Lab 19
Cranial Nerves &
Brain dissection
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Intro to the brain
The cranial nerves
Human and sheep brain anatomy
Get to work
CLEAN UP
Practical 4
• Thurs 12/6
• 50 points: about half brain models and half
book figures (with a few fresh brains too)
• Know:
– List of brain parts on objectives (names and locations
only; you will need to know functions on the exam
though)
– The 12 cranial nerves: names, locations, & functions
(shown in blue in this lecture)
Brief intro to the brain
External structures
• cerebral hemispheres
• cerebrum
• midbrain
• cerebellum
• pons
• medulla
• central sulcus
• precentral gyrus
• postcentral gyrus
• lateral sulcus
• longitudinal fissure
• frontal lobe
• parietal lobe
• occipital lobe
• temporal lobe
Internal structures:
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corpus callosum
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basal ganglia (nucleus)
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Caudate
Putamen
internal capsule
thalamus
hypothalamus
hippocampus
amygdala
pineal gland
pituitary gland
reticular formation
fornix
substantia nigra
cingulate gyrus
optic chiasm
lateral ventricles
mammilary bodies
corpora quadrigemina
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inferior colliculus
superior colliculus
Major Regions and Landmarks
Figure 14–1
Regions of the Adult Brain
• Telencephalon (cerebrum) – cortex, white
matter, and basal nuclei
• Diencephalon – thalamus, hypothalamus,
and epithalamus
• Mesencephalon –midbrain (brain stem)
• Metencephalon – pons (brain stem),
cerebellum
• Myelencephalon – medulla oblongata
(brain stem)
Some terms
• nucleus: collection of neuron cell bodies in
the CNS
• tract: collection of axons in the CNS
• ganglia: collection of neuron cell bodies in
the PNS
• nerve: collection of axons in the PNS
– Cranial nerves
– Spinal nerves
Tour through the brain
• From caudal/inferior to rostral/superior
The Brain Stem
• Includes:
– mesencephalon (midbrain)
– pons
– medulla oblongata
– Note: some consider the diencephalon part of
the brain stem as well
Anatomy:
Brain stem
Most cranial
nerves are
located in the
brain stem
Posterior view
Medulla Oblongata
Cerebellum
Cerebellum – side view
Mesencephalon
Mesencephalon
The Diencephalon
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Thalamus
Hypothalamus
Pineal gland
Pituitary gland
Figure 14–5a
Telencephalon
• Cerebrum
– Largest part of brain, includes huge wrinkly
cerebral hemispheres
• Basal nuclei
The Basal Nuclei (Ganglia)
Figure 14–14b, c
Lateral Ventricles
The Limbic System
Figure 14–11a
The Cerebral Cortex
4 Lobes:
frontal
parietal
temporal
occipital
Figure 14–12b
Cerebral Cortex landmarks
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Lateral sulcus
Longitudinal fissure
Central sulcus
Precentral gyrus (primary motor)
Postcentral gyrus (primary sensory)
Association areas are for integrating
information
Motor and Sensory Areas
of the Cortex
• Central sulcus separates motor and
sensory areas
Figure 14–15a
Cranial Nerves
Cranial Nerves
• 12 pairs connected to brain
Figure 14–18
Cranial Nerves
Figure 13.5a
Cranial Nerves
• Twelve pairs of cranial nerves arise from
the brain
• They have sensory, motor, or both sensory
and motor functions (mixed)
• Each nerve is identified by a number (I
through XII) and a name
• Four cranial nerves carry parasympathetic
fibers that serve muscles and glands
3 main types
of Cranial Nerves
Sensory nerves:
– carry somatic (touch) or special sensory
information
Motor nerves:
– axons of somatic motor neurons
Mixed nerves:
– mixture of motor and sensory fibers
Cranial Nerves
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I – Olfactory
II – Optic
III – Occulomotor
IV – Trochlear
V – Trigeminal
VI – Abducens
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VII – Facial
VIII – Vestibulococlear
IX – Glossopharyngeal
X – Vagus
XI – Accessory
XII – Hypoglossal
On Occasion, Our Trusty Truck Acts
Funny; Very Good Vehicle Anyhow
Summary of Function of Cranial
Nerves
Figure 13.5b
You need to learn:
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Names
Numbers
Locations
Main functions (in blue)
Lateral
view
Anterior View
The Olfactory Nerves (I)
Figure 14–19
Olfactory Nerves (I)
• Don’t originate or enter brainstem
• Primary function:
– special sensory (smell)
• Arises from the olfactory epithelium
• Passes through the cribriform plate of the
ethmoid bone
• Fibers run through the olfactory bulb and
terminate in the primary olfactory cortex
• Functions solely by carrying afferent impulses
for the sense of smell
The Optic Nerves (II)
Figure 14–20
Optic Nerves (II)
• Enter diencephalon
• Primary function:
– special sensory (vision)
• Arises from the retina of the eye
• Optic nerves pass through the optic canals
and converge at the optic chiasm
• They continue to the thalamus
(diencephalon) where they synapse
CNs III,IV,VI
• All motor only
• All innervate eye muscles
The Oculomotor Nerves (III)
Figure 14–21
Oculomotor Nerves (III)
• Primary function:
– motor (many eyeball movements, pupil
constriction, controlling lens shape)
• Origin:
– mesencephalon
• Destination:
– somatic motor: 4 extrinsic eye muscles:
– visceral motor: parasympathetic NS cell
bodies in the ciliary ganglion, got to intrinsic
eye muscles
The Trochlear Nerves (IV)
Figure 14–21
Trochlear Nerves (IV)
• Smallest CN
• Primary function:
– motor (eye movement: looking down)
• Origin:
– mesencephalon
• Destination:
– superior oblique muscle (that’s it!)
The Abducens Nerves (VI)
Figure 14–21
The Abducens Nerves (VI)
• Primary function:
– motor (eye movement: looking to the side)
• Origin:
– pons
• Destination:
– lateral rectus muscle (just one eye muscle)
The Trigeminal Nerves (V)
Figure 14–22
Trigeminal Nerves (V)
• Largest CN – it’s huge!
• Primary function:
– mixed (sensory and motor) to face
All sensory from face; motor for chewing
• Three branches
– ophthalmic branch (sensory)
– maxillary branch (sensory)
– mandibular branch (sensory and motor)
• Destinations
– sensory: sensory nuclei in pons
– motor: muscles of mastication
The Facial Nerves (VII)
Figure 14–23
Facial Nerves (VII)
• Primary function:
– mixed (sensory and motor) to face
Motor to facial muscles; taste
• sensory:
– taste receptors on anterior 2/3 of tongue
• motor:
– Facial muscles, parasympathetic to lacrimal
and salivary glands
**Bell’s Palsy
The Vestibulocochlear
Nerves (VIII)
Figure 14–24
Vestibulocochlear
Nerves (VIII)
• Primary function: special sensory
– vestibular branch:
• balance and equilibrium
– cochlear branch:
• hearing
• Origin: receptors of inner ear
• Destination: nuclei in both pons and
medulla
The Glossopharyngeal
Nerves (IX)
Figure 14–25
Glossopharyngeal
Nerves (IX)
• Primary function:
– mixed (sensory and motor) to head and neck
Mainly: swallowing, some salivary gland function
• Origins:
– sensory:
• posterior 1/3 of tongue
• part of pharynx and palate
• carotid bodies (blood pressure/CO2 sensors)
– motor:
• motor nuclei of medulla
The Vagus
Nerves (X)
Figure 14–26
Vagus Nerves (X)
• Primary function:
– mixed (sensory and motor) of thorax and
abdomen
– Only CN that extends beyond head and neck
– “Mr. parasympathetic” motor to para-NS
– Runs outside of spinal cord to visceral organs
– Originates in medulla
The Accessory Nerves (XI)
Figure 14–27
Accessory Nerves (XI)
• Primary function:
– motor to muscles of neck and upper back
• Origin:
– motor nuclei of spinal cord and medulla oblongata
• Two roots:
– The spinal root passes upward into the cranium via
the foramen magnum
– The accessory nerve leaves the cranium via the
jugular foramen
• Destinations:
– voluntary muscles of palate, pharynx, and larynx
– sternocleidomastoid and trapezius muscles
The Hypoglossal Nerves (XII)
Figure 14–27
Hypoglossal Nerves (XII)
• Primary function:
– motor (tongue movements)
• Origin:
– motor nuclei of medulla
• Destination:
– muscles of tongue which aid in speech
Gross Anatomy of the human brain
Human brain
Midsagittal
Coronal
Inferior
View
Sheep brain
Sheep brain inferior view
Midsagittal
Anterior
View
Follow instructions in lab book
• look at the meninges
• start by examining the external brain
– Ventral surface first, then dorsal
• then look internally without cutting (fig 19.12)
• cut it midsagittally to see inside
• Try a coronal cut to see what you can find
• Review Sheet due next Thursday
To find:
• Meninges
• Cranial nerves I – XII (?)
• fissures and sulci on
surface, lobes
• pineal gland
• corpora quadrigemina
(part of midbrain)
• midbrain
• pons
• medulla
• cerebellum
• mamillary body (just one)
• optic chiasm
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corpus callosum (central)
fornix
lateral ventricles
choroid plexus (inside
ventricles)
• hypothalmus
• “pituitatry gland” (hangs
off hypothalamus
• arbor vitae (inside
cerebellum)