Cerebellum and Intro to Cranial Nerves Flashcards
What are the functions of the cerebellum? (6)
1.) Ipsilateral motor function
2.) Balance and posture
3.) Fine tuned motor skills (via feedback cortex–>joints/muscles)
4.) Initiation, termination, coordination, and timing of movements: Allows you to start and stop without overshooting. Allows you simultaneously perform multi joint tasks
5.) Planning of motor movements
6.) Motor learning
How does the cerebellum exert motor influence? Rubrospinal?
SKELETAL muscle control, tone, posture
How does the cerebellum exert motor influence? Vestibulospinal?
BALANCE in response to HEAD movements
How does the cerebellum exert motor influence? Reticulospinal tract?
Influences REFLEXES and voluntary and autonomic
How does the cerebellum exert motor influence? Cerebral cortex?
Can influence the corticospinal tracts
What are the lobes of the cerebellum? Functions?
Anterior & posterior lobes: Provide subconscious movements
Floculonodular lobe: Regulates equilibrium
What separates the 2 hemispheres of cerebellum?
vermis (worm-like)
What are the gyri-like convolutions on the surface of the cerebellum?
Foli
What is the white matter in the cerebellum called?
Arbor vitae
Where is the gray matter of the cerebellum located?
peripherally around the arbor vitae (white matter)
What parts are included in the deep nuclei? Functions?
dentate, interposed (consists of emboliform and globose nuclei): voluntary movements
Fastigial: balance
What are the highways into and out of the cerebellum?
peduncles (sup., middle, and inferior)
Vestibulocerebellum
1.) Corresponds to what lobe?
2.) Functions?
3.) Major inputs?
4.) Major outputs?
5.) Problems with lesion?
1.) Floculo-nodular lobe
2.) balance, coordination of eye movements (reflexive)
3.) vestibular fibers from vestibulocochlear nerve and vestibular nuclei, VIII
4.) (via fastigial nucleus)
Vestibulospinal tract (motor balance)
Reticulospinal tracts (motor influences)
Medial longitudinal fasciculus
Runs from vestibular nuclei to interconnect occulomotor, trochlear and abducens nuclei in brainstem (eye movements)
5.) Nystagmus: rapid, uncontrollable eye movements that can cause problems with vision, depth perception, balance and coordination
What is the oldest part of the cerebellum?
archicerebellum (archi=first in Greek)
What is nystagmus?
rapid involuntary movements of the eyes that may be:
Side to side (horizontal nystagmus)
Up and down (vertical nystagmus)
Rotary
Spinocerebellum
1.) Corresponds to what lobe?
2.) Functions?
3.) Major inputs?
4.) Major outputs?
5.) Problems with lesion?
1.) majority of the vermis
2.) Adjusts movements as they are occurring, corrective feedback to fine-tube motor skills
3.) Spinocerebellar, cuneocerebellar tracts (proprioception from periphery), Corticopontocerebellar fibers (primary motor: copy from cortex)
4.) (via Interposed nuclei)
Rubrospinal, corticospinal
5.) Gait is affected: Because of loss of motor co-ordination.
What is the earliest stage in the evolution of the cerebellum?
paleocerebellum
Cerebrocerebellum (aka neocerebellum, pontocerebellum)
1.) Corresponds to what lobe?
2.) Functions?
3.) Major inputs?
4.) Major outputs?
5.) Problems with lesion?
1.) majority of the cerebellar hemispheres
2.) Planning movements
Rapid alternating movements
Fine dexterity (Quickness)
Initiation, termination, coordination and timing of movements
Motor learning
3.) Corticopontocerebellar (premotor and association areas)
Olivocerebellar
4.) (via Dentate nucleus)
Corticospinal, rubrospinal
5.) dysmetria, dysdiadochokinesia, asynergia
What is it called when motor coordination is lost?
ataxia
What is ataxia of laryngeal muscles? Symptoms?
dysarythria
jerky articulation, separation of syllables, changing sound intensities
What is ataxia of ocular muscles called? Symptoms?
Cerebellar Nystagmus
tremor of eyeballs that usually occurs when patient attempts to fixes eyes on an object off to the side.
What type of ataxia causes the inability to maintain an upright position, affecting gait? Symtoms?
Truncal ataxia
Unstable, wide gait with irregular steps and lateral bending
Disorders of the cerebellum or the posterior columns of the SC, commonly cause what?
ataxia
What is the inability to judge distance-movements “overshoot” and then overcompensation? Symptoms?
dysmetria
patient can’t touch finger to nose, heel to shin - leads to intention tremor
What is the inability to make rapidly alternating movements? Sypmtoms? How to test?
dysdiadochokinesia
test by asking patient to rapidly turn palm up and down: results in jumbled movements.
What is low muscle tone called?
hypotonia
What is the lack of co-ordination between muscles or other body parts which usually work together? (postural abnormalities)
asynergia
Which cranial nerve (s) innervates the anterior fossa? Which exact regions?
CN I only
Frontal, ethmoid, sphenoid
Which cranial nerve (s) innervates the middle fossa? Which exact regions?
CN II-VI
Sphenoid, temporal
Which cranial nerve (s) innervates the posterior fossa? Which exact regions?
CN VII-XII
temporal, occipital
All cranial nerves innervate the ipsilateral side except which one?
CN II
GSE
General Somatic Efferent
motor fibers to skeletal musculature (VOLUNTARY)
GSA
General Somatic Afferent
fibers that carry general sensation (touch, pressure, pain, proprioception , temperature changes, tickle and vibration)
GVE
(General Visceral Efferent): motor fibers to smooth muscle, glands, and viscera (INVOLUNTARY)
GVA
(General Visceral Afferent): fibers that carry visceral sensation (stretch of organ wall, pain, chemical changes, temperature change)
SVE
(Branchial Efferent/Special Visceral Efferent): motor fibers to skeletal, voluntary muscles that developed from branchial (pharyngeal) arches
SVA
(Special Visceral Afferent): taste & smell
SSA
(Special Somatic Afferent): vision, hearing & balance
The UMNs coming from the cortex send (mostly) (ipsilateral/bilateral) innervation to the nuclei of the cranial nerves, which then project to the (ipsilateral/bilateral) muscles?
bilateral innervation
ipsilateral muscles
Which cranial nerves are the exceptions for the motor pathway from cortex to muscles?
CN IV: the trochlear nucleus sends innervation to the CONTRALATERAL superior oblique muscle rather than the ipsilateral muscle.
CN VII: the lower part of the facial motor nucleus that innervates the lower face muscles receives ONLY contralateral innervation from the cortex rather than bilateral
The neurons in the hypoglossal nucleus that innervate the genioglossus muscle receive (ipsilateral/contralateral) innervation from the cortex rather than bilateral?
Contralateral
CN XII
(tongue)
Sensory components of the cranial nerve:
1st neuron
2nd neuron
3rd neuron
Ipsi/contra?
Where?
1st neuron is in the sensory ganglion of the cranial nerve.
2nd neuron in the ipsilateral (mainly) sensory nucleus of the C.N. nerve in the brainstem
3rd neuron in the thalamus (mainly contralateral) and terminates in the contralateral cortex
What is the exception for C.N. I? (in regards to sensory components)
The olfactory nerve (C.N. I); 1st neuron is in the olfactory epithelium, and 2nd nerve is in the olfactory bulb that goes to the olfactory areas of the brain.
What is the exception for C.N. II? (in regards to sensory components)
The Optic nerve (C.N. II): 1st neuron is in the retina, and 2nd neuron is in the thalamus, and from there, it goes to the visual cortex
CN 1: Olfactory nerve pathway? Foramina? Function?
1.) Receptors originate in the superior parts of the nasal cavity in the mucosal lining
2.) Axons enter cranial cavity through the olfactory foramina in the cribriform plate of ethmoid
3.) Synapse in olfactory bulbs inferior to frontal lobe within anterior cranial fossa
4.) Bulbs sit between frontal lobe and cribriform plate
5.)Signals travel into frontal cortex via olfactory bulb
Foramina: Olfactory foramina in cribriform plate of ethmoid bone
Function: special sense = smell!
Special Visceral Afferent (SVA)
How does CN I get injured? What’s the outcome? Test?
1.) Nasal trauma
2.) Fracture of ethmoid/cribriform plate
If fracture is suspected, do not intubate patient via nasal cavity!
3.) Tumor in anterior cranial fossa / frontal lobe
Lack of smell “anosmia”
CSF rhinorrhea - leakage of CSF from subarachnoid space due to trauma of the associated bones and meningeal layers (not seen with tumor)
Testing CN I = performed usually after head trauma
1. Ask the patient to identify commonly known odors such as vanilla, coffee, soap (with their eyes closed!)
How does CN II get injured? What’s the outcome? Test?
Pathway:
Receptors found in retina of the eyeball transmit signals via optic nerve to the optic chiasm and then optic tract
Travels posteriorly to synapse in:
1. Thalamus
2. Occipital lobe
Foramina: Optic canal of sphenoid
Function: special sense = Vision
Special Somatic Afferent (SSA)
Testing CN II =test each eye individually
Visual acuity test (Snellen eye chart)
Pupillary light response (discussed in L21)
What are the extrinsic muscles of the eye?
1.) superior rectus (CN III) Elevates and adducts eyeball
2.) inferior rectus (CN III) Depresses and adducts eyeball
3.) medial rectus (CN III) Adduction of eyeball
4.) inferior oblique (CN III) Abducts and elevates and laterally rotates
eyeball (extorsion)
5.) levator palpebrae (CN III) Elevates superior eyelid
6.) superior oblique (CN IV) Abducts, depresses and medially rotates
eyeball (intorsion)
7.) lateral rectus (CN VI) Abducts eyeball
How does CN II get injured? What’s the outcome? Test?
Pathway:
Nerve begins at midbrain and travels anteriorly towards orbit
Innervates several muscles of eyeball after passing through superior orbital fissure
Foramina: Superior Orbital Fissure of sphenoid (posterior orbit)
Function: nerve has 2 axon modalities:
General Somatic Efferent (GSE): Voluntary motor to levator palpebrae superioris, and several extraocular eye muscles: superior rectus, medial rectus, inferior rectus, and inferior oblique muscle
General Visceral Efferent (GVE): Visceral motor (parasympathetic) innervation to sphincter pupillae for pupil constriction
Synapses in ciliary ganglion
Common causes of injury:
Diabetic neuropathy
Aneurysm
Cerebral trauma
Increased intracranial pressure
Cavernous sinus syndrome
Patient presentation includes:
Ptosis – droopy upper eyelid
Mydriasis – permanent dilation of pupil
Strabismus – “lazy eye”
Eye position is “down and out”
Due unopposed action of superior oblique and abducens muscle
Diplopia – double vision
How does CN IV get injured? What’s the outcome? Test?
Pathway:
Originates at midbrain, travels toward eyeball, exits superior orbital fissure
Foramina: Superior Orbital Fissure (posterior orbit)
Function: voluntary motor to superior oblique muscle = normally pulls the eye down and out
General Somatic Efferent (GSE)
How does CN IV get injured? What’s the outcome? Test?
CN VI = Abducens Nerve
Pathway:
Originates at pons, travels toward eyeball, exits superior orbital fissure (along with ……?)
Foramina: Superior Orbital Fissure (posterior orbit)
Function: voluntary motor to lateral rectus muscle = normally Abduct the eye away from the midline
General Somatic Efferent (GSE)
Testing CN III, IV and VI =test each eye individually
Eye movement in “H” pattern, observe for differences
