biology final

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biology final
2010-05-01 16:22:14

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  1. neurons
    specialized cells of the nervous system that receive, encode and transmit information
  2. transduced
    conversion of information from sensory cells into electrical signals
  3. afferent neurons
    carry information into the system (to CNS)
  4. sensory neurons
    convert input into action potentials
  5. efferent neurons
    carry commands to effectors, like muscle cells (away from CNS)
  6. interneurons
    store information and help with communication between neurons in the system
  7. nerve net
    a simple network of neurons that does little more than provide direct lines of communication
  8. ganglia
    clusters of neurons
  9. brain
    one pair of ganglia that is larger and more central
  10. nerve impulses/action potentials
    electrical signals generated by neurons used to conduct signals from one site down the axon to a synapse with another cell
  11. axon terminal
    the fine nerve endings at the tip of each nerve
  12. Schwann cells
    type of glial cells that wrap around the axons of neurons in the peripheral nervous system providing electrical insulation (myelin)
  13. Oligodendrocytes
    similar funcions as Schwann cells
  14. Astrocytes
    glial cells which contribute to the blood brain barrier, permeable to fat-soluble molecules (like EtOH) but not to most polar solutes
  15. neural networks
    must contain at least afferent neuron to efferent neuron to effector
  16. membrane potential
    voltage across a membrane
  17. resting potential
    when the cell is at rest the interior of an electrically excitable cell is negative relative to the exterior with a potential (V) of ~-50 to -80mV
  18. action potential
    reversal of the resting potential is periodically observed. These APs carry information in the nervous system
  19. Which ion is primarily responsible for resting potential
  20. Nernst Equation
    the equation used to measure a single potential (V) across an electrical gradient
  21. Goldman-Field equation
    Takes into account multiple ion concentrations when calculating the potential difference across a membrane
  22. Where are Na+ Cl- and K+ hi?
    • Na+ and Cl- are high in the extracellular fluid
    • K+ is high in the cytoplasm
  23. How do electrical charges move across cell membranes?
    Through charged ions, minaly through channels (mainly K, Na, Cl, Ca)
  24. threshold potential
    the specific voltage at which voltage-gated ion channels are opened
  25. How does depolarization occur
    • A few Na+ channels initially open allowsing some inward Na+ flux (Na+ current)
    • If threshold is reached, many V-gates Na+ channels quickly change conformation and ope, permitting a large Na+ current (inward) which depolarized the cell
    • *Note that these Na+ channels are "double gated"
  26. How does repolariztion occur?
    At threshold, V-gated K+ channels slowly change conformation and open, permitting outward K+ current, which repolarized the cell
  27. refractory period
    • the amount of time it takes for a neuron to rearm itself
    • sets the upper limit on the AP frequency
  28. "All or None"
    sub-threshold stimuli do not produce an action potential, and the small depolariztion is not propagted. Once threshold is reached, AP is made
  29. Two ways to increase speed of conduction
    • incrase the diamter of the axon (invertebrates)
    • myelination of the axons(veterbrates)
  30. nodes of Ranvier
    • gaps in myelin that allow for electric signals to be conducted more quickly using saltaory conduction
    • ion channels are clustered at these
  31. Multiple schlerosis
    results from dmage to myelin in CNS
  32. synaptic cleft
    the narrow space between the pre-and the post-synaptic cells
  33. What determines the amount of neurotransmitter relased
    • the ammount of Ca++ enter the presynaptic cell
    • (Recall the Ca++ enters the cell at the synaptic cleft, NOT Na+)
  34. How can neurotransmitter actions be terminated
    • Enzymes may destroy the neurotransmitter
    • Neurotransmitter may idffuse away from synaptic cleft
    • Neurotransmitter may be taken back via active transport into the pre-synaptic cell for repackaging
  35. Fast (ionotropic) chemcial sunapses
    Post-synaptic NT receptor also functions as a ligand-gated channel. The nicotinic acetylcholine receptor is an ionotropic recept
  36. Slow (metabotropic) Chemical synapses
    Receptor (often G-protein coupled) stimulated a second messenger cascase which then affects ligand-gated channels
  37. If speed is so important in the nervous system, why have slow type synapses?
    Improved integration, longer lasting
  38. What are the two types of receptors for acetylcholine and what is the difference between them?
    • Nicotinic receptors - fast, tend to be excitatory in the CNS
    • muscarinic receptors - slow, tend to be inhibitory in the CNS
  39. GABA (gamma-amino butyric acid)/glycine
    • The most common inhibitory neurotransimitters in vertebrates
    • The postsynaptic cells at these inhibitory synapses have ligand gated chloride channels
    • when the channels are activated, they can hyperpolarize the postsynaptic membrane and make the postsynaptic cell less likely to fire an cation potential
  40. Excitatory Postsynaptic potential (EPSP)
    depolarize the postsynaptic membrane
  41. inhibitory postsynaptic potential (IPSP)
    hyperpolarize the postsynaptic membrane
  42. Summation
    It takes several EPSP to generate an AP
  43. Electrical synapses
    • Little delay at synapse
    • Current passes between the electrically souples cells, in either direction, usually, with litlte, if any, attenation of current
    • Not common because they cannot be inhibitted, little integration, not modifiable, large area required, do not allow for temporal summation
  44. Gap junctions
    coupling of neurons electrically using membrane proteins called connexons
  45. Neural plasticity
    the modification of neural fucntion resulting from experience
  46. synaptic plasticity
    • can result from changes in the synaptic efficieny, up- or down-regulation of the ability ot elicit an EPSP (and therefore APs) resulting from history of the synapse
    • Can be a form of learning