Sept 17, 2013
The notes only make sense when read alongside the slides. If something's on the slides,
it probably isn't in my notes.
esp = especially
90-95% of test questions are from lectures. rest is from
at the seat of thinking, feeling, consciousness
Central Nervous System (CNS) consists of brain and spinal
Peripheral Nervous System (PNS) further divided into
afferent (info coming in, i.e. visuals) and efferent info
(brain computes info, i.e.: I see a black box)
each neuron can connect up to 10 000 other neurons
PNS lies outside CNS
PNS subdivided into autonomic and somatic efferent system carries info out to systems, i.e. to cardiac
skeletal muscle control regulated by somatic: voluntary
Cells in CNS
neurons are excitable - can generate a signal and carry
COMPONENTS OF A NEURON
soma: cell body
dendrite: similar to a net that catches/receives incoming
axon: piece of wire that carries/conducts the signal (action
axon hilla: where the axon originates
axon terminal: where the neurotransmitters are released
presynaptic neuron: before the synapse. the one who
sends the signal.
post synaptic neuron: after the signal. the one who
receives the signal.
GLIAL CELLS supporting cells. glued to the system.
5 types of glial cells:
1. astrocytes - mop up transmitters. provide energy.
provide guidance for developing neurons (in babies for
example). called astrocytes because look like stars under a
2. ependymal - line cavity of the ventricles in brain
3. microglia - involved in phagocytosis. protection of
4. oligodendrocytes - used for myelienation (forming
found in CNS
myelin is insulation made of fat
piece of biological tissue is not a good conductor
signal that you put in, will lose signal by the time it reaches
its destination. signal will be blurry at destination.
but copper wires are good at conducting signals
form myelin/insulation. form several myelin sheaths.
myelienate specific sections of the axon. wraps a bunch of
5. schwann cells - found in PNS. form around one section
of an axon
myelin sheath helps transmit the signal more efficiently
shwann cell wraps around cell to form the myelin sheath NODE OF RANVIER
unlike coaxial cable, does not myelienate entire axon.
areas that are not myelienated. these exposed areas are
called node of ranvier.
in our body, the conduction velocity of the fastest
myelienated axon is 80m/sec
vs unmyelinated axon could be as slow as 2m/s
not all neurons are myelienated.
cats have more myelienation and therefore faster velocity
myelin forming cells
coaxial cable has insulation that helps better transmission
than just a copper wire. signal remains more faithful to
where it originated.
what would happen if we lost myelienation?
-trouble with coordination and balance
-sensations of numbness
one of the drugs used in alleviating sxs for MS are the ones that block potassium channels
-pores found in membrane through which ions can cross
-need them to generate signals
-found throughout plasma membrane, throughout neuron
i.e.: potassium can always cross through a potassium leak