Medulla Oblongata Flashcards
……replaces substantia gelatinosa in medulla & …..replaces Lissauer’s tract.
Spinal nucleus of trigeminal nerve
Descending fibers of spinal trigeminal tract
As we ascend in medulla, G&C tracts become…..while nuclei become…..
Smaller
Larger
Fibers from G&C sweep anteromedially forming…… . They ascend upwards forming…..
Internal arcuate fibers
Medial leminiscus
After decussation fibers from gracile are…..while from cuneate are…..
Anterior
Posterior
Mention nuclei of medulla
- Lower 4 cranial nerve nuclei
- The medulla contains many cerebellar relay nuclei: accessory cuneate nucleus, arcuate nucleus, nuclei of reticular formation, olivary nuclear complex.
Describe connections & function of spaccessory cuneate nucleus
C, it recieves fibers from cervical & thoracic spinal segments. It gives uncrossed fibers to cerebellum (cunei-cerebellar fibers or the dorsal external arcuate fibers) that pass in ICP
F, equivilant to Clarke’s nucleus recieves unconscious proprioception from UL & neck.
…..represents dorsally displaced pontine nuclei
Mention its function
Arcuate nucleus
Recieves afferents from cerebral cortex & gives efferents to cerebellum via ICP (ant external arcuate fibers)
Describe site of spinal trigeminal nucleus
Medial to spinal trigeminal tract, extends from trigeminal root at the pons to C2 segment
Reticular formation represents continuation of…..
Grey matter of spinal cord
Mention efferents of reticular formation
- Ascending fibers: to the thalamus via central tegmental tract
- Descending fibers: to spinal cord (reticulospinal tracts)
Mention functions the reticukar formation controls
- The activity of muscles
- Autonomic & endocrine functions
- Somatic & visceral sensations
- Arousal & level of consciousness. Lesion leads to loss of con. or coma
Mention structures which appear in open medulla
- Fourth ventricle & 3 trigones in its floor
- ICP
- Main inferior olivary nucleus
Mention parts of olivary complex
Principal inferior olivary nucleus, medial accessory nucleus, dorsal accessory nucleus.
Mention connections of olivary complex
Afferents
Cerebral cortex & red nucleus mainly to principal nucleus
Ascending fibers from the spinal cord to accessory nuclei
Brain stem nuclei: vestibular nuclei (medial & lateral) & spinal nucleus of V
Efferent: Olivi-cerebellar, firms climbing fibers
Posterior spinocerebellar tract arises from…., while cerebello-vestibular fibers arises from….
Clarke’s nuscleus
Flocculonodulat lobe
Mention ascending & descending tracts in medulla
- Medial leminiscus
- Medial longitudinal fasciculus ant to XII nucleus, adjacent to median raphe
- Spinothalamic tracts
- Dorsal spinocerebellat merges with ICP while ventral lies in retro-olivart area
- Spinal tract & nucleus if V lie in posterolateral part
Describe extension of hypoglossal nucleus
From hypoglossal tiprigone & extenspding in closed medulla
Hypoglossal nerve supplies all muscles of the tongue except …..
Palatoglossus
Describe origin of accessory nerve & supply
A) Spinal part of XI: originated from spinal nucleus in anterior horn cells from upper 5 cervical segments till motor decussation, supply sternomastoid & trapezius
B) Cranial part: lower part of nucleus ambiguus, supply palate except tensor palate & muscles of pharynx (except stylopharygeus) & larynx muscles
Mention nuckei of vagus & glossopharyngeal
X, dorsal motor nucleus of vagus, nucleus solitarius, nucleus ambiguus, spinal nucleus of trigeminal
IX, inferior salivatory nucleus, nucleus solitarius, nucleus ambiguus, spinal nucleus of trigeminal
Describe function of dirsal motorcnucleus of vagus
Largest parasympathetic nucleus in brainstem, to cardiac muscles & smooth muscles in thorax & abdomen
Function of inf salivatory nucleus
Para to IX relay in otic ganglion & gives secretory fibres to parotid gland
Site & function of nucleus ambiguus in X & IX
S, deep in medullary reticular formation between spinal nucleus of V & inferior olivary complex extends rostrally to upper end of dorsal nucleus of vagus while caudally it is in line the nucleus of cranial part of XI
F, Rostral part gives to IX which supplies stylopharyngeus while caudal part gives to X which supplies pharyngeal & intrinsic laryngeal muscles & striated muscles of palate & upper esophagus.
Site & function of nucleus solitarius in X & IX
S, lies ventrolateral to dorsal nucleus of vagus & extends all through the medulla
F, X, recieves special visceral sensation from tongue & epiglottis & general visceral from organs supplied by vagus, project to sensory thalamus & cerebral cortex
IX, recieves sensory imulses from post 1/3 of tongue, tonsils, auditory tube & Eustachian tube & post wall of pharynx.
function of spinal nucleus of trigeminal in X & IX
X, recieves general sensation from auditory branch of X, carries exteroceptive sensation from cutaneous area at back of ear & external auditory meatus
IX, recieves general sensation from the oropharynx, posterior 1/3 of tongue, tonsils, auditory tube & middle ear.
Functions of medulla
- It contains cranial nerve nuclei concerned with vital functions
- It conducts the ascending & descending tracts connecting spinal cord to higher centers
