Infectious Diseases

Disease- Any cause that impairs the function of an individual in some way; that is, it harms the individual.

Infectious disease-they are caused by an agent (pathogens) that can be passed from one organism to another e.g., measles

Non-infectious disease-cannot be passed on. Not caused by pathogens e.g., diabetes

Causes of the symptoms of a disease-Tissue destruction, blocked transport systems, a blocked gut, starvation or malnutrition due to overuse of resources, production of toxic substances. Inappropriate response of the host's defence mechanisms e.g., allergic responses or an attack on the organism's own body, as with auto-immune diseases.

Pathogens-disease causing agents

Causes of non-infectious-genetics, poor nutrition/obesity, environmental factors (pollution, radiation, stress)

Example of a Chromosomal Disease-Down syndrome/ Sickle cell disease

Primary pathogens-ones that cause disease any time they are present

Opportunistic pathogens-only cause diseases when the hosts defenses have been weakened, for example by poor nutrition, stress or infection by other pathogens

Major groups of Pathogens-prions, viruses, bacteria, fungi, protists, and parasite

Progress of disease-exposure, incubation period, infectious state, symptoms appears, recovery

Prions-Smallest known pathogenic molecule. They do not contain genetic materials

Causes of prion diseases-genetics and an infection

Workings of Prions-stimulate the organisms normal prion proteins to misfold to form infectious prion form and eventually plaques in the brain

Disease caused by prions-Creutzfeldt-Jakob disease (CJD)

Creutzfeldt-Jakob disease (CJD)-symptoms include dementia and sudden muscle contraction that leads to death.

Viruses-tiny particles, smaller than bacteria and other pathogens, which must invade living cells in order to reproduce; when they invade, the cells are damaged or destroyed in the process releasing new particles to infect other cells

Examples of viruses-Tobacco mosaic virus, Influenza (causes 'flu'), HIV virus (causes AIDS), T4 bacteriophage

bacteriophages-viruses that infect bacteria

Reason for Ineffectiveness of antibiotics on virus-they are not alive

Viruses are mutational because-they modify their capacity of virulence (attack)

Antigenic drift-Minor change a virus makes to its antigens on its surface

Antigenic shift-changes in antigens that occur when viruses exchange genetic material with other strains

Bacteria-single-celled organisms that lack a nucleus; prokaryotes

Types of bacteria-cocci, bacilli, spirilla

Coccus-A spherical bacterium.

Bacillus-Rod shaped bacteria

Spirillum-A spiral-shaped bacterium.

Flagellae- One or more attached to cell wall
Provide motility for some species

Anaerobic bacteria-bacteria that do not require oxygen to survive

Aerobic bacteria-Bacteria that require oxygen for survival

Exotoxins-are highly toxic chemicals released by bacteria into their environment.

Endotoxins-are highly toxic chemicals produced inside the bacterial cell that are released when the bacteria ruptures.

Tetanus-is a disease caused by the bacteria Cilostridium tetani.

Typhoid Fever-is a bacterial disease, caused by Salmonella typhi. It is transmitted through the ingestion of food or drink contaminated by the faeces or urine of infected people

Three groups of fungi that causes disease in humans-moulds, true yeasts and fungi-like yeasts

Examples of Parasitic fungal diseases-ringworm, athletes foot

Protists-single-celled or simple multicellular eukaryotic organisms that generally do not fit in any other kingdom

Pathogenic Protists-Plasmodium (causes malaria) Trypanosoma (causes sleeping sickness)Giardia (causes diarrhoea) Sarcodines (causes amoebic dysentery)

Primary host-the host from which the adult parasite gets its nourishment and in which sexual reproduction occurs

Secondary host (intermediate host)-an organism that harbors the sexually immature parasite and is required by the parasite to undergo development and complete its life cycle. It often acts as a vector of the parasite to reach its definitive host

Pathogenic Oomycetes-causes the diseases Blight, Downy mildew

Parasites-Involves the living together of two or more organisms where one benefits whilst the other is harmed.

Symbiont-The smaller participant in a symbiotic relationship, living in or on the host.

Host-an animal or plant that nourishes and supports a parasite

Vector-an organism that transfers a parasite from one host to another.

Tapeworm-Parasitic flatworm

Endoparasites-Parasites that live within the body of their host.

Ectoparasites-Parasites that feed on external surface of host.

Example of Pathogenic Nematodes- Trischinella spiralis

Trichinosis- disease caused by eating raw or undercooked meat, usually pork, infected with Trichinella larvae

Wuchereria bancrofti- causes elephantiasis

Ectothermic Animals- generally unable to increase their body temperature by internal heat production - poikilothermic

Endothermic Animals- are animals which maintain a higher body temperature independent of the temperature of their environment, by internal heat production - homeothermic.

Heterothermic Animals-are ectotherms in essence but they can somewhat control their temperature like endotherms.

Example of ectothermic homeotherm-Marine fishes that inhabit water with stable temperatures.

Example of Ectotherms-reptiles

Example of Endotherms-mammals and birds

Kleptothermy-Where animals share or even steal each others body warmth.

Torpor-extreme mental and physical sluggishness as during hibernation

Brumation- hibernation, like state that cold-blooded animals utilize during very cold weather

Aestivation- the shutting down of metabolic processes during the summer in response to hot or dry conditions

Insulation in animals- Endotherms use fur, feathers and fat layers for insulation to reduce heat exchange with the environment.

Vasodilation- A widening of the diameter of a blood vessel.

Vasoconstriction- the constriction of blood vessels, which increases blood pressure.

Countercurrent exchange-the exchange of a substance or heat between two fluids flowing in opposite directions

Countercurrent flow- the opposite movement of water against the flow of blood in the fish's gills

Hypothalamus-Heat loss centre in the brain

Thermoregulation-the maintenance of body temperature within a range that enables cells to function efficiently.

Mammal Regulatory Mechanisms in cold conditions-Vasoconstriction, increased metabolic rate, shivering, hair raised

Mammal Regulatory Mechanisms in hot conditions- Vasodilation, decreased metabolic rate, sweating, hair lowered.

Osmoregulation- The control of water balance.

Osmoconformers- An organism that allows its internal salt concentration to change with the salinity of the surrounding water

Osmoregulators- organisms that maintain their internal water balance and solute concentration within narrow limits

Antidiuretic Hormone- hormone secreted by the posterior pituitary gland which aids in water reabsorption by the kidney

Low water levels in the body- more ADH secreted

Higher water levels in the body- less ADH secreted

Function of the kidneys- excretion and osmoregulation

Nephron- functional unit of the kidney

Loop of Henle- section of the nephron tubule that conserves water and minimizes the volume of urine

Collecting duct- A segment of the nephron that returns water form the filtrate to the bloodstream.

Structural features of plants to prevent water loss- leaf spines, few stomata, stomatal hairs, sunken stomata, rolled leaves, thick waxy cuticles, extensive roots

Stomata- Small openings on the underside of a leaf through which oxygen and carbon dioxide can move

Stomatal hairs- Hairs around stomata to prevent water loss

Isobilateral leaves- Leaves that are rolled to prevent water loss

Structural Adaptation- a physical feature of an organism's body having a specific function that contributes to the survival of the organism

Example of structural adaptation- A hummingbird with a longer beak

CAM photosynthesis- is prevalent in desert plants that close their stomata during the day. An example of an adaptation that enables improved efficiency in water

Xerophytes- plants adapted to arid (dry) environments

Halophytes-plants that live in highly saline (salty) soil

Auxin- Indoleacetic acid (IAA), a natural plant hormone that has a variety of effects, including cell elongation, root formation, secondary growth, and fruit growth.

Gibberellins- A class of related plant hormones that stimulate growth in the stem and leaves, trigger the germination of seeds and breaking of bud dormancy, and stimulate fruit development.

Ethylene- plant hormone that stimulates fruits to ripen

Abscisic Acid- inhibits cell growth, helps close stomata

Mesophytes- plants that grow in moist habitats and well-aerated soil.

Hydrophytes-plants adapted to live in water.