PONS & MID-BRAIN
STRUCTURE/BLOOD SUPPLY/CRANIAL NERVES ATTACHMENTS
Lecture….by Prof. Ansari
Friday, January 15, 2016
(for MBBS SEMESTER II students only)
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OBJECTIVES
•STRUCTURE OF PONS AND MIDBRAIN.
•CRANIAL NERVES ATTACHMENT.
•OTHER NUCLEI PRESENT AT THESE LEVELS.
•BLOOD SUPPLY
•CROSS SECTION- GREY MATTER AND WHITEMATTER.
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PONS
•It is a part of brain stem.
•It lies between midbrain and medulla oblongata.
•It has a basilar part/ ventral part, and a dorsal part whichforms the floor of IV ventricle.
•Three cranial nerves are related to pons, trigeminal nerveis attached to the pons on ventral part.
•Abducent nerve is related at the lower border of pons andpyramid.
•Occulomotor nerve arises at the upper border of pons, inthe interpeduncular fossa.
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CRANIAL
NERVES
ATTACHED
AT THE BASE
OF BRAIN
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CROSS SECTION OF PONS
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BASILAR PART
TEGMENTUM PART
IV
VENTRICLE
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NUCLEI OF CRANIAL NERVES IN PONS
•Facial nerve nuclei, motor /sensory/autonomic.
•Trigeminal nuclei, motor/ mainsensory/spinal/ mesencephalic.
•Abducent nucleus / purely motor.
•Nuclei pontis.
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Floor of IV ventricle
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WHITE FIBERS AT PONS
•CORTICOPONTINE FIBERS
•CORTICOSPINAL FIBERS
•CORTICOPONTOCEREBELLAR FIBERS
•CORTICONUCLEAR FIBERS
•TRAPEZOID BODY
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OVERVIEW OF PONS
MESENCEPHALON
•It is at the cranial end of pons.
•It has a dorsal portion called as tectum.
•The ventral portion is called as cerebral peduncle.
•The space between the two cerebral peduncle is theinterpeduncular fossa.
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Structures in theinterpeduncular fossa
•1.Optic nerve
•2.Optic chiasma
•3.Optic tract
•4.Tuber cinereum
•5.Mammillary bodies
•6.Ant.perforatedsubstance.
•7.Olfactory tract
•8.Pons
•9=Uncus
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Cross section of midbrain
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Inferior colliculus
Superior
Cerebellar
Peduncle
decussation
Substantia
nigra
Substantia
nigra
Cerebral peduncle
Cerebral peduncle
PAG
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Superior colliculus
Oculomotor fibers
VARIOUS NUCLEIAT MIDBRAIN
•Oculomotor nucleus
•Trochlear nucleus
•Mesencephalic nucleus
•Red nucleus
•Substantia nigra
•Edinger-Westphal nucleus
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White matter at mesencephalon
•Superior cerebellar peduncles decussations
•Medial lemniscus/lateral lemniscus/trigeminallemniscus/spinal lemniscus
•Crus cerebri
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BLOOD SUPPLY OF PONS &MIDBRAIN
•CORTICAL BRANCHES AND CENTRAL BRANCHES ARISEFROM BASILAR ARTERY AND CIRCLE OF WILLIS.
•PONTINE HAEMORRAGE LEADS TO BURSTING HEADACHE, PINPOINT PUPIL, AND HYPERTHERMIA.
•INJURY TO THE CORTICOSPINAL FIBERS LEADS TOHEMIPLEGIA.
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CIRCLE OF WILLIS
RED NUCLEUS AND SUBSTANTIANIGRA
•THEY ARE CONCERNED WITH THE EXTRAPYRAMIDALTRACT.
•INJURY TO THESE NUCLEI WILL RESULT IN TREMORS,PARKINSONISM, AND NYSTAGMUS.
•THESE SYMPTOMS CAN BE CORRECTED BYSUPPLIMENTING THE NEUROTRANSMITTER DOPAMINE.
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Periaqueductal gray
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• Stimulation of the dorsal and lateral aspects of the PAG (in the rat)can provoke defensive responses characterised by freezingimmobility, running, jumping, tachycardia, and increase in bloodpressure.
• Stimulation of the caudal ventrolateral PAG can result in animmobile, relaxed posture known as quiescence.
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PAG
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RED NUCLEUS
CEREBRAL
AQUEDUCT
A 62-year old male has sustained several injuries from a car accident.Upon administering a neurological examination, you suspect that thepatient has damage to the right caudal medulla. Why do you think this?
A. The patient's right eye exhibits hypertropia and he complains of diplopia,
B. The patient's tongue deviates towards to right when you asked him to stick it out and hisuvula deviates towards the left when you ask him to say, "aahhh". (Your Answer)
C. The patient has a loss of taste on the right anterior 2/3rds of his tongue
D. The patient exhibits anosmia (inability to smell)
E. The patient complains of excruciating pain on the right side of his face
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