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?
white
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:
http://www.nationalmssociety.org/Symptoms.asp]
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:
http://www.nationalmssociety.org/treatments.asp
Here's another interesting site:
http://www.med.harvard.edu/publications/On_The_Brain/Volume5/Number4/MSf.html
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