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Brainstem and Cranial Nerves – 1
Human Neurobiology
ANHB 2217
Avinash Bharadwaj
Semester 1, 2006
Week 2
Brainstem and Cranial Nerves
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Two topics in one…?
10 out of 12 cranial nerves attached to
brainstem.
Anatomically and functionally inseparable!
For ease of understanding :
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Lecture 1 : General features and important
concepts.
Lecture 2 : More details of cranial nerves and
brainstem.
Brainstem
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Rostral part of the brain
Similarities with the spinal cord
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Attachments of nerves – cranial nerves
Masses of grey matter inside
Tracts of white matter
Special features
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Other nuclei and their connections
Central canal, fourth ventricle
Distinct regional morphology
Connections with the cerebellum
Reticular formation
And more…!
Brainstem :Major Divisions
Cerebellar
peduncles
Midbrain
Pons
Medulla
oblongata
Superior
Middle
Inferior
Lab exercise! … And what are the other parts seen here?
Cranial Nerves
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Unlike spinal nerves…
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No constant pattern
Motor, sensory or mixed
Special sensory nerves (vision, taste, hearing etc)
Twelve pairs
Attached to the brainstem except first two.
Understanding of functions and pattern important!
Names and Numbers…
Understand the names!
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Olfactory
I
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Facial
VII
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Optic
II
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Vestibulocochlear VIII
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Oculomotor III
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Glossopharyngeal IX
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Trochlear
IV
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Vagus
X
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Trigeminal
V
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Accessory
XI
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Abducens (t) VI
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Hypoglossal
XII
Attachments
III
IV
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I
Cerebrum
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II
Diencephalon
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III, IV
Midbrain
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V
Pons
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VI, VII, VIII
Junction :
Pons-Medulla
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IX, X, XI, XII
Medulla
oblongata
V
VI
XII
VII, VIII
IX
X
XI
Cranial Nerve Nuclei
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Motor nuclei
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Groups of neurons whose axons form a motor
nerve
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Compare with cells of ventral horn of spinal grey
matter.
Sensory nuclei
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Groups of neurons that sensory nerve fibres
synapse with.
Axons from these nuclei go to other parts of
the CNS.
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Compare with cells of spinal cord (dorsal grey
matter) which give rise to tracts.
Functional Components
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Efferent (Motor),
Afferent (Sensory)
Somatic : To / from “body wall” structures
Visceral : To / from visceral structures
(smooth/cardiac muscle, glands)
General
Special
Special senses or developmentally “special”
structures
Such components are described for spinal nerves also, we
shall understand them better with the ANS.
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Functional Components
Nuclei
(Neurone groups)
SSA
Alar
Basal
GSA
SVE
SVA
GSE
GVE
GVA
Brainstem Organisation
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Tracts
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Long tracts passing through
Tracts beginning or terminating in the brainstem
Tracts within the brainstem
Nuclei
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Nuclei of cranial nerves
Other nuclei
Reticular formation
But first, some general features of the brainstem!
Medulla Oblongata
IV Ventricle
ICP
P
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O
Inf. cerebellar peduncle
Pyramid and Olive
G Cu
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Central canal
Cuneate and
gracile tubercles
Pons
Tegmentum
Basilar
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Basilar part, tegmentum, MCP
MCP
Midbrain
Tectum
SC
Tegmentum
Crus
Nerve III and Midbrain
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Oculomotor
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“Extrinsic” Muscles of the eyeball : GSE
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Nucleus close to the midline
Constrictor of the pupil (smooth muscle)
GVE
 Edinger-Westphal nucleus
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SC
ST
CP
III
RN
SN
C-Sp
CP
Nerve IV
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IC
Trochlear nerve
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A muscle of the eyeball winds around a trochlea
(pulley)
GSE
Exceptional course