MOD 2 Flashcards
(48 cards)
A toxic event inolves 5 steps. What are they
- generation of a contaminant
- release of contaminant
-
movement of contaminant to a receptor
.4. exposure at a high temp enough contaminant level for a long enough amount of time - a response
contaminant
def
a polluting / poisonus substance that makes smth impure
to have a response , the dose needs to be
high enough
is it possible for orgs to be exposed to a toxicant obtained in diet, air, water or soil?
yes
the _____ dose or concentration of toxicant, the ____ time it takes for a response
the HIGHER the dose/concentration of the toxicant the LESS time it takes for a response
what are the 4 ways we can be exposed to toxicants?
- oral
- Injection
- Topical/surface
- Respiratory
exposure routes
in Oral,, how is toxicant given
administration of toxicant by mouth or diet
org is given a specific dose/amount of toxicant
exposure routes
units for dose in oral route is expressed as
weight of toxicant / weight of organism
1mg kg-1 = 1ppm
1ug Kg-1 = 1ppb
exposure routes
Injection route - explain
org injected w toxicant
- exposure to the dose can be done via intravenous, subcutaneous, intraperitoneal injection
exposure route
topical or surface - explain
toxicant/drug that is applied to the skin in an applicable dose
exposure route
respiratory - explain
2 forms of respiratory
Organism is exposed to a specific concentration of toxicant
1. exposure from air -> inhalation via lungs
2. exposure from water -> uptake via gills
units of exposure in respiratory is
expresses as weight of toxicant/volume of air or water
1mg L-1 = 1ppm
1ug L-1 = 1ppb
How Do We Measure Toxicity?
Use a bioassay
bioassay definition
biological test that measures the effect of a toxicant (harmful substance) on a living organism or group of organisms
point of bioassay
The idea is to observe biological responses — like death, growth inhibition, or behavioral changes , after exposure to a substance.
give an example of a bioassay
Lethality - how many orgs die at given dose
Helps determine:
- Whether a chemical is toxic.
- How toxic it is (e.g., compared to other chemicals).
- Threshold levels of exposure that cause harm or death.
orgs that are used in bioassays that r used for checking the water
rainbow trout
daphnia magna
hyalella azteca (and in sediment)
plants (and in air , soil, or water)
orgs used in bioassays in soil
earthworm
plants (air or water also)
3 important parts of bioassays
- test org
- exposure time - time to allow for the response to occur at the dose/concentration of toxicant
- dose/concentration of the toxicant - amount of toxicant to develop a response within a given period
2 types of toxicity response
- Lethal - response is death
- Sublethal - response under the level that directly causes death
- can be molecular, biochemical, individual, species, or community level
What type of toxicity response involves enzyme inhibition?
Biochemical-level sublethal toxicity.
What enzyme breaks down acetylcholine in a healthy neuron-to-neuron signal pathway?
Acetylcholinesterase (AChE)
What does acetylcholinesterase (AChE) do in the synapse?
It breaks down acetylcholine (ACh) to stop the nerve signal and prevent overstimulation
What happens when AChE is inhibited/prevented to act normal?
Acetylcholine accumulates in the synapse, leading to continuous stimulation of the postsynaptic cell
