Download 7-3_FuncOrgAsc_HernáthF

Function and organization of ascending pathways in the
spinal cord.
Ascending pathway: A nerve pathway that goes upward from the spinal cord toward the brain
carrying sensory information from the body to the brain.
Dorsal Column-Medial Lemniscal Pathway
Fasciculus gracilis: Functionally carries sensory modalities like light touch, vibration,
proprioception. For example these signals can help differentiate two points. This pathway
originates from thick myelinated fibres from mechano and proprioreceptors from sacral,
lumbal. and up to the sixth thoracic segments. The signals arrive at the nucleus gracilis in the
medulla oblongata where they synapse, this is where the tract termiates but the pathway
continues in the second order neurons. After decussation they deliver the information to the
thalamus ventral posterolateral nucleus(VPL) where they synapse with the third order neurons
that carry the signals to the cortex.
Fasciculus cuneatus: Functionally carries sensory modalities like light touch, vibration,
proprioception. This pathway originates from thick myelinated fibers from mechano and
proprioreceptors from the sixth thoracic segment upwards including all cervical segments.
The signals arrive at the nucleus cuneatus in the medulla oblongata where they synapse, this is
where this tract terminates but the pathway continues in the second order neurons. After
decussation they deliver the information to the thalamus(VPL) where they synapse whit the
third order neurons that carry the signals to the cortex.
Anterolateral System
Tractus spinothalamicus: Functions carries the sensation of crude touch, pressure (anterior
spinothalamic tract), pain and heat (lateral spinothalamic tract). Its first order neurons that
arise from the periphery are thin or non myelinated, they synapse on neurons in the I. IV. and
V. lamina of the grey matter in the substantia gelatinosa or in the nucleus proprius at the tip of
the dorsal horn. The second order neurons decussate here and goes to the thalamus(VPL)
where they synaps with the third order neurons that carry the information to the primary
sensory cortex.
Spinocerebellar tracts
Tractus spinocerebellaris posterior: Carries information of proprioreceptors (muscle spindles
and golgi tendon organs) from the ipsilateral trunk and lower limbs, that are important in
movement coordination and posture. Originates from the ipsilateral Clarke column and
terminates on the cerebellar cortex.
Tractus spinocerebellaris anterior: Conveys proprioceptive information that help our brain
coordinate and refine movements . Originates from neurons in the V. VI. and VII. lamina of
the grey matter. The fibres decussate twice so it terminates on the ipsilateral cerebellar cortex.
There are two more tracts that I didn't mention in the slides the cuneocerebellar tract and the
rostral spinocerebellar tract these carry the proprioceptive information of the neck, the upper
trunk and limbs. The first order neurons ascend in the fasciculus cuneatus and terminate in the
accessory cuneate nucleus, Clark homologue at cervical levels. Terminates on the cerebellar
cortex without decussation.
Sources:
http://teachmeanatomy.info/neuro/pathways/ascending-tracts-sensory/
http://braininfo.rprc.washington.edu/
Slides from the previous year
Functional Neuroanatomy
https://en.wikipedia.org
http://www.blackwellpublishing.com/patestas/chapters/10.pdf