The Nervous System

electrical signals

sent via changes in ion concentrations within a neuron

local potential (in dendrites and soma) and action potentials (down axon)

chemical signals

sent between neurons via neurotransmitters

inhibitory post synaptic potential (IPSP)

hyperpolarization from K+ or Cl- channels opening

excitatory post synaptic potential (EPSP)

depolarization from Na+ channels opening

action potential

caused by a sudden rush of Na+ ions into the axon, the membrane potential reverses and the inside of the cell becomes positive

synapse

site of action for most psychoactive drugs

axodendritic and axosomatic

synapse type

open ion channels → EPSPs, IPSPs

signaling cascade → protein expression or function

axoaxonic

synapse type

presynaptic facilitation or inhibition

open ion channels → affect NT release

signaling cascade → protein function

classical neurotransmitters

amino acids, monoamines, acetylcholine, purines

synthesized from dietary precursors

made by enzymes in the axon terminals and then transported into small vesicles

non-classical neurotransmitter

neuropeptides, lipids, gases

synthesized in the cell body and then packaged into large vesicles

protein synthesis dependent

vesicular transporters

move transmitters into vesicles through active transport

make use of an electrochemical gradient across the vesicle membrane

SNARE proteins

mediate vesicle fusion with the cell membrane

botulinum toxin

cleaves SNARE proteins involved in vesicle fusion

at neuromuscular junction, this leads to paralysis

endocytosis

vesicle membrane is retrieved from the terminal membrane

vesicle recycling

new (empty) vesicles can be refilled with NT rapidly

autoreceptors

receptors on the same neuron releasing the NT and they provide feedback (usually negative feedback)

modulate the activity of the cell depending on location

terminal

autoreceptor type that modulates NT release

somatodendritic

autoreceptor type that modulates NT synthesis or firing

plasma membrane transporters

located in the nerve terminal and remove NT from cleft

retrograde transmission

signaling from post synaptic to pre synaptic cell

gases and lipids pass through membranes and signal to the presynaptic terminal (no vesicles)

ionotropic receptors

ligand gated ion channels

comprised of 4-5 subunits (separately encoded proteins) bound together to form an ion channel

fast, rapidly reversible

metabotropic receptors

G protein coupled receptors that use second messengers to open an ion channel or trigger cellular changes

comprised of 1 subunit with 7 transmembrane domains coupled to intracellular G protein

slower, longer lasting

protein kinases

modify other proteins by adding phosphate groups to them (phosphorylation)

target ion channels, receptors, cytoskeletal proteins, transcription factors, all of which regulate neuronal excitability and synaptic plasticity

protein phosphatases

dephosphorylate proteins

transcription factors

family of proteins that bind to regulatory sites on genes to promote or suppress transcription of DNA to mRNA

type of immediate early gene - first genes to be transcribed into mRNA and then translated into protein quickly after there is neuronal activation

c-Fos

transcription factor and an IEG

used as a marker of neuronal activation

can be used to visualize neuronal activity after administration of a drug, like cocaine

epigenetic effects

can potentially change gene expression for a lifetime and such changes may even be passed on to future generations