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TPR Bio passage in science workbook


Full Member
5+ Year Member
Jul 25, 2009
  1. Pre-Medical
    Bio passage 37, page 572, #4

    4.) which of the following is NOT generally a characteristic of axons

    a. presence of protein-synthessizing machinary
    b.abundance of microtubules and actin filaments
    c. presence of ion channels in the plasma membrance
    d. ability to transmit action potentials in one direction only

    the answer is A, but i put down B.

    Isn't the mylein sheath (which is composed of protein) produced by Schwann cells/Oligodendrocytes on axons?


    Full Member
    Feb 17, 2011
    In your bedroom
    1. Pre-Medical
      Well I thought it was A because axons tend to recycle the proteins used during synaptic transmission, and thus they would have less protein synthesizing structures.

      Not all axons are myelinated and myelin sheaths are composed of cells/parts of cells that are flattened out and rolled over the axon itself. They don't really relate to microtubules. As for the axon itself, it has a lot of microtubules and actin filaments to maintain its shape and carry out axoplasmic transport.

      MT Headed

      snow, PBR, and bears
      Lifetime Donor
      10+ Year Member
      May 27, 2011
      teh Big Sky!
      1. Medical Student
        Axons, and especially the terminal portion of the axons, exist to dump vessicles of neurotransmitter into the synaptic cleft.

        Where did those membrane-bound vessicles of neurotransmitter (protein) get manufactured? In the Rough ER. In the neuron's cell body. Not in the axon portion. A is incorrect.

        How did those membrane-bound vessicles get there? They were transported from the cell body down the axon to the terminal portion of the axon. They were walked down the cytoskeleton. That runs down the axon. B is correct.
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