Monday, Feb 27

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Monday, Feb 27
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D. At any point in time, both inhibitory and
excitatory messages exist as output of binding at
different receptors coupled to different ion
channels (or as result of changes via
metabotropic receptor binding). Cell body sums
the changes in voltage across the membrane to
decide if it will fire. 1. spatial summation
- sums across all of the postsynaptic
potentials triggered by messages coming into the
neuron 2. temporal summation - sums at a
particular point in time Result of summation
1. The membrane changes enough to move to
firing threshold of -55 mV and the cell fires
2. The membrane does not change enough - no
firing
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VI. Action potential - the threshold controlled
change in voltage that occurs as a neuron takes
action to send a message gates open and
positively charged sodium ions rush in Threshold
is -55 millivolts Positive ions rush in
Voltage spikes to 50 millivolts.
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Directionality of firing of the Action Potential
- always travels from start of axon (axon
hillock) down to the axon terminals.
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• Action potentials
• are all-or-none events (fire like a gun)
  crossing the voltage threshold for firing
  pulling the trigger
• have same electrical strength (like bullet from
  same gun) and remain at that strength as they
  travel down the axon
• reach the axon terminal and cause changes in
  area that result in the release of
  neurotransmitter substances
• many nerve impulses are conducted down
  myelinated axons travel more quickly

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E. Fate of chemical messages 1. Neural messages
are very short-lived 2. Neurotransmitters are
broken down or removed from synaptic space
(reuptaken) almost as soon as they are
released.
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F. What happens to neuron after an action
potential? Tries to return to resting potential.
Brief period of inability to fire (1) longer
period of reduced ability to fire (2). 1.
Absolute Refractory Period short period after
which an action potential occurs during which the
neuron is insensitive to inputs 2. Relative
Refractory Period period of reduced sensitivity
during which only strong stimuli can elicit an
action potential Maximum response rate for
certain neurons 1200 action potentials/second
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• I. How drugs work
• alter synthesis of neurotransmitter (nt)
• alter transport of nt to axon terminal
• alter storage of nt
• alter release of nt
• mimic neurotransmitter and activate or block the
  receptor
• alter breakdown or reuptake of nt

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• II. Major neurotransmitters, related diseases and
  drugs
• A. GABA
• major inhibitory neurotransmitter - keeps
  cortical excitation under control helps
  relaxation of mind and body
• found in basal ganglia, brainstem, and
  throughout cortex

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• GABA Relevant illnesses
• epilepsy - uncontrolled neural activity that
  causes seizures
• anxiety - nervousness agitation
• Relevant drugs
• Alcohol self-medication of anxiety
• Valium Librium Xanax - antianxiety drugs
• Date rape drugs
• Anticonvulsants - treat seizure disorders due to
  uncontrolled excitation of neurons

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Dose-Response Relationship for the Acute
Behavioral Effects Blood alcohol level weight
of alcohol in 100 ml of blood Estimates for a 150
lb person drinking on an empty stomach (rate not
given) 0.04 beginning to feel the effects
(overly friendly mild euphoria mild
effects on motor coordination 0.08 Legally
intoxicated 0.25 a staggering drunk 0.35
passed out at level of surgical anesthesia 0.4 -
0.5 lethal level for non-regular
drinker Therapeutic Index 0.5/0.05 10 Not a
good margin of safety.
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• B. Endocannabinoids
• endogenous substances similar to active
  chemicals in marijuana (Cannabis)
• found in cortex, basal ganglia, cerebellum
• roles in recovery from stress
• Relax Eat Sleep Forget Protect

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• B. Endocannabinoids
• Relevant diseases ??????
• Relevant drugs
• Marijuana - drug of use/abuse and drug with
  medical value
• Marinol - prescription THC used as antiemetic
  for cancer and AIDs patients

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C. Glutamate - excitatory actions throughout
cortex, basal ganglia - arousal attention -
important in learning and memory - mediates
excitotoxicity that can cause cell death
(following injury disease) - involved in some
aspects of repair
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Glutamate Relevant illnesses Epilepsy Consequen
ces of head trauma Schizophrenia Relevant
drugs For Epilepsy mostly under
development For Schizophrenia - under
development For generalized head trauma - under
development
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• D. Norepinephrine
• excitatory neurotransmitter
• made in brainstem and sent throughout brain
• important role in arousal
• in sympathetic nervous system - stimulates heart
  and lungs

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• Relevant illnesses
• Depression - not enough NE in some cases
• Mania - too much NE in some cases
• Relevant drugs
• many antidepressants (especially older ones)
• Lithium - used to treat mania
• stimulants - amphetamine cocaine
• Stimulate release and block reuptake of
  norepinephrine (also dopamine)

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E. Dopamine - 3 main tracts/roles 1.
Hypothalamus to pituitary - important in hormonal
control 2. Midbrain to basal ganglia -
important in control of movement 3. Midbrain to
limbic system and frontal cortex - pleasure
reward emotion attention activity thought
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• Dopamine
• Relevant illnesses
• Substance abuse disorders - reward center also
  an addiction center
• Parkinsons disease - movement related disorder
  - not enough DA
• Attention deficit/hyperactivity disorders - not
  enough in prefrontal brain in some cases
• Schizophrenia - a mental disorder involving
  disturbances in thought overactive Dopamine
  system in some cases

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• Relevant drugs
• L-dopa - used to treat Parkinsons
• Amphetamine and cocaine - stimulant drugs
  (possibly any addictive drug)
  Methamphetamine - speed meth chalk crank
• Inhaled form - ice crystal glass
• Cocaine - coke blow toot snow
• Inhaled form - crack base rock
• Ritalin and Amphetamine - used to treat
  attention deficit disorders
• Thorazine, Haldol, Clozapine, Risperdal - drugs
  used to treat schizophrenia - reduce DA activity