Chapter 8 (exam 3) Flashcards
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
- depolarization
- 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
Saxitoxin
- 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
Batrachotoxin
- 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
Eutrophication
- 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
Organophosphates
- 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
