The Spinothalamic
Tracts
These tracts carry
conscious pain,
temperature, crude
touch, and pressure.
There is a lateral
and an anterior
tract. They carry
this information
first to the thalamus
of the brain which
receives all
conscious
sensations, and then
terminate in the
areas of the cerebral
cortex which
perceive these
sensations.
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The Spinocerebellar
Tract
This tract carries
unconscious
proprioception
(muscle sense) to the
cerebellum which is
responsible for
muscle
coordination. The
fibers either do not
cross, or cross and
recross so that they
innervate the
cerebellum on the
same side.
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The Fasciculus
Gracilis and
Fasciculus Cuneatus
These tracts carry
discriminative touch
(the gracilis) and
conscious
proprioception (the
cuneatus).
Discriminative
touch allows you to
specifically localize
the location whereas
crude touch does
not. The fibers of
these tracts go first
to the medulla
where they synapse
and cross. Then
through a pathway
called the medial
lemniscus they pass
to the thalamus.
Then on to the
cerebral cortex for
perception.
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The Corticospinal
Tract
The corticospinal
tract originates in
the cerebral cortex
where voluntary
motor control is
localized. There are
two branches, the
lateral and the
anterior. The lateral
crosses in the
medulla in an area
known due to its
appearance as the
pyramids. The
anterior does not
cross. These fibers
are called "upper
motor neurons" and
they synapse with
"lower" motor
neurons in the cord
which lead to the
skeletal muscles.
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