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Lab 19. Cranial Nerves & Brain dissection. Today. 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:

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lab 19

Lab 19

Cranial Nerves &

Brain dissection

  • Intro to the brain
  • The cranial nerves
  • Human and sheep brain anatomy
  • Get to work
practical 4
Practical 4
  • Thurs 12/6
  • 50 points: about half brainmodels 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

cerebral hemispheres






central sulcus

precentral gyrus

postcentral gyrus

lateral sulcus

longitudinal fissure

frontal lobe

parietal lobe

occipital lobe

temporal lobe

Internal structures:

corpus callosum

basal ganglia (nucleus)



internal capsule





pineal gland

pituitary gland

reticular formation


substantia nigra

cingulate gyrus

optic chiasm

lateral ventricles

mammilary bodies

corpora quadrigemina

inferior colliculus

superior colliculus

Brief intro to the brain
regions of the adult brain
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
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
Tour through the brain
  • From caudal/inferior to rostral/superior
the brain stem
The Brain Stem
  • Includes:
    • mesencephalon (midbrain)
    • pons
    • medulla oblongata
    • Note: some consider the diencephalon part of the brain stem as well
anatomy brain stem
Anatomy:Brain stem

Most cranial nerves are located in the brain stem

the diencephalon
The Diencephalon
  • Thalamus
  • Hypothalamus
  • Pineal gland
  • Pituitary gland

Figure 14–5a

  • Cerebrum
    • Largest part of brain, includes huge wrinkly cerebral hemispheres
  • Basal nuclei
the basal nuclei ganglia
The Basal Nuclei (Ganglia)

Figure 14–14b, c

the limbic system
The Limbic System

Figure 14–11a

the cerebral cortex
The Cerebral Cortex
  • 4 Lobes:
    • frontal
    • parietal
    • temporal
    • occipital

Figure 14–12b

cerebral cortex landmarks
Cerebral Cortex landmarks
  • 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
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 nerves1
Cranial Nerves

Figure 13.5a

cranial nerves2
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
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 nerves3
I – Olfactory

II – Optic

III – Occulomotor

IV – Trochlear

V – Trigeminal

VI – Abducens

VII – Facial

VIII – Vestibulococlear

IX – Glossopharyngeal

X – Vagus

XI – Accessory

XII – Hypoglossal

Cranial Nerves

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you need to learn
You need to learn:
  • Names
  • Numbers
  • Locations
  • Main functions (in blue)

Anterior View

Lateral view

olfactory nerves i
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
The Optic Nerves (II)

Figure 14–20

optic nerves ii
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
oculomotor nerves iii
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
trochlear nerves iv
Trochlear Nerves (IV)
  • Smallest CN
  • Primary function:
    • motor (eye movement: looking down)
  • Origin:
    • mesencephalon
  • Destination:
    • superior oblique muscle (that’s it!)
the abducens nerves vi1
The Abducens Nerves (VI)
  • Primary function:
    • motor (eye movement: looking to the side)
  • Origin:
    • pons
  • Destination:
    • lateral rectus muscle (just one eye muscle)
trigeminal nerves v
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
facial nerves vii
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

vestibulocochlear nerves viii
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
glossopharyngeal nerves ix
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
The Vagus Nerves (X)

Figure 14–26

vagus nerves x
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
accessory nerves xi
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
hypoglossal nerves xii
Hypoglossal Nerves (XII)
  • Primary function:
    • motor (tongue movements)
  • Origin:
    • motor nuclei of medulla
  • Destination:
    • muscles of tongue which aid in speech
follow instructions in lab book
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

Cranial nerves I – XII (?)

fissures and sulci on surface, lobes

pineal gland

corpora quadrigemina (part of midbrain)





mamillary body (just one)

optic chiasm

corpus callosum (central)


lateral ventricles

choroid plexus (inside ventricles)


“pituitatry gland” (hangs off hypothalamus

arbor vitae (inside cerebellum)

To find: