lecture 7 - medulla, CNs IX-XII Flashcards
describe the development of the internal features of the medulla oblongata
- alar plates move laterally forming the afferent (sensory) columns
- basal plates remain medially forming the efferent (motor) columns
- sulcus limitans separates motor columns & sensory columns
what are some external features of the medulla?
- olives
- pyramids
- decussation
- anterior median sulcus
- CNs Ix-XII
what are some internal features of the medulla?
- posterior median sulcus
- anterior median fissure
- fasciculus gracilis
- fasciculus cuneatus
- nucleus gracilis
- nucleus cuneatus
- CN V nucleus
- central canal
- pyramids
- decussation
- medial longitudinal fasciculus
- posterior spinocerebellar, anterior spinocerebellar and lateral spinothalamic tracts
describe the pyramids at the level of the decussation of the pyramids
in the inferior portion of the medulla, they cross the midline plane and continue down the spinal cord as the lateral white column corticospinal tract
describe the fasciculus gracilis and fasciculus cuneatus at the level of the decussation of the pyramids
- gracilis = medial
- cuneatues = lateral
- both come from the cord and climb posterior to the central gray matter (both appear as posterior extensions of the cenral gray matter)
describe the substantia gelatinosa of the posterior gray column at the level fo the decussation of the pyramids
becomes continuous with the nucleus of the spinal tract of CN V
describe the lateral and anterior white columns at the level of the decussation of the pyramids
same arrangement as the cord
what is the decussation of the pyramids aka?
the great motor cross-over
where does the decussation of lemnisci occur?
- in the inferior medulla a short distance above the decussation of the pyramids
- anterior to the central gray matter
- posterior to the pyramids
what is the decussation of the lemnisci aka?
the great sensory cross-over
describe the formation of the lemnisci at the level of the decussation of the lemnisci
- cuneatus nucleus and gracilis nucleus are the ends of the fasciculus cuneatus and the fasciculus gracilis
- the nuclei = the relay stations
- internal arcuate fibers cross the midline to form the medial lemnisci on the opposite side
describe the location of the lemnisci at the level of the decussation of the lemnisci
- located btwn the olivary nuclei and behind the pyramids
- only begins at next section level
- oriented anteroposteriorly
what is the function of the lemnisci?
to convey sensory information to the thalamus
what is situated lateral to the arcuate fibers at the level of the decussation of the lemnisci?
nucleus of the spinal tract of CN V
what is situated laterally to the nucelus of the spinal tract of CN V at the level of the decussation of the lemnisci?
the spinal tract (of CN V) itself
where/what is the MLF (at the level of the decussation of the lemnisci)?
small tract of nerve fibers on both sides of the midline posterior to the medial lemnisci
what is the function of the MLF?
connects vestibular and cochlear nuclei to the nuclei that control the external eye muscles (oculomotor, trochlerar and abducens)
describe the reticular formation at the level of the decussation of the lemnisci
- obscured by the internal arcuate fibers
- consists of a diffuse group of nerve cells and fibers located behind the olivary nuclei
- extend through the pons and the midbrain
where are the olives located?
at the inferior portion of the 4th ventricle
what occurs at the level of the olives?
a dramatic increase in the amount of gray matter
describe the olivary nuclear complex (inferior olivary nucleus) at the level of the olives
- nerve cells send dibers medially across the midline to enter the cerebellum through the inferior cerebellar peduncle
- gray matter is crumpled and opens medially
- gives rise to olives
what is the function of the olivary nuclear complex?
voluntary muscle movement
describe the vestibulocochlear nuclei at the level of the olives
made up of 4 vest nuclei:
- -medial, inferior, lateral and superior vestibular nuclei
- -at this level only medial and lateral can be seen
and 2 cochlear nuclei:
- -anterior = on the anterolateral part of the inferior cerebellar peduncle
- -posterior = on the peduncle lateral to the 4th ventricle
describe the nucleus ambiguus at the level of the olives
- large motor nucleus deep in the reticular formation
- nerve fibers join CNs IX, X and XI
