connect to brain

sensory/motor systems of head/neck

sensory projections

body to spinal cord

motor

spinal cord to muscles

unresponsive

brief period after action potential fires

another action potential cannot be generated

regenerated along length of axon

usually only one direction

speed at which action potential is propagated along the length of the axon

larger is faster

action potential jumps from node to node

saltatory conduction

EPSP

postsynaptic membrane depolarization

pushes closer to threshold

summation at axon hillock of postsynaptic potentials from across the cell body

summation of postsynaptic potentials that reach the axon hillock at different times

closer in time means mroe complete summation

control ion channel

ligand-gated ino channels

complex arrangements of proteins

fast and brief

recognize synaptic NT but don't control ion channels directly

slow and longer lasting

NT binding causes molecular cascade

second messengers

synapse in which signal flows from postsynaptic neuron to presynaptic neuron

counter to norm

3 Na+ out for two K+ in

causes net build up of positive charged particles outside neuron

active trasnport--consumes energy

 Na/K pump established gradient

voltage gated Na+ channels open when threshold is reached

create local pos. charges triggering next to open

does not diminish with distance

once started, goes to completion

nodes of ranvier-voltage gated channels

sodium goes from one node to another through myelin covered areas

action potential reaches end of axon and calcium channels open

calcium enters causing molecular cascade

vesicles move to membrane and fuse

dump contents into synaptic cleft

ligand gated channels-NTs bind

PSP: passive propagation, graded, excitatory or inhibitory

Action Potential: active propagation, all or none, one type

bind to a different site than the NT and prevents NT from having its effect

activate receptor, but not as well as endogneous agonist

prevents more efficient molecules from binding

effective dose 50

drug that produces half maximum response

lethal dose 50

dose that produces death in half subjects

need more and more drug for same effect

given repeated amounts of drug in increasing doses

brain responds to changes

upregulation or downregulation

a given amount of drug produces larger effect than before

given large dose of drug and then smaller dose some time later

metabolites of drugs are active

side effects

enkephalins-endogenous peptides, relieves pain, addictive

endorphins

dynorphins-potent, quick