Download ANPS 019 Beneyto-Santonja 11-02

ANPS 019 Beneyto-Santonja 11/02/12
Cranial Nerves
Each Cranial Nerve is Unique  Learn name, Roman numeral, functions
4 Classifications of Cranial Nerves
1. Sensory nerves  carry somatic sensory information (touch, pressure, vibration,
temperature, and pain)
2. Motor nerves  axons of somatic and autonomic motor neurons
3. Mixed nerves  have both motor and sensory fibers
4. Special sensory nerves  carry sensations (smell, taste, sight, hearing, balance)
Olfactory Nerve (CN I)  Special Sensory; Smell
 Located in cribiform plate of ethmoid bone
 Cells synapce in olfactory bulb
 Projection neurons form olfactory tract
 Synapse in thalamus (what smell is) & limbic system (emotion of smell)
 The only sense that doesn’t need to relay through the thalamus
Optic Nerve (CN II)  Special Sensory; Vision
 The optic nerve is a CNS nerve
 Myelinated by oligodendrocytes and can’t regenerate
 Two visual pathways:
o Optic Nerve  Chiasm  Tract  Thalamus  Occiptal Lobe = object
recognition
o Optic Nerve  Chiasm  Tract  Superior Colliculus = tracking objects
Eye movements involve 6 eye muscles innervated by 3 cranial nerves: III, IV, & VI
Eyes movements are Complex!
 To look right:
o The right medial rectus must relax
o The left medial rectus must contract
o The right lateral rectus must contract
o The left lateral rectus must relax
 The left cortex sends the command to look right. The brainstem sorts out the “mixed”
signals to each eye appropriately
Oculomotor Nerve (CN III)
 Somatic Motor
o Eye movement (4 of 6 eye muscles)
o Muscle that keeps eyelid up
o Damage results in droopy eyelid (ptosis)
 Visceral Motor/Autonomic parasympathetic innervation
o Pupil constriction & lens focusing
Trochlear Nerve (CN IV)  only CN that exits from the dorsal side of brainstem
 Somatic Motor for eye movement: rolls eye down and out
Abducens Nerve (CN VI)
 Somatic motor for eye movement: horizontal eye movements
CN III, IV, VI  Object Tracking
 Smooth pursuits
 Saccade- rapid tracking
Trigeminal Nerve (CN V)  Mixed: sensory and motor
 Largest cranial nerve  3 major branches
o General sensations of face
o Muscles of mastication (chewing)
Facial Nerve (CN VII)
 Somatic motor: muscles for facial expression
 Special sensory: taste from anterior 2/3rds of tongue
 Visceral motor: Autonomic parasympathetic fibers to tear and nasal mucous
glands/salivary glands
Corneal blink reflex
 CN V feels the pain
 CN VII closes the eyelid
Vestibulocochlear Nerve (CN VIII)
 Special sensory – balance & hearing
 Special sensory:
o Vestibular branch balance and equilibrium
o Cochlear branch hearing
 Destination: vestibular and cochlear nuclei in pons and medulla oblongata
Bell’s Palsy
 Possible symptoms of Bell’s Palsy
o Droopy eyelid, dry eye, or excessive tears
o Facial paralysis, twitching, or weakness
o Drooping corner of mouth, dry mouth, impaired taste
Glossopharyngeal Nerve (CN IX)  Mixed: sensory and motor
 Sensory
o Taste: posterior 1/3 of tougue
o Taste: part of pharynx & palate
o Carotid arteries (blood pressure)
 Somatic Motor
o Motor neurons in medulla to innervate swallowing muscles in pharynx
 Visceral Motor
o Autonomic parasympathetic to parotid gland for salivation
Vagus Nerve (CN X)  Mixed (sensory and motor)
 Autonomics: Slows heart rate
 Major parasympathetic innervation to thoracic & abdominal viscera
 Sensory
o Taste from part of the pharynx
o Visceral organs
 Somatic motor: swallowing
 Visceral motor:
o Palate, pharynx
o Digestive, respiratory, and cardiovascular systems
Accessory Nerve (CN XI)
 Motor: Throat (larynx, pharynx); swallowing
 Neck muscles (sternocleidomastoid, trapezius); maintain position of head
Hypoglossal Nerve (CN XII)
 Somatic Motor – tongue movements
 CN XII Tongue Muscle  Tongue atrophies and deviates toward side of defect
Summary of Cranial Nerves
#
Nerve
I
Olfactory
II
Optic
III
Oculomotor
IV
Trochlear
V
Trigeminal
VI
Abducens
VII
Facial
VIII
Vestibulocochlear
IX
Glossopharyngeal
X
Vagus
XI
Spinal Accessory
XII
Hypoglossal
Types
Sensory
Sensory
Motor
Motor
Both
Motor
Both
Sensory
Both
Both
Motor
Motor
Location
Forebrain
Retina
Midbrain
Midbrain
Pons
Pons
Pons
Pons
Medulla
Medulla
Medulla
Medulla
Cranial Nerve
 Midbrain
o CN III – Oculomotor
o CN IV – Trochlear
 Pons
o CN V – Trigeminal (general sensation)
o CN VI – Abducens
o CN VII – Facial
o CN VIII – Vestibulocochlear (part)
 Medulla
o CN V – Trigeminal (pain & temp)
o CN VIII – Vestibulocochlear (part)
o CN IX – Glossopharyngeal
o CN X – Vagus
o CN XI – Accessory
o CN XII – Hypoglossal
Function
Smell
Vision
Eye movement, pupil constriction
Eye movement
M: Chewing, S: Senses
Eye Movement
M: facial expression, S: taste
Equilibrium & hearing
M: pharynx muscles, S: taste
M: visceral muscle, S: taste
Pharynxn and neck muscles
Tongue muscles