Week 5 Pt 2 - Control Of Movement Flashcards
What are the roles of cerebellum?
- Coordinate movement
- Monitor and make corrective adjustments of activities initiated by other parts of the brain
- Maintain balance and posture
- Modulate eye movement
- Motor learning
What does the cerebellum not initiate?
Movement
What does the deep cerebellar nuclei consist of?
Fastigial, interposed and dentate nucleus
What does the cerebellar peduncles consist of?
3 pairs
Connect cerebellum to other parts of the CNS
What are the three major functional divisions?
- Vestibulocerebellum
- Spinocerebellum
- Cerebrocerebellum
Vestibulocerebellum
Flocculonodular lobe
Spinocerebellum
Vermis and paravermal zone
Cerebrocerebellum
Lateral zones of the cerebellar hemispheres
What is inferior cerebellar peduncle?
Axons from the spinal cord
Spinocerebellar and cuneocerebellar tract
Connect Medulla to cerebellum
What does the major pathway of the inferior cerebellar peduncle form?
Contralateral olivary nuclei
What is the middle cerebellar peduncle?
Axons of pontine nuclei that carry a copy of messages sent down the corticospinal tract
Connect pons to cerebellum
What is superior cerebellar peduncle?
Main efferent pathway from the cerebellum
Cafes the axons of the deep cerebellar nuclei
Connect the cerebellum to midbrain
What does the fastigial nuclei project to?
Vestibular nuclei
Where does the dentate nucleus project to?
Thalamus then to cortex
Where does the interposed nuclei project to?
Red nucleus
What are the afferents of vestibulocerebellum?
Arise from vestibular nucleus
Terminate in flocculonodular lobe
What do afferents of vestibulocerebellum conduct?
Vestibular signals about head position and movements
What are the efferents of vestibulocerebellum?
From flocculonodular lobe to fastigial nucleus
Vestibular nuclei —> vestibulospibal Tract
Reticular formation in brainstem —> reticulosponal tract
Motor nuclei innervating extraocular muscles
What regulates the tone of the antigravity muscles?
Vestibulospinal and reticulospibal tract
What does the efferents to cranial nuclei regulate?
Movement of the eyeballs during head movements to maintain stable vision
What is the afferents for spinocerebellum?
Posterior (dorsal) Anterior (ventral) Spinal cerebellar tract Cuneocerebellar tract Proprioception input from muscle spindle, Golgi tendon organ, touch/pressure
What is the efferent of spinocerebellum?
Cerebellocerebral tract via thalamus
Cerebellorubral tract to red nucleus in midbrain
Reticulospinal and rubrospinal tract
What modulates the motor neurons in the spinal cord?
Reticulospinal and rubrospinal tract
What is the afferents of cerebrocerebellum?
Originate in the cerebral cortex via pontine nuclei
What does the afferents input of cerebrocerebellum carry?
Motor information: the motor commands from motor areas
Sensory information: the present postural state of the body from the somatic sensory areas
What is the efferent input of the cerebrocerebellum?
From cerebellar cortex to dentate nucleus
Through superior peduncle to terminate in VL nucleus of contralateral nucleus
Motor areas of the cerebral cortex
What does the cerebello-dentato-thalamo-cerebral pathway mediate?
The role in adjusting the plan of the motor command before being discharged from cerebral cortical motor areas to LMN
What is activated when the equilibrium is disturbed?
Vestibular receptors
Where does the vestibular receptors signal to?
Vestibulocerebellum to initiate immediate corrective signals
Where are the corrective signals sent to?
- The vestibular nuclei and reticular formation
2. The superior colliculus
What does the vestibular nuclei and reticular formation do?
Adjust the tone and contractility of the axial and proximal limb muscles
Help maintain equilibrium during change in head position
What do superior colliculus do?
Coordinate eye movements with head movements during acceleration
Maintain clear vision
Keep equilibrium during head movements
What is the principal region for the postural adjustment?
Vermis
Where does the vermis receive sensory information from?
Muscles
Joint proprioceptors
On position of body
What does vermis output control?
Vestibulospinal and reticulospinal tract
Define coordination of voluntary movements
Ones ability to proceed smoothly and precisely from one movement to the next in proper succession
What does the spinocerebellum receive when the motor cortex send commands to spinal cord for a voluntary movement?
Efference copy of the intended motor command through cortico-ponto-cerebellar pathway
What happens as the movement proceeds?
The spinocerebellum receives proprioceptive signals about actual motor performance via spinocerebellar tract
What does the intermediate zone of the spinocerebellum act as?
Comparator that compares the motor intentions of higher centres with actual performance of muscles
What occurs when there is any error in performance or deviation from originial plan?
The intermediate zone and interposed nucleus send corrective signals back to the motor cortex and the red nucleus to correct muscle actions
What is the predictive and camping mechanism?
The cerebellum receives information regarding the velocity and direction of the intended movement
What does the cerebellum predict?
How far that part of the body will move in a given time
Uses this information to determine the precise time to damp the movement
Sends it’s decision to the motor cortex to stop ongoing movement exactly at the intended position
Planning the sequence of movements
The cerebrocerebellum uses information provided from motor cortex and basal ganglia to achieve the goal of the movement
The plan of the movement sequence is transmitted from cerebrocerebellum to motor cortex
Used to adjust the final motor command before it is discharged to LMN
Timing of Movements
Cerebrocerebellum provides perfect timing of voluntary movements
Computes the appropriate timing for onset and termination of contraction of each of muscles
Define motor learning
A set of internal processes associated with practice or experience leading to relatively permanent changes in the capability for skilled behaviour
What is the early stage in motor learning?
When a person first performs a complex motor act the degree of cerebellar adjustment of the onset and termination of the successive muscle contractions involved in movement is almost always inaccurate
Cerebellar neuronal circuit learn to make more accurate movement next time
What is intermediate stage in motor learning?
After motor act has been repeated many times (motor training), the successive steps of motor act become gradually more precise
What is late stage in motor learning?
Once the cerebellum has perfectly learned its role in different patterns of movement, it establishes a specific “stored programme” for each of the learned movements
What is specific signs of cerebellar damage?
- Ataxia
- Dysmetria
- Nystagmus
- Dysarthria
- Infection tremor
- Dysdiadochokinesia
What is ataxia?
Lack of voluntary coordination of muscle movements
What is dysmetria?
A lack of coordination of movement typified by the undershoot or overshoot of intended position with hand, arm and leg
What is Nystagmus?
Flicking eye movements
What is dysarthria?
Slurred speech
What is Dysdiadochokinesia?
Inaccuracies in rapidly repeated movements
What is cerebellum particularly susceptible to?
Effects of alcohol
What are central pattern generators?
Microcircuits
Neuronal networks that contain the necessary information to coordinate a specific motor pattern such as breathing, walking and chewing
What can CPG be activated by?
Will
Triggered by sensory stimuli as in a protective reflex or swallowing
What is walking produced by?
CPGs in the spinal cord
What is chewing movements controlled by?
Brainstem circuits that generate alternating activity between jaw-opener and closer muscles
Eye movements
saccadic eye movements
What does spinal cord contain?
CPGs for locomotion and protective reflexes
What does brainstem contain?
CPGs for breathing, chewing, swallowing and saccadic eye movements
What does hypothalamus in the forebrain Contain?
Centres that regulate eating and drinking
What can rhythmic patterns be intervened by?
supraspinal commands
Where is inspiratory centre located?
Nucleus tractus solitarius
What does inspiratory centre emit?
Repetitive burst of inspiratory action potentials
How is the basic rhythm of respiration generated?
Mainly by neurons in the DRG
Where is ventral respiratory group located?
Nucleus ambiguus rostrally
Nucleus retroambiguus caudally
What does the VRG Contain?
Both inspiratory and expiratory neurons
What is the neurons of VRG during normal quiet respiration?
Totally inactive
What is VRG responsible for?
Motor control of inspiratory and expiratory muscles during exercise
Where is apneustic centre situated?
Lower pons
What is the function of Apneustic centre?
Increases depth of inspiration by acting directly on the inspiratory centre
What is apneusis?
Abnormal pattern of breathing
Characterised by deep, gasping inspiration with a pause at full inspiration followed by a brief, insufficient release
Where is the pneumotaxic centre situated in?
Upper pons
Formed by nucleus parabrachialis
What is the function of pneumotaxic centre?
Antagonises the apneustic centre
Cyclically inhibits inhalation
The centre limits the burst of action potential in the phrenic nerve
Decreases the tidal volume and regulate the respiratory rate
What does an absence of pneumotaxic centre result in?
Increase in depth of respiration
Decrease in respiratory rate
What are motor pools?
The cell bodies of motor neurons arranged in groups in spinal cord and brain stem
What does each motor pool activate?
One muscle
Where do motor neurons that activate muscles in limbs, torso or neck have their cell bodies in?
Region of spinal cord grey matter - ventral horn
What are muscles in the neck and arms activated by?
Motor neurons in cervical spinal cord
What are muscles in the chest, legs and pelvic region activated by?
Thoracic, lumbar and sacral spinal cord
What is the small bundle of axons called that each motor neuron axon exits the spinal cord?
Ventral root
What does the ventral root and dorsal root join to form?
Segmental nerve
Where do motor neurons that activate muscles in the head have their cell bodies have their cell bodies in?
Brainstem
Brainstem: midbrain, pons and Medulla
What are motor neurons and the set of muscle fibres it contacts called?
Motor unit
What are examples of descending spinal input from brainstem cell groups called?
reticular formation
Vestibular nuclei
The red nucleus
superior colliculus
What are the spinal inputs referred to as?
Reticulospinal Vestibulospinal Rubrospinal Tectospinal Corticospinal
What influences automatic, axial, postural and locomotor movements?
Reticulospinal
Vestibulospinal
Tectospinal
What influences voluntary, distal and fine movement control?
Rubrospinal
Corticospinal axons
Where does reticulospinal axon from pons generally project to?
Same side of the spinal cord
Where does the reticulospinal axons from Medulla project to?
Both sides of the spinal cord
Where are Basal Ganglia and cerebellum locates in?
Basal forebrain
Hindbrain
What is the role of vestibular nucleu?
Mediate vestibuloocular reflex
Head rotation in one direction causes equal and opposition eye rotation
Maintain stable head and body posture during standing and locomotion
What is the role of Red nucleus?
Midbrain
Voluntary control of fingers, hands and arms
What is the role of superior colliculus?
Integrate visual, auditory and somatosensory input
Initiate eye and head movement
Command centre for saccade control
What is the role of cerebellum?
Found in hindbrain
