Neuroscience Review

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Learning Objectives

Analyze the structure & function of various parts of

brainstem.

Identify cranial nerves attached to Medulla.

Demonstrate external features of medulla.

Differentiate the distribution of Gray and White

matter in medulla.

Demonstrate connections of CN & named nuclei in

medulla and relate with their functions.

Compare & contrast sensory & motor decussation in

medulla.

Identify Pyramid, Olive, Faciculus

gracilus, Faciculus cuneatus on

external surface of medulla.

Identify Vagal, Hypoglosssal &

Vestibular triangles; Obex, area

postrema and Facial Colliculus in

floor of 4th ventricle.

LOs continued…………….

White matter of spinal cord Descending Tracts

Cortico Spinal

Tectospinal

Rubrospinal

Reticulospinal

Vestibulospinal

Hypothalamospinal

Ascending Tracts

Dorsal Column(Fasciculus Gracilus& Cuneatus)

Spinothalamic (Anterior & Lateral)

Spinocerebellar (Anterior & Posterior)

Spinovestibular

Spinotectal

Spinoreticular

Spino-olivary

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BRAIN VESICLES

• PROSENCEPHALON

– Diencephalon

– Telencephalon

• MESENCEPHALON

• RHOMBENCEPHALON

– Metencephalon

– Myelencephalon

Medulla Oblongata

• Ascending and descending tracts

• Named nuclei (Inferior olivery nuclear

complex)

• Cranial nerve nuclei (VI, VII, VIII, IX, X, XI,

XII)

Pons

• Basal portion (Bridges between ipsilateral

cerebral hemisphere and contralateral

cerebellar hemisphere)

• Dorsal portion

– Ascending and descending tracts

– Cranial nerve nuclei (V, VI, VII, VIII)

Midbrain

• Tectum (roof having superior and inferior

colliculi)

• Tegmentum (ascending and descending

tracts, CN nuclei of III & IV nerve, red

nucleus, substantia nigra etc)

Diencephalon

• Constitute central core of cerebrum

– Thalamus

– Hypothalamus

– Subthalamus

– Epithalamus

– Metathalamus

Telencephalon

• The most well developed part of CNS

– Cortex (the peripheral gray matter)

– Medulla (central white matter)

• Projection fibers

• Association fibers

• Commissural fibers

– Corpus striatum (deep seated basal nuclei)

Morphology of Medulla Oblongata

• Medulla is 3 cm long

• Upper limit clearly marked by lower border

of basal pons

• Inferior limit at rootlets of 1st cervical spinal

nerve

Dorsal surface of Medulla

On dorsal surface junction of medulla and pons is

marked by a line passing through inferior edge

of middle cerebellar peduncles (ICP)

– Closed part of medulla Fasciculus gracilis

Fasciculus cuneatus

– Open part of medulla Floor of 4th ventricle

CN attached to Medulla

• Hypoglossal attached to venterolateral

sulcus between pyramid and olive)

• 9th, 10th, 11th CN to dorsal olivary sulcus

• 7th & 8th at junction of Medulla and Pons

well laterally

• Abducent at junction of base of pyramid

and basal pons

Cranial nerve nuclei

Medulla –Hypoglossal nucleus, Nucleus

ambiguous, DMN of Vagus, Vestibular

nuclear complex, Auditory nuclei, Spinal

trigeminal nucleus, Tractus solitarius nucleus

Pons – Abducent nerve nucleus, facial nucleus,

trigeminal nuclei (Chief sensory nucleus,

motor nucleus)

Midbrain – 3rd & 4th nerve nuclei,

mesencephalic nucleus of trigeminal

Named Nuclei in Brain stem

Inferior olivary nuclear complex

Pontine nuclei

Inferior Salivatory Nucleus

Superior Salivatory Nucleus

Red nucleus of midbrain

Substantia nigra

Reticular formation nucli

Brainstem Ascending tracts• Dosral Column Tracts / Posterior Column Tracts

– Fasciculus Gracilis

Medial Lemniscus

– Fasciculus Cuneatus

• Spinocerebellar Tracts

• Spinotectal Tracts

• Spinothalamic Tracts Spinal Lemniscus

• Spinoreticular

• Lateral Lemniscus

• Trigeminal lemniscus

Descending tracts of Brainstem

• Corticospinal Tract

• Corticonuclear

• Cortico-pontocerebellar

• Rubrospinal

• Reticulospinal

• Vestibulospinal

• Medial longitudinal fasciculus

• Tectospinal

Medullary Nuclei

1. Inferior olivary nuclear complex (inferior olivary

nucleus, medial accessory olivary nucleus,

dorsal accessory olivary nucleus)

– Afferents by

• Central tegmental tract from corpus striatum & red nucleus

• Cortico-olivary fibers

• Spino-olivary fibers

– Efferent by

• Olivo-cerebellar fibers through ICP

• Olivo-spinal

Medullary Nuclei

2. Gracile Nuclus

3. Cuneate Nucleus

4. Arcuate nucleus

5. Lateral cuneate nucleus

Cranial Nerve Nuclei in Medulla

• Hypoglossal nucleus

• Nucleus ambiguus

• Dorsal motor nucleus of vagus

• Nucleus of solitary fasciculus

• Ventibulo-cochlear nuclear complex

• Nucleus of the trigeminal spinal tract

Cranial Nerve Nuclei in Medulla

• Ventibulo-cochlear nuclear complex

– Dorsal cochlear nucleus

– Ventral cochlear nucleus

– Superior vestibular nucleus

– Medial vestibular nucleus

– Lateral vestibular nucleus

– Inferior vestibular nucleus

NA

PONS

• Basal Pons

• Tegmentum

• Only cranial nerve attached to pons is

trigeminal

Internal structure

• Pontine nuclei

• Cranial nerves Nuclei (5th, 6th, 7th)

&

• Fiber tracts• ML, SL, LL

• Corticopontine fibers

• Pontocerebellar fibers

• Corticospinal fibers

• Motor nucleus

• Chief sensory nucleus

• Mesencephalic nucleus

• Spinal nucleus

5thCN Nuclei in Pons

• Superior salivary nucleus lies along side the facial nucleus.

• It is parasympathetic in function.

• It provides axons which pass out in nervous intermedius part of facial nerve and reach to pterygopalatine and Submandibular ganglia.

• Its lower part is called inferior salivatory nucleus. Its fibers joins to the glossopharyngeal nerve to reach to otic ganglion.

MIDBRAIN

• It connect Diencephalon to the Pons &

Cerebellum.

• It is the shortest segment of brainstem.

• Not more than 1.5 cm in length.

• Topographically it lies in posterior fossa .

• Its upper part passing through tentorial

notch.

Midbrain

Crus cerebri

Substancia Nigra Cerebral peduncle

Tegmentum

Tectum is the roof of midbrain

• 3rd & 4th cranial nerves leave midbrain.

• Occulomotor nerve leaves through the

medial surface of crus on the ventral

surface.

• Trochlear nerve leaves the dorsal surface

of midbrain just below the inferior colliculi.

Internal structure

• Each crus contains corticospinal , cortico

nuclear and corticopontine fibers.

4th CN

Cerebellar Peduncles

• Inferior cerebellar peduncle– Posterior spinal cerebellar tracts

– Olivocerebellar tract

– Vestibulo-cerebellar tract

– Cuneocerebellar tract

– Cerebelovestibular

• Middle cerebellar peduncle – Pontocerebellar

• Superior cerebellar peduncle – Anterior spinocerebellar

– Dentatorubrocerebellar

– Cerebellospinal fibers

COMPONENTS OF

CRANIAL&SPINAL NERVES• Afferent components

– Special somatic afferent• Optic nerve

• Cochlear

• Vestibular

– General Somatic Afferent• Dorsal gray horn of spinal cord

• Graycile and nuclei

• Special Visceral afferent

• Taste

• Olfaction

• General Visceral afferent (for visceral reflexes)

• Dorsal grayhorn / nucelus and tractus solitarius

Efferent components

• General somatic efferent– Motor horn of spinal cord

– Occulumotor trochlear abducents hypoglossal nuclei

• Special visceral efferent– Supply muscles of branchail arches origin

– Trigeminal motor nucleus

– Fascial motor nucleus

– Nucleus

– Ambiguos

– Accessory nucleus

• General visceral efferent– Preganglionic neurons of ANS, adinger westphal nucelus, lacrimtary

nucleus, salivartory nuclei, dosral motor nucleus of vagus

• Special somatic efferent

• Centrifugal fibers of 8th nerve and optic nerve.

Nervous System

Central Peripheral

Somatic

Autonomic

Somatic

Autonomic

Somatic Nervous

System (Afferent)

Somatic

Nervous

System

(Eff.)

RESPONSE OF SNS & ANS

• SOMATIC NERVOUS SYSTEM

– Voluntary

– Focused, precise and specific function /

response

• AUTONOMIC NERVOUS SYSTEM

– Mass discharge in sympathetic nervous

system (Fight or flight response )

– Discrete localized response by

parasympathetic

PARASYMPATHETIC

ANS

ANS-Parasympathetic

CN III

CN VII

CN IX

Vagus

FUNCTIONS OF PARASYMPATHETIC

• Decreased HR & force of contraction

• Vasodilator

• Secretomotor and relax sphincters in GIT

• Genital erectile tissue engorged

• Emptying of urinary bladder

• Action is discrete and localized because at

synapsis divergence is less and Ach is

rapidly deactivated Acetylcholinesterase.

Sympathetic ANS

Distribution of Sympathetic nerves

• White rami communicants - preganglionic

• Somatic branches through grey rami

communicants to all spinal nerves

supplying BV, sweat glands & erector pili.

• Vascular branches spread along BV.

• Visceral branches through Splanchnic

nerves carry preganglionic fibers to

prevertebral ganglia.

3rd CN

3rd CN

4th CN

6th CN

MLF

5th CN

7th CN

7th CN

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9th CN

10th CN

11

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N

12th CN

Boundaries between

• Midbrain and diencephalon

– Posterior commissure Mammillary bodies)

• Diencephalon and Telencephalon

– (Interventricular foramen Optic Chiasma)

Components of Diencephalon

• Thalamus

• Hypothalamus

• Subthalamus

• Epithalamus

• Metathalamus

Morphology of thalamus

• Largest sensory relay station to cortex

• 3 x 1.5 x 1.5 cm

• Medial, Lateral, Dorsal &Ventral Surfaces

• Relation to 3rd ventricle & internal capsule

• Divisions into nuclei

• External medullary lamina

• Internal medullary lamina

Medial Geniculate nucleus

• AFF: Inferior Colliculus / inferior branchium

• EFF: Auditory radiations to Temporal lobe

Lateral geniculate nucleus

• AFF: Retina / OT / opposite visual filed

• EFF: Geniculocalcarine tract

VPN

• AFF: ML / SL / TL

• EFF:

– Sensory cortex (3,1,2,5,7)

– Medial nucleus

– Nonspecific nuclei

VA & VL nucleus

• AFF:

– Dentate N.

– Substantia nigra

– Corpus striatum

• EFF:

– Motor cortex (4,6)

Nonspecific nuclei

• AFF:

– VPN

– Intralaminar Nuclei

• EFF:

– Association cortex

Thalamic syndrome

• Korsakoff’s syndrome

• Sensory loss of opposite ½

• Threshold to pain increase

• Spontaneous pain, laughing, crying

• Intractable pain

• Emotional instability

• Amnesia

Subthalamus

• Subthalamic N.

• Fiber tracts – dentatothalamic SL, ML, TL,

Lenticular fasciculus, Ansa lenticularis

• Substantia nigra

• Zona incenta (Red nucleus)

• Hemiballisnus ?

Epithalamus

• Pineal gland

– Biological clock + circadian rhythm

– Neuroendocrine tranducer

– Epiphysis cerebri

• Habenular nucleus

– AFF:• Stria medullaris thalami, Stria terminalis

– EFF: • Habenulo interpeduncular fasciculus

Hypothalamus

• Medial area – Suprachiasmatic

• Supraoptic nucleus

• Paraventricular nucleus Hypothalamohypophygeal tract

• Anterior nucleus / preoptic area

– Tuberal • Ventromedial tuberal nucleus

• Dorsomedial nucleus

• Arcuate nucleus

– Mamillary • PHN

• MMN

• LMN

• Lateral area

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White matter of cerebrum

• Comissural fibers

• Association fibers

• Projection fibers