The Nervous System-Part II Neurotransmitters

Action Potentials Target Neurotransmitter Release

Neurotransmitters Found in CNS and PNS Over 100 in the body Can be excitatory or inhibitory Once released neurotransmitters will be decomposed by enzymes or up-taken by transporters in the pre-synaptic membrane Classified as: acetylcholine, monoamines, amino acids, neuropeptides and gases

Excitatory vs. Inhibitory Neurotransmitters Excitatory neurotransmitters Increase postsynaptic membrane permeability to Na+ Threshold is reached for message to be sent Inhibitory neurotransmitters Decrease permeability to Na+ Decreases chance nerve impulse will occur.

Acetylcholine (ACh) First neurotransmitter discovered (1921) Excitatory in the CNS and PNS Skeletal muscle neuromuscular junctions & synapses between the brain and spinal cord Message causes muscles to contract or continues impulses Nicotine inactivates ACH receptors and causes brain to create more receptors

Glutamate Found in the CNS, generally excitatory helps send messages in the brain Involved in learning and memory Alcohol inhibits glutamate receptor function Monosodium Glutamate (MSG) is a food additive that stimulates glutamate receptors in the taste buds!

Serotonin Found in the CNS, primarily inhibitory Responsible for sleep, mood and temperature regulation Antidepressants (Prozac, Zoloft, Paxil, etc) work by allowing serotonin to accumulate in the synapse, “SSRI’s” or Selective Serotonin Reuptake Inhibitors feel more content LSD mimics serotonin, and MDMA releases excess serotonin

Dopamine CNS and PNS, primarily excitatory AKA “the brain reward” Regulates emotions, moods and subconscious control of skeletal muscle Reward Pathway Cocaine interferes with the process by which dopamine is taken back up (leaves more in the synapse) Methamphetamine excess dopamine release

Dopamine - cont’d Dopamine also sends signals that help coordinate your skeletal muscle movements Parkinson’s Disease deficient dopamine production tremors

GABA CNS, generally inhibitory Found in the brain Prevents the receptor nerve from being overstimulated When it accumulates it has a sedative effect Valium, Xanax and Ativan work by allowing GABA to accumulate More GABA, more relaxed

Norepinephrine CNS and PNS, primarily excitatory Found in the brain, promotes feeling good, low levels linked to depression Alertness, regulation of moods In the PNS may excite or inhibit based on receptors

Endorphins Primarily inhibitory, cause release of substance P Flood the synaptic cleft during pain or stress Usually inhibit neurons from firing, causing an analgesic effect At lower levels can excite the next neuron Reduces pain and makes one feel good “Opiates” (heroin, codeine, morphine, oxycodone, hydrocodone, etc) bind to endorphin receptors and mimic endorphins

Anandamide Involved in working memory, regulation of feeding behavior, generation of motivation and pleasure Anandamide receptors are called cannabinoid receptors A lot of cannabinoid receptors in the hippocampus (short term memory), cerebellum (coordination) and basal ganglia (unconcious muscle movement) of brain THC (found in marijuana) mimics anandamides and binds to cannabinoid receptors How Marijuana Works in the Brain