Copyright ©Mark Nelson, 2002. All rights reserved.
Chapter 2: Cellular and Molecular Building Blocks
What you need to know
(exam questions will be a drawn from this subset of material)

What is ... (p. 17-18)
    the reticular theory?  
    the INCORRECT idea that the NS is a continuous meshwork of cytoplasm
    the neuron theory (or neuron doctrine )?
    the CORRECT idea that the NS is composed of discrete cellular elements (neurons)
    a syncytium?
    a cellular network having multiple nuclei and cytoplasmic continuity (e.g., heart muscle)

Who was Santiago Ramon y Cajal? (p. 18-19)
    famous Spanish neuroanatomist  (1854-1932); considered to be the "father of modern neuroscience"
    Was he a supporter of the reticular or the neuron theory?
     neuron theory
    When did he get the Nobel prize?  For what accomplishments?
    1906 Nobel prize for Physiology or Medicine; for elucidating the structural organization of the NS

Who was Camillo Golgi? (p. 18-19)
    famous Italian neuroanatomist (1843-1924); contemporary of Cajal; developed Golgi stain technique
    Was he a supporter of the reticular or the neuron theory?
    reticular theory
    When did he get the Nobel prize?  For what accomplishments?
    shared the 1906 Nobel prize with Cajal; for elucidating the structural organization of the NS
    What technique did he pioneer?
    Golgi staining technique for visualizing individual neurons based on silver impregnation

What's special about the Golgi staining technique? (p. 19-20)
    only stains about 5% of the cells; those that are stained are stained completely revealing detailed structure.
    because the staining was sparse indivual neurons could be visualized without background clutter.

What technique did Cajal use to obtain support for the neuron doctrine? (p. 19-20)
    the Golgi technique;
    somewhat ironic since Cajal used Golgi's technique to provide evidence against Golgi's view of NS organization (reticular theory)

Sketch a typical neuron. Label the soma, axon, dendrites (p. 21)
    see Fig. 2-2

What is a typical size range for... (Not in Text)
    neurons come in a variety of shapes and sizes, but here are some typical values
    for dendritic arbor of a single neuron? 100 microns
    the soma diameter? 10 microns
    the axon length? few millimeters

Sketch examples of the following types of neurons: (p. 22, Table 2-1)
    anaxonal, monopolor, bipolor, multipolar
    See Table 2-1; NOTE: the labels are switched for monopolar and bipolar in the textbook!

Sketch a chemical synapse. (p. 23, Fig 2-3 A)
    Label the presynaptic neuron, postsynaptic neuron, synaptic cleft and synaptic vessicles.
    See Fig. 2-3 A
    What determines which side is presynaptic and which is postsynaptic?
    synaptic vessicles are on the presynaptic side

Sketch an electrical synapse. (p. 23, Fig 2-3 B; p. 37, Fig. 2-11 A)
    see Fig 2-3B or Fig. 2-11 A (either is fine, the later is a bit more informative)
What determines which side is presynaptic and which is postsynaptic?
    structurally it is ambiguous; functionally it can sometimes be defined by the direction of "information flow"
    What is a gap junction? (p. 37)
    same thing as an electrical synapse
    What is a connexon? (p. 37)
    specialized channel proteins that form gap junctions

What are glial cells? (p. 25-26)
    non-neuronal cells in the nervous system
    What's the approximate ratio of glial cells to neurons in the brain?
    2-5 times more glial cells than neurons
    What are the four main types of glial cells?
    astrocytes (astroglia); microglia; oligodendrocytes (oligodendroglia); Schwann cells
    For each type, what is its main function?
    astrocytes - structural support; scaffolding; maintain chemical environment
    microglia - defensive and clean-up functions
    oligodendrocytes - form myelin sheath around axons in central nervous system
    Schwann cells - form myelin sheath around axons in peripheral nerves

What is myelin? (p. 27-28)
    multiple layers of cell membrane wrapped around axons to form an electrical insulator
    What cells form myelin?
    glial cells; specifically oligodendrocytes in the CNS and Schwann cells for peripheral nerves
    What's its function?
    speeds up the conduction of nerve impulses along axons
    What color does it appear in the brain?
    What is the most common demylenating disease? (Not in Text)
    Multiple sclerosis (MS)
    What are the symptoms?
The symptoms of MS are highly variable, depending on the areas of the central nervous system that have been affected. Symptoms of MS are unpredictable and vary from person to person and from time to time in the same person. For example: One person may experience abnormal fatigue, while another might have severe vision problems. A person with MS could have loss of balance and muscle coordination making walking difficult; another person with MS could have slurred speech, tremors, stiffness, and bladder problems. Even severe symptoms may disappear completely and the person will regain lost functions.
[From National MS Society:]

    What are the treatments?
Currently there is no "cure" for MS. Treatment typically involves strategies to slow disease progression and manage specific symptoms.
For more detail see the National MS Society website:
Here's another interesting site:
What is a node of Ranvier? (p. 28)
    periodic gaps in the myelin sheath along an axon which allow propagation of nerve impulses

Sketch an ion channel(p. 36, Fig. 2-10)
    see Fig. 2-10
    What determines whether it is in a open state or a closed state?
    typically some sort of conformational change takes place to open or occlude the central pore

What's the difference between an ion channel and an ion pump ? (p. 39, Table 2-4)
    ion pumps require energy in the form of ATP; ion pumps are slower; ion pumps work against a concentration gradient

What's the difference between an ionotropic receptor and a metabotropic receptor? (p. 39, Fig. 2-13)
    ionotropic - the receptor protein is part of a channel\receptor protein complex;  fast direct influence on channel gating
    metabotropic - the receptor protein acts through a biochemical cascade; slow, indirect influence on channel gating

What is axonal transport(p. 43-46)
    a system for transporting subcellular components to/from distant neurites (along both axons and dendrites, despite the name)
    What does anterograde transport refer to?
    transport away from the soma
    What does retrograde transport refer to?
    transport toward the soma
    Using the fastest form of axonal transport, about how long does it take to move something 1 mm?
    fast anterograde rate is about 400 mm/day; it would take about 3-4  minutes to go 1 mm (a typical neurite length)
    What forms the intracellular "highways" along with substances are transported?
    microtubules are cytoskeletal elements that provide a structural network for axonal transport
    What are kinesin and dynein?
    two molecular motor proteins that are involved in axonal transport