Chapter 8 (exam 3) Flashcards Preview

Toxicology > Chapter 8 (exam 3) > Flashcards

Flashcards in Chapter 8 (exam 3) Deck (20):

Neuro Subdivisions


-CNS - brain and spinal cord

-Peripheral nervous system - carries motor and sensory info

--somatic - voluntary muscle movement

--autonomic - involuntary control of organs and endocrine glands


Neuro Anatomy

neurons - conduct info

--dendrite, soma, cytoplasm, myelin sheath, node of ranvier, schwann cells, axon terminal

-glial cells - suporting cells do not directly conduct info


Neuron Function

(-70mV) resting, influx of calcium, open sodium gated channels, depolarization to (+30mV), repolarization using sodium potassium pump

-many targets to prevent full cycle (inhbit na/k pump, voltage gated channels, k channels



Voltage gated sodium channels

-open when E increases

-flood into axon, sequentially open the channels


-repolarization using the Na/K ATPase pump (active transport)

--antiporter enzyme

--3 na out and 2 k in

--k channel is passive so k flows out (recycled)


Terminus of neuron

-vesicles carry the neurotransmitters (NT)

-NT - chemical signaling, stored in vesicles, lipid membrane

-lipid membrane of the vesicle merges witht the terminus membrane to release the NT

-Ca2+ ions through voltage gated calcium channels in the terminus following an action potential, divalent and bond to protein in vesicle membrane and to terminus membrane

-NT into synapse, diffusion gradient, post synaptic receptor


NT in Synapse

-move to post synaptic receptor via random diffusion

-geometry of the terminus and post synaptic cell favors contact

-reuptake the NT into the terminus, or degrade the NT

-tox target the terminus and synapse (prevent docking, bind to post syn receptor)

--antagonist - bind to hypostimulate

--agonist - bind to hyperstimulate (spasms)


Tetrodotoxin (TTX)

-produced by puffer fish, may also be used in sushi

-bind to voltage gated sodium channels

-hypostimulation - paralysis

-slow transport of sodium into the axon

-slow action potential (half)

-LD50 - 11-532 micro/kilo dependent on exposure, in mice

1-4mg in human fatal

(+) charge on TTX binds to sodium channel to prevent depolarization



-produced by dinoflagellates marine algae

-paralytic shellfish poisoning

-accumulate in shellfish due ot feeding mechanism, filtering water

-same mechanism as TTX

-lethal in humans as low as 0.5mg

-amino nitrogen protonated and have (+) charge pka = 8.24, 11.6



-poison dart frogs

-obtained by diet - captive frogs are not poisonous

-bind to voltage gated sodium channels

--liphilic and can act on either side of the membrane (unlike TTX and STX)

-more likely to bind to interior because harder to diffuse

-lethal dose (200micrograms)


domoic nad kainic acid

-produced by algae in harmful algal blooms

-resemble NT glutamate

--hyderstimulation, excitotoxicity

--excess calcium in the cell

--release ROS and RNS

--lipid peroxidation

--similar to methamphetamine

-nonpolar section may increase time on the receptor

-effect memory - cross clood brain barrier in CNS



-increase N and P

-increase algal growth

-more dead algal blooms

-decay via bacteria

-bacteria uses oxygen

-also, less solar penetration and less macrophytes which habitat larvae


Toxicants of Myelin

-lead and tin - damage mydlinating cells and decrease conduction velocity

-splits myelin and leave water fillef vacuoles and damage ion gradient control

-organo tin species

- tributyl tin more nonpolar, used to paint ships and decrease barnicles


Acetylcholinesterase (AcChase)

-remove NT AcCh from synapse, stops signal

-located on post synaptic membrane

-AcCh + R = AcChR

-decreases the conc in the synapse, equation shift left and the receptor releases the AcCh

-active site requires "catalytic triad"

--serine, histidine, aspartic acid

-overall mechanism stabalizes the O in serine in order to be deprotonated, histidine removes the H, O as a nucleophile for AcCh


AcChase mechanism

A image thumb


-chemical warfare agents and pesticides

-unlike ATP because it is organic

-aging of OP makes it permanently stable, stable to hydrolysis

-hyperstimulation - spasms, uncontrolled muscle contractions

SLUDGE - salivation, lacrimation (tears), urination, defecation, GI emesis (vomit)


Aging CWA

-if leavign group hydrolyzes off of an OP (similar to choline group in AcCh), the remaining residue will be permanently bound to AcChase

-OP does not bond to the receptor, but to the AcChase

A image thumb


-similar to OPs

-no aging

-pesticises, no CWA

-product is more stable than when AcCh binds to the AcChase

-stable to hydrolysis



-binds to AcCh receptor and blocks signal transmission


-greater affinity for the receptor than AcCh

-from plant

-alone results in hypostimulation, buys time and prevents hyperstimulation

-DOES NOT interact with the OP

-functional antagonist


Botulinum Toxin

-produced by clostridium botulinum

-anaerobe present in soils

-improperly canned food

-250 kD protein

-temperature stable and cooking does not degrade

-inhibits the release of vesicles contraining AcCh

--cleaves SNARE proteins that dock vesicle with the terminus membrane


Honey in Infants

-low gut acidity, Clostridium botulinum can grow

-human gut normally prevents growth

-inhibit release of vesicles containing NT (AcCh)

-cleave protein that dock vesicles with terminus

-LD50 on order fo ng/kg