Download The Nervous System

The Nervous System-Part II
Neurotransmitters
Action Potentials Target
Neurotransmitter Release
Neurotransmitters
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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