Activity 3: Cranial Nerves and Identifying and Testing Cranial Nerves
The cranial nerves are part of which nervous system and not the other?
Part of the PNS and not the CNS
How many pairs of cranial nerves are there?
12 pairs of cranial nerves
The 12 pairs of the cranial nerves serve what 2 body parts?
1. Head
2. Neck
What is unique about the vagus nerves (X) in regard to the other nerves?
It extends into the thoracic and abdominal cavities.
What are the only 2 nerves that do not arise from the brain stem and do not pass through the foramina to reach their destination?
1. Olfactory nerves (I)
2. Optic nerves (II)
What does OO, OTTAF-VGVAH stand for?
On Occasion, Our Trusty Truck Acts Funny-Very Good Vehicle AnyHow
On Occasion, Our Trusty Truck Acts Funny-Very Good Vehicle AnyHow
List the cranial nerves based on this mnemonic.
I. Olfactory nerve
II. Optic nerve
III. Oculomotor nerve
IV. Trochlear nerve
V. Trigeminal nerve
VI. Abducens nerve
VII. Facial nerve
VIII. Vestibulocochlear nerve
IX. Glossopharyngeal nerve
X. Vagus nerve
XI. Accessory nerve
XII. Hypoglossal nerve
Most cranial nerves are what kind of nerves?
Mixed nerves
What are mixed nerves?
Containing both motor and sensory fibers
What are 3 pairs of cranial nerves that are primarily or exclusively sensory in function?
1. Olfactory nerve (I)
2. Optic nerve (II)
3. Vestibulocochlear nerve (VIII)
How come the olfactory nerves (I) are not visible on the brain model?
They consist of only short axons that run from the nasal mucossa through the cibriform foramina of the ethmoid bone.
What from the olfactory nerves (I) is visible on the brain model, and what kind of points do they act as?
Olfactory bulbs which act as synapse points
Sheep Brain vs Human Brain
Compare the cerebrum, brain stem, and cerebellum. Which of these structures is obviously much larger in the human brain?
The cerebrum
Sheep Brain vs Human Brain
Axons of olfactory neurons run from the nasal mucosa through the cibriform foramina of the ethmoid bone to synapse with what?
Olfactory bulbs
Sheep Brain vs Human Brain
How does the size of the sheep's olfactory bulbs compare with those of humans?
Sheep=shorter and thicker (larger)
Sheep Brain vs Human Brain
Is the sense of smell more important for protection and foraging in sheep or humans?
More important for sheeps
Sheep Brain vs Human Brain
The optic nerve (II) carries sensory impulses from which part of the eye?
Retina of the eye
Sheep Brain vs Human Brain
Which nerve is involved in the sense of vision?
Optic nerve (II)
Sheep Brain vs Human Brain
What 2 structures protrude from the ventral aspect of the hypothalamus? (Hint: posterior to the optic chiasma)
1. Infundibulum (immediately posterior to the optic chiasma)
2. Mammillary body
Sheep Brain vs Human Brain
What is different with the sheep's mammillary body versus that of a human's?
The sheep's mammillary body is a single rounded eminence, whereas in humans, it is a double structure.
Sheep Brain vs Human Brain
What are cerebral peduncles?
Fiber tracts
Sheep Brain vs Human Brain
Cerebral peduncles connect what 2 brain parts?
1. Cerebrum
2. Medulla oblongata
Sheep Brain vs Human Brain
The large oculomotor nerves (III) and trochlear nerves (IV) provide motor fibers to what muscles of what body part?
To extrinsic muscles of the eyeball.
Sheep Brain vs Human Brain
The pons and the medulla oblongata are composed primarily of what?
Ascending and descending fiber tracts.
Sheep Brain vs Human Brain
What are the 2 functions of trigeminal nerves (V)?
1. Involved in chewing
2. Involved in sensations of the head and face
Sheep Brain vs Human Brain
Abducens nerves (VI) do what to the eye?
Abduct the eye
Sheep Brain vs Human Brain
Facial nerves (VII) are involved in what 3 functions?
1. Taste sensation
2. Gland function (i.e. salivary and lacrimal glands)
3. Facial expression
Sheep Brain vs Human Brain
Vestibulocochlear nerves (VIII) are involved in what 2 functions?
1. Hearing
2. equilibrium
Sheep Brain vs Human Brain
Vestibulocochlear nerves (VIII) are mostly what type of nerves?
Sensory nerves
Sheep Brain vs Human Brain
Glossopharyngeal nerves (IX) contain ____ fibers that innervate throat structures and sensory fibers that transmit ____ stimuli.
Motor fibers that innervate throat structures and sensory fibers that transmit taste stimuli.
Sheep Brain vs Human Brain
Vagus nerves (X) serve what 3 body parts?
1. head
2. thorax
3. abdominal cavity
Sheep Brain vs Human Brain
Accesssory nerves (XI) serve muscles of what 3 body parts?
1. Neck
2. Larynx
3. Shoulders
Sheep Brain vs Human Brain
Hypoglossal nerves (XII) stimulate muscles of what 2 body parts?
1. tongue muscles
2. neck muscles
Sheep Brain vs Human Brain
How does the depth of the fissures in the sheep's cerebral hemispheres compare to that in the human brain?
Sheep brain has less deep fissures.
Sheep Brain vs Human Brain
How does the cerebellum of the sheep and human differ?
The sheep's cerebellum is not divided longitudinally.
Sheep Brain vs Human Brain
What dural fold is missing in the sheep brain that is present in humans?
The falx cerebelli is missing in sheep brains, because in humans, this structure separates the cerebellar hemispheres.
Sheep Brain vs Human Brain
In the sheep brain, what connects the cerebellum to the medulla?
The inferior cerebellar peduncles.
Sheep Brain vs Human Brain
In the sheep brain, what connects the cerebellum to the pons?
The middle cerebellar peduncles.
Sheep Brain vs Human Brain
In the sheep brain, what connects the cerebellum to the midbrain?
The superior cerebellar peduncles.
Sheep Brain vs Human Brain
What is the function of the corpora quadrigemina?
Act as reflex centers for vision and hearing.
Sheep Brain vs Human Brain
In both brains, what is the thin nervous tissue membrane that is ventral to the corpus callosum and separates the lateral ventricles?
Septum pellucidum
Sheep Brain vs Human Brain
How does the size of the fornix in the sheep brain compare with the human fornix?
The sheep fornix is larger.
Sheep Brain vs Human Brain
Why is the sheep fornix larger than the human fornix?
The fornix in sheeps is involved in the memory of smell, a sense that is more important in sheeps.
Sheep Brain vs Human Brain
In both brains, what forms the floor of the third ventricle?
The hypothalamus
Sheep Brain vs Human Brain
In both brains, what forms the anterior walls of the fourth ventricle?
Cerebral peduncles
Sheep Brain vs Human Brain
T/F. In both brains, the medulla oblongata continues into the spinal cord without any obvious anatomical change.
True.
Sheep Brain vs Human Brain
In both brains, when does the spinal cord begin?
When the fourth ventricle narrows to a small canal.
What is the origin of the olfactory nerve (I)
Olfactory epithelium
The olfactory nerve (I) is purely what type of nerve?
Purely sensory nerve
What is the function of the olfactory nerve (I)?
Carries afferent impulses associated with smell
What is the origin of the optic nerve (II)?
Retina of eye
What type of nerve is the optic nerve (II)?
Purely sensory nerve
What is the function of the optic nerve (II)?
Carries afferent impulses associated with vision.
What is the origin of the oculomotor nerve (III)?
Midbrain
What type of nerve is the oculomotor nerve (III)?
Primarily motor nerve
What is the function of the oculomotor nerve (III)?
Carries somatic motor fibers to inferior oblique and superior, inferior, and medial rectus muscles to direct eyeball.
What is the origin of the trochlear nerve (IV)?
Midbrain
What type of nerve is the trochlear nerve (IV)?
Primarily motor
What is the function of the trochlear nerve (IV)?
Provides somatic fibers to superior oblique muscle that moves the eyeball.
What is the origin of the trigeminal nerve (V)?
From the face
What type of nerve is the trigeminal nerve (V)?
Mixed nerve
What are the 2 functions (sensory and motor) of the trigeminal nerve (V)?
1. Sensory fibers conduct sensory impulses from skin of face
2. Motor fibers innervate muscles of mastication
What is the origin of the abducens nerve (VI)?
Pons
What type of nerve is the abducens nerve (VI)?
Primarily motor nerve
What is the function of the abducens nerve (VI)?
Carries somatic motor fibers to lateral rectus muscle that abducts the eyeball
What is the origin of the facial nerve (VII)?
Pons
What type of nerve is the facial nerve (VII)?
Mixed nerve
What are the 2 functions (motor and sensory) of the facial nerve (VII)?
1. Supplies motor fibers to muscles of facial expression
2. Carries sensory fibers from taste receptors to tongue
What is the origin of the vestibulocochlear nerve (VIII)?
Inner ear equilibrium and hearing apparatus
What type of nerve is the vestibulocochlear nerve (VIII)?
Mostly sensory nerve
What is the 2 functions (vestibular and cochlear branches) of the vestibulochochlear nerve (VIII)?
1. Vestibular branch transmits impulses associated with sense of equilibrium
2. Cochlear branch transmits impulses associated with hearing
What is the origin of the glossopharyngeal nerve (IX)?
Medulla oblongata
What type of nerve is the glossopharyngeal nerve (IX)?
Mixed nerve
What are the 2 functions (motor and sensory) of the glossopharyngeal nerve (IX)?
1. Somatic fibers serve pharyngeal muscles
2. Sensory fibers carry impulses from pharynx
What is the origin of the vagus nerve (X)?
Medulla oblongata
What type of nerve is the vagus nerve (X)?
Mixed nerve
What are the 2 functions (motor and sensory) of the vagus nerve (X)?
1. Somatic motor fibers carry impulses to pharynx and larynx
2. Transmits sensory impulses from viscera
What is the origin of the accessory nerve (XI)?
Medulla oblongata
What type of nerve is the accessory nerve (XI) but what is it primarily in function?
Mixed nerve but primarily motor in function
What are the function of the accessory nerve (XI)?
Provides somatic motor fibers to sternocleidomastoid and trapezius muscles.
What is the origin of the hypoglossal nerve (XII)?
Medulla oblongata
What type of nerve is the hypoglossal nerve (XII) but what is it primarily in function?
Mixed nerve but primarily motor in function
What is the function of the hypoglossal nerve (XII)?
Carries somatic motor fibers to tongue muscles
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Identify the blanks.
