NB Test 3

Cerebellar role in movement

Constant monitoring of cortical motor output ​
Correction of discrepant movements​
Error—control of rapid, alternating, and sequential movements (DDK)​

Structures in addition to cerebellum that influence movement

Primary motor cortex—fine movement details​
Premotor and supplementary motor cortices—movement planning

Cerebellum regulates

Muscle tone ​
Range of Motion​
Motor learning ​
Potential cerebellum participation in cognitive processing

Corrective efferent fibers

to the motor cortex and spinal cord, decrease or stop movements

Cerebellum innervation pattern

Ipsilateral cerebellar sensorimotor organization to input source and output targets​
Effect of lesion always on the body ipsilateral to the cerebellar lesion ​
This is accounted by the double crossing of cerebellar fibers

Major parts of cerebellum

Cerebellar cortex​
Hemispheres (L & R) and lobes (Anterior, posterior floculonodular lobe)​
Three cerebellar peduncles

Three transverse lobes of cerebellum

Paleocerebellum (anterior)
Neocerebellum (posterior)
Archicerebellum (flocculonodular)

Paleocerebellum function

motor tone and walking position

Neocerebellum function

coordination of cortically directed skilled movements

Archicerebellum function

equilibrium and eye movements

Three longitudinal regions of cerebellum

Vermis
Paravermal
Lateral

Vermis function

maintenance of body posture

Paravermal function

ipsilateral movements

Lateral cerebellum region function

skilled movements

Three cerebellar peduncles

Inferior, middle, and superior

Cerebellar peduncles, afferent:efferent ratio

40:1

Afferent cerebellar peduncle

inferior and middle (to cerebellum)

Efferent cerebellar peduncle

superior (from cerebellum)

Inferior cerebellar peduncle function

Vestibular system​
Upright posture maintenance​
Momentary changes in rate and strength during ongoing movements​

Middle cerebellar peduncle function

Crossed afferents from motor cortex ​
Visual and auditory input for directional context​

Superior cerebellar peduncle projections

Crossed cerebellar projections to contralateral motor cortex

Additional cerebellar efferent pathways

Spinal cord (Modulation of muscle tone and reflexes)
Brainstem and reticular formation (Cranial nerve nuclei for speech, Spinal motor neurons—control of muscle tone during movement​, Vestibular nuclear complex—connections for equilibrium)

Corticospinal tracts

Motor, DESCENDING
Lateral corticospinal (crosses at pyramidal decussation (IN MEDULLA), fine limb movement, Skeletal muscle control during skilled tasks)
Anterior corticospinal (crosses within the spinal column (NOT in brainstem)​
central axial and girdle muscles, Uncrossed anterior corticospinal tract - TRUNK MOVEMENT/POSTURAL MUSCLES FOR UPPER BODY)

Dorsal columns

Sensory (fine touch and proprioception)
both cross at the medial lemniscus in the lower medulla​
fasciculus gracilis (sacral & lumber)​
fasciculus cuneatus (thoracic and cervical)

Anterolateral system

cross in the spinal column (usually after ascending a segment or two)​
Spinothalamic​ (localization of pain and temperature​)
Spinoreticular​ (alertness and arousal in response to pain)​
Spinotectal (tectum - sup and inf. colliculi)​
orients head to stimuli

Midbrain-Diencephalon Junction slice

Posterior commissure ​
Pineal gland - BIG LIGHT GRAY CIRCLE - TELLTALE SIGN THAT YOU'RE STILL IN THE DIENCEPHALON​
Subthalamic nucleus (between internal capsule and red nucleus)​
Posterior thalamus​
Pulvinar​
Geniculate (medial/lateral) bodies ​
Optic tract​
​
POSTERIOR ABOVE, ANTERIOR BELOW - TRANSVERSE SLICE​
NUCLEI WILL APPEAR LIGHTER AND WHITE MATTER TRACTS DARKER BC THIS IS A STAIN​
RED NUCLEUS \= NEARLY MIDLINE, LOOK LIKE EYES​
SUBTHALAMUS NUCLEI \= DIRECTLY BETWEEN RED NUCLEUS AND INTERNAL CAPSULE

Rostral midbrain slice

Rostral midbrain (MOST SUPERIOR PORTION OF MIDBRAIN)​ Pes pedunculi/CRUS CEREBRI - FUNCTION LIKE A SHELF THAT THE CEREBRUM SITS ON TOP OF​ Tectum and tegmentum ​ Colliculi—superior and inferior (BOTH PART OF TECTUM)​ Cerebral aqueduct​ Central gray of reticular formation ​ Red nucleus—cerebellar efferents (INFO FROM CEREBELLUM)​ Substantia nigra—Parkinson disease​ Oculomotor nucleus/nerve​ RETICULAR FORMATION = GRAY MATTER// IMPORTANT FOR CONSCIOUSNESS AND AROUSAL, REGULATORY FUNCTIONS, RESPIRATION AND HEARTBEAT​

Important, midbrain is *after decussation* of sensorimotor tracts from spinal cord.

Caudal midbrain slice

Inferior colliculi—auditory reflex (PREVENTS DAMAGE FROM LOUD NOISES) and relay (AUTOMATIC MUSCULAR RESPONSES - E.G. OPENING YOUR EYES TO NOISE - THAT DO NOT ROUTE THROUGH THE MOTOR CORTEX, GO DIRECTLY TO MUSCLES)​
Cerebral aqueduct - WE HAVE NOT GOTTEN TO THE 4TH VENTRICLE YET​
Superior cerebellar peduncle and decussation​
Lateral (auditory) and medial (somatosensation--touch) lemniscus​
CRUS CEREBRI COMES TOGETHER, BECOMES MORE HOMOGENOUS​
PONTINE FIBERS​
SITE OF CEREBELLAR FIBER DECUSSATION

Midbrain syndromes

DAMAGE TO MIDBRAIN MOTOR TRACTS -\> Contralateral paralysis of upper and lower limbs and trunk​
Ipsilateral paralysis of eyeball muscle with eye fixed laterally and a dilated pupil​
Contralateral limb in coordination (ataxia)​
Loss of contralateral discriminative touch (TELL DIFFERENT TEXTURES OR TEMPERATURES)​
Cranial nerve symptoms and frequent altered consciousness (PASS IN/OUT OF CONSCIOUSNESS)

Rostral pons/pons-midbrain junction slice

Central gray of reticular formation​
Trochlear nerve root/nucleus (OPENS AND CLOSES eyelids)​
Medial longitudinal fasciculus—discriminative touch​
Lateral lemniscus—auditory pathway​
Superior cerebral peduncle, decussation

Middle pons slice

Cerebellar peduncles—middle and superior​
Trigeminal nuclear complex​
Corticospinal-corticopontine fibers (SEND INFO UP AND DOWN THE SPINAL CORD)​
Lateral lemniscus—auditory pathway​
Fourth ventricle​
Facial nerve/nucleus​
Abducens nucleus/nerve (eye movement)

Lower pons slice

Pontine (motor) nuclei with corticospinal tract​
Fourth ventricle - HUGE AT THIS POINT - IDENTIFYING FEATURE​
Cerebellar peduncle (middle)​
Vestibular nuclear complex​
Spinal tract of trigeminal nerve​
Trigeminal nerve nuclear complex​
Medial lemniscus (somatosensation--touch)

Pontine symptoms

CONTRALATERAL SYMPTOMS​
Contralateral hemiplegia (sensorimotor decussation is inferior) and contralateral losses of discriminative touch​
Medially deviated eye (paralysis of the ipsilateral lateral rectus muscle), double vision involving the abducens nerve​
Unsteady gait​
Ipsilateral facial palsy, vertigo, nausea, and deafness in the ipsilateral ear - IPSILATERAL BC THESE INVOLVE CRANIAL NERVES

Key medulla structures

Corticospinal fibers (pyramidal tract)​
Pyramidal decussation (contralaterality)​
Dorsal lemniscal column (fasc. gracilis and cuneatus)​
Sensory decussation (contralaterality)​
Medial lemniscus (discriminative touch)​
Inf. cerebellar peduncle ​
Principal (inf.) olivary nucleus​
Reticular formation (cortical regulator)​
Cranial nerve nuclei

Rostral medulla slice

Spinal trigeminal nucleus​
Inferior cerebellar peduncle (CEREBELLAR INTERFACE WITH PONS)​
Cochlear and vestibular nuclear complex ​
Glossopharyngeal nerve​
Taste and regulation of swallowing ​
Pyramids (compact motor fibers)​
Medial lemniscus (discriminative touch - SPECIFICS - HOW MUCH PRESSURE AND WHERE TOUCH IS HAPPENING)​
Medial longitudinal fasciculus​
Interconnecting motor nuclei of the ocular cranial nerves

Mid-medulla slice

Hypoglossal nuclei​
Principal (inferior) olivary nucleus ​
Proprioceptive efferents to the cerebellum ​
Inferior cerebellar peduncle (restiform body)​
Nucleus ambiguus​
Glossopharyngeal (swallowing) and vagus (muscles of resonance, swallowing, and phonation) nerves ​
Reticular formation (REGULATES SLEEP/WAKE AND OTHER AUTONOMIC FUNCTIONS)​
SPINOCEREBELLAR TRACTS (FEED INTO THE CEREBELLUM)

Caudal/lower medulla slice

Pyramids​
Pyramidal tract and its decussation (THIS IS WHERE THE SWITCHOVER HAPPENS - AT THE BASE OF THE MEDULLA)​
Lateral corticospinal tract​
Nuclei and fasciculi of gracilis and cuneatus (IMPORTANT FOR INCOMING SENSORY SIGNALS FROM PERIPHERY, SENDS ON TO THALAMUS)​
Int. arcuate fibers (FIBERS THAT ALLOW CROSSOVER), sensory decussation, and medial lemniscus​
Medial longitudinal fasciculus​
Spinal trigeminal tract/nucleus​
Reticular formation​
Hypoglossal nerve/nucleus

Hierarchical neuronal motor network (least-\>most complex)

Spinal cord​
Cerebellum​
Basal ganglia​
Motor cortex​
(LISTED LEAST TO MOST COMPLEX)​

Spinal cord innervation pattern

Organized ipsilateral to its output and reflex input​
Spinal innervation involves ipsilateral muscles
MOTOR NERVE ALSO RECEIVES INFORMATION VERTICALLY FROM THE CORTEX, BUT IF ACTIVATED BY THE SENSORY NERVE SEEN LEFT CAUSES A REFLEX (DOES NOT PASS THROUGH THE BRAIN)

Spinal cord internal anatomy

Outer white matter with central gray area​
Dorsal (sensory) and ventral (motor cells) horns

Spinal Cord Cross-Sections

Same anatomical parts at all levels​
Centrally located gray matter​
Peripherally located white matter​
Fasciculi—dorsal, lateral, and anterior​

Size and shape change​ (Variable white-to-gray ratio​, Less grey matter lower down​)

Variable shape​ (more oblong at the cervical level (similar to brain stem shape), rounder at the bottom, but becoming slightly oblong in sacral sections)

Extrapyramidal tracts

AREN'T PART OF THE PYRAMIDS
Tectospinal tract—regulation of neck and body movements for startle reflexes E.G. WHEN YOU HEAR A NOISE AND TURN TO LOOK AT IT​
Rubrospinal tract—regulation of muscle tone for limb extension against gravity (ACCOUNTS FOR GRAVITY WITHOUT YOU CONSCIOUSLY THINKING ABOUT IT)​
Vestibulospinal tract—stabilization of head WHILE MOVING

Dorsal lemniscal system

Ascending tracts
SENSORY

Cervical section anatomy

NECK
Slender gray matter and large white matter

Cervical section fasciculi

Dorsal lemniscal column—fasciculi of gracilis and cuneatus)​
Corticospinal tract—below decussation (ISPILATERAL DAMAGE) - motor to skeletal muscles ​
Lateral column—spinothalamic and spinocerebellar pathways

Thoracic section anatomy

BOTTOM OF NECK TO MID-BACK
Enlarged white matter ​
Distinct dorsal and ventral horns​

Thoracic section fasciculi

Fasciculus gracilis—discriminative touch from lower body (HIPS AND LOWER)​
Fasciculus cuneatus—discriminative touch from upper body (ABOVE HIPS TO SHOULDERS/NECK)​
Lateral corticospinal tract—motor FROM CORTEX TO PERIPHERY​
Spinothalamic tract—SENSORY FOR pain/temperature VIA THAMALUS​
Spinocerebellar tracts—unconscious proprioception

Lumbar section anatomy

LESS MATERIAL AS YOU GET LOWER IN SPINAL CORD​
Larger dorsal and ventral horns

Lumbar section fasciculi

Dorsal lemniscal​
Fasciculus gracilis​
Lateral corticospinal tract ​
Anterolateral system​
Spinothalamic tract—pain/temp.​
Spinocerebellar tracts—unconscious proprioception

Sacral section anatomy

Larger gray matter (ALMOST NO WHITE MATTER AROUND SIDES)​
Prominent dorsal and ventral horns

Sacral section fasciculi and nuclei

Major fasciculi:​
Fasciculus gracilis—sensation from sacral to midthoracic level​
Lateral corticospinal tract—motor fibers TO LEGS AND FEET​
Spinothalamic tract—pain and temperature​

Sensory nuclei​
Substantia gelatinosa​
Nucleus proprius—pain and temperature​

Spinal clinical syndromes

Limb paralysis (IF DAMAGE IN MOTOR TRACTS - LATERAL CORTICOSPINAL TRACTS)​
Loss of pain/temperature (IF IN SPINOTHALAMIC TRACT)​
Loss of discriminative touch (IF IN DORSAL LEMNISCAL COLUMN)

Spinal cord sections (superior-\>inferior)

Cervical
Thoracic
Lumbar
Sacral

General cranial nerve function

Functionally Similar to Spinal Nerves​
Brainstem location ​
Innervation of muscles of head, neck, face, larynx, tongue, pharynx, & glands​
Essential for speech, resonance, & phonation

Cranial nerve mnemonic

On Old Olympus' Towering Top, a Finn and German Viewed A Hop

Olfactory projections connect into

olfactory bulbs

Optic nerve connects into

optic chiasm

CN 1

Olfactory Nerve (CN I) ​
Sensation of smell

CN II

Optic Nerve (CN II)​
Visual sensation \= EXCLUSIVELY SIGHT​

CN III

Oculomotor Nerve (CN III)​
Motor nerve​
Eyeball movement

CN IV

Trochlear Nerve (CN IV) ​
Motor nerve​
Eyeball movement

CN V

Sensory- head, face, & oral structures ​ Motor- jaw movement (OPEN CLOSE AND SOME FRONT-BACK// NOT CHEWING MUSCLES)​

VERY IMPORTANT FOR SPEECH - BOTH SENSORY AND MOTOR

CN VI

Abducens Nerve (CN VI)​
Motor nerve​
Eye movement through lateral rectus muscle - PULLS KEEPS EYES FROM FACING INWARD - PRIMARILY STABILIZING - IF OVERACTIVE CAN LOCK EYES INTO PLACE

CN VII

Primarily motor nerve​
Muscles of facial expression - EYEBROWS, SMILING, ETC.​
Sensory nerve- taste from anterior two-thirds of tongue

CN VIII

Vestibulocochlear Nerve (CN VIII) - AKA AUDITORY NERVE​
Sensory nerve- equilibrium and hearing​
RECEIVES FROM BOTH VESTIBULAR SYSTEM AND COCHLEA - COCHLEAR IMPLANTS CONNECT TO THIS

CN IX

Glossopharyngeal Nerve (CN IX)​
Motor: swallowing​
Sensory: touch & taste from posterior third of tongue and pharynx

CN X

Vagus Nerve (CN X) - MEANS WANDERER - GOES THROUGHOUT MANY STRUCTURES INCLUDING IN TORSO​
Motor & sensory for pharynx, larynx, & soft palate​

CN XI

Spinal Accessory Nerve (CN XI)​
Motor nerve ​
Muscles controlling head movement, E.G. NODDING

CN XII

Hypoglossal Nerve (CN XII)​
Motor nerve for muscles of tongue​
DAMAGE -\> SPEECH DISORDERS, ESP. ARTIC

Midbrain cranial nerve nuclei

All eye -related​
(Edinger-Westphal nucleus, Oculomotor nucleus,) \= BOTH INNERVATE III, and Trochlear nucleus \= INNERVATED IV​
​
(VIII STRADDLES PONS AND MEDULLA, VII HAS NUCLEI IN BOTH PONS AND MEDULLA)

Pons cranial nerve nuclei

Trigeminal nerve nuclear complex (motor), primary sensory nucleus (spinal trigeminal and mesencephalic nuclei)* \= V, Abducens motor nucleus \= VI, Facial nucleus (motor + sensory) \= VII

(VIII STRADDLES PONS AND MEDULLA, VII HAS NUCLEI IN BOTH PONS AND MEDULLA)

Medulla cranial nerve nuclei

Salivatory nuclei (Pons?) \= VII AND IX,Cochlear & vestibular nuclear complexes \= VII AND IX AND X (pons/medulla), nucleus solitarius \= VII AND IX AND X, dorsal motor nucleus \= X (AUTONOMIC ACTIVITY OF ORGANS), hypoglossal nucleus \= X, nucleus ambiguus \= X, and spinal trigeminal nucleus \= V

Corticonuclear/bulbar fibers

Corticonuclear (bulbar) fibers​
Motor cells (UMNs \= UPPER MOTOR NEURONS) in precentral gyrus​
Descend through internal capsule (WHITE MATTER TRACT)- genu ​
Activation of CN motor nuclei (LMN) in the brainstem​
INFORMATION TRAVELS FROM CORTEX TO NUCLEUS OF RELATED CRANIAL NERVE VIA CORTICONUCLEAR FIBERS - \> INFORMATION SENT OUT FROM NUCLEUS ALONG CRANIAL NERVE TELLS MUSCLES TO MOVE​

CORTICOBULBAR FIBER AXONS BRING INFORMATION DOWNWARD - TRACTS INTERFACE WITH CRANIEL NERVE NUCLEI​
​
DAMAGE CAN OCCUR AT ANY POINT ALONG THIS PATHWAY

Sensory cranial nerve pathways

Three-order (THREE-STEP AS OPPOSED TO THE TWO-STEP PROCESS FOR MOTOR) nuclei & fibers​
All sensory nerves have 3 stages (orders)

BILATERAL corticonuclear innervation

(Complex Motor Innervation, CONNECTIONS TO BOTH CORTICES)​

Facial (CN VII)- upper face​
Trigeminal (CN V)- masticators​
Vagus (CN X)- pharynx & larynx​
Glossopharyngeal (CN IX)- pharynx

UNILATERAL corticonuclear innervation

Facial (CN VII)- lower facial muscles​
Spinal accessory (CN XI)- Sternocleidomastoid & trapezius muscles​
Hypoglossal (CN XII)- lingual muscles​
CN III, IV, VI- ocular muscles

Importance of blood in the CNS

Oxygen supplier to the brain (also glucose)​
Remover of metabolic waste (PRODUCED BY ACTION POTENTIALS AND BRAIN FUNCTION), carbon dioxide from nerve cells ​

Brain's Metabolic Need (BRAIN NEEDS A LOT OF OXYGEN)​
20% oxygen & metabolized glucose (WHILE BEING ONLY 5% OF BODY'S MASS)​
750 mL blood per min for 50 mL/100 g tissue (VERY DENSELY SUPPLIED IN ARTERIES AND CAPILLARIES) to ensure optimal functioning

Circulatory Interruption Implications

Umbra: 6 minutes DEPRIVED OF BLOOD SUPPLY -\> GUARANTEED DAMAGE, BUT AS FEW AS 2-3 MINUTES CAN CAUSE MAJOR EFFECTS

Ischemic penumbra: Idle cells survival for 20 minutes without collateral circulation ​
Survival to 6-8 hours with some collateral supply ​

Umbra vs. penumbra

Umbra \= SET OF CELLS IMMEDIATELY AFFECTED BY BLOOD SUPPLY DISRUPTION

Penumbra \= STUNNED/IDLE CELLS - INDIRECTLY AFFECTED

Infarct

BLOOD SUPPLY DAMAGE

Arteries

Supply oxygenated blood ​
Arterioles and capillaries (slow blood circulation for exchanging nutritive substances)​
Lots of smooth muscle so they contract/EXPAND and change their diameter TO KEEP BLOOD PRESSURE CONSTANT AND HELP BLOOD MOVE FORWARD

Veins

Return deoxygenated blood - WASTE REMOVAL​
Thinner than arteries (without as much smooth muscles - MORE OF A PASSIVE PROCESS)​
Lower average blood pressure than in arteries

Capillary beds

Exchange site, DEOXYGENATED BLOOD IS REOXYGENATED, GOES THROUGH THE CYCLE AGAIN

In brain, capillaries are surrounded by

astrocytes, creating a lipid barrier​

Can pass through BBB

Lipid soluble substances pass beyond (caffeine, anesthetics, alcohol, nicotine etc.)​
Water-soluble substances​
Glucose​
Dissolved gasses (oxygen)​
Or carrier-mediated transport

Generally CANNOT pass through BBB

Hormones
Antibodies (makes treatment of cerebral infections difficult​)

Areas that lack BBB

(Release hormones therefore need access to blood stream​)

Hypothalamus​
Pituitary​
Pineal gland

Major arteries

(common, internal, external) carotid
vertebral
(anterior, middle, posterior) cerebral
basilar
anterior spinal

Cerebrovascular systems

Vertebral-basilar System
Carotid System
Circle of Willis

Vertebral basilar system

Vertebral arteries :
Anterior spinal artery- PERFUSES Lower medial medulla, ventral 2/3rd of spinal cord​
Posterior spinal artery- PERF. dorsal 1/3rd of cord​
Posterior inferior cerebellar- PERF. ipsilateral posteroinferior cerebellum

Basilar artery

Anterior inferior cerebellar arteries​
Labyrinthine (aka internal auditory) artery​
Pontine branches - PERFUSES STRUCTURES ON THE PONS​
Continuation into posterior cerebral artery

Carotid system

Common carotid artery division -SPLITS INTO 2 PORTIONS: ​
External carotid​
facial muscles, forehead, oral, & nasal cavities ​
Internal carotid (GOES INTO the carotid foramen in petrous bone)​
Blood supply to brain

ICA

Internal carotid artery

Circle of Willis

ALLOWS BLOOD TO FLOW IN ALL DIRECTIONS​
- CIRCULAR CONNECTION / REDUNCANCY ALLOWS BLOOD FLOW TO BYPASS DAMAGE ON ONE SIDE

Anastomotic Connection​
Anterior & posterior communicating arteries​
Vascular equalization on both sides (SHOULD BE EQUAL PRESSURE)​
Little blood flow through communicating arteries​
Cortical arteries- External brain structures​
Central arteries- Internal brain structures

Ophthalmic artery

Distribution: Orbits plus surrounding facial areas​
Symptoms: Vision loss

MCA

Middle cerebral artery
COMMONLY IMPLICATED IN APHASIA​

Lenticulostriate

Distribution- diencephalon and basal ganglia, internal capsule

Symptoms from MCA damage

Symptoms of circulatory interruption: ​
Contralateral hemiplegia, contralateral impaired sensory functions​

Aphasia (dominant hemisphere), temporal-visual-spatial deficit (non-dominant ANGULAR GYRUS DAMAGE), homonymous hemianopia (BLINDNESS IN ONE VISUAL FIELD IN BOTH EYES), and involuntary movements (lenticulostriate artery)

ACA

Anterior cerebral artery

Cortical arteries

Anterior cerebral artery (ACA)​
Symptoms of circulatory interruption: ​
Paralysis of legs & feet​
Prefrontal lobe symptoms of reduced thinking, reasoning, & impaired planning (abulia - lack of will - EXECUTIVE DYSFUNCTION)