Flashcards in Brainstem III: Medulla Deck (19):
What are the 2 major decussations in the medulla?
Dorsal columns become medial lemniscus (ascending pathway)
pyramidal tracts (descending pathway)
Fasiculus gracilis and cuneatus
continues from dorsal column of spinal cord for conscious proprioception, vibratory sense, and fine tactile info.
Come up and synapse into nuclei
Location of nucleus gracillis and cuneatus with respect to one another
gracillis - medial
cuneatus - lateral
Fibers traveling in pyramids carry what?
Motor fibers continue into spinal cord as CST pathways or stop at cranial nerve nuclei as corticobulbar pathways...pyramidal decussation fibers become dorsolateral CST (90%) and 10% remain uncrossed as ventral CST
Difference between "closed" and "open" medulla
"open" medulla contains more "open" 4th ventricle and is more rostral
Gracillis and cuneatus get sensation from which parts of body
gracillis - lower body (under T6)
cuneatus - upper body
Lesion of pyramidal tract results in what?
Upper motor lesion symptoms (i.e. HYPERreflexia)
Medial lemniscus arises from what?
Dorsal columns of spinal cord (ascending somatosensory fibers)
Pathway of fasciculus gracilis and cuneatus
terminate and synase with neurons of nucleus gracilis and cuneatus respectively. 2nd order neurons from these nuclei decussate to ventral aspect as internal arcuate fibers to form medial lemniscus. Lemniscus ascends rostrally through medulla and terminates in VPL of thalamus
Medial longitudinal fasciculus (MLF)
Ascending fibers from vestibular nuclei to III, IV, VI (eye movements) and descending from medial vestibular nucleus which projects to neck muscles for visual tracking function
Spinal nucleus of V
- extends through medulla as far as C2
- mediates pain and temperature of head, replaces substantia gelatinosa
What other pathways are in medulla?
SST - pain and temp from contral lateral side (ducessation ocurs in spinal cord)
spinocerebellar - proprioceptions from muscle spindle fibers to cerebellum (remains ipsilateral)
tectospinal tract - from superior colliculus of midbrain, follows MLF to cervical levels and mediates neck postural movements
What are the decussation fibers from nucleus gracillis and cuneatus called as they form medial lemniscus?
Internal arcuate fibers
Where does the medial lemniscus terminate?
VPL of thalamus
Accessory cuneate nucleus
at edge of nucleus cuneatus, muscle spindles and Golgi tendon organs of UPPER limb...projects to ICP as cuneocerebellar tract (unconscious proprioception of upper limb)
Medial medullary syndrome
- lesion of anterior spinal branches of vertebral arteries
- loss of sensation from contralateral body (medial lemniscus)
- contralateral upper motor neuron paralysis (pyramids, CST)
- ipsilateral tongue paralysis (hypoglossal nucleus XII)
What structures are in the medial medulla?
From ventral to dorsal:
pyramids (CST), medial lemniscus (DC), tectospinal tract (coordinating eye and neck), MLF (vestibular nuclei with eye muscle III, IV, VI), and hypoglossal nucleus
What structures are in the lateral medulla?
inferior olivary nucleus (relay for afferent signals to cerebellum