Download Lab 19

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Lab 19
Cranial Nerves &
Brain dissection
Practical 4
Intro to the brain
The cranial nerves
Human and sheep brain anatomy
Get to work
CLEAN UP
Brief intro to the brain
• 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)
Major Regions and Landmarks
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
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)
Figure 14–1
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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
Tour through the brain
• From caudal/inferior to rostral/superior
– Cranial nerves
– Spinal nerves
The Brain Stem
Anatomy:
Brain stem
• Includes:
– mesencephalon (midbrain)
– pons
– medulla oblongata
– Note: some consider the diencephalon part of
the brain stem as well
Posterior view
Most cranial
nerves are
located in the
brain stem
Medulla Oblongata
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Cerebellum
Cerebellum – side view
Mesencephalon
Mesencephalon
The Diencephalon
Telencephalon
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Thalamus
Hypothalamus
Pineal gland
Pituitary gland
• Cerebrum
– Largest part of brain, includes huge wrinkly
cerebral hemispheres
• Basal nuclei
Figure 14–5a
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The Basal Nuclei (Ganglia)
Lateral Ventricles
Figure 14–14b, c
The Limbic System
The Cerebral Cortex
4 Lobes:
frontal
parietal
temporal
occipital
Figure 14–11a
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
Figure 14–12b
Motor and Sensory Areas
of the Cortex
• Central sulcus separates motor and
sensory areas
Figure 14–15a
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Cranial Nerves
Cranial Nerves
• 12 pairs connected to brain
Figure 14–18
Cranial Nerves
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
Figure 13.5a
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
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Summary of Function of Cranial
Nerves
You need to learn:
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Names
Numbers
Locations
Main functions (in blue)
Figure 13.5b
Anterior View
Lateral
view
The Olfactory Nerves (I)
Figure 14–19
Olfactory Nerves (I)
The Optic Nerves (II)
• 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
Figure 14–20
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Optic Nerves (II)
CNs III,IV,VI
• Enter diencephalon
• Primary function:
• All motor only
• All innervate eye muscles
– 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
The 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
Figure 14–21
The Trochlear Nerves (IV)
Trochlear Nerves (IV)
• Smallest CN
• Primary function:
– motor (eye movement: looking down)
• Origin:
– mesencephalon
• Destination:
– superior oblique muscle (that’s it!)
Figure 14–21
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The Abducens Nerves (VI)
The Abducens Nerves (VI)
• Primary function:
– motor (eye movement: looking to the side)
• Origin:
– pons
• Destination:
– lateral rectus muscle (just one eye muscle)
Figure 14–21
The 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
Figure 14–22
– sensory: sensory nuclei in pons
The 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
Figure 14–23
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The 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
Figure 14–24
The 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
Figure 14–25
The 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
Figure 14–26
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The 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
Figure 14–27
The Hypoglossal Nerves (XII)
Hypoglossal Nerves (XII)
• Primary function:
– motor (tongue movements)
• Origin:
– motor nuclei of medulla
• Destination:
– muscles of tongue which aid in speech
Figure 14–27
Gross Anatomy of the human brain
Human brain
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Midsagittal
Inferior
View
Coronal
Sheep brain
Midsagittal
Sheep brain inferior view
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Follow instructions in lab book
Anterior
View
• 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)
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