Ch 15: Brain and Cranial Nerves

Discuss the organization of the brain,
including the major structures and their
functions

Describe the meninges of the spinal cord and
brain, and integrate the formation and flow of
CSF with this information.

Describe the structures that constitute the
BBB and their functions

Review the cranial nerves, again giving a
brief function of each.
Major Brain Subdivisions

Telencephalon (= Cerebrum)

Diencephalon
(Thalamus and hypothalamus)

Mesencephalon

Metencephalon
(Pons and cerebellum)

Myelencephalon (= Medulla
oblongata)
Brainstem
Gray & White Matter Organization
In brain stem similar
to spinal cord (nuclei
around ventricles, tracts
on outside)
In cerebrum and
cerebellum: white
matter covered
with layer of neural
cortex (grey)
Cranial Meninges
1. Dura mater - strong, "tough mother"
a. falx cerebri
b. falx cerebelli
c. tentorum cerebelli
2. Arachnoid - spidery,
holds blood vessels
3. Pia mater - "delicate
mother"
Longitudinal
fissure
Arachnoid granulations: This is where the CSF produced in the choroid
plexuses of the ventricles and which has circulated into the subarachnoid space
is reabsorbed.
Four Ventricles
CSF filled chambers
Communicating with central canal of spinal cord
Lined by ependymal cells
CSF: Cerebro-Spinal Fluid

Formation in ventricles by specialized
ependymal cells of choroid plexuses (~500
mL/day; total volume ~ 150 mL)

Functions
– transport medium, in
– shock absorption
– buoyancy (floats the brain)
Fig 15.6

CSF circulation: Ventricles → central canal →
subarachnoid space

Reabsorption into circulation via arachnoid
granulations into superior sagittal sinus.
Blood Brain Barrier (BBB)
what is it?
3 areas in brain don’t have BBB
1. portion of hypothalamus
2. pineal gland (in diencephalon)
3. choroid plexus
Cerebrum
Two hemispheres
separated by
longitudinal fissure
 Gyrus (gyri) separated by sulcus (sulci)


Major lobes named
after overlaying bones
Cerebral Hemispheres . . .

. . have functional regions (motor, sensory
and association areas)

. . . have some functional differences (in
spite of anatomical resemblance)
→ Lateralization of cortical functioning

. . . receive information and generate
commands for opposite side of body
Cerebral Cortex and Central White Matter
Gray surface (cortex) with white tracts internally
Commissures – connect corresponding gyri of the
two hemispheres
1) corpus callosum
2) anterior commissure
Projection tracts (fibers) – connect more or less
vertically
Association tracts (fibers) – connect one gyrus to
another in the same hemisphere
Basal (or cerebral) Nuclei
Misnomer: basal ganglia
Gray matter internal to the cerebral cortex, below
floor of lateral ventricles.
Fig 15.11
Function: modulate motor output from the cerebral
cortex. Subconscious control of skeletal muscle
tone and coordination of learned movement
patterns.
Parkinson's disease is caused by the loss of at least
80% of the dopaminergic neurons in basal nuclei
and substantia nigra (resting tremor)
Diencephalon
Epithalamus
Pineal gland - produces melatonin,
sets diurnal cycles
Thalamus (~12 nuclei)
Hypothalamus
Just superior to optic chiasma
Infundibulum - connects to pituitary gland
Some functions:
Control of autonomic nervous system
Coordination of nervous and endocrine systems
Secretion of hormones - ADH and oxytocin
Mesencephalon)
= Midbrain
Corpora quadrigemina = 2 pairs of sensory nuclei
1.
2.
Superior colliculi (relay station for visual information)
Inferior colliculi (relay station for auditory information
Substantia nigra - regulates motor output
Cerebral peduncles - ascending and descending
tracts to thalamus
Nuclei of ori for CN III and IV
Metencephalon:
Cerebellum
Hemispheres and lobes
Cortex -gray surface
with folia - fine ridges and
sulci - grooves between the ridges
Purkinje cells , axons of which become
arbor vitae (white matter) in center
Regulation of posture and balance
Metencephalon: Pons
Myelencephalon: Medulla oblongata

Mostly ascending and descending
tracts

Nuclei of ori for many cranial nerves

Location of autonomic
nuclei involved in
respiratory and
cardiovascular control

Relay stations for
sensory and
motor neurons
Cranial Nerves

Twelve pairs:
– 2 attach to forebrain (Telen- &
Diencephalon)
– 10 attach to
brainstem
(Mes-, Met- and Myelencephalon)

Names relate to
appearance or function

Classification ?
Olfactory Nerve (= CN or N I)
1º function?
Origin?
Destination? _____________(By way of
cribiform plate of ethmoid)
Only CN directly attached to Cerebrum
Optic Nerve (N II)
1º fu?
ori?
dest? - by way of
optic foramen
of sphenoid to
Diencephalon
(optic chiasma)
and to occipital
lobe
Oculomotor (N III)
C: Motor
O: Mesencephalon
D: Somatic motor to superior, inferior, medial
recti and inferior oblique; visceral motor to
intrinsic eye muscles
by way of superior orbital fissure
Trochlear (N IV)
C: Motor
O: Mesencephalon
D: superior oblique
by way of superior orbital fissure
Trigeminal (N V)
C: Mixed
three major branches
1. ophthalmic (sensory)
2. Maxillary (sensory)
3. Mandibular (mixed)
O: face / nuclei of pons
D: sensory nuclei in pons / muscles of mastication
Abducens
(CN VI)
C: Motor
O: Pons
D: Runs lateral rectus eye muscle
Facial (N VII)
C: Mixed
O: sensory from taste receptors of
anterior 2/3 of tongue / motor from pons
D: Sensory to sensory nuclei of pons /
motor muscles of facial expression,
visceral motor to tear gland.
Vestibulocochlear (N VIII)
C
O ?
D
Glossopharyngeal (CN IX)
C: mixed
O: sensory from
posterior 1/3 of
tongue / motor from
medulla oblongata
D: medulla /
muscles for
swallowing, parotid
gland
Vagus (N X)
C: Mixed
O: Sensation from pharyngeal area and
outer ear / motor from medulla
D: Sensory to medulla / visceral motor
to thoracic and abdominal
cavities and their organs. Major
motor pathway for ANS
Accessory (N XI) and
C: Motor
O: Motor nuclei of medulla and spinal cord
D: Swallowing, trapezius & scm muscles
Hypoglossal (N XII)
C: Motor
O: Motor nuclei of medulla
D: Tongue musculature
Mnemonic
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