lots more viruses.
Transmission of diseases (direct and indirect)
· Direct Transmission
o Happens through direct contact with the infected person or their body fluids.
o Diseases transmitted this way are also called contagious diseases.
· Indirect Transmission
Occurs through an intermediary agent
This includes
· Vectors like some insects,
· Contaminated objects and surfaces
· Airborne pathogens,
· Contaminated water,
· Droplet contact (like Sneezing and Coughing)
Disease outbreaks (plague, epidemic, and pandemic)
Plague: Contagious diseases that spread rapidly through a population and resulted in high death rates.
Epidemic: Occur when many people in a particular area have the disease in a relatively short time
Pandemic: Occur when a disease spreads rapidly worldwide
Malaria:
· Caused by the protozoa Plasmodium.
· Transmitted by the bite of an infected female Anopheles mosquito.
· Australia has the Anopheles mosquito, but none are infected.
· Globally it kills 1 million a year
· Can be passed from mother to unborn child
2.2 – Immune System
1st line of defence
First line defence-physical and chemical barriers
Stops pathogens from entry to the body.
2nd line of defence
Second line defence-phagocytes, inflammation
Also known as Inflammation and is a general response to damage/infection.
What happens:
Damage/infection occurs.
The body sends extra White Blood Cells called Phagocytes to the area.
This is done by increasing the blood flow to that area
The Phagocytes consume and destroy foreign material
This cleans up the area.
The damage that occurs and the extra blood that is sent to the area is responsible for the 5 signs of inflammation:
⋄ Pain
⋄ Heat
⋄ Redness
⋄ Swelling
⋄ Loss of Function
3rd line of defence
Third line defence- B lymphocytes and T lymphocytes
» Uses cells to fight off infection and remember different pathogens
» It's specific for a given pathogen and results in a memory of the pathogen
» Is run by white blood cells called lymphocytes
» Works by detecting antigens as ‘non-self’ and attacking the pathogen that they’re a part of.
ü Type of immunity (active vs passive, natural vs artificial)
This response from the 3rd line of defense creates immunity.
Immunity: Resistance to a particular disease-causing pathogen. It means that you won’t develop the disease.
Active vs Passive:
Active: The body actively produces antibodies
Passive: The body passively receives antibodies
Natural vs. Artificial
• Natural: Immunity occurs due to natural causes
• Artificial: Immunity occurs due to human intervention
ü Vaccinations (how do they work and booster shots)
Topic 2 – Keeping The Status Quo
3.1 – Detecting and Responding
ü External and Internal Environments
Our body can experience change from 2 places our internal and external environment
ü Receptors
All changes are detected by special cells called Receptors
ü Types of receptors
Chemoreceptors detect Chemicals
Photoreceptors detect Light
Mechanoreceptors detect Pressure
Thermoreceptors detect Temperature
Nociceptors detect Tissue Damage ( Pain)
ü The 5 basic senses
Sight
Hearing
Taste
Smell
Touch
ü Homeostasis
A state of balance among all the body systems needed for the body to survive and function correctly.
ü Stimulus Response model
Stimulus Response Model
Stimulus: Stimuli happens
Receptor: Stimuli detected by specific Receptors
Control Centre: Information about stimuli sent to Control Centre. Control Centre decides what to do.
Effector: Message about what to do sent to effectors
Response: Effectors respond to stimuli
3.2 – Nervous system
The Nervous System can be split into two main parts:
ü Central Nervous system
Brain and spinal cord
⋄ Control centre and major pathway for nerve impulses
ü Peripheral Nervous system
Sensory receptors and nerves
⋄ Inform the CNS of changing conditions
⋄ Transmit decisions made by CNS to effectors
ü Sensory Neurons
Carries signals from receptors TO the CNS
ü Interneurons
Carries signals WITHIN the CNS
ü Motor Neurons
Carries signals FROMthe CNSto effectors
ü Neuron Structure
Axon: Section of a neuron that signal travels along
Dendrites: Branch like structure that relays the signal towards the cell body
Synapse: Gap between axon of one neuron and dendrite of the next
Myelin: Fatty white substance that insulates the axon speeding up the message
ü The 5 senses and the nervous system
Sight-Photoreceptor
Hearing-Mechanoreceptor
Taste-Chemoreceptors
Smell- Chemoreceptors
Touch- Nocioreceptors, Mechanoreceptors, Thermoreceptors
ü Sending messages along nerves
Signals are transmitted along Neurons as electrical impulses.
⋄ The electrical impulse only travels in one direction along the neuron.
⋄ The impulse is created by moving ions in and out of neuron to create an electrical charge that then travels along the neuron.
ü Sending messages between nerves (neurotransmitters)
Neurotransmitters are used to transmit a signal across a Synapse.
⋄ Electrical impulse triggers the release of neurotransmitters.
⋄ Neurotransmitters are released into the synapse and diffuse across.
⋄ They're received by receptors on the next neuron and trigger an electrical impulse.
ü Reflexes
⋄ Involuntary responses that occur so quickly that we don't have time to think about them.
⋄ Occur through a reflex arc
⋄ Signal gets to the spinal cord, a response is generated and sent to the effector before the signal is fully processed by the brain.
ü Malfunctions in the nervous system (neurotoxins)
Neurotoxins are chemicals that can interfere with our nervous system interacting with or blocking neurotransmitters.
3.3 – Endocrine System
The Endocrine system is made up of a series of glands which release hormones responsible for controlling different bodily functions.
ü Endocrine glands
The major glands of the endocrine system include the:
⋄ Hypothalamus
⋄ Pituitary
⋄ Thyroid
⋄ Adrenal
⋄ Pancreas
⋄ Ovaries/Testes
ü Hormones
» Chemical messengers
» Produced by Endocrine glands
ü How hormones work
Released directly into the bloodstream
» Bind specifically to target receptor
» Specific for only particular target cells that have the correct target recepfor the hormone
ü Endocrine vs Nervous system
Both the Nervous system and Endocrine system send signals around body. However, they do this in very different ways.