Lecture 5 Flashcards
What are 6 functions of the cerebellum?
- affects ipsilateral motor function
- balance & posture
- find tuning of skilled (coordinated) motor functions Via feedback: compares what cortex said to do with what joints/muscles really did and corrects
- Initiation, termination, coordination, and timing of movements: Allows you to start and stop without overshooting. Allows you simultaneously perform multi joint tasks (ie bring arm over head: not first bend elbow, then shoulder etc)
- Planning of motor movements
- Motor learning`
How does the cerebellum exert motor influence?
- Rubrospinal (skeletal muscle control, tone, posture)
- Vestibulospinal (balance in response to head movements)
- Reticulospinal tract (influences reflexes and voluntary and autonomic
- Connections to the cerebral cortex, which can then influence the corticospinal tracts
What are the structures that make up the cerebellum?
- Anterior & posterior lobes; Provide subconscious movements
- Floculonodular lobe; Regulates equilibrium
- vermis
- foli
What do the anterior & posterior lobes of the cerebellum provide?
Provide subconscious movements
What does the floculondodular lobe of the cerebellum regulate?
Regulates equilibrium
“worm-like” part that separates the 2 hemispheres of cerebellum
vermis
gyri-like convolutions on the surface of the cerebellum
foli
How is the cerebellum connected to the brainstem?
via cerebellar peduncles
- superior –> midbrain
- middle –> pons
- inferior –> medulla
Which cerebellar peduncle is mostly output?
superior
Which cerebellar peduncles are mostly output?
middle & inferior
rapid involuntary movements of the eyes
nystagmus
What is nystagmus a result of?
injury or disconnect to an input or output of vestibulocerebellum
What are three movements the eye may do in nystagmus?
- Side to side (horizontal nystagmus)
- Up and down (vertical nystagmus)
- Rotary
An inability to coordinate muscle activity during voluntary movement; most often due to disorders of the cerebellum or the posterior columns of the spinal cord; may involve the limbs, head, or trunk
ataxia
ataxia of laryngeal muscles
Dysarythria
What are symptoms of Dysarythria?
jerky articulation, separation of syllables, changing sound intensities
ataxia of ocular muscles
Cerebellar Nystagmus
What are symptoms of Cerebellar Nystagmus?
tremor of eyeballs that usually occurs when patient attempts to fixes eyes on an object off to the side
inability to maintain an upright position (affects gait)
Truncal ataxia
What are symptoms of Truncal ataxia?
Unstable, wide gait with irregular steps and lateral bending
“wrong distance” can’t judge distance- movements “overshoot”, and then overcompensate
Dysmetria
What are symptoms of Dysmetria?
patient can’t touch finger to nose, heel to shin - leads to intention tremor
What are 3 subdivisions of ataxia?
- dysarythria
- cerebellar nystagmus
- truncal ataxia
What are cerebrocerebellar lesions?
- ataxia (+ dysarythria, cerebellar nystagmus, truncal ataxia)
- dysmetria
- dysdiadochokinesia
- hypotonia
- asynergia
“without ability to make rapidly alternating movements”
Dysdiadochokinesia
What are symptoms of Dysdiadochokinesia?
loss of ability to predict where a body part will be at a given time, leading to the next movement in a sequence starting too early or too late.
How do you test for Dysdiadochokinesia?
test by asking patient to rapidly turn palm up and down: results in jumbled movements
low muscle tone
hypotonia
Lack of co-ordination between muscles or other body parts which usually work together. (postural abnormalities)
Asynergia
- Lack of coordination among various muscle groups during the performance of complex movements, resulting in loss of skill and speed. When severe, results in decomposition of movement, wherein complex motor acts are performed in a series of isolated movements; caused by cerebellar disorders
All cranial nerves innervate the ipsilateral (same) side except?
CN II
T/F: motor fibers will provide efferent innervation to the same side and sensory fibers will carry afferent information from the same side
True
Nuclei of Cranial nerves III – XI originate within brainstem and nerves exit off brainstem, except?
CN I and II which originate in specific locations
What is the code for motor fibers to skeletal, voluntary muscles that developed from branchial (pharyngeal) arches?
SVE: (Branchial Efferent/Special Visceral Efferent)
What is the code for taste & smell?
SVA: (Special Visceral Afferent)
What is the code for vision, hearing, and balance?
SSA: (Special Somatic Afferent)
Which codes are specific to cranial nerves only?
- SVE
- SVA
- SSA
The UMNs coming from the cortex send mostly (not always!) __ __ to the nuclei of the cranial nerves (i.e. LMNs), which then project to the __ __ (with one exception!)
bilateral innervation; ipsilateral muscles
Cortex to cranial nuclei in the brainstem
Corticobulbar or corticonuclear (UMN)
Cranial nerves nuclei to the muscles by
lower motor neurons
The __ nucleus sends innervation to the contralateral superior oblique muscle rather than the ipsilateral muscle
trochlear (CN IV)
The lower part of the __ motor nucleus that innervates the lower face muscles receives ONLY contralateral innervation from the cortex rather than bilateral
facial (CN VII)
Those neurons in the __ nucleus that innervate the genioglossus muscle receive contralateral innervation from the cortex rather than bilateral
hypoglossal (CN XII)
Where is the first and second neuron/nerve of CN I? Where does it go?
- 1st neuron is in the olfactory epithelium
- 2nd nerve is in the olfactory bulb that goes to the olfactory areas of the brain
Where are the 1st and second neurons of CN II? Where does it go?
- 1st neuron is in the retina
- 2nd neuron is in the thalamus, from there, it goes to the visual cortex
What is the pathway, foramina, and function of CN I?
Pathway:
- Receptors originate in the superior parts of the nasal cavity in the mucosal lining
- Axons enter cranial cavity through the olfactory foramina in the cribriform plate of ethmoid
- Synapse in olfactory bulbs inferior to frontal lobe within anterior cranial fossa - Bulbs sit between frontal lobe and cribriform plate
- Signals travel into frontal cortex via olfactory bulb
foramina: olfactory foramina of ethmoid
function: special sense = smell (special visceral afferent (SVA))
How does the olfactory nerve get injured?
- Nasal trauma
- Fracture of ethmoid/cribriform plate - If fracture is suspected, do not intubate patient via nasal cavity!
- Tumor in anterior cranial fossa / frontal lobe
What is the outcome of injury to the olfactory nerve?
- 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)
How do you test for CN I?
Ask the patient to identify commonly known odors such as vanilla, coffee, soap (with their eyes closed!)
What is CSF rhinorrhea?
leakage of CSF from subarachnoid space due to trauma of the associated bones and meningeal layers (not seen with tumor)
What is the pathway, foramina, and function of CN II?
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
*do not travel ipsilateral
Foramina: Optic canal of sphenoid
Function: special sense = Vision
- Special Somatic Afferent (SSA)
How do you test for CN II?
test each eye individually
1. Visual acuity test (Snellen eye chart)
2. Pupillary light response (discussed in L21)
Where does the optic nerve connect after leaving each eye?
optic chiasm
What are the extrinsic eyeball muscles?
- rectus (superior, inferior, medial, lateral)
- oblique (superior & inferior)
What is the muscle the elevate the eyelid?
levator palpebrae superioris
What are the intrinsic eyeball muscles?
- pupillary constrictor
- pupillary dilator
Which nerve innervates rectus (superior, inferior, and medial), inferior oblique, and levator palpebrae?
CN III
Which nerve innervates superior oblique?
CN IV
Which nerve innervates lateral rectus?
CN VI
What is the pathway, foramina, & function of CN III?
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
What are common causes of injury of the oculomotor nerve?
- Diabetic neuropathy
- Aneurysm
- Cerebral trauma
- Increased intracranial pressure
- Cavernous sinus syndrome
How will a patient present with injury of oculomotor nerve?
- 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
What is the pathway, foramina, and function of CN IV?
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)
What is the pathway, foramina, and function of CN VI?
Pathway: Originates at pons, travels toward eyeball, exits superior orbital fissure
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)
How do you test for CN III, IV, & VI?
test each individually
- H-test –> observe differences
What is the white matter of the cerebellum called?
arbor vitae
How it the gray matter (cortex) of the cerebellum arranged?
peripherally arranged around arbor vitae
What are the deep nuclei of the cerebellum? What are their functions?
- Dentate, Interposed (consists of emboliform and globose nuclei): both voluntary movements
- Fastigial: balance
What does the spinocerebellum correspond to?
majority of the vermi
What are the functions of the spinocerebellum?
- Adjusts movements as they are occurring
- Corrective feedback to fine-tune motor skills
- Allows you to make quick adjustments so you don’t all of a sudden become unsteady** (ex., standing on one leg)
What are the major inputs to the spinocerebellum?
- Spinocerebellar, cuneocerebellar tracts (proprioception from periphery)
- Corticopontocerebellar fibers (primary motor: copy from cortex)
What are the major output of the spinocerebellum?
(via Interposed nuclei)
Rubrospinal, corticospinal
What are common problems that arise due to lesions of the spinocerebellum?
Gait is affected: Because of Loss of motor co-ordination.
Where are the first, second, and third neurons mainly located with reference to cranial nerves?
- 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 are other names for cerebrocerebellum?
neocerebellum or pontocerebellum
What does the cerebrocerebellum correspond to?
majority of the cerebellar hemispheres
What are the functions of the cerebrocerebellum?
- Planning coordinated movements
- Rapid alternating movements (ex., running)
- Fine dexterity (Quickness)
- Initiation, termination, coordination and timing of movements
- Motor learning
What are the major inputs to the cerebrocerebellum?
- Corticopontocerebellar (premotor and association areas)
- Olivocerebellar
What are the major outputs to the cerebrocerebellum?
(via Dentate nucleus)
Corticospinal, rubrospinal
What does the vestibulocerebellum correspond to?
Floculo-nodular lobe
What are functions of the vestibulocerebellum?
- Balance
- Coordination of eye movements
- As things are moving past your body (allows us to scan periphery but not moving head) ensures you don’t get dizzy, those who do are EXTRA sensitive to this movement
What are major inputs to the vestibulocerebellum?
Vestibular fibers from vestibulocochlear nerve and vestibular nuclei
What are major outputs to the vestibulocerebellum?
(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)
