The Brainstem Flashcards
What does the brainstem consist of?
Medulla oblongata + pons + midbrain
Axons that arise in the cerebral cortex and terminate in the brainstem.
Corticobulbar tract
Where does the brainstem lie?
Upon the basal portion of the occipital bone (clivus)
The brain stem nuclei receive from or send fibers to 10 pairs of cranial nerves that are attached to the surface of the brainstem.
CN (3 to 12)
Complex and heterogeneous matrix of neurons on the brainstem.
Reticular formation
What are the functions of the reticular formation?
- control level of consciousness.
- perception of pain.
- regulation of cardiovascular and respiratory systems.
- influence movement, posture and muscle tone.
On the dorsal surface of the medulla, the midline is marked by.
Dorsal median sulcus
The dorsal columns.
Located on the caudal part of the medulla
The dorsal columns consist of.
- fasciculus gracilis.
- fasciculus cuneatus.
(they contains first order sensory neurons)
What is the closed portion of the medulla?
The caudal two-thirds of the medulla that contains the central canal
Where does the central canal of the spinal cord opens into the fourth ventricle?
In the rostral medulla (referred to as the open medulla)
The fourth ventricle is widest at.
At the level of the pontomedullary junction
What is foramen of Luschka?
Lateral aperture in the brainstem, provides a passage for the CSF within the fourth ventricle to reach the subarachnoid space
The superior and inferior cerebellar peduncles forms the ……… walls of the rostral part of the fourth ventricle.
The lateral walls
Four paired elevations at the dorsal aspect of the midbrain, which are parts of the visual and auditory systems.
The superior (visual) and inferior (auditory) colliculi.
Emerges immediately caudal to the inferior colliculus.
The trochlear nerve CN4
The pyramidal or corticospinal tracts cross over at the decussation of the pyramids to form.
The lateral corticospinal tract
Elongated elevation lies lateral to the pyramid.
The olive
The ventral part of the pons is dominated by transverse system of fibers.
The transverse pontine fibers / pontocerebellar fibers.
The pontocerebellar fibers originate from.
The pontine nuclei
How does the pontocerebellar fibers enters the cerebellar hemispheres?
By passing through the middle cerebellar peduncle.
Large column of descending fibers on either side of the ventral midbrain.
Crus cerebri
The two crura cerebri are separated in the midline by.
A depression called interpeduncular fossa
The crus cerebri is continuous rostrally with.
The internal capsule of the cerebral hemispheres
The crus cerebri consist of.
The corticobulbar and the corticospinal fibers
At the transition from spinal cord to medulla, the dorsal horn is replaced by the caudal part of the.
Trigeminal sensory nucleus
Regarded as the brainstem homologue of the dorsal horn, since it receives primary afferent fibers conveying general sensation from the head.
The trigeminal sensory nucleus
The majority of the fibers of the ……….. medulla decussate to form the lateral corticospinal tract.
The ventral medulla
The first order sensory neurons of the dorsal columns ascend ………. into the medulla.
Ipsilaterally
The axons of the second order neuron course ventrally and medially as internal arcuate fibers, …………. in the midline.
Decussating
The second order neuron of the dorsal columns ascend through the brainstem after decussating as.
The Medial lemniscus
The medial lemniscus terminate in.
The ventral posterior (VP) nucleus of the thalamus. (Which project the to the somatosensory cortex in the postcentral gyrus)
The dorsal columns carry impulses concerned with.
Proprioception and discriminative (fine) touch
Lesion of the dorsal columns leads to.
Loss of proprioception causes sensory ataxia ( high steppage + unsteady gait ). Exacerbated when the eyes are closed (Romberg’s sign)
Dorsolateral to the pyramid and lateral to the medial lemniscus.
The inferior olivary nucleus (within the prominence of the olive)
In the cerebellum, axons originating from the inferior olivary nucleus, known as climbing fiber, end in the excitatory synapses in.
The dentate nucleus and upon Purkinje cells of the cerebellar hemispheres
Forms part of the floor of the fourth ventricle.
The dorsal surface of the rostral medulla
Immediately beneath the floor of the fourth ventricle, just lateral to the midline.
Hypoglossal nucleus (motor innervation of muscles of the tongue)
Lies lateral to the hypoglossal nucleus.
The dorsal motor nucleus of the vagus (containing preganglionic parasympathetic neurons)
What is area postrema?
The most caudal aspect of the ventricular floor where the BBB is absent.
Central site of action of emetics.
The area postrema
Where does the vestibular nuclei are located?
In the lateral part of the floor of the fourth ventricle.
Ventromedial to the hypoglossal nucleus, close to the midline.
The medial longitudinal fasciculus
It links the vestibular nuclei with the nuclei supplying the extraocular muscles.
The medial longitudinal fasciculus
The dorsolateral part of the rostral medulla is dominated by the.
The inferior cerebellar peduncle or the restiform body
Consist of fibers passing between the medulla and the cerebellum.
The inferior cerebellar peduncle (restiform body)
Connections between the vestibular nuclei and the cerebellum.
Olivocerebellar fibers
Conveying proprioceptive information from the lower limb.
Olivocerebellar + dorsal spinocerebellar tracts
Where does the cochlear nuclei are located?
On the dorsal and lateral aspects of the inferior cerebellar peduncle
Medial to the inferior cerebellar peduncle and ventral to the vestibular nuclei.
The nucleus solitarius
Receives visceral afferent fibers entering the brainstem in the facial, glossopharyngeal and vagus nerves.
The solitarius nucleus
The nucleus ambiguus, which lie ventral to the nucleus solitarius, send motor fibers into.
The glossopharyngeal and vagus nerves and cranial roots of the accessory nerve.
The pons is divided into.
- ventral or basal (tectum).
- dorsal (tegmentum).
The pontocerebellar fibers, that are oriented in the ventral part of the pons, pass into the ……………….. side of the cerebellum.
Contralateral
What are the fibers that becomes separated from the pyramids by the intervening transverse pontocerebellar fibers?
- medial lemniscus.
- spinal lemniscus.
- trigeminal lemniscus (trigeminothalamic tract).
Marks the boundaries between the ventral and tegmental portion of the pons.
The medial lemniscus
A group of transverse running fibers, located close to the ascending lemniscus fibers but dorsal to the pontocerebellar fibers.
The trapezoid body
Consist of acoustic fibers crossing the brainstem from the cochlear nuclei.
Trapezoid body
They ascend into the midbrain as the lateral lemniscus and terminate in the inferior colliculus.
The acoustic fibers of the trapezoid body
What are the nuclei that lie in the pontine tegmentum?
- abducens nucleus.
- facial motor nucleus.
- trigeminal sensory nucleus.
The trigeminal sensory nucleus reaches its maximum extent in the pons, adjacent to the origin of the ……………….. nerve.
Trigeminal nerve
What forms the lateral walls of the fourth ventricle in the rostral pons?
The superior cerebellar peduncle.
What forms the roof of the fourth ventricle in the rostral pons?
The superior medullary velum
A major site of noradrenergic neurons.
Locus coeruleus
The midbrain is divided into dorsal and ventral portions at the level of.
The cerebral aqueduct
The dorsal portion of the midbrain is known as.
The tectum
The tectum is consist of.
Inferior and superior colliculi
The ventral portion of the midbrain is known as.
The tegmentum
Bounded ventrally by the massive fiber system of the crus cerebri.
The tegmentum
Constitute part of the ascending acoustic (auditory) projection.
The inferior colliculus (caudal part of the midbrain)
The ascending auditory fibers run in the ……………. , which terminate in the ………..
Runs in the lateral lemniscus, which terminate in the inferior colliculus
Efferent fibers from the inferior colliculus terminate in the.
Medial geniculate nucleus of the thalamus ( which in turn projects to the auditory cortex of the temporal lobe )
The superior colliculus of the rostral midbrain is part of the…….. system.
Visual system
What are the main afferent fibers of the superior colliculus?
Corticotectal fibers originating from the visual cortex and from the frontal eye feild
What does the corticotectal fibers concerned with?
- Controlling eye movements ( smooth pursuit + saccadic eye movements).
- accommodation reflex.
This nucleus has connections with nearby midbrain preganglionic parasympathetic neurons ( Edinger-westphal nucleus ) mediating pupillary light reflex.
Pretectal nucleus
Ventral to the periaqueductal grey at the level of the superior colliculus lie the ………… nucleus.
The oculomotor nucleus
Ventral to the periaqueductal grey at the level of the inferior colliculus lie the …………. nucleus.
The trochlear nucleus
Near the oculomotor nucleus lies the …………….. nucleus.
The Edinger - westphal nucleus
Links the oculomotor and the trochlear nuclei to the abducens nucleus (pons) and the vestibular nuclei (medulla).
The medial longitudinal fasciculus
At the level of the inferior colliculus, the central portion of the tegmentum is dominated by.
The superior cerebellar peduncle (brachium conjunctivum)
At which level does the superior cerebellar peduncle decussate?
Beneath the inferior colliculus
At the level of the superior colliculus , the central portion of the tegmentum is occupied by.
The red nucleus (involved in motor control)
The efferent fibers from the red nucleus cross in the ventral tegmental decussation and descend to the spinal cord in the …………….. tract.
The rubrospinal tract
The most ventral part of the midbrain tegmentum is occupied by the.
Substantia nigra
The substantia nigra consist of two nuclei.
- The pars compacta.
- The pars reticulata.
What is the function of the pars compacata?
They consist of melanin containing neurons, that synthesize dopamine.
The neurons of the pars compacata project to the.
The striatum ( caudate nucleus + putamen ) of the basal ganglia.
The neurons of the pars compacata extends dorsomedially into a region known as.
The ventral tegmental area
The origin of the ascending mesolimbic dopaminergic pathway.
The ventral tegmental area (VTA)
The non-pigmented subdivision of the substantia nigra.
The pars reticulata
A functional homologue of the internal globus pallidus.
The pars reticulata
Lies ventral to the substantia nigra.
The crus cerebri
What are the fibers that constitute the crus cerebri?
Corticospinal - corticobulbar - corticopontine
What is reticular formation?
Complex matrix of neurons that extends throughout the length of the brainstem.
connects superior colliculus to lateral geniculate body.
The superior brachium
connects inferior colliculus to medial geniculate body.
Inferior brachium
Nerve at the level of the superior colliculus.
Oculomotor nerve
Nerve at the level of the inferior colliculus.
Trochlear nerve
Descending tracts originate from the medullary and pontine reticular formation and influence muscle tone and posture.
The reticulospinal tracts
Ascending fibers of the reticular formation.
Reticular activating system (cholinergic)
A series of midline nuclei that extend throughout the length of the brainstem (serotogenic ).
The raphé nuclei
The raphé nuclei has ascending fibers to forebrain that are involved in.
Mood and cognitive function and in the neural mechanisms of sleep.
A group of pigmented neurons that lies in the rostral pontine tegmentum.
The locus coeruleus
The principal noradrenergic cell group of the brain.
The locus coeruleus
What are the s and s of unilateral brainstem lesion ?
- ipsilateral CN dysfunction.
- ipsilateral incoordination.
- contralateral spastic hemiparesis, hyperreflexia and +ve Babinski sign.
- contralateral hemisensory loss
