Spinal Decending Tracts Flashcards
Anterior Corticospinal
In the Anterior Funiculus
Most cross in cord after they come out of the tract. Only has about 5-15% of total corticospinal fibers
Terminates as tract by mid thoracic cord level T6
Function unclear
Effect on SAME side due to fibers crossing after they leave tract
Lateral Corticospinal
In lateral Funiculus
Most fibers cross in pyramids of M.O. Contains 85-95% of Corticospinal fibers
Runs entire length of the spinal cord
Starting and accomplishing skilled voluntary movements. Especially distal extremities
Effect on OPPOSITE side
Special info on Coritcospinal tracts
Only axons that begin in the cerebral cortex and run uninterrupted to the spinal cord
Decrease in fibers as they descend
Many synapse with Lamina 7 which then synapse with neurons in lamina 9 to extend to PNS and innervate muscle
A few axons terminate directly on lamina 9 (Gian pyramidal Betz cells)
Tectospinal Tract
Originates in superior colliculus of midbrains tectum
fibers cross as they descend
most terminate in upper four cervical cord levels
function is postural reflex enhancement with sight and auditory stimuli. Trap and steinocleidomastioid are adjusted via accessory nerve
Rubrospinal tract
Originates in nucleus ruber (red nucleus)
fibers cross in midbrain as they defend
fibers may reach ALL cord levels but mainly influence hand and foot
FLEXORS of hand and foot contralateral
Vestibulospinal tract
Origin in lateral part of vestibular nucleus (Deiters Nucleus) of MO
Tract runs entire cord length
Function EXTENSOR musculature of hands and feet. Ipsilateral
Medial Reticulospinal Tract
Anterior funiculus
origin is pons tegmentum
No crossing
Terminate at all cord levels in medial part of ventral horn
Helps autonomics
Lateral Reticulospinal tract
Lateral funiculus
Origin is M.O.
Uncrossed
terminate in all cord levels in medial part of ventral horn
helps autonomics
Fasiculus proprius (propriospinal system)
Spinospinal fibers originate and terminate in cord
extend short distances up or down
may or may not cross
Coordination for spinal reflexes
Dorsolateral tract (of Lissauer)
between rexed lamina 1 and posterior lateral sulcus of cord
run short distances up and down cord synapse in gray horns (often lamina 2)
