cell bio 5c

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  1. in a cell with 30 million sodium ions, the movement of how many ions can set up a membrane potential of 100mV?
    6000 ions
  2. what is the voltage distribution across membrane based on?
    charge distribution
  3. what is a membrane potential?
    the electrical potential required to balance the flux of an ion through a selective channel driven by its concentration gradient
  4. which direction does sodium and potassium move?
    sodium moves in, potassium moves out for nerve impulses through sodium and potassium channels
  5. what is the basis of the membrane potential
    • ion channels control the membrane potential
    • membrane potential is determined by unequal distribution of charge on two sides of the membrne (capacitor-like)
    • b/c of potassium leak channels, resting membrane potentials are near the K+ equilibrium potential
  6. what are the common features of a neuron?
    • dendrites (receive signals)
    • cell bodies (synthetic center)
    • axons (relay signal and can be myelinated)
    • synapse (release new signal)
  7. what do you call a highly reliable synapse between a motor neuron and a skeletal muscle cell?
    neuromuscular junction: stimulates an action potential in the muscle plasma membrane
  8. what kind of axons are myelinated?
    long axons in PNS and white matter in brain
  9. what is in the cell body of a neuron?
    ER, golgi, make synaptical vesicles (neurotransmitters)
  10. what happens during depolarization?
    sodium channels open
  11. what happens in an action potential?
    voltage gated Na channels open, which changes membrane potential; K channels open based on electrochemical gradient (voltage gated) Na goes into cell, K goes out. K leaks
  12. what is the rising phase of action potential mean?
    • due to opening of voltage gated sodium channels
    • closed sodium channel=membrane polarized
    • open sodium channel (membrane depolarized)
    • channels close to inactivated state that is refractory to activation of 1msec
  13. what is the structure of voltage gated channels?
    • have six helices (S5 and S6 line pore)
    • charged S4 helix acts as a voltage sensor
    • nonhelical segments ling pore provide selectivity filter
  14. what protein acts as the ball on the ball on a chain model?
    Raw3-IP on the cytoplasmic side
  15. what is the declining phase of action potential mean?
    Na channel inactivation and opening of voltage gated K channels
  16. how is the threshold reached?
    volrage channel trigger some Na channels to open which make other Na channels open
  17. what happens during the action potential?
    • action potentials involve a coordinated series of channel openingsĀ 
    • small depolarizations trigger self-reinforcing openings of voltage gated sodium and potassium channels
    • peak of action potential approaches Na equilibrium potential
  18. how can tetrodoxtoxin kill you?
    • binds voltage gated sodium channels
    • first isolated from fish of the order tetraodontidae (fish with 4 strong teeth); has a high dissociation constant (binds really tightly to sodium channels, blocks sodium channels from working
  19. how can depolarizations be produced?
    • electrical stimulation
    • ions entering the cells in response to an excitatory neurotransmitter (Ache)
  20. why is partial depolarizations necessary?
    to open voltage gated channels; opening and closing of ion channels produces electrical signals that can be sent rapidly down
  21. describe propagation of an action potential
    • Ca is outside cell, rushes in when voltage changes, through gated channels, Ca release causes synaptic vesicles to fuse with membrane, releasing neurotransmitter into synaptic cleft, which binds to receptors
    • sodium channels leaks, propagates and stimulates voltage gated Na channels next to it to propagate signal
    • K channels activated, goes out of cell, convert ligand gated channel to potential change, initiate new action potential on other side
  22. what is a synapse?
    connection between domain signaling nerve to responding nerve cell
  23. how do you get rid of extra neurotransmitters?
    • enzyme that degrades it
    • endocytosized
    • can be reused
  24. what does Na entry do to membrane potential? what is the purpose of inactivation?
    Na entry depolarizes adjacent membrane, but inactivation prevents action potential from spreading in reverse?
  25. how do we know that action potential is unidirectional?
    put in electrodes, shows the shift of electrical signal
  26. what are the tasks of the nerve cells?
    receive, conduct, and transmit signal through action potential without weakening; ensure that signal is reamplified
  27. what opens in response to depolarization?
    Na channels that further depolarize
  28. what triggers the depolarization of membrane?
    electrical impulse
  29. what makes up the refractory component?
    6 pass transmembrane protein, domain of channel that will block channel
  30. what can make signals conducted more rapidly?
    in wider and myelinated axons
  31. what axons have the most rapid signal transductions?
    proprioception, touch, pan and temperature
  32. what are nodes of ranvier?
    spaces between glial cells, uninsulated segments of axonal membrane located at 1mm intervals
  33. which cells are usually myelinated?
    either inside brain glial cells or outside brain peripheral nervous system (schwann cells)
  34. what kind of conduction results as a result of myelination?
    saltatory conduction
  35. what is the insulator of myelin called?
    myelin sheath
  36. what does the declining phase of action potential involve?
    inactivation of Na channels and continued entry of K ions through voltage gated K channels
  37. what initiates an action potential?
    binding of neurotransmitter to ligand gated channels in postsynaptic membrane initiates
  38. what causes action potential to arise?
    if the membrane potential at the axon hillock reaches threshold
  39. how does the synaptic stimulation change the membrane potential?
  40. what kind of synapses are excitatory and inhibitory?
    • ligand gated cation channels-excitatory
    • ligand gated Cl-channels -inhibitory
  41. how does cocaine affect the transmission of action potential?
    targets dopamine transporter (prevent dopamine from being transported back to signaling neuron, keep sending signal in the synaptic cleft
  42. how does antidepressants create affect action potential?
    target norepinphrine or serotonin uptake (block the reuptake)
  43. how many synapses are in the CNS?
  44. what are cajal bodies?
    mRNA processing maturation of snRNP particles
  45. what structures are found in the nucleus?
    cajal bodies, PML bodies, speckles
  46. what are speckles in the nucleus
    clusters of interchromatin granules, involved in RNA processing, not transcription sites
  47. what makes proteins function in the nucleus?
    transcription factors
  48. how can biochemists study the nucleus?
    grounding cells up and doing differential centrifugation, in vitro look at function--no organelles found in nucleus
  49. how do geneticists study the nucleus?
    mutagenesis in yeasts, look for secretion mutants in ER, Golgi pathway; identify proteins in the secretory pathway by doing mutagenesis
  50. how do we see where components of nucleus lie?
    use antibodies that are made to differnt components of nucleus and see that idff component within nucleus are localized differently
  51. what is the function of the nucleolus?
    genes that encode ribosomes are concentrated there; these genes are most likely duplicated; different copies of ribosomal genes whose job is to make ribosomal RNA
  52. what is the major structure of nucleolus?
    1-5 per nucleus; transcriptionally active rRNA gene clusters; nearly 700 proteins in involved in rRNA synthesis
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cell bio 5c
2013-02-03 15:44:46
cell bio

cell bio
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