Brainstem Flashcards
Midbrain=
Mesencephalon
Pons=
Metencephalon (along with cerebellum)
Medulla=
Myelencephalon
CN nuclei in midbrain?
3 and 4
CN nuclei in pons
5, 6, 7, 8
CN nuclei in medulla
9, 10, 11, 12
Level of CN3 exiting midbrain
Ventral midbrain at the level of the superior colliculus in the interpeduncular sulcus
Superior colliculus associated with?
Visual system
Inferior colliculus associated with?
Hearing
Which is the only cranial nerve to exit from the dorsal brainstem and at what level?
Trochlear.
Inferior colliculus
Why does the trochlear nerve exits from the posterior brainstem?
Pineal gland is the embryological rudimentary eye.
Trochlear nerve was likely associated with that.
Where does the trigmeinal emerge from the pons?
Mid-pontine level.
Anterolateral region.
What level do the 6, 7 ,8th cranial nerves emerge?
Ponto-medually junction
In what order from medial to lateral do the 6th, 7th and 8th CN emerge?
6 medial, 7 then 8 most laterally.
6th 7th nerve palsy.
Location of lesion?
?medial ponto-medullary sulcus/junction.
As more medial structures and internal genu of facial nerve intimately related to CN6 nuclei
7th 8th nerve palsy
Lateral pontomedullary problem/IAM
Etymology of vagus
Wanderer
Location of hypoglossal nerve
Emerges from the ventral medulla at the sulcus between pyramid and olive.
3 divisions from ventral to dorsal of brainstem
Basis
Tegmentum
Tectum
Tegmentum etymology
Covering
Tectum etymology
Roof
Descending tracts found in which portion of brainstem?
Basis
Ascending tracts found in which portion of brainstem?
Tegmentum
Relation between motor and sensory nuclei in braistem
Motor medial, sensory lateral.
Supplementary motor grey matter in medulla
Superior and inferior olivary nuclei
Location of supplementary grey matter in the brainstem
Ventral tegmentum
Supplementary grey matter in pons
Pontine nuclei
Supplementary grey matter nuclei in midbrain
SN and red nuclei
Cranial nerve nuclei arrangement
Dorsal tegmentum
Location of special grey matter in brainstem
Tegmentum lateral to motor nuclei
In simple terms what is the reticular formation
As grey matter and white matter ascends in the brainstem and decussates the grey matter is broken up into the indiviudal nuclei but also fragments of grey matter interspersed with white matter in the ventral tegmentum which is the reticular formation
Neurones in the anterior horn are?
Motor
Draw the general arrangement of structures in the medulla.
Dorsal sensory neurones develop embryologically from the?
Alar plate
Ventral motor neurones develop embryologically from the?
Basal plate
Lateral grey horn neurones are involved in?
Visceral function
Arrangement of efferent neurones from medial to lateral in SC
General somatic efferents
General visceral efferents
Arrangement of afferent fibres from lateral to medial in SC
General somatic afferents
General visceral afferents
Location of hypoglossal nuclear tract
Tegmentum of medulla medially adjacent to fourth ventricle (GSE)
Location of vagus nuclear tract
Dorsal nucleus is lateral to hypoglossal nuclei (GVE) in tegementum of medulla.
From what embryological structure do the special muscles in head and neck derive?
Branchial pouch
Where are the SVE nuclei found in the medulla
Anterolateral to the GVE tract as the nucleus ambiguus
Where are the CN nuclei for 3 and 4 found?
Just lateral to midline in midbrain
What is the remaining GSE nuclei and where is it found?
Midline in the pons (GSE column)
Where are the nuclei involved in lacrimation and salivation
Latearl to GSE tract as the superior and inferior salivary nuclei in the pons.
(Superior portion of the superior salivary gland contributes to lacrimation)
Structures supplied by nucleus ambiguus?
Muscles of the larynx and pharynx
Location of facial nerve nuclei
In the SVE column at the pontomedullary junction.
Location of the motor nucleus of trigeminal
Midpons in the SVE column.
CNs receiving fibres from the nucleus ambiguus
9, 10 and cranial portion of 11
Location of GVA tract
Lateral to GVE
Location of SVE in brainstem
Lateral to the GVA
Components of nucleus solitarius?
Medially- GVA
Laterally- SVA
SVA in medulla
Taste
What carries taste fibres from the vallecula of the tongue?
X
Which nerves carry taste sensation and to what do they connect?
7, 9, 10
Nucleus solitarius
Location of special somatic afferent in brainstem
Medial to general somatic
What recieves auditory stimuli?
Ventral and dorsal cochlear nucleus, ventral and dorsal to inferior cerebellar peduncle
Fine touch trigeminal sensation goes to?
Principle nucleus
Pain and temperature sensation in trigeminal goes to which nucleus?
Spinal
Proprioceptive information goes to which trigeminal nucleus?
Mesencephalic
Rhombencephalon=
Pons, medulla and cerebellum
What is the inferior border of the medulla?
Pyramidal decussation
With which nuclei of the thalamus do reticular formation systems connect?
Intralaminar nuclei of thalamus
Which then connect with all parts of cortex.
Most important function of ascending reticular formation
Consciousness
What are the functions of the medullary reticular formation?
Cardiac centre
Vasomotor centre
Respiratory centre- Inspiratory centre
Gastrointestinal centre
Location of area postrema?
Adjacent to fourth ventricle
Next to chemoreceptor trigger zone
Near GIT connecting nervous system.
What is significant about the area postrema
Portion of the medulla in which there is a break in BBB to allow chemical substances to influence neurones in area postrema.
Ascending pathways of medulla
Dorsal column-
Fasciculus gracilis + cuneatus
Nucleus cuneatus and gracilis
Internal arcuate fibres
Medial leminisci
Spinothalamic-
Anterior and lateral tracts.
Spinotectal tract
Dorsal column sensations
Fine touch
Proprioception
Vibration
Two-point discrimination
What happens to dorsal column tracts on reaching medulla?
Synapse with nucleus gracilis and nucleus cuneatus which is located in the posteroinferior portion of the medulla.
Second order neurones originate there and decussate
Where do second-order dorsal column fibres synapse?
VPL nucleus of thalamus
What is the name of the decusssating dorsal column fibres in the inferior medulla?
Internal arcuate fibres
How do the second order fibres of dorsal column ascend?
Medial lemniscus
Left medial lemniscus fibres carry what modality?
Dorsal column from right body.
Spinotectal tract involved in?
Spinovisual/ Spinoauditory reflexes
What forms in the medulla from the spinothalamic and spinotectal tracts?
Spinal lemniscus
Which tracts make up the spinal lemniscus?
Anterior and lateral spinothalamic tracts
Spinotectal tract
Right spinal lemniscus injury
Left spinotectal and spinothalamic information
Descending pathways of the medulla
Corticospinal
What proportion of corticospinal fibres decussate at the level of the medulla?
90%
LMN to lower limb come from which corticospinal tract?
Lateral corticospinal tract
Axial musculature LMN come from which corticospinal tract?
Anterior (i.e. do not decsusate in medulla but cross at the level of crossing)
How is the medulla connected to the cerebellum?
Inferior cerebellar peduncle
What is the accessory cuneate nucleus?
Nucleus at dorsal portion of medulla near to cuneate nucleus.
Receives fibres from upper limb which subsequently enter the cerebellum via the inferior cerebellar peduncle as the cuneocerebellar pathway
Cuneocerebellar fibres carry
Proprioceptive information from the upper limb via the accessory cuneate nucleus in the medulla to the cerebellum via the inferior cerebellar peduncle
Origin of dorsal spinocerebellar tract
Fibres from lower limb, travel ipsilaterally along with cuneocerebellar pathway into the cerebellum via inferior cerebellar peduncle (though not via accessory cuneate nucleus)
Origin of ventral spinocerebellar pathway
Lower limb, second order neurone decussates , pass through medulla, pons and then through superior cerebellar peduncle where they decussate again to return to their original side.
What is the difference between dorsal spinocerebellar tract and ventral cerebellar tract?
Dorsal ipsilateral and passes through inferior cerebellar peduncle.
Ventral decussates ( in SC and then within the cerebellum) twice and passes through superior cerebellar peduncle.
Lower limb proprioception carried by?
Dorsal and ventral spinocerebellar tract
Upper limb proprioception carried by?
Cuneocerebellar tract (via accessory cuneate nucleus)
What are the posterior parthways of the medulla?
7
Cuneocerebellar tract
Dorsal spinocerebellar tract
(Ventral spinocerebellar tract)
Olivocerebellar tract
Arcuato-cerebellar tract
Reticulo-cerebellar pathway
Central tegmental pathway
Passage of olivocerebellar tract?
From olivary nucleus in medulla to contralateral cerebellum via inferior cerebellar peduncle
What area in the midbrain communicates with the inferior olivary nucleus?
Red nucleus via rubro-olivary fibres
Function of rubro-olivarycerebellar tract?
Important control of motor movements
Function of corticopontocerebellar tract
Allows cerebral cortex to influence cerebellar function
Components of corticopontocerebellar tract
Corticopontine tract-> pontine nuclei-> cerebellum via middle cerebellar peduncle
What are arcuate nuclei?
Inferiorly dispalced pontine nuclei found in the medulla
What fibres are present in the central tegmental pathway
Rubro-olivary
Reticulothalamic fibres
Central taste pathway (from nucelus solitarius to thalamus)
What nucleus of the thalamus receives taste information?
VPM nucleus