Medulla Oblongata

Question 1

……replaces substantia gelatinosa in medulla & …..replaces Lissauer’s tract.

Answer 1

Spinal nucleus of trigeminal nerve
Descending fibers of spinal trigeminal tract

Question 2

As we ascend in medulla, G&C tracts become…..while nuclei become…..

Answer 2

Smaller
Larger

Question 3

Fibers from G&C sweep anteromedially forming…… . They ascend upwards forming…..

Answer 3

Internal arcuate fibers
Medial leminiscus

Question 4

After decussation fibers from gracile are…..while from cuneate are…..

Answer 4

Anterior
Posterior

Question 5

Mention nuclei of medulla

Answer 5

1. Lower 4 cranial nerve nuclei
2. The medulla contains many cerebellar relay nuclei: accessory cuneate nucleus, arcuate nucleus, nuclei of reticular formation, olivary nuclear complex.

Question 6

Describe connections & function of spaccessory cuneate nucleus

Answer 6

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.

Question 7

…..represents dorsally displaced pontine nuclei
Mention its function

Answer 7

Arcuate nucleus
Recieves afferents from cerebral cortex & gives efferents to cerebellum via ICP (ant external arcuate fibers)

Question 8

Describe site of spinal trigeminal nucleus

Answer 8

Medial to spinal trigeminal tract, extends from trigeminal root at the pons to C2 segment

Question 9

Reticular formation represents continuation of…..

Answer 9

Grey matter of spinal cord

Question 10

Mention efferents of reticular formation

Answer 10

1. Ascending fibers: to the thalamus via central tegmental tract
2. Descending fibers: to spinal cord (reticulospinal tracts)

Question 11

Mention functions the reticukar formation controls

Answer 11

1. The activity of muscles
2. Autonomic & endocrine functions
3. Somatic & visceral sensations
4. Arousal & level of consciousness. Lesion leads to loss of con. or coma

Question 12

Mention structures which appear in open medulla

Answer 12

1. Fourth ventricle & 3 trigones in its floor
2. ICP
3. Main inferior olivary nucleus

Question 13

Mention parts of olivary complex

Answer 13

Principal inferior olivary nucleus, medial accessory nucleus, dorsal accessory nucleus.

Question 14

Mention connections of olivary complex

Answer 14

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

Question 15

Posterior spinocerebellar tract arises from…., while cerebello-vestibular fibers arises from….

Answer 15

Clarke’s nuscleus
Flocculonodulat lobe

Question 16

Mention ascending & descending tracts in medulla

Answer 16

1. Medial leminiscus
2. Medial longitudinal fasciculus ant to XII nucleus, adjacent to median raphe
3. Spinothalamic tracts
4. Dorsal spinocerebellat merges with ICP while ventral lies in retro-olivart area
5. Spinal tract & nucleus if V lie in posterolateral part

Question 17

Describe extension of hypoglossal nucleus

Answer 17

From hypoglossal tiprigone & extenspding in closed medulla

Question 18

Hypoglossal nerve supplies all muscles of the tongue except …..

Answer 18

Palatoglossus

Question 19

Describe origin of accessory nerve & supply

Answer 19

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

Question 20

Mention nuckei of vagus & glossopharyngeal

Answer 20

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

Question 21

Describe function of dirsal motorcnucleus of vagus

Answer 21

Largest parasympathetic nucleus in brainstem, to cardiac muscles & smooth muscles in thorax & abdomen

Question 22

Function of inf salivatory nucleus

Answer 22

Para to IX relay in otic ganglion & gives secretory fibres to parotid gland

Question 23

Site & function of nucleus ambiguus in X & IX

Answer 23

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.

Question 24

Site & function of nucleus solitarius in X & IX

Answer 24

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.

Question 25

function of spinal nucleus of trigeminal in X & IX

Answer 25

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.

Question 26

Functions of medulla

Answer 26

1. It contains cranial nerve nuclei concerned with vital functions
2. It conducts the ascending & descending tracts connecting spinal cord to higher centers