Neural Basis Exam 4 M10- M11

cerebellum

the primary structure responsible for

coordination of fine movement

• It integrates somatic information, particularly related to vestibula, function, muscle and joint sense, and perception of body in space

• It works with the cerebrum in fine- tuning the motor plan for optimal execution

• It is involved in monitoring and maintaining the background movement that supports fine motor control

• Structurally, the cerebellum has more neurons than the cerebrum!

vestibulocerebellum

part is responsible for integrating

vestibular information about

where the body is in space with

the motor plan

spinocerebellum

this component integrates proprioceptive (body sense of

position and movement in space) from joints and muscles, and controls gait and stance

neocerebellum

This component is responsible for execution of voluntary motor plans initiated by the cerebral cortex

anatomy of cerebellum

Second largest structure

of the CNS

• Positioned beneath cerebrum and behind

brainstem

• Responsible for coordination of movement and integration of sensation

• Note 4th ventricle

• Note that cerebellum is posterior to pons

3 lobes of cerebellum

anterior

postereior (middle)

flocculondular

external cerebellum landmarks

Two hemispheres: left

and right

• Three lobes

– Anterior lobe:

– Posterior lobe:

• Neocerebellum =

"newest cerebellum”

– Flocculonodular lobe

• Vestibulocerebellum

flocculondular lobe

From posterior/inferior: flocculonodular lobe

• Right and left flocculi

• Central nodulus

comparison of anatomical and functional cerebellum

Note horizontal orientation

divides cerebellum into

anatomical structures:

– anterior lobe

– Middle lobe

– Flocculonodular lobe

• Longitudinal functional

divisions are

– Spinocerebellum (Vermal

section; aka

paleocerebellum)

– Neocerebellum (Lateral

aspect of each hemisphere,

aka pontocerebellum or

cerebrocerebellum)

– Archicerebellum

(flocculonodular lobe)

topological organization and functional organization

The cerebellum has a

topological “map” much like

the precentral and postcentral

gyri

– Frankly, most of the primary

reception areas of the brain

have a topological map!

• Anterior lobe: leg, arm, face

muscle coordination

• Posterior lobe: interaction with

cerebral cortex; motor

planning

• Flocculonodular lobe:

vestibular interaction; body in

space

• Spinocerebellum: Medial

vermal portion: proprioception

and joint sense for lower body,

for gait and stance

vermis

Means "worm"

– Separates

hemispheres

– Defines

intermediate and

lateral cerebellar

regions of

posterior surface

cerebellar peduncles

afferent pathways

are inputs to the cerebellum

• Superior cerebellar peduncle

receives contralateral arm &

leg sense to superior lobe

• Middle cerebellar peduncle

receives cortical input about

motor plan and spinal input

with proprioceptive

information projecting to

posterior lobe

• Inferior cerebellar peduncle

sends vestibular information

to flocculonodular lobe, as

well as somatic sense to

anterior and posterior lobes

superior cerebellar peduncle

receives information about arm and leg sense; this

information goes the anterior cerebellar lobe.

middle cerebellar peduncle

mediates information from the cerebral cortex about

the motor plan; it also mediates spinal proprioceptive input. This information

projects to the posterior lobe

inferior cerebellar peduncle

mediates vestibular information. This information is

sent to the flocculonodular lobe. This peduncle also sends somatic (body) sense to

the anterior and posterior lobes.

cellular structure of cerebellum

Cerebellar

cortex

(outer layer)

• 3 layers

• 5 cell types

• 4 nuclei

layers of cerebellar cortex

Outermost is called the

molecular layer

– Contain Stellate and basket

cells, and dendrites of

Purkinje cells

• Intermediate is the Purkinje

layer

– Contains Purkinje cells

• Innermost is the granular

– Contains granule cells &

Golgi cell bodies

deep to granular is white matter

Cerebellar white

matter (Efferent &

afferent fibers)

• Nuclei of white matter:

– Dentate nucleus:

efferent

– Fastigial nucleus:

afferent

– Globose (globular)

nucleus: afferent

– Emboliform nucleus:

afferent

dentate nucleus

Projects to

motor nuclei of thalamus

– Project to ventrolateral and

ventromedial nuclei, which

project to motor planning and

execution areas of cortex (BA 46,

9, 4, 6, 7b)

• Motor command from cerebral

cortex to pontine nuclei to

cerebrocerebellum

• Output of dentate nucleus to

motor thalamus and then to

motor strip, SMA and premotor

region

• In this way cerebellum evaluates

motor plan and alters it to reflect

current state of the body’s joints

and muscles

fastigial nucleus

Receives vestibular

input from

vestibulocerebellum

– Projects to vestibular

nuclei and reticular

formation

– Provides functional

loop for maintenance of

balance

globose and emboliform nuclei

Input to vermis from cerebral

cortex

• Input to vermis also from

dorsal and ventral

spinocerebellar tracts re:

joint, muscle and cutaneous

sense

• Emboliform and Globose

nuclei send output to red

nucleus

• Rubrospinal tract

– Project to red nucleus for

muscle tone, posture and

background movement

superficial molecular layer

Contains parallel

fibers from

granule cells

– Contains stellate

cells, which are

interneurons that

connect purkinje

dendrites

– Basket cells, which

are interneurons

that connect

purkinje dendrites

purkinje layer

is the only

output of the

cerebellum

– Dendrites of _

cells extend

throughout the

molecular layer

– The function of the

_ cell is to

inhibit nuclei of

cerebellum

onitor when

target is reached

– Inputs from granular cells

and mossy fibers

– Purkinje cells inhibit dentate

gyrus, which is otherwise

excitatory

• Mossy & climbing fibers excite

_, which inhibit output

of cerebellum

• Stellate and basket cells

inhibit _ which allows

output of cerebellum

• When a target is being

approached, mossy and

climbing fibers activate

_

• _ then signals

termination of movement

granular layer

This is the deepest

layer of the

cerebellar cortex

(gray matter)

• _ layer

includes:

– Granule cells

– Mossy fibers

– Purkinje axons

– Climbing fibers

(axons of the

inferior olive of

brainstem

mossy fibers and climbign fibers of granule cells

excite Purkinje cells,

and when Purkinje are excited they inhibit the output of the dentate nucleus

stellate and basket cells

inhibit Purkinje cells, which functionally allows the dentate

nucleus to be active.

pathways of cerebellum

Pathways include:

1. Information from the cortex about the motor plan is via

– Corticopontine tract: information about the motor plan to the pontine nuclei and inferior olive

– Olivocerebellar tract and pontocerebellar tract: delivers information from the corticopontine tract

efferent to the cerebellum: this provides the motor plan from areas 4 and 6 (motor and

premotor)

2. Information about where the body is in space is via

– Vestibulocerebellar tract: balance from vestibular system

3. Information about muscle spindle and GTO from the limbs is via

– Reticulocerebellar tract: muscle tension (GTO) from spinal cord (joins with cortical output)

– Cuneocerebellar tract: this mediates upper limb stretch sensors (muscle spindle)

– Dorsal and rostral spinocerebellar tract: muscle spindles (stretch) & GTO (tension)

– Ventral (anterior) spinocerebellar tract: skin, deep tissue (pain and GTO)

4. Output from the cerebellum to the cortex is via

– Dentothalamic and dentorubral tracts: Efferent from the cerebellum to the cerebral cortex

corticopontine tract

information about motor plan to pontine nuclei and

inferior olive (not shown)

olivocerebellar and pontocerebellar tracts

Efferent from the inferior olive and

pontine nuclei to the cerebellum: this provides the motor plan from areas 4

and 6 (motor and premotror)

vestibulocerebellar tract

balance from vestibular system

reticulocerebellar tract

muscle tension (GTO) from spinal cord (joins with

cortical output)

cuneocerebellar tract

this mediates upper limb stretch sensors (muscle

spindle)

dorsal, ventral, and rostral spinocerebellar tract

skin, deep tissue (pain and GTO tension), muscle spindles (stretch)

dentorubral and dentothalamic tracts

from dentate nucleus of cerebellum to

red nucleus and thalamus, ultimately to brainstem (via superior peduncle)

tracts passing through inferior cerebellar peduncle

– Olivocerebellar tract: this is efferent from the

cortex to the cerebellum: this provides the motor

plan from areas 4 and 6 (motor and premotor)

– Reticulocerebellar tract: muscle tension (GTO) from

spinal cord (joins with cortical output)

– Vestibulocerebellar tract: balance from vestibular

system

– Cuneocerebellar tract: this mediates upper limb

and neck stretch sensors (muscle spindle)

– Dorsal spinocerebellar tract: mediates lumbar

region muscle spindle, GTO, pain and tactile sense

corticopontine pathway

Input from pontine nuclei and

nucleus reticularis tegmenti pontis

and lateral reticular nucleus, giving

rise to reticulocerebellar tract

– Middle peduncle mediates

information from motor cortex and

spinal cord

– So information about motor plan and

ongoing motor commands from

cerebrum is shared with cerebellum

through middle peduncle

tracts passing through superior cerebellar peduncle

Afferent:

– The ventral (anterior)

and rostral

spinocerebellar tracts

provides muscle

spindle/GTO

information from the

lower body

• Efferent

– From purkinje

– To dentate nucleus

– To red nucleus

– Also to reticular

formation of brainstem

– To cerebral cortex motor

and premotor regions

• This gives cerebellar

feedback

– Concerning the plan that

was sent from cerebrum

– Concerning current

effect of motor act, so

plan can be modified

corticopontine tract

servs pontine nucleus and inferior olivary nucleus

cerebellum and motor control

Vestibulocerebellum provides information about position

in space

• Anterior lobe integrates sensory information about

antigravity muscles

• Posterior lobe (neocerebellar component) involved in fine

motor activity, especially of hands

• Also:

– Cerebellum provides internal timing mechanism for cognitive

tasks

– Involved in emotion identification, executive function, music and

working memory

– Language: expressive, receptive, semantic discrimination

– Speech: sequencing and adapting motor sequences

ataxia

Arises from damage to

cerebellum

• Loss of coordinated

movement

• for gait: clumsy, wide-

stepping gait

• For manual

movement: difficulty

apprehending object

when reaching for it

– Past-pointing

– Undershoot and

overshoot

– Eye-hand

coordination

mixed dysarthria

arises from conditions that

affect multiple neuroanatomical systems

amyotropic lateral sclerosis (ALS)

This disorder is also known as

– Lou Gherig’s Disease

– Motor neuron disease

• The pathology is a degeneration of motor neurons in the

pyramidal pathways (corticospinal and corticobulbar)

• The dysarthria is classified as mixed spastic-flaccid, caused

by degeneration of upper and lower motor neurons.

• When the disease reaches the corticobulbar (brainstem)

motor neurons the result is death

• Death typically comes within 2-5 years from respiratory

failure because of inability to sufficiently oxygenate

multiple sclerosis

a disease of the immune system

• Something causes the immune system to attach the nervous system

• The result is patchy areas of demyelination throughout the brain

• The diagnostic criteria include the notion of “multiple” lesions, at

varying locations.

• The “sclerosing” element is the development of a type of scar

tissue or “sclerosis” on the damage axon

– The speech is characterized by spastic dysarthria signs (reduced rate,

increased harshness, hypernasality) with ataxic signs (loss of

coordination).

– The speech may be a different type of “mixed” besides spastic-ataxic if

non cerebellar structures are affected, for instance, but spastic-ataxic

is most dominant

ipsilateral organization

spinal cord

–    Generally left side of spinal cord serves left half of body

–    Decussation has already occurred

–    Reflex stimulation on left side causes response on left side (for single segment reflexes)

–    Lower motor lesions are ipsilateral to the signs of those lesions (e.g., unilateral flaccidity)

interior organization

spinal cord

outer ring of whet matter (ascending and descending myelinated tracts)

inner core of gray matter (cell bodies)

dorsal (posterior) horns sensory columns

ventral (anterior) horns motor cells for lower motor neurons which will project out of spinal cord through

anterior roots

commissures connect dorsal and ventral gray columns

dermatomes

correspond to a single spinal cord segment and what it innervates

hypalgesia

decrease sensitivity to pain or touch

analgesia

loss of pain sense

hypesthesia

reduced sense of touch

anesthesia

loss of touch sensation

cervical cord

muscles and sensory input for thoracic cord

thoracic cord

fewer muscles to innervate and fewer sensory inputs

lumbar cord

large, reflecting massive musculature of legs

sacral cord

large amount of gray and relative paucity of white columns

trasnverse sections

spinal cord segments correspond to vertebral segments. Sensory dermatomes correspond to a single spinal cord segment and what it innervates.

general notions about tracts

•         These are the projection pathways of the central nervous system

•         They convey information to and from the cerebrum, and to and from the periphery

•         All sensation from the body passes through these pathways

•         All motor commands from the cortex passes through these pathways

spinal column organization

dorsal- ascending sensory fibers

lateral- both descending and ascending fibers

ventral- both descending and ascending fibers

corticospinal tract

motor innervation of skeletal muscle of neck, trunk, and extremities

primary efferent pathway

corticobulbar tract

activates muscles of head and neck

primary efferent pathway

tectospinal tract

extrapyramidal; visual orientation

extrapyramidal descending pathway

rubrospinal tract

activate flexors, inhibit extensors

extrapyramidal descending pathway

vestibulospinal tract

posture and head stabilization

extrapyramidal descending pathway

pontine reticulospinal tract

inhibit reflexes

extrapyramidal descending pathway

medullary reticulospinal tract

inhibit reflexes

extrapyramidal descending pathway

fasciciulus gracilis

kinesthetic sense (movement), touch, muscle spindle, GTO

ascending pathway

fascicculus cuneatus

kinesthetic sense (movement), touch, muscle spindle, GTO

ascending pathway

anterior spinothalamic tract

light touch form

ascending pathway

lateral spinothalamic tract

pain and thermal senses

anterior spinocerebellar tract

muscle spindle and GTO

ascending pathway

posterior spinocerebellar tract

muscle spindle and GTO

ascending pathway

corticostriate

connect basal ganglia, prefrontal cortex, thalamus

descending pathway

corticothalamic fibers

provide reciprocal communication re: sensation

descending pathway

corticopontocerebellar fibers

facilitate feedback in learning

descending pathway

extrapyramidal tracts

indirect pathway

background pathway- smooth motor control, postural regulation

pathway

motor cortex

internal capsule

brainstem decussation

spinal cord

synapse w/ LMN

muscle activation

lesions above level of decussation

contralateral deficits

spastic

strained- spasm, tight voice

lesions below level of decussation

ipsilateral deficit

flaccid

slurred, breathy, weak speech

gray matter

cell bodies

dorsal root ganglia

nuclei with afferent spinal nerves

motor nuclei

ventral side of spinal cord

ventral horns

efferent spinal nerves

dermatome

different spinal nerves

corticospinal tract

tract associated w/ activation of spinal nerves

coricobulbar tract

associated w/ activation of cranial nerves

spinal nerves

used for gestures`

ataxia or ataxic

loss of coordinated movement

gait; clumsy, wide-stepping

Irregular, uncoordinated speech pattern

. - Scanning Speech

- Changes in speech volume

mixed dysarthria

conditions that affect multiple neuroanatomical systems

spastic

strained tight

involuntary movment

slow, strained, efforful, possibly slurred

upper motor lesion

flaccid

refers to a state of reduced muscle tone, leading to weakness and loss of firmness in muscle structure.

spanning speech

a neurological speech disorder characterized by slow, broken-up speech where words are divided into separate syllables, often with noticeable pauses.

It sounds monotone, choppy, or robotic, with unusual stress on syllables. It is commonly caused by cerebellar lesions, often in multiple sclerosis

UPM vs LPM

UPM- stimulate group of muscles; fibers are stiff

LPM- innervate muscle fiber itself