[BNS} MIDBRAIN

PONTOMIDBRAIN JUNCTION; Superior Pontine Sulcus

The caudal limit of the midbrain is called? This is marked by which structure ventrally?

MIDBRAINDIENCEPHALIC JUNCTION; Mamillary Bodies and Posterior Commissure

The rostral limit of the midbrain is called? This is marked or demarcated by the imaginary line connecting to which structures?

Posterior Commissure

the inferior wall of pineal stalk that holds the pineal gland in place dorsally

CORPORA QUADRIGEMINA

Tectum of the midbrain

CN III, IV, and mesencephalic nucleus (for non-conscious proprioception of the muscles of mastication)

What are the cranial nerve nuclei found in the midbrain

Crus cerebri

Structure that contains Basis only

Basis pedunculi

Refers to Basis + Substancia nigra

Cerebral peduncle

Basis + tegmentum

Optic chiasm and optic tract

The rostral limit of the ventral surface of the midbrain houses which structures

Interpeduncular fossa

The space between the two crus cerebri with structures belonging to the diencephalon

Mamillary bodies, Tuber cinereum, Infundibulum, Pituitary gland, CN III

Give structures found in the Interpeduncular fossa

Exit of CN IV (Trochlear Nerve)

Only cranial nerve that exits dorsally in the ponto-midbrain junction

Pineal Gland, Lateral and Medial Geniculate Body

Structures located in the rostral limit of the midbrain

Superior quadrigeminal brachium (Recall: SSL)

This structure allows for the communication between Superior colliculi (for visual reflexes) and LGB (for vision)

Inferior colliculi

Serves as the auditory relay nucleus in the midbrain that receive fibers of the lateral lemniscus (principal ascending auditory pathway)

Inferior quadrigeminal brachium

Inferior colliculi communicates with the medial geniculate body of the thalamus (hearing) via

True

T/F: The level of Superior Colliculus demarcates the upper ½ midbrain

False

T/F: The lower ½ midbrain has a wider interpeduncular fossa

Substancia nigra

The largest nucleus of the midbrain and the most ventrally located structure in tegmentum that lies in the junction between the basis and tegmentum

Audio-visual reflex

Inferior colliculus also send signals to the superior colliculus for what kind of reflex

Pons = Superior Olivary Nucleus

Midbrain = Inferior Colliculus

What are the two auditory relay nucleus in the pons and midbrain

PYRAMIDAL TRACT

What tract occupies the middle or intermediate 3/5 of the basis (crus cerebri)

Corticospinal and Corticobulbar Tract

What are the tracts that comprises the pyramidal tract

Arnold’s Bundle (Frontopontine)

What tract occupies the medial 1⁄5 of the basis coming from the frontal lobe

Turck’s Bundle (Parieto-occipitotemporopontine)

What tract occupies the lateral 1⁄5 of the basis coming from the frontal lobe

False; Contralateral

T/F: Lesions in the pyramidal tract at the level of the midbrain (above the pyramidal decussation) will result in ipsilateral hemiparesis

True

T/F: Substancia Nigra is functionally related more to the basal nuclei for modulation and regulation/fine-tuning of movement for finesse

Pars Compacta (dorsal)

Which structure in the substancia nigra contains dopamine (dopaminergic neurons) and serves as the major source of dopamine to the striatum

Pars Reticulata (ventral)

Which structure in the substancia nigra contains GABA

Periaqueductal gray (PAG)

The cerebral (sylvian) aqueduct or Iter is surrounded by which structure that functions in modulating descending pain

T

T/F: PAG is seen throughout the midbrain and is exclusive to it

Decussation of the SCP

This structure originates from the deep cerebellar nuclei to the contralateral red nucleus/thalamus and is the anatomical basis for communication between one cerebellar hemisphere with the opposite cerebral hemisphere

True

T/F: The decussation of the trochlear nerve root is within midbrain

trochlear nucleus = contralateral

trochlear nerve = ipsilateral

always remember that if nerve = ipsilateral

Trochlear nucleus has _______ innervation, but the trochlear nerve has ________ innervation

Superior oblique muscles (extraocular muscle)

Addtl info: causes intorsion and inferolateral deviation of the eyeball

The GSE function of the CN IV innervates which muscle

Superior Colliculus

This structure in the upper half of the midbrain (in the tectum) is responsible for visual reflexes and facilitates visual orientation and tracking

Retina, Inferior Colliculi

The Superior Colliculus receives fibers from which of the following structures

Lemniscal crescent

This structure in the tegmentum of the midbrain is comprised of medial lemniscus, spinal lemniscus, trigeminal lemniscus

It has already terminated below in the lower half (inferior colliculus)

Why is the lateral lemniscus missing from the lemniscal crescent?

Ventral tegmental area of Tsai (VTA)

This feature is distinct in the upper half of the midbrain which contains dopaminergic neurons and has a connection with the ventral striatum (n. accumbens) for reward pathway such as addiction

Red nucleus

This receives axons of the deep cerebellar nuclei from the contralateral cerebellar hemisphere and serves as termination of fibers in SCP after decussating

Parvocellular

Division of fibers from the cerebellar hemisphere rostrally

Magnocellular

Division of fibers from the cerebellar hemisphere caudally

Rubro-olivary tract, Inferior olivary nucleus

Parvocellular Division gives rise to which structures

Rubro-olivary tract

Major tract that passes through the central tegmental tract (CTT)

Inferior olives of the medulla (same side) = ipsilateral

Rubro-olivary tract contains uncrossed descending fiber tracts that terminate at

Inferior olivary nucleus

This structure is located at the medulla on the same side which also serves as a cerebellar relay nucleus

Olivo-cerebellar tract

The Inferior olivary nucleus gives rise to the tract that gies back to the cerebellum

Rubrospinal decussation

Magnocellular division gives rise to this decussation immediately at the ventromedial part of the midbrain tegmentum

Rubrospinal tract

The rubrospinal decussation becomes this tract that terminates at the spinal motor neurons at Rexed Lamina IX (crossed = contralateral) and is for the control of flexor muscle tone

Superior colliculus

The tectospinal tract originates and receives fibers from which structure

dorsal tegmental decussation of Meyner

The tectospinal tract decussates at which structure

Visual tracking = reflex movement of head and neck in response to visual stimuli

Function of the Tectospinal Tract

Ventral part of the periaqueductal gray (PAG)

Oculomotor nerve nuclear complex (CN III) located at which structure

False; does not have connection

T/F: Oculomotor nerve nuclear complex (CN III) has a synaptic connection with the Mesencephalic nucleus of V

Oculomotor somatic nuclear group

Origin of oculomotor nerve rootlets

Ptosis and Down & out look

Lesions to the somatic cell group of the oculomotor nerve nuclear complex (CN III) results to

Edinger-Westphal nucleus

Visceral cell column originates from which nucleus

GVE visceromotor parasympathetic for pupillary constriction; synapses at the Ciliary Ganglion

What type of function of the visceral cell column of the oculomotor nerve nuclear complex (CN III), and where does it synapse?

Dilated pupil

Lesion to the visceral cell column of the oculomotor complex results to

Ptosis, Down & out look, Dilated pupil (Recall: PDD)

Triad of Oculomotor lesion

parasympathetic fibers (pupillary constriction; GVE)

Fibers that are superficially located in the oculomotor nerve trunk

somatic fibers (levator palpebra and extraocular muscles; GSE)

Fibers that are internally located in the oculomotor nerve trunk

Pupillary dilation

Extrinsic compression of the oculomotor nerve results to

CN II

Afferent limb of the Pupillary Light reflex

Pretectal nucleus in the midbrain-diencephalic junction

Coordinating center of the Pupillary Light reflex

Parasympathetic division/ component of oculomotor nerve (III)

Efferent limb of the Pupillary Light reflex

Direct light reflex = pupillary constriction on the same eye

Consensual light reflex = pupillary constriction on the opposite eye

Direct light reflex = pupillary constriction on the _________

Consensual light reflex = pupillary constriction on the _________

Medial longitudinal fasciculus (MLF)

Linkage of the nuclei of CN III, IV, and VI is mediated by this structure for Horizontal Conjugate Gaze

Paramedian pontine reticular formation (PPRF) nuclei

Coordinating center of the Horizontal Conjugate Gaze

Horizontal Conjugate Gaze

This refers to the lateral movement of the eye that requires the abduction of one eye (through lateral rectus) and adduction of other eye (through medial rectus)

Rostral interstitial nucleus of MLF (RiMLF)

Coordinating center of Vertical Conjugate Gaze that is located in the midbrain-diencephalic junction

Trochlear n. (Superior Oblique) + Oculomotor subnucleus (Inferior Rectus)

Downward gaze requires the coordination of which structures

Oculomotor subnucleus (Inferior Oblique and Superior Rectus)

Upward gaze requires the coordination of which structures

Posterior commissure

This commissure plays a role in both the (a) pupillary light reflex, and (b) vertical conjugate gaze

T/F: Lesion of the MLF can result to strabismus

Basilar a. (Posterior Cerebral a. and SCA) and ICA

Main blood supply of the Midbrain

Crossed Hemiplegia

Vascular syndrome of the Midbrain