LecturePhysio_-_MotorSystem

Motor System PLANNING Basal Ganglia

1

EXECUTION (6b) (4)

(2) (3) (1)

Idea

Cortical Association Area

(2)

Premotor, Supplementary Motor and Motor Cortex

(5b) (5a)

Brainstem (6a)

(3) (2)

Spinal Cord

(4)

(7a)

(7a)

Lateral Cerebellum

Muscles (8a)

(9a)

Intermediate Cerebellum

Figure 1: Motor System Impulse Map NOTES: (2) Lateral Cerebellum initially received impulses from the cortical association area (4) Motor Commands are generated

The motor system is part of the nervous system responsible for controlling and regulating the activity of motor muscles. • Before skeletal muscle activity is observed, Central Nervous System (CNS) should be activated, primarily neurons of the Cortical Association Areas of the cerebral cortex. • However, the generated impulse do not directly proceed to the cortical motor neurons, without being sequenced and coordinated by the accessory motor system comprising of the basal ganglia and lateral cerebellum, and the cerebral cortex. o Lateral Cerebellum  Alias: Neocerebellum, cerebro-cerebellum  Movements Involved: Fast movements  Functions: • Involved in planning the movement that will happen in the next sequential movement (Movements to Come) o !Present: Seriously disturb rapid movement • Provide appropriate timing for each succeeding movement o !Present: Failure of smooth progression of movements  Cannot predict how far different parts of the body will move in a given time  Unable to determine when the next sequential movement needs to begin • Succeeding movement may begin too early or, more likely, too late • Helps time events other than movement of the body o Predict how rapid a person is approaching an object o Basal Ganglia  Movements Involved: Fast and Slow Movements  Also intimately related with the corticospinal tract • Almost all motor and sensory nerve fibers connecting the cerebral cortex and spinal cord pass through the internal capsule.  Function: • With Corticospinal Tract: o Control complex patterns of motor activity  !Present: Diffulty performing any skilled subconcious movement (e.g. Writing, Hammering)

Castillo, Aileen Page 1

Motor System

2

Caudate Nucleus: Plays a major role in the cognitive control of motor activity1 • With Cerebral Cortex: o Determine how rapid the movement is to be performed [TIME] o To control how large the movement will be [SPACE] Motor impulses are generated and transmitted to the brainstem and spinal cord. o With regards to the Brainstem:  Axial muscles and Proximal muscles • Responsible for posture  Communication is mediated by the intermediate cerebellum/Paleocerebellum • Paleocerebellum  cortex  brainstem o With regards to the spinal cord  Distal muscles of the body • Responsible for accurate and precise motor activites For effective activity of skeletal muscle, the muscle send impulses back to the CNS to the spinal cord. Thalamus relay motor impulses and do not modify motor impulses. They serve as neurons that allow intercommunication between diff parts of the CNS involved in the motor control. o

•

• •

What parts of the CNS have minimal effect on skeletal muscle? The limbic system (Amygdala hippocampus and parahippocampal region) and most especially, the hypothalamus: more concerned with visceral tissue activity. Motor Areas of the Brain: Cerebral Cortex, Basal Ganglia, Cerebellum, Brainstem, Spinal Cord Movement can be classified as: • Reflexes o Rapid, stereotyped involuntary responses o Least affected by a stimulus o (X) Cortical Neuron Involvement, (√) Spinal cord & Brainstem Neurons Involvement NOTE: Reflexes CANNOT be considered involuntary movement since skeletal muscles are DEPENDENT on neuronal stimulation. Involuntary movement observed in smooth and cardiac muscles, impulses are generated by the muscle themselves. • Voluntary Movements o Movement characterized by two features; o Purposeful (goal directed) o Largely learned (improves with practice) o (√) Cortical Neuron Involvement [Precentral gyrus, Cerebro-cerebellum], (√) Spinal cord & Brainstem Neuron Involvement • Rhythmic Motor Patterns o Stereotype, repetitive movements that occur in reflex-like fashion after voluntary initiation • Muscles which are frequently utilized, muscle activity will become almost like a reflex 1

Guyton, pg. 709

Castillo, Aileen Page 2

Motor System

o o

3

• Example: Driving a Car  Learned motor movements involve Example: Postural support movement (e.g. upright head position) (√) Cortical Neuron Involvement, (√) Spinal cord and Brainstem Neuron Involvement

An intact reflex arc is required for motor activity to occur. A reflex arc is the basic unit of integrated reflex activity involving the following components: • Sensory organs (Figure 2): involve stretch receptors; for intrinsic muscle control; operate on a subconscious level o Muscle Spindles/Intrafusal Muscle Fibers  Small skeletal muscle fiber whose central region has few or no actin and myosin filaments Figure 2 Muscle spindle showing its relation to the large • Thus the central extrafusal skeletal muscle fibers. (Guyton, pg 674) potion does not contract  Groups Ia and II Afferents, arranged in parallel with extrafusal muscle fibers  Detect both static and dynamic changes in muscle length (Stretch Sensitive Receptors)  Are encapsulated in muscle mantle; In the belly of the muscle  The muscle spindle receptor can be excited in 2 ways: • Annulospiral Sensory Ending: Lengthening the whole muscle, streching the midportion • Flower Spray Ending: Contracting the end portion [Innervated by γ motoneruons], streching the midportion  Types of Sensory Ending • Primary Ending/Annulospiral ending o Group Ia o innervate both the nuclear bag and nuclear chain o detect amount of muscle stretch but more sensitive to te rate of change of muscle length o velocity Figure 3 Efferent Neurons and corresponding sensitive fibers sensory endings o Importance: tells the CNS, most especially the spinal cord, that the muscle is contracting/in motion due to the increase frequency of muscle length change o Involve in dynamic movement/kinesthesia • Secondary Endings/Flower Spray o Group II o innervate only the nuclear chain fibers o not sensitive to rate of change of muscle length o provides information about the static length of the muscle

Castillo, Aileen Page 3

Motor System o

o

Importance: Tell center of the starting length of the muscle; tell the center that the muscle is not contracting/not moving Involve in static movement

Golgi Tendons  Group Ib afferents, arranged in series with extrafusal muscles fivers.  Detect muscle tension (Tension Sensitive Receptors) Afferent neurons o Classification based on conduction velocity  Type Aα > Type Aß > Type Aδ o

•

NOTE: conditional operands used above illustrates the proportion of fiber type used by the motor system

Classification based on fiber diameter [commonly used classfication]  Group Ia, Group Ib and Group II Center o Area where sensation is perceived o Spinal cord/Brainstem, Cerebral cortex and others Efferent neurons Figure 3 Sensory Endings o α motor neuron  Effectors: Extrafusal muscle fiber • Make up the bulk of the muscle • Provide the force muscle contraction or generate tension o γ motor neuron  Effectors: Muscle Spindles/Intrafusal muscle fiber [Yes, the sensory organ]  Function: Maintain sensitivity of the muscle even if it is stimulated, by increasing the adequate stimulus  2 types of γ motoneurons • Dynamic γ fibers o ↑ spindle sensitivity to the rate of change of stretch (nuclear bag) o ↑ phasic activity of Ia fibers • Static γ fibers o ↑ spindle sensitivity to steady, maintained stretch (nuclear chain) o ↑ tonic activity of Ia fibers NOTICE: Muscle spindle are sensory receptor with an afferent nerve and an efferent nerve. • Types of intrafusal fibers based on the arrangement of the nuclei o Nuclear bag fibers  Nuclei Arrangement: Clusters  Thicker than nuclear chain  Detect the rate of change in muscle length (fast, dynamic changes)  Are innervated by a group Ia afferent  Have nuclei collected in a central bag region o

•

•

Castillo, Aileen Page 4

4

Motor System o

•

5

Nuclear chains  Nuclei Arrangement: Chains/Rows  Thinner than nuclear bag  Detect static changes in muscle length  are more numerous than nuclear bag fibers

NOTE: The finer the movement of the muscle, the greater the number of intrafusal muscle spindles (e.g. distal body parts: hands, feet and head). Once spindle is activated, the muscle contracts (Myotatic Reflex/Strech Reflex). Strech muscle fiber  Group Ia and Group II  Dorsal root  Dorsal horn  α and γ Neurons  Contract muscle Effectors o Produce a reflex action  Reflex Action • May involved simultaneous contraction of some muscles and relaxation of other muscle [Agonist and Antagonist] • May involve either somatic or visceral responses which could occur simultaneously • Involves activation of one or several synapses [skeletal{motor neuron} and visceral{autonomic neuron} synapses] • Happens even without conscious perception • Impulses are modified in various parts of the CNS o Types of Reponses  Static Response • Weak, continuous: for posture/balance • Involves activity of the nuclear bag and nuclear chain[more activity] • Involves activation of group Ia and group II neurons [more activity] • Activates α motorneurons and static γ fiber  Dynamic response • Strong, sudden: for carrying load, when doing work • Involves activity mostly of the nuclear bag; same activity of the nuclear chain • Greater activity of the group Ia neurons • Oppose sudden changes in muscle length • Activates α motor neurons and dynamic γ fibers

Receptor Afferent Nerve Efferent Nerve Effect Impulses Number of Synapse

Myotatic Reflex Muscle Spindle Group Ia α and γ motor neurons Contract Muscle [α motor neurons] Maintain Sensitivity of muscle [γ motor neurons] Stimulatory 1, immediately synapse with the anterior motor neurons

Other Names

o

Myotonic Reflex

Castillo, Aileen Page 5

Inverse Myotatic Reflex Golgi Tendon Group Ib α and γ motor neurons Relax Muscle [α motor neurons] Maintain Sensitivity of muscle [γ motor neurons] Inhibitory 2, synapse with an inhibitory interneuron and an anterior motor neuron.

Motor System

6

Alias: Myotatic reflex/Muscle spindle - stretch sensitive receptor Group Ia and II sensory neurons Stimulates the alpha motorneurons as well as the gamma motorneurons  Resulting to muscular contraction Inverse Myotatic Reflex  Alias: • Inverse Stretch • Lengthening Response Reflex: Bear in mind, a muscle relaxing, is simply reverting to its resting length, not increasing the length of its fiber.  • Autogenic Inhibitory Reflex: when a muscle develop tension/muscle contract, that tension is inhibited by the Inverse Myogenic Reflex. Thus Muscle Relaxes • Disynaptic and Polysynaptic Reflex: Synapses with the inhibitory interneuron and anterior motor neuron o Since, # of synapsescontraction < # of synapsesrelaxation ∴ Durationcontraction < Durationrelaxation  GTO-tension sensitive receptor  Group Ib sensory neurons  Stimulates an inhibitory interneuron (spinal cord)  Inhibiting the alpha motor neurons  Resulting to muscular relaxation   

o

Motor Areas of the Nervous System • Spinal Cord o Rexed Laminae (Gray Matter)  Lamina 7: contains cells of the dorsal nucleas (Clarke's column) and ventral column • Posterior spinocerebellar tract. It also contains the intermediolateral nucleus in thoracic and upper lumbar regions  Lamina 8 & 9: motor neurons in the medial and lateral regions • Medial: controls axial muscles • Lateral: controls distal muscles  Lamina 10: neurons around the central canal o Complete transaction of the spinal cord  Permanent Paraplegia • Initially Flaccid, then becomes Spastic Paraplegia  Loss of Sensations  Spinal Shock • Loss of spinal reflex • Loss of Autonomic functions: Symphathetic and Parasymphathetic o Some Parasymphathetic nerve arise from cranial nerves  Last for a minimum of 2 weeks • 1st to recover: Sensory Function • Recovery is possible for some somatic and autonomic reflexes (e.g. knee jerk, withdrawal/flexor/pain reflex, micturition and erection) • Age (1/α) Recovery Period

Castillo, Aileen Page 6

Motor System

•

7

 Observed below the level of injury Brainstem o Function: Provides background contraction: trunk, neck and proximal portions of the limbs o Supports the body against gravity  Antigravity Muscles: Extensors • Only the arm antigravity muscles are flexors o Reticular Activating System: Responsible for wakefulness

Figure 4 Inputs to the motor system of the brainstem

Brainstem[Pons] + Vestibular Nuclei[via Medial and Lateral Vestibulospinal tract] + Cerebellum • Continuous involuntary maintenance of posture • Affects axial antigravity muscles • Vestibular nuclei specifically selectively control the excitatory signals to the different antigravity muscles to maintain equilibrium in response to signals from the vestibular apparatus2

Motor Center

Brainstem Medullary Reticular Formation Lateral Reticular Formation Anterior Motor Neuron

Anti gravity muscles 2

Guyton, 692

Castillo, Aileen Page 7

Rubrospinal tract

Motor System

8

Figure 5 Extensor Inhibition

Cortex + Medullary Neurons • Transmit inhibitory to the antigravity muscles • Counteract stimulatory activity of the pons

Brainstem Control of Posture • Reticulospinal tract o Affects activity of proximal muscles and muscles of the trunk o Affects mostly extensors o The excitatory and inhibitory reticular nuclei constitute a controllable system that is manipulated by motor signals from the cerebral cortex o Pontine reticulospinal tract  Generally stimulatory on both extensors and flexors, but greater effect on extensors  Originates in the nuclei in the pons and projects to the ventromedial spinal cord o Medullary reticulospinal tract  Generally inhibitory on both extensors and flexors, but greater effect on extensors  Thus, you can flex the body part and change position (e.g. Changing head position)  Originates in the medullary reticular formation and projects to spinal cord interneurons in the intermediate gray area Figure 6 Decerebrate and decorticate postures o Transections  Above Pontine Reticular Formation/Between pons and midbrain • Decerebrate Rigidity o Explanation: Blockage of strong cortical, red nucleus, and basal ganglia input to the medullary reticular nuclei; Lacking this input renders the medullary reticular inhibitor system non-functional  Cortex and midbrain are not capable of exerting their effects on the muscles of the body  The highest center controlling the muscles is the pons, which is excitatory o Characterized by:  ↑ excitability of extensors  + tonic labyrinthine reflexes  + tonic neck reflex  + spinal reflex  - righting reflex (midbrain function) NOTE: Righting reflex is a midbrain function.

o Castillo, Aileen Page 8

Physical Characteristics

Motor System    

Extension and hyperpronation of arms Extension and internal rotation of legs Opisthotonos (Arching of neck and back)

Above Midbrain • Decorticate Rigidity o Explanation: Cause of hyperextension of lower extremities, same as decerebrate; Cause of hyperflexion of upper extremities is due to rubrospinal excitation3 o Characterized by:  + righting reflex  + tonic labyrinthine reflex  + tonic neck reflex  - spontaneous movement (automation) o Physical Characteristics  Flexion of arms with extension and internal rotation of legs  Body is extended except upper extremities o Common Cause: Stroke, Hunger/Hyperglycemia[due to its dependency on glucose]

Cerebral cortex  Motor cortex o Anterior to the central sulcus occupies the posterior 1/3 of the frontal lobe o 3 sub areas  Primary Motor Area (BA 4) • Origin of motor commands, after modification of the basal ganglia and lateral cerebellum • Cortical efferent zone, start of motor impulses that are directed towards muscle • Site of the motor homunculus • # muscle spindles α homunculus representation  Premotor Area • Responsible for setting posture at the start of planned complex motor activity • Received major input from the posterior parietal cortex and its output influences chiefly the medial descending pathway • Anterior premotor cortex [develops a “motor image”]  Posterior Premotor cortex [Excites successive pattern of motor activity  {(Primary motor cortex) || (Basal Ganglia + Thalamus  Primary motor Cortex)}  Supplementary Motor Area • Concerned with mental rehearsal of planned motor activity • Causes complex contraction that is usually bilateral affecting mostly the upper extremities • Needs stronger stimulation to cause contraction • Contractions are often bilateral 3

Ganong, Chapter 16

Castillo, Aileen Page 9

9

Motor System

10

Actors have a developed Supplementary Motor Area, whereas Athletes have a developed Cerebrocerebellum. 

Posterior Parietal Cortex(PPC, Somatic Sensory Association Area, BA 7) and the Somatic Sensory Areas(SSA, BA 3,1,2) o Generate motor responses  Sensation must occur before Motor impulses are generated o PPC project to the premotor area and the supplementary motor area o SSA project to the primary motor cortex  Other specialized cortical areas that control motor function o Broca’s Area  Vocal cord muscles o Voluntary eye movement field/Frontal Eye movement field  Voluntary movement of the eyes towards different objects  Controlling eyelid (e.g. Blinking) o Head rotation area  Elicits head rotation; closely associated with the eye movement field o Area of Hand Skill  (X): Motor Apraxia, uncoordinated and nonpurposeful movements Descending Pathways LEFT o Passes through the internal capsule o (X): Motor Problems o Corticobulbar tract [Face and Neck] o Concerned with the activity of the motor nuclei of LEFT RIGHT several cranial nerves ( ) o Can influence motorneurons controlling neck muscles, facial muscles, jaw muscles and extraocular muscles and tongue; in other words, neck up  Except posterior portion of the Figure 7 Corticobulbar Tract head[cervical muscle] o Have ipsi and contra control, ipsi: upper portion; contra: upper and lower portion  Given, the reference point = Motor nucleus • Lesion Before: (x) Contra, Lower • Lesion After: (x) Ipsi, Upper and Lower o Corticospinal tract/Pyramidal Tract/Upper motor neurons [Trunk and Limbs] o Most important output pathway from the cerebral cortex o Passes through the posterior limb of the internal capsule o Origin (%):  30: primary motor area  30: premotor area  40: parietal area o Comprises of 80% Lateral Corticospinal tract and 20% medial Corticospinal tract o Lateral Corticospinal tract [Distal Muscles]  Constitutes 80% of the fibers  Projection fibers are mostly coming from the primary motor cortex  Fibers cross at the midline of the medullary pyramid 

Castillo, Aileen Page 10

Motor System

11

Concerned with control of distal musculature (hands, fingers, lower legs and feet)  Only have contralateral control  Generally facilitates activity of flexor muscles and inhibits extensors  Mediates fine and skilled movements  Includes the rubrospinal tract • Corticorubral and Rubrospinal tract o (+) Flexor and (-) Extensors: Distal Muscles of the arms Medial Corticospinal tract [Proximal/Truncal Muscles]  Constitutes 20% of the fibers  Projection fibers are mostly coming from the premotor cortex  Fibers don't cross at the midline of the medullary pyramid • Fibers cross at the level of the spinal cord  Concerned with the control of axial muscles (trunk and proximal limbs)  Have contralateral and ipsilateral control  Mediates postural adjustments and gross movements  Assist the brainstem in adjusting posture  Includes reticulospinal, vestibulospinal and tectospinal tracts • Lateral Vestibulospinal tract o Powerful (+) of extensors and (-) of flexors o Concerned with maintenance of posture with accompanying movement of the head and maintenance of postural tone • Tectospinal tract o Controls activity of neck muscles in response to visual and auditory stimuli • Corticotectal tract o Concerned with the turning movement of the head and eyes associated with reaching movements of the arm o Affects mostly reflex than voluntary eye movements 

o

Vestibulo-ocular reflex: Reflex movement of the eyeball Corticotectal tract: Voluntary eye movements

•

Median Longitudinal Fasciculus o Concerned with reflex movements of the head and neck in response to visual and vestibular stimuli

NOTE: Flexor: intrinsic movement; Extensors: postural adjustment

Upper motor neurons o Neurons in all motor pathways under direct/indirect control by the cerebral cortex, cerebellum and basal ganglia o Corticobulbar: Neurons before the motor neurons of the CN o Corticospinal: Neurons before the ventral horn o Pyramidal System Lesion (Upper Motorneuron Lesions) o Hypotonic muscles o Weakness and clumsiness o Initially no muscle atropy  disuse atrophy o Difficulty of performing voluntary movements Castillo, Aileen Page 11

Motor System o o

12

Hyperactive reflexes No fasciculation/Fibrillation Fasciculation: involuntary minute muscle twitches; muscle fascicles; visible Fibrilations: involuntary minute muscle twitches; muscle fiber; not visible but felt

o o o

Spasticity (Clasp knife reaction/clonus)  Clonus/Clasp Knife reaction: Resistance to contraction Positive Babinski sign Observed: Contralaterally

Lower motorneurons o α and γ motorneurons of the spinal cord and the motor components of the cranial nerve nuclei o Neurons having final direct link with the muscles o Lower Motorneuron Lesions o Muscle weakness and immediate atrophy o Hypoactive/absent reflexes o Flaccidity o Fasciculation/Fibrilations o Negative Babinski sign o Observed: Ipsilaterally Extrapyramidal system o Rest of the descending motor pathway o Some areas of the brainstem o Some areas of the basal ganglia o Subthalamic nucleus o Substantia nigra o Cerebellum o Some spinal pathways o Vestibular nuclei o Extrapyramidal System Lesions o Muscular Rigidity o Involuntary movements (Hypokinetic or Hyperkinetic) o No muscle weakness o No reflex changes Basal Ganglia o For feedback regulation of movements (corrects and evaluates movement as they happen) o Involved BEFORE and AS we perform the movements o Plays an essential role in initiating most motor activities (A.P. are noted first in the basal ganglia before the cortical motor areas) o For cognitive control of motor activities o Affects all skeletal muscle o Functions of the Basal Ganglia o Inhibition of motor tone/Damping Function Castillo, Aileen Page 12

Motor System

13

So no jerky movement/tremors will occur; So movements are smooth and well coordinated o Controls gross intentional (voluntary) movement [striatum] o Provides background muscle tone for intended movement  Assist the brainstem neurons in the maintenance of posture o Involved in the planning/programming of motor activities o Essential for the initiation and execution of slow movements [globus pallidus external segment] o Essential for regulating fast movements [globus pallidus internal segment] 2 Important Pathways o Direct pathway  Enhances motor activity  Controls rapid motor activity  Decrease activity will cause hypokinetic behavior o Indirect pathway  Reduces motor activity  Controls slow motor activity  Decrease activity will cause hyperkinetic behaviour Basal Ganglia Injuries o Hyperkinetic defects  Huntington’s Chorea • Excessive rapid movement affecting face and upper extremities • Characterized by trinucleotide repeat expansion. o Commonly, cytosine-adenine-guanine (CAG) repeats • Caudate n.: underactivity of GABA/Ach or Overactivity of Dopamine • Loss of intrastriatal GABAnergic and cholinergic neurons • Releases the pallidum from inhibition  hyperkinesia • An autosomal dominant disorder (abnormal gene is located near the end of the short arm of chromosome 4) • Age onset: 30 to 50 

o

o

Sydenham's chorea: Bacterial in origin Huntington’s chorea: Neurological disorder

Athetosis • Excessive slow movement, worm like • Neurons of the Corpus Striatum or Thalamus are affected • Associated with cerebral palsy • Writhing movements  Dystonia • Simultaneous contraction of all skeletal muscles of the body  Hemiballismus • Subthalamic n. • Excessive rapid movement/Violent movement of upper and lower extremities [one side] Hypokinetic Defects  Paralysis Agitans (Parkinson’s disease) 

o

Castillo, Aileen Page 13

Motor System •

• • •

14

Results from widespread destruction of the substantia nigra and pars compacta that connects dopamine-secreting nerve fibers to the caudate nucleus and putamen  ↓in dopaminergic activities with relative ↑in cholinergic activities Nigrostriatal tract Age group: usually 60 and above o Youngest: 29, Micheal J. Fox Signs and Symptoms of Parkinson's o Have hypokinetic and hyperkinetic defect, since the damage is extrapyramidal in nature o Hypokinetic defects  Akinesia: Absence of movements  Bradykinesia: Slow in initiating movements  Lack of facial expressions (masked face)  Lack of associated movements  Difficulty in initiating and stopping movements  Shuffling (festinating) gait  One small step at a time o Hyperkinesia defects  Cog-wheel rigidity: "catches" during passive motion  Lead pipe rigidity  Passive (resting) tremors: "pill rolling"

Cerebellum • Involved in the feed forward regulation of motor activities: planning of movement before they are initiated [lateral regions] • Plays major role in the timing of motor activities and in rapid sm. progression from one movement to the next - motor coordination (vermis/intermediate regions). o Control of balance or equilibrium o Synergy - controls rate, force, range and direction of movement [spinocerebellum] o Essential for motor learning (olivary nuclei) [cerebrocerebellum] • Anatomical and Functional Division o Neocerebellum/Cerebrocerebellum/Lateral Regions  Control of voluntary movements as well as learned movements (highly skilled, rapid, integrated movements) • Feedforward regulation: Lateral Cerebellum; Feedback regulation: Basal Ganglia  Prediction of movements (planning, programming and timing of movements)  Braking action and damping action  Received input from the cerebral cortex by way of the pontine nuclei o Spinocerebellum/paleocerebellum/Intermediate regions  Control of muscle tone and posture (truncal muscles)  Maintenance of equilibrium during movement  Provides smooth and coordinated movement of the extremities (proximal areas) Castillo, Aileen Page 14

Motor System

•

15

 Control of rapid motor activities  braking and damping actions  Control of rate, force, range and direction of ongoing movements  Receives input from the spinal cord o Vestibulocerebellum/Archicerebellum/Posterior regions  Maintenance of equilibrium and posture  Controls the balance between agonist and antagonist muscles during rapid changes in body positions  Regulates eye movement, stance and gait (equilibrium and learning induced changes in Vestibulo-ocular Reflex)  Dominated by vestibular input Clinically, the cerebellum is divided sagitally o Injury to the midline zone  Location: Anterior and posterior vermis, the flocculonodular lobe and the fastigial nuclei  Disorder of stance and gait  ataxia • Feet uses sideward movement to move forward  Malequilibrium • False Positive Romberg's test o Open eyes, swaying movement  Titubation: tremor of the body and head  Tilted posture of the head  Nystagmus o Injury to the lateral zone  Location: Cerebellar hemispheres, the dentate and the nuclei of each side  Decomposition of movement: difficulty performing movements involving several joints  "jerky, irregular" • E.g. Cannot flex fingers simultaneously  Past-pointing  Disorder of stance and gait  Ataxia • Ataxic stance: Bent forward, feet wide apart  Hypotonia  Dysarthria: Slurring of speech  Dysdiadochokinesia/Dysrhythmokinesia  Intention tremor  Impaired check and rebound: difficulty returning to original position  Nystagmus  Test Range, Direction of motion and Rapidity of movement o Finger to nose test  Slow movement, with difficulty o Finger - nose - finger test o Heel to shin test  (x) Cerebellum: Foot immediately moves away from the leg

Differentiating a Cerebellar Problem from a Basal Ganglia Problem Differentiating a Cerebellar problem from an (X) (X) Basal Ganglia intoxication Cerebellum Both have the same gait, but an Intoxicated person moves backward, whereas a person with a cerebellar problem moves forward. 

Castillo, Aileen Page 15

Motor System Walk Stand

Ataxic Gait X Tremor

Castillo, Aileen Page 16

One small step at a time √ Tremor

16