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The brain stem ii
1. PONS & MI D-BRAI N
STRUCTURE/BLOOD SUPPLY/CRANIAL NERVES
ATTACHMENTS
Lecture….by Prof. Ansari
Wednesday, January 8, 2014
(for BDS SEMESTER II students only)
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2. OBJECTIVES
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Structure of pons and midbrain.
Cranial nerves attachment.
Other nuclei present at these levels.
Blood supply
Cross section- grey matter and white matter.
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3. 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 which
forms the floor of IV ventricle.
• Three cranial nerves are related to pons, trigeminal nerve
is attached to the pons on ventral part.
• Abducent nerve is related at the lower border of pons and
pyramid.
• Occulomotor nerve arises at the upper border of pons, in
the interpeduncular fossa.
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14. 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
the interpeduncular fossa.
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19. White matter at mesencephalon
• Superior cerebellar peduncles decussations
• Medial lemniscus/lateral lemniscus/trigeminal
lemniscus/spinal lemniscus
• Crus cerebri
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20. Blood supply of pons &midbrain
• Cortical branches and central branches arise from basilar
artery and circle of Willis.
• Pontine hemorrhage leads to bursting head ache,
pinpoint pupil, and hyperthermia.
• Injury to the Corticospinal fibers leads to hemiplegia.
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22. Red nucleus and substantia nigra
• They are concerned with the extrapyramidal tract.
• Injury to these nuclei will result in tremors,
Parkinsonism, and nystagmus.
• These symptoms can be corrected by supplementing the
neurotransmitter dopamine.
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24. Electrical stimulation of the PAG results in
immediate and profound analgesia
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Stimulation of the dorsal and lateral aspects of the PAG (in the rat)
can provoke defensive responses characterized by freezing
immobility, running, jumping, tachycardia, and increase in blood
pressure.
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Stimulation of the caudal ventrolateral PAG can result in an
immobile, relaxed posture known as quiescence.
• It also plays a role in female copulatory behavior.
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27. A 62-year old male has sustained several injuries from a car accident.
Upon administering a neurological examination, you suspect that the
patient 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 his uvula deviates towards the left when you ask him to say, "aahhh".
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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