ME03 - Motor System 2 - Cerebellum, Basal Ganglia Flashcards
Also called the little brain
Helps control the rate, range, force, and direction
of movements (SYNERGY)
o sequences motor activities
o monitors and makes corrective adjustments in motor activities while they are being executed silent area of the brain
Cerebellum
Electrical excitation does not cause any sensation. True or False?
TRUE
Damage does not produce paralysis. True or False?
TRUE
Where is Cerebellum located?
Located dorsal to the pons and medulla and protrudes from under the occipital lobes
3 Lobes of Cerebellum
ANTERIOR, POSTERIOR, FLOCCULONODULAR
Crosswise folds in the Cerebellar Cortex
Folia
Lie deep beneath the folded mass of cerebellar cortex
Deep Cerebellar Nuclei
Nuclei of Cerebellum from Medial to Lateral
DENTATE, EMBOLIFORM, GLOBOSE, FASTIGIAL
What are the Brainstem Attachments of Cerebellum
superior cerebellar peduncles to MIDBRAIN
middle cerebellar peduncles to PONS
inferior cerebellar peduncles to MEDULLA OBLONGATA
Contains a somatotopic map of the body surface
VERMIS and INTERMEDIATE ZONE
o Axial portions of the body lie in the vermis
o Limbs and facial regions lie in the intermediate zones
Lateral portions of cerebellar hemispheres do not have topographical representations. True or False?
TRUE
Function of the lateral portion of cerebellar hemisphere
o Receive input signals exclusively from cerebral cortex
o Plays important roles in planning and coordinating the body’s rapid sequential muscular activities
3 Layers of Cerebellar Cortex
Granular Layer | Purkinje Cell Layer | Molecular Layer
Innermost layer that contains granule cells, Golgi type II cells and glomeruli
Granular Layer
Middle layer that contains inhibitory Purkinje cells
Purkinje Cell Layer
Outermost layer that contains stellate and basket cells, dendrites of Purkinje and Golgi type II cells and parallel fibers (axons of granule cells)
Molecular Layer
2 Types of Fibers that are known as Excitatory Cerebellar Inputs
Climbing Fibers | Mossy Fibers
o Originate in the INFERIOR OLIVE
o Demonstrate complex spikes
_ Action potentials beginning with a strong spike and followed by a trail of weakening secondary spikes
o Function in conditioning Purkinje cells (motor learning)
CLIMBING FIBERS
o Form the bulk of the input, originating in the cortico-, vestibulo-, reticulo- and spinocerebellar tracts_o demonstrate SIMPLE SPIKES
Much weaker short-duration action potentials in Purkinje cells
MOSSY FIBERS
What are the Different Afferent Pathways to the Cerebellum
Pontocerebellar System | Olivocerebellar Projections | Spinocerebellar Fibers | Reticulocerebellar Fibers | Vestibular Fibers
o Largest afferent projections
o Originate from the basilar pontine nuclei
PONTOCEREBELLAR SYSTEM
Originate from the inferior olivary nuclei
OLIVOCEREBELLAR PROJECTIONS
Originate in spinal cord or medulla
SPINOCEREBELLAR FIBERS
Originate from brainstem
RETICULOCEREBELLAR FIBERS
Originate from vestibular nuclei and vestibular apparatus
VESTIBULAR FIBERS
What are the Cells seen in Cerebellum
Purkinje cells | Granule cells | Golgi Type II Cells | Stellate Cells | Basket Cells | Glomerulus
o central neurons with fan-shaped dendritic trees
o always inhibitory with GABA as its neurotransmitter
Purkinje cells
o smallest and most numerous neurons in the brain
o parallel fibers are axons of granule cells
o excitatory input from mossy fibers which use glutamate as its neurotransmitter
Granule cells
o small interneurons with numerous arborizations
o inhibitory in function
Golgi Type II Celks
o inhibitory star-shaped cells found in superficial cerebellum
Stellate Cell
o inhibitory cells whose axons form baskets around Purkinje fibers and are found in deep cerebellar layers
Basket Cells
o complex of synapses having a mossy
fiber at its core
o synapsing with axons of Golgi type II neurons and dendrites of granule cells
Glomerulus
Modulates Purkinje cell output
Cerebellar Interneurons
All of the cerebellar interneurons are inhibitory EXCEPT _______________
Granule Cells
Have excitatory input to basket cells, stellate cells, Golgi II
cells, and Purkinje cells
Granule Cells
Inhibits Purkinje cells (via parallel fibers)
Basket cells and Stellate cells
Inhibit granule cells, thereby reducing their excitatory effect on Purkinje cells
Golgi II cells
Only output of the cerebellar cortex
Purkinje Cells
Output is always inhibitory, using _______________ as NT
GABA
Inhibitory output modulates the output of the cerebellum and regulates rate, range, and direction of movement (synergy). True or False
TRUE
Projects to fastigial nucleus, vestibular nucleus and reticular formation
Vermis
Project to globose and emboliform nuclei (interposed nuclei)
Intermediate Zone
Project to the dentate nucleus, ventral anterior thalamic nuclei and cerebral cortex
Lateral Hemispheres
Follow the Cerebellar Pathway
Cortex»_space; Pons*»_space; Cerebellum»_space; Dentate nucleus*»_space; Red Nucleus»_space; Thalamus»_space; Corticospinal tract
o consists of the small flocculonodular lobes
o for control of balance and eye movement
Vestibulocerebellum
Consists of lateral zones of cerebellar hemispheres
For planning and initiation of movement
Cerebrocerebellum
o consists of vermis and intermediate zones
o for control of rate, force, range, and direction of movement (synergy)
Spinocerebellum
o During nearly every movement, certain muscles must be rapidly turned on and
then quick turned off
TURN ON/TURN OFF FUNCTION
TURN ON/TURN OFF FUNCTION is made possible by
Made possible by interplay of mossy and climbing fibers and Purkinje cells
What fibers are involved in Motor Learning?
CLIMBING FIBERS. Climbing fibers modify sensitivity to parallel fiber input
o when mismatch between anticipated result of movement and its actual result occurs, climbing fiber input is more vigorous
o as movement is practiced, mismatch declines gradually
o During any movement, momentum develops and must be overcome to stop the movement
o Appropriate learned, subconscious signals from spinocerebellum stop the movement precisely at the intended point
Damping Function
Patient with cerebellar lesion assumes unsteady stance and reeling gait (like a drunk person)
Ataxia
How does a Patient with Ataxia compensate?
To compensate, he assumes a broad-based stance and a broad-based gait
Failure to meter the contractions that set the distance of motion
Dysmetria
Inability to perform rapid alternating movements
Dysdiadochokinesia
Failure of a movement to be terminated at a proper time
Past Pointing
Difficulty in maintaining position against sudden unexpected displacement
Overshooting
Slowness and slurring of speech
Dysarthria
Volume of voice varies from low to high from peak to peak
Scanning Speech
Tremor of intentionally maintained head or trunk posture or of a limb suspended in front of the body
POSTURAL, POSITIONAL or STATIC TREMOR
Unsteady oscillations of the head or trunk
TIUTIBATION
o Tremor as a limb approaches its target
o Results from cerebellar overshooting and failure of the cerebellar system to “damp” the motor movements
INTENTION, END-POINT or KINETIC TREMOR
Jerkiness of eye movement
o rapid, tremulous movements of the eyes rather than steady fixation
Nystagmus
What is affected in Nystagmus?
Nystagmus is due to failure of damping by the cerebellum
Occurs especially when the flocculonodular lobes of the cerebellum are damaged
Decreased tone of the peripheral body musculature on the side of the cerebellar lesion
Hypotonia
What is affected in Hypotonia?
Results from loss of cerebellar facilitation of the motor cortex and brain stem motor nuclei
Extremity tested swings to and fro several times like a pendulum after eliciting the reflex seen in HYPOTONIA
Pendulous reflexes
What are the Different Cerebellar Syndromes
ANTERIOR (ROSTRAL) VERMIS SYNDROME_- involves the anterior cerebellar lobe ; o ataxia of the lower limbs only
POSTERIOR (CAUDAL) VERMIS SYNDROME - involves the flocculonodular and posterior lobes ; o axial ataxia without extremity ataxia
CEREBELLAR HEMISPHERE SYNDROME - cerebellar signs lateralized to one half of the body
PANCEREBELLAR SYNDROME_- bilateral cerebellar signs due to involvement of all cerebellar lobes
Deep cerebral nuclei involved in motor control
modulates thalamic outflow to the motor cortex to plan and execute smooth movements
demonstrates programming functions
o generate basic patterns of movement in response to cues from cortical association areas
Basal Ganglia
Components of Basal Ganglia
Globus Pallidus | Putamen | Caudate Nucleus | Subthalamic Nucleus of Substantia Nigra
Globus Pallidus x Putamen = Lentiform Nucleus
Putamen x Caudate Nucleus = Striatum
Lentiform Nucleus + Striatum = Corpus Striatum
CORPUS STRIATUM + SUBTHALAMIC NUCLEUS OF SUBSTANTIA NIGRA = BASAL GANGLIA
NT used in connections between striatum and substantia nigra
Dopamine
Dopamine in relation to Basal Ganglia Pathways
o inhibitory on the indirect pathway (D2 receptors)
o excitatory on the direct pathway (D1 receptors)
o overall action is excitatory
Responsible for the COGNITIVE CONTROL OF MOTOR ACTIVITY o most of our motor actions occur as a consequence of thoughts generated in the mind
CAUDATE NUCLEUS
Controls the speed and size of movement
Basal Ganglia
Locus for Spatial Coordination
Posterior Parietal Cortex
TIMING AND SCALING FUNCTIONS are lost with lesions in the?
Basal Ganglia, specifically CAUDATE NUCLEUS
snake-like or writhing movements of the hand and arm or face
result from lesions of the GLOBUS PALLIDUS
Athetosis
flailing movements of the extremities
result from lesions to the SUBTHALAMIC NUCLEUS OF LUS
Hemiballismus
brief, irregular, non-purposeful movements that are vaguely comparable to dancing
result from lesions to the CORPUS STRIATUM (specially on caudate nucleus)
Chorea
Results from widespread destruction of the dopaminergic cells in the substantia nigra
Parkinson’s Disease
Manifestations of Parkinson’s Disease
o cogwheel rigidity
o resting pill-rolling tremor
o slowness or difficulty in initiating
movement (bradykinesia, akinesia) o postural instability (shuffling or
FESTINATING gait)
Autosomal dominant genetic disorder caused by CAG trinucleotide repeats
o displays ANTICIPATION with succeeding generations
Huntington’s Disease
Characteristics of Huntington’s Disease
Characterized by flicking movements in individual muscles (chorea)
o leads to progressive severe distortional movements
Huntington’s Disease is caused by the depletion of what neurotransmitters?
Depletion of GABA and acetylcholine from many areas of the brain