Cranial Nerves Flashcards
(110 cards)
1
Q
What does the name and number of a cranial nerve indicate?
A
The number indicates the rostrocaudal order in which they emerge from the brain. The names are descriptive of the structures they innervate.
2
Q
Where do cranial nerves originate?
A
The brain.
3
Q
What kind of function do cranial nerves have?
A
Either motor, sensory, or mixed.
4
Q
Cranial nerves are part of which portion of the nervous system?
A
Peripheral nervous system.
5
Q
Are cranial nerves paired?
A
Yes.
6
Q
The development of cranial nerves is associated with the development of what other structure?
A
The brain.
7
Q
Describe the development of CN 1.
A
As the neural tube develops, the neuroectoderm develops into the olfactory placode which develops into the olfactory nerve; ectodermal in origin.
8
Q
Describe the development of CN 2.
A
It is an outgrowth of the neural tube; the diencephalon gives rise to the optic vesicles which develop into the optic nerve as well as the retina.
9
Q
Describe the development of CN 3-12.
A
All develop from the neural crest, which originates from the dorsal part of the neural tube as a group of multipotent and migratory cells capable of developing into multiple structures.
10
Q
Is CN 1 sensory, motor, or both?
A
Sensory.
11
Q
Is CN 2 sensory, motor, or both?
A
Sensory.
12
Q
Is CN 3 sensory, motor, or both?
A
Motor.
13
Q
Is CN 4 sensory, motor, or both?
A
Motor.
14
Q
Is CN 5 sensory, motor, or both?
A
Both.
15
Q
Is CN 6 sensory, motor, or both?
A
Motor.
16
Q
Is CN 7 sensory, motor, or both?
A
Both.
17
Q
Is CN 8 sensory, motor, or both?
A
Sensory.
18
Q
Is CN 9 sensory, motor, or both?
A
Both.
19
Q
Is CN 10 sensory, motor, or both?
A
Both.
20
Q
Is CN 11 sensory, motor, or both?
A
Motor.
21
Q
Is CN 12 sensory, motor, or both?
A
Motor.
22
Q
What is the mnemonic for remembering whether a cranial nerve is sensory, motor, or both functions?
A
Some Say Money Matters But My Brother Says Big Brains Matter Most.
23
Q
Which cranial nerves are purely sensory?
A
1, 2, and 8.
24
Q
Which cranial nerves are purely motor?
A
3, 4, 6, 11, and 12.
25
What are the cranial nerves of the eye muscles?
3, 4, and 6.
26
Which cranial nerves are in the vagal group?
9, 10, and 11 (all exit together through the jugular foramen).
27
From an evolutionary standpoint, CN 12 is considered to be what?
The first cervical nerve.
28
Grey matter and white matter of the brain and spinal cord contain what structures?
Grey: neuronal cell bodies. White: myelinated axons.
29
What is the olfactory nerve responsible for?
Olfaction/smell.
30
Where does the olfactory nerve originate?
The olfactory bulb.
31
True or false: the olfactory nerve is a single nerve.
False: it is made up of numerous non-myelinated axons.
32
What is myelin made up of?
Schwann cells in the PNS and oligodendrocytes in the CNS.
33
Where are the cell bodies of CN 1 situated?
Within the olfactory epithelium in the olfactory bulb; axons pass through the cribriform plate of the ethmoid bone to enter the olfactory bulb where they synapse.
34
What is the olfactory bulb?
Two extensions of the brain made up of grey matter that rest on the cribriform plate.
35
Where are olfactory areas within the brain situated?
At the ventral aspect of the temporal lobe.
36
What are the olfactory areas within the brain?
- Olfactory bulb at the base of the frontal lobe
- Piriform complex at the ventral aspect of the brain
- Limbic system just adjacent to the temporal lobe.
37
What are the functions of the olfactory bulb?
Receives sensory input from nasal passages and communicates with the cerebral hemisphere via the olfactory peduncle.
38
The olfactory bulb is highly developed in what species?
Dogs.
39
What are the characteristics of the piriform complex?
- Main cortical area associated with olfaction
- Not part of the temporal lobe of the brain.
40
What is the limbic system associated with in relation to the olfactory nerve?
Associated with memory related responses to olfactory stimuli.
41
What are the two parts of the limbic system?
Includes the hippocampus and the amygdala.
42
What does osmia mean?
Smell.
43
What is the difference between anosmia and hyposmia?
Anosmia: complete loss of smell. Hyposmia: reduced ability to smell.
44
Pathologies that affect the ability of an animal to smell include what?
- Infection
- Tumors
- Age-related atrophic changes: as an animal ages, the olfactory epithelium degenerates and brings about reduction in olfactory ability; the reason why service dogs retire as they age.
45
Describe how you would examine the ability of CN 1.
- Have the dog stand in front of you with a treat in one hand and put both hands in front of the dog with fists closed; can also use scented toys.
- See if the dog can identify where the treat/toy is located.
46
What is the role of the optic nerve?
Transmits information from the eye to the brain; also responsible for visual acuity which is the ability to see clearly/spatial awareness/color vision.
47
Where do the axons of CN 2 accumulate?
At the optic disk, which is the blind spot on the retina.
48
CN 2 is enclosed by what?
Enclosed by dura mater and surrounded by the retractor bulbi muscle situated within the periorbita.
49
Where does CN 2 exit the eyeball?
At the caudoventral margin.
50
CN 2 emerges from the brain case at what point?
The optic canal.
51
What is the optic chiasm?
Point where the optic nerve deposits and axons of the brain tracts emerge that feed each eye via incomplete decussation.
52
Describe the incomplete decussation that occurs at the optic chiasm.
- About 75% of the axons decussate.
- Decussating fibers are largely from the medial/nasal aspect of each retina.
- Decussation creates a broad visual field, binocular field, and uniformity in processing manner.
53
Problems with the optic nerve are called what?
Optic neuropathies; result in partial or complete blindness.
54
What are the causes of neuropathies associated with the optic nerve?
- Trauma: pulling during enucleation
- Tumor (brain or eye)
- Congenital
- Nutrition (vitamin A deficiency)
- Glaucoma (compression of nerve)
- Infection/inflammation: most common cause.
55
Describe how you would test the integrity of an animal's optic nerve.
See if the dog bumps into things while walking in an unfamiliar area or check pupillary light reflex.
56
How is blindness treated in dogs?
Blind halo.
57
CN 3, 4, and 6 all pass through what structure to exit the brain?
Orbital fissure along with the ophthalmic branch of CN 5.
58
Where does the oculomotor nerve originate from?
Midbrain; nuclei specifically within the tegmentum (motor and parasympathetic).
59
What is the function of the oculomotor nerve?
Motor function to extrinsic and intrinsic (parasympathetic) muscles of the eye (movement of eye except laterally, movement of upper eyelid, and pupillary constriction).
60
What muscles does the oculomotor nerve innervate?
Levator palpebrae superioris, rectus muscles except lateral, and ventral oblique muscle.
61
Describe the course of the oculomotor nerve.
- Comes from the midbrain aspect of the brainstem and courses on the ventral aspect of the peduncles and then rostrally through the orbital fissure.
- As soon as it enters the orbit it branches into dorsal and ventral branches.
- Parasympathetic nerve courses along with the ventral branch and synapses with postganglionic neurons in the ciliary ganglion.
62
What do the dorsal, ventral, and parasympathetic branches of the oculomotor nerve innervate specifically?
- Dorsal: levator palpebrae superioris muscle and dorsal rectus muscle.
- Ventral: medial rectus, ventral rectus, and ventral oblique.
- Parasympathetic: ciliary muscle and pupillary muscles responsible for constriction.
63
What does the blue arrow indicate?
Ophthalmic nerve
64
What does the red arrow indicate?
Optic nerve
65
What does the white arrow indicate?
Lateral rectus muscle (innervated by CN 6)
66
What does the black arrow indicate?
Dorsal rectus muscle (innervated by CN 3)
67
What does the purple arrow indicate?
Ventral rectus muscle (innervated by CN 3)
68
Which nerves share a common sheath of dura mater with the oculomotor nerve?
Abducens and ophthalmic nerve
69
How would you examine the integrity of the oculomotor nerve?
Pupillary reflex test
## Footnote
Both pupils should contract, but more so in the stimulated eye.
70
What is anisocoria?
Unequal pupillary size
## Footnote
Have to have equal amounts of light going into each eye to determine if there is a true case of anisocoria.
71
What actions of the eye is the trochlear nerve responsible for?
Downwards movement and medial rotation of the eye (dorsal oblique muscle)
72
Where does the trochlear nerve originate?
Midbrain
73
What is the smallest of the cranial nerves?
Trochlear nerve; has the longest intracranial length but a very short length outside of the cranial cavity.
74
What is the only cranial nerve that courses from dorsum to ventrum?
Trochlear nerve
75
Which cranial nerve is the only one with complete decussation?
Trochlear nerve; decussates within the brain tissue before it exits the brain.
76
Why does the trochlear nerve have its name?
Trochlear = pulley; tendon of insertion of the dorsal oblique muscle passes through a loop of fibrous tissue called the trochlea.
77
What happens when the trochlear nerve is damaged?
Trochlear nerve palsy: dorsal oblique muscle dysfunction that results in extrusion of the eyeball and outward rotation.
78
Where is the nucleus of the abducens nerve located?
On the caudal aspect of the pons
79
What muscles does the abducens nerve provide motor function to?
Lateral rectus and retractor bulbi muscle
80
Describe the relationship between the facial nerve and the abducens nerve.
The facial nerve forms a loop around the nucleus of the abducens nerve called the internal genu.
81
What is strabismus?
Lazy eye due to an unopposed rectus muscle
## Footnote
If it is pulled only laterally, then there is oculomotor damage; if it is pulled only medially, then there is abducens damage.
82
What is the largest sensory nerve of the head?
Trigeminal nerve
83
Describe the sensory and motor innervation of the trigeminal nerve.
Sensory innervation to the head, and motor innervation to the muscles of mastication.
84
Where is the sensory nucleus for the trigeminal nerve located?
Midbrain, pons, and medulla
85
Where is the motor nucleus for the trigeminal nerve located?
In the metencephalon, deep to the locus caeruleus of the rhomboid fossa.
86
What is the role of each branch of the trigeminal nerve?
Ophthalmic: sensory; Maxillary: sensory; Mandibular: mixed.
87
What are the results of damage to the trigeminal nerve?
Dropped jaw and sunken head.
88
Where are the nuclei of the facial nerve located?
Motor, sensory, and parasympathetic all located within the medulla oblongata.
89
What is genu syndrome?
Impairment of the abducens and facial nerves together due to an issue with the internal genu.
90
What are the parasympathetic, sensory, and motor functions of the facial nerve?
Parasympathetic: salivary glands; Sensory: tongue; Motor: facial expression muscles.
91
What signs result from damage to the facial nerve?
Uneven facial expression, loss of blink reflex, difficulty closing the eye, muzzle sagging.
92
Where are the nuclei of the vestibulocochlear nerve located?
Cochlear and vestibular nuclei situated within the medulla oblongata.
93
What are the functions of the vestibulocochlear nerve?
Cochlear: hearing; Vestibular: balance and equilibrium.
94
What signs result from damage to the vestibulocochlear nerve?
Torticollis, circling, ataxia.
95
What are the two branches of CN 9?
Lingual and pharyngeal branches.
96
Where are the nuclei of the glossopharyngeal nerve located?
Motor, sensory, and parasympathetic nuclei all originate within the medulla oblongata.
97
Describe the motor, sensory, and parasympathetic functions of the glossopharyngeal nerve.
Motor to pharyngeal muscles; Sensory for taste at the back of the tongue; Parasympathetic to salivary glands.
98
What results from damage to the glossopharyngeal nerve?
Dysphagia, pharyngeal paralysis, excessive drooling.
99
How can the integrity of CN 9 be tested?
Checking the gag reflex.
100
Which cranial nerves exit through the jugular foramen?
CN 9, 10, and 11.
101
Where is the nucleus of the vagus nerve located?
In the medulla.
102
What are the motor, sensory, and parasympathetic functions of the vagus nerve?
Motor to laryngeal muscles; Parasympathetic to thoracic and abdominal structures; Sensory to thoracic and abdominal structures.
103
What results from paralysis of the vagus nerve?
Loss of stomach tone, bloat, colic in horses.
104
How does vagus nerve paralysis manifest between different species?
Manifests differently depending on the animal.
105
What is the origin of the accessory nerve?
Medulla and spinal cord.
106
What is the role of the accessory nerve?
Motor to the muscles of the forelimb and neck.
107
What is the origin of the hypoglossal nerve?
The medulla oblongata near the ventral floor of the 4th ventricle.
108
What is the role of the hypoglossal nerve?
Motor to the muscles of the tongue.
109
What is the most caudal of the cranial nerves?
The hypoglossal nerve.
110
What are the results of damage to the hypoglossal nerve?
Tongue deviation, muscle atrophy, dysphagia.
