SGD Group 4 October, 2012 y

Embryology: developed from Mesencephalon

MIDBRAIN BOUNDARIES

Lateral

Superior Brachium Inferior Brachium

Posterior

Tectum

Suprior colliculi Inferior colliculi

Anterior

Crura Cerebri

Medial

Tegmentum

MIDBRAIN By: MATHET

Crura Cerebri

-surrounds the interpeduncular fossa

On the medial side is the OCULOMOTOR NERVE

Its floor is perforated by many blood vessels in the region called posterior perforated substance

Superior Brachium

- links lateral geniculate to superior colliculus

Inferior Brachium

- links medial geniculate to inferior colliculus

SGD Group 4 October, 2012

Posterior side

Anterior Side

Tectum or quadrigeminal plate

Divides into:

Superior colliculi

- Visual reflex

Inferior colliculi

- Lower auditory refle

Tegmentum -contains all descending and ascending tracts from spinal cord Contains:

1. Oculomotor nuclei 2. Mesencephalic

Reticular formation 3. Red nucleus

Structures that divides each boundaries: Cerebral aqueduct – separates tectum from tegmentum Substantia nigra

- Separates tegmentum from crura cerebri

SGD Group 4 October, 2012 Nuclei of the Midbrain Location Afferent

Connection Efferent Connection

Function

Inferior Colliculus (Large Nucleus of Gray Matter)

Tectum Cochlea Major brainstem auditory relay transmitting impulses from lateral lemniscus to medial geniculate body

Parabigeminal nucleus Ventrolateral to inferior colliculus

Functions with superior colliculus in processing visual information

Trochlear nucleus Posterior to medial longitudinal fasciculus

Superior oblique muscle

Works with trochlear nerve in movement of superior oblique muscle

Mesencephalic nucleus of CN V Lateral to cerebral aqueduct

Proprioreceptors on Teeth, periodontum, temporomandibular joints; Muscles spindles of muscles of mastication

Proprioception (Deep pressure);(Stretch)

Substantia nigra Between tegmentum and crus cerebri

Muscle tone

Superior colliculus Tectum Retina Visual reflex

Oculomotor nucleus

Lateral somatic columns - Dorsal cell nucleus - Intermediate cell nucleus - Ventral cell nucleus - Medial cell nucleus Caudal central nucleus Visceral nuclei

- Edinger Westphal nucleus

- Anterior median nucleus

Nucleus of Perlia

Posterior to medial longitudinal nucleus

Motor neurons of Extraocular muscles, Pupillary sphincter and lens thru ciliary ganglion

Innervates inferior rectus muscle Innervates inferior oblique muscle Innervates medial rectus muscle Innervates superior rectus muscle Innervate levator palpebral muscle Accommodation of lens; Pupillary light reflex Ocular convergence

Accessory Motor Nuclei Interstitial nucleus of Cajal

Nucleus of Darkshewitsch

Nuclei of Posterior

Commissure

Relationship with other nuclei Nucleus prepositus Rostral interstitial

nucleus of MLF

Lateral to Middle longitudinal fasciculus (MLF) Ventrolateral border of central gray matter Dorsolateral and dorsal to central gray matter

Slow rotatory and vertical eye movements and smooth pursuit eye patterns Upward eye movement Downward eye movement

Red nucleus Between cerebral aqueduct and substantia nigra

Acts in close conjunction with the motor cortex and cerebellum in controlling motor behavior

Source: Snell Neuroanatomy and Carpenters Human Neuroanatomy

SGD Group 4 October, 2012

Locations of each Midbrain nuclei

SGD Group 4 October, 2012 Fiber Tracts of the Midbrain Origin Termination Function

(Motor Tracts)

Corticospinal Tract Anterior Corticospinal Tract Lateral Corticospinal Tract

Pyramidal cells of Layer V of cerebral Cortex

Nucleus proprius of Lamina IV, Dorsal horn cells of Lamina V and VI and Intemediate zone cells of Lamina VII

Controls movement of torso, upper limbs and lower limbs

Corticonuclear Tract/ Corticobulbar Tract

Motor cortex of Frontal Lobe

Motor neurons of brainstem motor nuclei

Controls muscles of head, face and neck

Temporopontine Tract Temporal Lobe Pontine nuclei Carries information to the cerebellum about the type and strength of motor impulse generated in the cortex

Frontopontine Tract Frontal Lobe Pontine nuclei

Medial longitudinal fasciculus Medial Vestibular nucleus, Superior Colliculus

Trochlear , Abducens and Occulomotor nuclei

Carries information of the direction that the eye would move; Integrates movements directed by gaze centers (frontal eyefield) and information about head movement

Decussation of Rubrospinal Tract Red nucleus Lamina V, VI and VII of spinal cord

Control of muscle tone on flexor muscle groups

Sensory Tract

Lateral Lemnisci Cochlear nucleus Inferior Colliculus Principal ascending auditory pathway; connects superior olivary complex with inferior colliculus

Trigeminal Lemnisci Principal sensory nucleus of Trigeminal system

Ventroposteromedial nucleus (VPMn) of Thalamus

Conveys the nociceptive and thermal sense

Spinal Lemnisci/ spinothalamic tract Lateral Spinothalamic Tract

Anterior Spinothalamic Tract

Posterior marginal nucleus of Lamina I, nucleus propius of Lamina IV; and Dorsal horn nuclei of Lamina V

Ventral Posterolateral nucleus(VPLn) in Thalamus

Transmits pain and temperature Transmits crude touch and pressure

Medial Lemnisci/ Reil’s band/ Reil’s ribbon

Gracile nuclei and cuneate nuclei

Ventral posterolateral nucleus (VPLn) of thalamus

Constitutes the 2nd

neuron of posterior column pathway,; conveys kinaesthetic sense and discriminative tactile sense

(Source: Snell Neuroanatomy and wikipedia)

SGD Group 4 October, 2012

Posterior side: Pontine Tegmentum

Embryology: Developed from Metencephalon

Boundaries of Pons

Posterior

Pontine Tegmentum

Anterior

Basal Part (Pons Proper)

PONS By: Mathe Monje

Pontine Tegmentum - Contains:

1. Cranial nerve nuclei of CN V, VI, VII and VIII 2. Ascending and descending tracts 3. Reticular formation

Structures found: (from medial to lateral)

1. Median sulcus 2. Medial eminence 3. Sulcus limitans 4. Vestibular area

5. Substantia ferruginea – superior to medial eminence 6. Facial Colliculus – inferior to medial eminence; bulb like; Facial nucleus + Abducens nucleus 7. Superior Cerebellar peduncle – lateral limit of posterior surface of pons

Pons Proper - Consists of orderly arranged transverse and

longitudinal fiber bundles intercalated between collections of pontine nuclei

Structures found: (from medial to lateral)

1. Groove for basilar artery

2. Motor root of Trigeminal nerve (smaller)

3. Sensory Root of Trigeminal Nerve (larger)

4. Middle Cerebellar peduncle

(On the groove between pons and medulla: from medial

to lateral)

5. Abducens Nerve

6. Facial Nerve

7. Vestibulocochlear Nerve

SGD Group 4 October, 2012 Nuclei of Pons Location Afferent Connection Efferent

Connection Function

(Caudal Part)

Facial nucleus Facial Motor

Nucleus

Superior Salivatory nucleus

Posterior to lateral part of Medial lemniscus

Branchiomeric muscles of the face Lacrimal gland

Influence facial expression Influence secretion of lacrimal gland (by pterygopalatine ganglion)

Abducens Nucleus Above striae medullares and subjacent to medial eminence

Motor neurons of Lateral rectus muscles via CN VI

Together with fibers of Paramedian Pontine Reticular formation (PPRF) enables conjugate horizontal gaze/ deviation of eyes

Rostral Interstitial Nucleus of MLF

Tegmentum Together with fibers of Paramedian Pontine Reticular formation (PPRF) enables vertical eye movements

Medial Vestibular nucleus Lateral to abducens nucleus

Utricle and saccule Coordinate head and trunk Movement

Spinal nucleus of CN V Anteromedial aspect of inferior cerebellar peduncle

Receives information about deep or crude touch, pain and temperature from ipsilateral face

Pontine nuclei Pons (Obviously..hehe)

Allow modification of actions in the light of their outcome or correction of errors

Cranial Part

Motor nucleus of Trigeminal Nerve

Upper part of pons along lateral margin of 4

th ventricle

Motor neurons of Muscles of mastication

Innervates muscles of mastication , tensor tympani, myolohyoid and anterior digastric muscles

Principal Sensory Nucleus of Trigeminal Nerve

Lateral side of Motor nucleus of Trigeminal Nerve

Sensory neurons of skin of face and head , mucus membranes of nose and mouth, teeth and cranial dura

Touch, pain and thermal sense

Superior Olivary nucleus Medial Superior

Olive

Lateral Superior Olive

Medial Nucleus of

Trapezoid Body

Pons (wala na ko makta nga specific location niya)

Ipsilateral and contralateral stimulation for low frequency sounds. Ipsilateral stimulation for high frequency sounds. Contralateral stimulation Localization of sounds

Cochlear nuclei Dorsal Cochlear

nucleus

Ventral Cochlear nucleus

Dorsal aspect of Inferior Cerebellar peduncle Ventral surface of Inferior Cerebellar peduncle

Cochlea

Preserve or even enhance the timing information that is provided by each fiber of the cochlear nerve

Fiber Tracts: Spinal Tract of CN V, Lateral Lemnisci, Medial Lemnisci and Spinal Lemnisci (refer location and function on Table 2)

Source: Snell Neuroanatomy, Carpenters Human Neuroanatomy and wikipedia)

SGD Group 4 October, 2012

Caudal Part of Pons

Transverse Section at the level of Trigeminal Nuclei