Brainstem and Cranial Nerves – 1

Human Neurobiology

ANHB 2217

Avinash BharadwajSemester 1, 2006

Week 2

Brainstem and Cranial Nerves

Two topics in one…? 10 out of 12 cranial nerves attached

to brainstem. Anatomically and functionally

inseparable! For ease of understanding :

Lecture 1 : General features and important concepts.

Lecture 2 : More details of cranial nerves and brainstem.

Brainstem Rostral part of the brain Similarities with the spinal cord

Attachments of nerves – cranial nerves Masses of grey matter inside Tracts of white matter

Special features Other nuclei and their connections Central canal, fourth ventricle Distinct regional morphology Connections with the cerebellum Reticular formation And more…!

Brainstem :Major Divisions

Midbrain

Pons

Medullaoblongata

Cerebellar peduncles

Superior

Middle

Inferior

Lab exercise! … And what are the other parts seen here?

Cranial Nerves Unlike spinal nerves…

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!

Olfactory I

Optic II

Oculomotor III

Trochlear IV

Trigeminal V

Abducens (t) VI

Facial VII

VestibulocochlearVIII

GlossopharyngealIX

Vagus X

Accessory XI

Hypoglossal XII

Attachments

I Cerebrum II Diencephalon III, IV Midbrain V Pons VI, VII, VIII Junction :

Pons-Medulla

IX, X, XI, XII Medulla oblongata

IIIIV

VVI

VII, VIII

IXXXI

XII

Cranial Nerve Nuclei Motor nuclei

Groups of neurons whose axons form a motor nerve

Compare with cells of ventral horn of spinal grey matter.

Sensory nuclei Groups of neurons that sensory nerve

fibres synapse with. Axons from these nuclei go to other

parts of the CNS. Compare with cells of spinal cord (dorsal

grey matter) which give rise to tracts.

Functional Components 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.

Functional Components

Basal

Alar

GSESVE

GVE GVAGVA

SVA

GSA

SSANuclei(Neurone groups)

Brainstem Organisation Tracts

Long tracts passing through Tracts beginning or terminating in the

brainstem Tracts within the brainstem

Nuclei Nuclei of cranial nerves Other nuclei Reticular formation

But first, some general features of the brainstem!

Medulla Oblongata

Central canal Cuneate and

gracile tubercles

G Cu

Inf. cerebellar peduncle Pyramid and Olive

PO

ICPIV Ventricle

Pons

Basilar part, tegmentum, MCP

Basilar

Tegmentum MCP

Midbrain

SC

Tegmentum

SN

Crus

Tectum

Nerve III and Midbrain Oculomotor

“Extrinsic” Muscles of the eyeball : GSE

Nucleus close to the midline Constrictor of the pupil (smooth

muscle) GVE Edinger-Westphal nucleus

SCIII

SNRN

C-Sp

CP

CP

ST

Nerve IV

Trochlear nerve A muscle of the eyeball winds around a

trochlea (pulley) GSE Exceptional course

IC