Brainstem

Midbrain

Pons

Medulla Oblongata

Anatomically the brainstem includes the

Cardiovascular

Respiratory

the brainstem contains vital centers for

Brainstem

an area where all sensory information goes TO and FROM the brain

Olfactory

Optic

10 of the 12 pairs of cranial nerves are attached to the brainstem except:

Midbrain (Mesencephalon)

Lies between the diencephalon and the pons

Highest portion of the brainstem

Cerebral aquedact

Also known as the central cavity

Pyramidal (corticospinal) tracts

Cerebral peduncles contains

Ventral (anterior) Surface of the brain

Location of the cerebral peduncles

Superior Cerebellar peduncles

connects the cerebellum to the pons and midbrain

contains the dentatorubrothalamic fibers and the ventral spinocerebellar tract

Periaqueductal Gray matter

What gray matter surrounds the cerebral aqueduct

Fight and Flight Reaction

Mediates response to visceral pain

Periaqueductal gray matter is involved in two related functions

Corpora Quadrigemina

the largest nuclei in the midbrain

Divided into the superior and inferior colliculi

Superior colliculi

A nuclei in midbrain that acts in visual reflexes

Inferior Colliculi

nuclei in the midbrain that act in reflexive response to sound

Transverse Groove

Vertical Groove

What divides the Corpora Quadrigemina or colliculi

Substantia nigra

Red Nucleus

What two pigmented nuclei is imbedded in the white matter of the midbrain

Substantia Nigra

neuronal cell bodies that contain melanin

Functionally linked to the basal nuclei

Red Nucleus

lies deep to the substantia nigra

Largest nucleus of the reticular formation, related to sleep wake cycle

Tectum

part of the midbrain posterior to the cerebral aqueduct; it has four small surface swellings

Tegmentum

is located between the tectum and the base (basis pedunculi)

contains cranial nerve nuclei and sensory pathways

Basis Pedunculi (Crus Cerebri)

Forms the base of the midbrain and contains corticospinal, corticobulbar, and corticopontine tracts

Pedunculus Cerebri (Cerebral Peduncle)

Includes and the collective term for tegmentum and basis pedunculi (crus cerebri)

Pretectum (Pretectal Area)

is located between the superior colliculus and the habenular trigone

Superior Colliculus

For Visual Reflexes

Receives visual input from the retina and from frontal (area 8) and occipital (area 19) eye fields.

Receives auditory input from the inferior colliculus to mediate audiovisual reflexes

is concerned with detection of movement in visual eye fields, thus facilitating visual orientation, searching, and tracking

Frontal Area 8

Occipital Area 19

Superior Colliculus receives visual input from the retina and from frontal (_________)__ and Occipital (______) eye fields

(what brodmann’s Area)

Commissure of the superior colliculus

interconnects the two superior colliculi

Brachium of the Superior Colliculus

conducts retinal and corticotectal fibers to the superior colliculus and to the pretectum, thus mediating optic and pupillary reflexes

Aqueduct of sylvius

Other term of cerebral aqueduct

Periaqueductal gray matter

surrounds the cerebral aqueduct

Oculomotor Nucleus of CN III

give rise to GSE fibers (General somatic efferent fibers = motor fibers)

projects crossed fibers to the superior rectus

projects crossed and uncrossed fibers to the levator palpebrae

Medial Recti

Inferior Recti

Superior Recti

Infeior Oblique

Superior Levator palpebrae

Extraocular Muscles that is innervated by CN III

Edinger-Westphal Nucleus of CN III

gives rise to GVE (General Visceral Efferent fibers) preganglionic parasympathetic fibers that terminate in the ciliary ganglion

Postganglionic fibers from the ciliary ganglion innervates the ciliary body (accomodation) and the sphincter muscle of the iris (pupillary light reflex)

Medial Longitudinal Fasciculus

contains vestibular fibers that coordinate eye movements.

interconnects the ocular motor cranial nerves (CN III, CN IV, and CN VI).

CN III

CN IV

CN VI

The medial longitdunal fasciculus interconnects which oculomotor cranial nerves?

Central Tegmental Tract

contains rubro-olivary and reticulothalamic fibers, and rubrothalamic tract (under afferent system responsible for sensation)

also contains lemnisci

extends from the midbrain to the inferior olivary nucleus

Red Nucleus

is located in the tegmentum at the level of the oculomotor nucleus (the level of the superior colliculus)

receives bilateral input from the cerebral cortex

receives contralateral input from the cerebellar nuclei

gives rise to the crossed rubrospinal tract

gives rise to the uncrossed rubro-olivary-tract

exerts facilitatory influence on flexor muscles

Cerebral Cortex

The Red Nucleus receives bilateral input from the

Cerebellar Nuclei

The red nucleus receives contralateral input from the

Flexor Muscles

The red nuclues exerts facilitatory influence on

Medial Lemniscus

mediates dorsal column modalities to the ventral posterolateral nucleus of the thalamus

Spinal Lemniscus

contains the lateral and ventral spinothalamic tracts and the spinotectal tract

Substantia Nigra

Includes pars compacta and pars reticularis

Basis Pedunculi

Forms the base of the midbrain and contains corticospinal, corticobulbar, and corticopontine tracts

Nucleus of the Inferior Colliculus

is an auditory relay nucleus that receives binaural input from the lateral lemniscus

projects to the medial geniculate body via the brachium of the inferior colliculus

Lateral Lemniscus

projects binaural auditory information to the inferior collicular nucleus

Commisure of the Inferior Colliculus

Interconnects the inferior collicular nucleus and its opposite partner

Brachium of the Inferior Colliculus

conducts auditory information from the inferior collicular nucleus to the medial geniculate body

Cerebral Aqueduct

is located between the tectum and tegmentum

is surrounded by the periaqueductal gray matter

interconnects the third and fourth ventricles

hydrocephalus

blockage (aqueductal stenosis) results in

Periaqueductal Gray Matter

is the central gray matter that surrounds the cerebral aqueduct

Locus ceruleus

Mesencephalic nucleus and tract

Dorsal tegmental nucleus

Dorsal nucleus of raphe

Nuclear Groups of Periaqueductal Gray Matter

Dorsal tegmental nucleus

Contains enkephalinergic neurons that play a role in endogenous pain control

Dorsal nucleus of raphe

Contains serotonergic neurons

Trochlear Nucleus of CN IV

gives rise to GSE fibers, which encircle the periaqueductal gray matter, decussate in the superior medullary velum, and exit the midbrain from its dorsal aspect to innervate the superior oblique muscle

Decussation of the Superior Cerebellar Peduncles

is most conspicuous structure of this level

Interpeduncular Nucleus

receives input from the habenular nuclei via the habenulointerpeduncular tract (fasciculus retroflexus of Meynert)

Substantia Nigra

receives gamma-aminobutyric acidergic (GABA-ergic) input from the caudatoputamen (striatonigral fibers).

projects dopaminergic fibers to the caudatoputamen (nigrostriatal fibers)

projects nondopaminergic fibers to the ventral anterior nucleus, ventral lateral nucleus, and mediodorsal nucleus of the thalamus (nigrothalamic fibers)

Medial Lemniscus

Lateral Lemniscus

Trigeminal Lemniscus

the ones who relay sensory information to the brain including the tectral tegmental tract

Mesencephalic nucleus of the trigeminal nerve

Trochlear nucleus

Components of Periaqueductal gray Matter

Posterior Commisural Level (Pretectal Region)

is a transition area between the mesencephalon and the diencephalon

pinakatuktok bago mag-midbrain

Posterior Commisure

Pretectal Nucleus

2 Regions of the Posterior Commisural Level (Pretectal Region)

Posterior Commisure

marks the caudal extent of the third ventricle (pinaka-end of third ventricle)marks the rostral extent of the cerebral aqueduct

interconnects pretectal nuclei, thus mediating consensual pupillary light reflexes

demarcation point kung saan mag-eend na ang third ventricle para maging cerebral aqueduct papuntang fourth ventricle between the pons and cerebellum

Pretectal Nucleus

receives retinal input via the brachium of the superior colliculus

projects to the ipsilateral and contralateral Edinger-Westphal nucleus (of the oculomotor nerve), thus mediating the pupillary light reflexes

Pons

extends from the inferior pontine sulcus to the superior pontine sulcus

connected to the cerebellum by the middle cerebellar peduncle (basically, pons connects to the midbrain and the medulla oblongata)

1 inch

How long is the Pons

CN V

CN VI

CN VII

CN VIII

The pons contains the nucleus of these Cranial Nerves

Motor Nuclei

Sensory Nuclei

Two general groups of cranial nerve nuclei:

Corticobulbar tracts

Corticospinal tracts

Corticopontine tracts

Pontine Nucleus

Consists of the base which contains the efferent fibers/tracts:

Cranial Nerve Nuclei

Reticular Nuclei

Major Ascending sensory pathways

Tegmentum contains the:

Pneumotaxic Center

Apneustic Center

Two autonomic respiratory centers

Upper pons

Pneumotaxic Center is located in the

Lower pons

Apneustic center is located in the

Pneumotaxic Center

Apneustic Center

they control the rhythm of perspiration

Trigeminal Motor Nucleus

Trigeminal-main Sensory Nucleus

2 Nuclei of the Trigeminal Nerve

Basilar Groove

vertebral arteries join together at the level of pontomedullary junction to become the basilar artery embedded in this groove

Abducens Nerve

Facial Nerve

Vestibulocochlear Nerve

Besides trigeminal nerve, what nerves can we also see at the level of the pons

Abducens, Facial, Vestibulocochlear

Medial to Lateral order of AFV Nerves

Dorsal and Ventral Cochlear Nuclei

Receive auditory input from the cochlea through SSA fibers via the cochlear branch of CN VIII.

Are auditory relay nuclei that give rise to the ipsilateral and contralateral lateral lemniscus

Trapezoid Body

is formed by decussating fibers of the ventral cochlear nuclei

contains the acoustic striae, medical lemnisci, exiting abducent (CN VI) fibers, and aberrant corticobulbar fibers

Superior Olivary Nucleus

is an auditory relay nucleus at the level of the trapezoid body

receives input from the cochlear nuclei

contributes bilaterally to the lateral lemniscus

Lateral Lemniscus

is a pontine auditory pathway extending from the trapezoid body to the nucleus of the inferior colliculus

conducts a preponderance of contralateral cochlear input

Corticobulbar tract

synapses in the motor nuclei of the cranial nerves except in the ocular motor nuclei of CN III, IV, and VI

Corticospinal tract (Pyramidal Tract)

synapses in the ventral horn of the spinal cord

Corticopontine Tract

synapses in the pontine nuclei

Central Tegmental Tract

Juxtarestiform Body

Middle Cerebellar Peduncle

Superior Cerebellar Peduncle

Pontine Nuclei

Cerebellar Pathways and Relay Nuclei

Juxtarestiform Body

forms part of the inferior cerebellar peduncle

contains vestibulocerebellar, cerebellovestibular, and cerebelloreticular fibers

Middle Cerebellar peduncle

contains pontocerebellar fibers

connects the pons to the cerebellum

Pontine Nuclei

are cerebellar relay nuclei in the base of the pons

give rise to pontocerebellar fibers that constitute the middle cerebellar peduncle

Medullopontine Junction

Dorsal and ventral cochlear nuclei of CN VIII are found at the

Medial, Lateral, and Superior Vestibular nuclei of CN VIII

receive proprioceptive (SSA) input from the semicircular ducts, utricle, saccule, and cerebellum (ears)

project to the cerebellum and the MLF

the lateral vestibular nucleus give rise to the lateral vestibulospinal tract

Medial Longitudinal Fasciculus

contains vestibular fibers of CN VIII that coordinate eye movements via CN III, CN IV, and CN VI

mediates nystagmus and lateral conjugate gaze

Abducent Nucleus of CN VI

underlies, in the caudal medial pontine tegmentum, the facial colliculus of the rhomboid fossa

projects exiting fibers through the trapezoid body and through the corticospinal tract of the base of the pons

Lateral Rectus Muscle

Abducent nucleus of CN VI gives rise to GSE fibers that innervate the

Superior Salivatory Nucleus of CN VII

includes the lacrimal nucleus

gives rise to the GVE preganglionic parasympathetic fibers that synapse in the pterygopalatine and submandibular ganglia

Spinal Trigeminal Tract & Nucleus of CN V

This can be seen in your midpontine.

Motor Nucleus of CN V

lies in the lateral midpointine tegmentum at the level of entrance of the trigeminal nerve

lies medial to the principal sensory nucleus of the trigeminal nerve

receives bilateral corticobulbar input

Mastication

Motor nucleus of CN V gives rise to SVE (Special Visceral Efferent Fibers) fibers that innervate muscles of

Principal Sensory Nucleus of CN V

lies lateral to the motor nucleus of CN V

receives discriminative tactile and pressure sensation input from the face

gives rise to the trigeminothalamic fibers that join the contralateral ventral trigeminothalamic tract

gives rise to the uncrossed dorsal trigeminothalamic tract, which terminates in the ventral posteromedial nucleus of the thalamus

Mesencephalic Nucleus

extend from upper pons to the upper midbrain

contain pseudounipolar neurons

receive input from muscle spindles and pressure receptors (muscle of mastication and extraocular muscles)

Locus Cereleus

melanin-containing nucleus in the pons and midbrain

important nucleus of the monamine system that projects noradrenergic axons to all parts of the CNS

principal site of synthesis ng norepinephrine