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2010-09-23 20:52:41
Nuerotransmitters NT

Neurotransmitters (NT) Notes
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  1. Criteria to be a NT
    • Synthesized and stored in presynaptic neuron
    • Released by presynaptic neuron
    • Produces a response in postsynaptic cell:
    • •Response is same when experimentally applied as that which occurs naturally upon release from presynaptic neuron
    • Locally degraded
  2. Cholinergic:
    Cells that produce and release Ach
  3. Noradrenergic:
    Neurons that use Norepinephrine (NE)
  4. Glutamatergic:
    synapses that use glutamate
  5. GABAergic:
    Synapses that use GABA
  6. Peptidergic:
    Synapses that uses peptides
  7. True or False: Action Potentials lessen as they move down the axon.
  8. True or false: A greater stimulus results in a greater size of an action potential?
  9. True or false: Greater currents do not result in greater size of action potentials?
  10. ______ _______: rapid depolarization of membrane to approximately 40 mV.
    Rising Phase
  11. __________: when the inside of the cell has a positive charge.
  12. ________ _______: rapid depolarization to a negative status in the neuron.
    Falling phase
  13. __________: last part of the falling phase when the membrane potential is greater than -65 mV.
  14. Fibers have gated Na channels that open when stimulated by ________, which triggers the channel opening.
  15. Na enters the cell, which _________ the cell membrane. If the __________ is great enough then the critical level (or ________) is met and an AP is achieved.
    • depolarizes
    • depolarization
    • threshhold
  16. Action potentials are "_______-or__________". Depolarization must reach threshold to generate AP.
    All or nothing
  17. _______ _______: how frequently neuron fires and action potentials are produced.
    firing frequency
  18. ______ _______ _______: can't generate another AP for approximately 1msec.
    Absolute Refractory Period
  19. _________ ________ _________: several seconds at the end of ARP when it is difficult to initiate another AP.
    Relative Refractory Period
  20. _______ _______: Na channels close quickly and K remain open so permeability switches back to K.
    Falling phase
  21. ___________ & ___________: developed voltag clamp in 1950. The clamp was used to measure membrane potential at any value they chose. They could measure conductance based on currents flowing across a membrane.
    Hodgkin and Huxley
  22. Na ion is stripped of most but not all of its _____. What is left helps Na pass selectivity filter.
  23. _____ _______: This individual attached the tip of an electrode to a small patch of the cell membrane, and removed a small section to measure ion currents. Thus, we can look at a single channel and study the properties of the Na channel.
    Edwin Neher
  24. Properties of Voltage-gated Na channels:
    -Open with (little, much) delay.
    -Stay open (1, 10, 100 msec), then close.
    -Can't open again until Vm returns to (positive, negative)value.
    -Changes from -80 to -65mV has (large, small) effect
    -Changes from -65 to -40mV (opens, closes) Na channels.
    -Need (1,100,1000's) of gated channels in a square micrometer to get an AP; Not due to 1 or a couple gated Na channels.
    • -little
    • -1
    • -negative
    • -small
    • -opens
    • -1000's
  25. __________: generalized epilepsy with febrile seizures. Causes increased temperature resulting in seizures due to slowing of Na channel inactivation, which prolongs the AP's.
  26. __________: in puffer fish. Clogs Na pore which blocks the formation of AP's. The result is fatal due to paralysis of diaphragm due to nerve and muscle block. If serverd correctly, numbness should be felt around the mouth.
    Tetrodotoxin (TTX)
  27. __________: found in clams, muscles, shellfish that feed on certain dinoflaggelates. It blocks sodium channels and if fatal due to paralysis of diaphragm due to muscle and nerve block.
  28. _________: found on the skin of Colomiban frogs. Causes sodium channels to open at more negatve values and stay open longer. This scrambles AP codes/information being sent.
  29. _______: bind to voltage gated Na channels preventing Na from docking and thus prevents AP's. Affects ______ axons more than _____ axons.
    • Anesthetics
    • smaller, larger
  30. __________: where enough voltage gated Na channels open so permeability of Na is greater than the permeability of K.
  31. _________ ________: Negative potential on Na ion; is driving force on Na ions so Na ions rush into cell casuing depolarization.
    Rising Phase
  32. ________: Na channels close at positive membrane voltage but permeability continues to favor Na so membrane voltage goes toward that of Na.
  33. _______ _______: Sodium channels become inactive and K channels open and K rushies out of the cell so that the membrane voltage moves toward negative.
    Falling Phase
  34. _________: Occurs when voltage gated K channels are open and normal membrane permeability moves toward that of potassium. The membrane is hyperpolarized until voltage gated K cahnnels close and the Na-K pump reestablishes resting potential.
  35. ________ _______ ___________: Sodium channels are inactive once cell has been strongly depolarized. No action potential can be generated until membrane voltage goes sufficienty negative and the Na channels deinactivate.
    Absolute Refractory Period
  36. ________ ________ _______: Membrane potential stays hyperpolarized until Voltage gated K channels close, thus even more current would be needed to bring membrane voltage to threshold for AP.
    Relative Refractory Period
  37. Na-K pump is always working to restore membrane potential to _____ mV.
  38. AP _______: influx of positive charges depolarizes part of the membrane just beyond the AP until it reaches threshold and causes its own AP.It ultimately reaches down the length of the axon and initiates synaptice transmission.
  39. True or false: AP conduction can go back on itself.
    False: goes in one direction.
  40. AP conduction can be inititiated and move in either direction _________ _________.
    Antidronic conduction
  41. AP conduction usually only goes one direction: __________ ___________>
    arthodronic conduction
  42. True or false: During AP conduction, the speed of the AP depends on how far ahead the depolarization is.
  43. Determine if the conduction will be FASTER OR SLOWER: narrow axon with many open membrane pores, most of the current will flow out across the membrane.
  44. FASTER or SLOWER AP conduction: wide axons and few pores.
  45. Increased or decreased diameter of the axon results in increased action potential conduction velocity.
  46. 3 factors affecting excitability of an axon:
    axon size, number of voltage gated channels, smaller axons require greater depolarization to reach AP threshold (more sensitive to anesthetics)
  47. __________: layers of glial cells (schwann, oligodendrocytes). Facilitate AP movement down axon and increases conduction velocity.
  48. ______ of ________: breakes where ions cross membrane to generate AP's.
    Nodes of Ranvier
  49. In sensory nerve cells, the sensory nerve endings are the _____-_______ zone.
    spike-initiation zone
  50. _______ _______: demyelinating disease resulting in weakness, impaired coordination, vision and speech impairments. Cause sensory and motor problems.
    Multiple Sclerosis
  51. ________-_______ Syndrome: attacks myelin of PNS which slows conduction velocity. (saltatory conduction is disrupted).
    Guillain-Barre syndrome
  52. _______: NT throughout CNS and at all neuromuscular junctions
  53. ________: amino acid that is precursor for dopamine, norepinephrine, and epinephrine.
  54. Tyrosine hydroxylase (TH) converts tyrosine to ______.
  55. Dopa is converted to ________ by enzyme dopa decarboxylase.
  56. In _______ disease, dopaminergic neurons in brain slowly degenerate which decreases available dopamine.
  57. B-hydoxylase converts dopamine to ______>
  58. Phentoalamine N-methyltransferase converts NE to _________>
  59. 2 processes possible after NT's have heen through uptake:
    • 1. loaded into vesicle for reuse
    • 2. Destroyed by MAO
  60. ______ and _______ block catecholamine uptake which prolongs NT action in cleft.
    cocaine and amphetamine
  61. _________: derived from amino acid tryptophan. Important regulators of sleep, mood, and emotions.
    Serotoninergic neurons
  62. Tryptophan is converted int 5-HTP by ________ ________.
    tryptophan hydroxylase
  63. 5-HTP is converted to _____ by 5-HTP decarboxylase.
    5 HTP
  64. Once serotoninergic neurons have been released they can either be _______ into vesicles or _______ by MAO's.
  65. GAD makes _____ from Glutamate. _____ is major source of synaptic inhibition in the NS.
  66. The major ______ NT in the brain is converted to the major _____ NT in the brain.
  67. ______: key in cellular metabolism. Concentrated in vesicles in many PNS and CNS synapses; released in Ca spiks.
  68. __________: small lipids that can be released from postsynaptic neuron and act on presynaptic terminals resulting in retrograde signaling thus they are retrograde messengers.
  69. _____: most studied structure at NMJ. 5 protein subunits,4 different polypeptide as subunits, and excitatory at NMJ.
    nicotinic Ach receptor
  70. Glutamate Gated _______: permeable to Na and K, but not Ca. Activation allows Na into cells and depolarization. Excitatory at CNS synapse.
  71. Glutamate-gated _____: excitatory by admitting Na but are permeable to Ca. Voltage dependent membrane voltage blocked by Mg but when stimulated moves Mg and Ca enters and K moves out.
  72. True or False: Glutamate-gated AMPA and NMDA often co-exist.
  73. _________: Glutamate at high levels kills neurons by overexciting them.
  74. GABA mediates most CNS _______.
    Glycine mediates at _______.
    Too much inhibition results in _____ _____ _____.
    Too little inhibition results in ______>
    • inhibition
    • rest
    • loss of consciousness
    • seizures
  75. Benzodiazapines (increase, decrease) number of channel openings.
  76. Barbiturates (increase, decrease) duration of channel opening.