medulla Flashcards
medulla provides attachment to which cranial nerves
glossopharyngeal
vagus
accessory
hypoglossal
what does the upper part of the medulla form
the caudal part of the floor of the fourth ventricle
what does the lower half of the medulla form
The lower half of the medulla is closed and contains the central canal which below
becomes continuous with the central canal of the spinal cord and above opens into
the fourth ventricle
how is the medulla separated from the cerebellum
dorsally by the cavity of the fourth ventricle
what is the medulla divided by
anterior median fissure
what sulcus in the medulla gives attachment to hypoglossal nerve rootlets
Anterolateral sulcus
what sulcus gives attachment to glossopharyngeal, vagus & cranial part of accessory nerve
Posterolateral sulcus
in the anterior area of the M.O. what is the pyramid produced by
produced by the
underlying corticospinal,
corticobulbar and Corticopontine fibres
what covers the ventral
surface of pyramid
Arcuate nuclei
the Lateral area between the anterolateral
sulcus and posterolateral sulcus is continuous with what
lateral funiculus of the spinal cord
what is the olive
is an elevation produced by
the underlying inferior olivary
nucleus
what tracts are present in the lateral area
It is occupied by ventral spino-
cerebellar tract, dorsal spino-
cerebellar tract, lateral spino-
thalamic tract (spinal lemniscus), spino-olivary and olivo-spinal tracts
where does the facial nerve emerge
between the olive and pons
what forms the floor of
the fourth ventricle
Supero-medial zone of the posterior area
what is the Tuberculum cinereum produced by
the underlying spinal
nucleus and spinal tract of trigeminal nerve
- The spinal nucleus of trigeminal below extends up to second c2 beyond which it becomes continuous with substantia gelatinosa of Rolando
what is the function of the corticospinal tract
concerned with the
skilful, voluntary movements
what area does the corticospinal tract originate from
Takes origin from areas 4,6,312
what is the path of the corticospinal tract
Axons from these neurons
descend the corona radiata, posterior
limb of internal capsule,
middle two-third of crus
cerebri, basilar part of pons and
pyramid of medulla oblongata
In the lower medulla 90% of
fibres decussate and enter into
the lateral funiculus as the lateral
cortico-spinal tract
8% fibres pass uncrossed in the
anterior funiculus as the anterior
cortico-spinal tract
how does the lateral corticospinal tract terminate
55% of fibres terminate in the cervical
segment of the spinal cord
20% of fibres terminate in the thoracic
segments of the cord
25% of fibres terminate in the lumbo-sacral
segments of the cord
how does the anterior corticospinal tract terminate
THIS TRACT ONLY FOUND IN PRIMATES (MAN)
It extends up to mid-thoracic level
Depending on the level of termination all the
fibres of the tract cross the middle line in the
anterior white commissure and terminate in
the contra-lateral spinal grey matter
The spinal tract of Trigeminal nerve conveys what
pain & thermalsensations from the ipsilateral trigeminal area of the face and forehead, and are relayed into the spinal nucleus of V nerve
how is the trigeminal lemniscus formed
The axons of second sets of neurons arise from the spinal nucleus of the V nerve, cross to the opposite side, and form the trigeminal lemniscus
terminate in the VPM nucleus of thalamus
how does the The spinal nucleus extend
caudally to the second cervical
segment and cranially to the pontomedullary junction
The anterolateral funiculus on each side between the pyramid and spinal tract of
trigeminal contains the:
- Ventral and dorsal spinocerebellar tract
- Ventral and lateral spinothalamic tract
- Spino-tectal tract
- Spino-olivary tract
- Vestibulo-spinal tract
- Rubro-spinal tract
what happens in medulla oblongata at the level of sensory decussation?
The nucleus gracilis and cuneatus become more pronounced and fibres of fasciculus
gracilis and fasciculus cuneatus terminate in these nuclei
The internal arcuate fibres arising from these nuclei decussate with the corresponding fibres of opposite sideand turn upwards as medial lemniscus on the opposite side
- Formation of medial lemniscus
- The medial lemniscus ends in the VPL nucleus
of thalamus
what does the Accessory cuneate nucleus do
carries proprioceptive sensation from the upper limb to the cerebellum of the
same side through inferior cerebellar peduncle
what does the Hypoglossal nucleus do
Occupies the hypoglossal triangle in
the floor of the 4th ventricle
- It supplies all the muscles of the
tongue except the palatoglossus
what does the Dorsal nucleus of vagus do
occupies the vagal
triangle in the floor of the 4th ventricle
The preganglionic fibers arising
from this supply the heart, smooth
muscles and glands of respiratory
and alimentary system
where does the Nucleus of tractus solitaries receive fibres from
It receives taste fibers from VII, IX
and X nerve
what does the Nucleus of tractus solitaries do
Lies behind the dorsal nucleus of
vagus
Efferents from the solitary nucleus
carrying taste sensations ascend on
the contralateral side and terminate
in VPM of thalamus
what does the Medial longitudinal bundle consist of
Is a small compact tract which interconnects different cranial nerve nuclei (3rd, 4th, 6th, 8th, and spinal nucleus of 11th)
how is the medial leminiscus formed
The lateral and anterior spinothalamic tracts collectively form the spinal
lemniscus
what does the Inferior olivary nuclear complex – beneath the olive consist of
Principal inferior olivary nucleus
Medial accessory olivary nucleus
Dorsal accessory olivary nucleus
what are the afferent Connections of olivary complex of nuclei:
Afferents – from cerebral cortex, red
nucleus, basal nuclei, thalamus,
periaqueductal grey of mid brain and
spinal cord
what are the efferent Connections of olivary complex of nuclei:
Efferents:
Olivo-cerebellar tract from the
inferior olivary nu.
Parolivo-cerebellar fibres from
medial and dorsal accessory
olivary nu.
Both sets of fibers cross the median
plane and reach the cerebellum
through inferior cerebellar
peduncle
Parolivo-cerebellar fibers project to
the cerebellar vermis
what do the Arcuate nuclei do
They are the displaced pontine nuclei, lie on the surface of the pyramid
b. Receive fibers from the cerebral cortex and send efferent fibers (anterior external arcuate
fibers) to the cerebellum of the opposite side
what is the blood supply of the medulla
It is supplied by:
- Branches arising from the vertebral
arteries
Anterior and posterior spinal
arteries
Posterior inferior cerebellar
arteries
- Basilar artery and its branch
Anterior inferior cerebellar artery
what is lateral medullary syndrome
Lesion/block in the branches of posterior
inferior cerebellar A supplying the medulla
oblongata
what are the symptoms of lateral medullary syndrome
Vertigo – sensation of whirling and loss of balance
Nystagmus – rapid involuntary movements of the eye
Ataxia – loss of full control of bodily movements
Dysmetria – lack of coordination of movement
Dysdiadokokinesis – inability to perform rapid alternate movements
Palatal myoclonus – rapid spasm of palatal muscles
Dysphagia – difficulty in swallowing
* Gag reflex or pharyngeal reflex
Miosis – excessive constriction of pupil
Anhydrosis – failure of sweat glands to secrete
what is medial medullary syndrome
(Dejerine syndrome)
Lesion/block in the vertebral
artery branches supplying the
medulla oblongata
