Control Of Movements Flashcards
Sensory input
Proprioception input - position information
Vestibular input - balance information
Visual input - position information
Processed by the central nervous system and nuclei in the brain to produce movement output
Sensory feedback
Proprioceptive feedback
Check what we are doing
Decide if the movements are appropriate
Proprioceptors
Receptors send proprioceptive information to the spinal tract pathways
Spinocerebellar pathway
Dorsal column pathway
Proprioceptors: muscles and tendons
Spinocerebellar pathway
Muscle spindles - muscle length, rate of length change
Golgi tendon organ - tension in muscles
Proprioceptors: skin
Dorsal column pathway
Pacinian corpuscel - pressure, vibration
Ruffini endings - tension, stretch
Proprioceptors: joints
Dorsal column pathway
Kinaesthetic receptors - pacinian receptors, Ruffini endings, limb position, rate of position change
Sensory pathways: Spinocerebellar
Unconscious Proprioception
Sensory pathways: dorsal column
Fine touch
Vibration
Conscious Proprioception
Sensory pathways: spinothalemic
Temperature
Course touch
Pain
Targets for proprioceptive information: somatosensory cortex and associative areas
Early understanding of what is happening
Early cognition
Targets for proprioceptive information: primary motor cortex
Initiation of motor control
Targets for proprioceptive information: pre-motor cortex
Develops patterns off movement
Control muscles
Targets for proprioceptive information: basal ganglia/ nuclei
Scaling - how big the movements are, tiny or huge
Action selection - choose appropriate movements over inappropriate movements
Targets for proprioceptive information: cerebellum
Refinement of motor control
Develop feedback mechanisms
Balance and posture
Targets for proprioceptive information: brainstem nuclei
Refinement of motor control Develop feedback
Targets for proprioceptive information: spinal cord
Spinal reflex loops
Vestibular system
Inner ear
Organs embedded in the bones of the skull
Move as the head moves
Measure and sense acceleration and movement of the head
Vestibular system: semi-circular canals
Three
At right angles to each other
Measure angular acceleration
Filled with fluid
Vestibular system: otolith organs
Utricle - measures horizontal acceleration
Saccule - measures vertical acceleration
Set at different orientations
Filled with fluid
Vestibular system: scarpa’s ganglion
Two parts
Collection of sensory nerve cell bodies
Carries information from the semi-circular canals and otolith organs to the brainstem via the vestibular nerve
Otolith organs function as accelerometers: support cells
Within the otolith organs
Attached to the skull
Move when the skull moves
Otolith organs function as accelerometers: hair cells
Stereocilia - shortest which are attached apically
Kinocilium - tallest which are attached apically
Otolith organs function as accelerometers: stereocilia
Embedded within the gel above
Act as sensors
Sense the relationship between the hair cells and otoliths
Otolith organs function as accelerometers: otoliths
Within gelatinous mass
Made of calcium carbonate
Inertia - try to stay still as they have significant mass while the gel and hair cells move
Otolith organs function as accelerometers: head up right
Steady stream of action potentials in the vestibular nerve
Otolith organs function as accelerometers: head tilted forward
Stereocilia bend towards kinocilium
Hair cells depolarise
Nerve fibre is excited
Increase in action potentials in the vestibular nerve
Otolith organs function as accelerometers: head tilted backwards
Stereocilia bend away from kinocilium
Hair cells hyperpolarises
Nerve fibre is inhibited
Decrease in action potentials in the vestibular nerve
Ampullae
Swellings at the base of semi-circular canals
Endolymph - filed that fells the ampullae
Cupula - gel like structure
Moving your head causes the Endolymph to move and deflect the ampulla and cupula this deflects the hair cells causing information to travel o the brainstem
Vestibular nuclei
Concentrations of nerve cells
Inputs and outputs are on both sides of the brain stem
Vestibular nuclei: inputs
Vestibular nerve - balance, acceleration and directional movement information
Input of the head from the inner ear to vestibular nuclei
Vestibular nuclei: output target
Oculomotor complex
Extensor muscles
Cervical spinal cord
Cerebellum
Vestibular nuclei: output targets - Oculomotor complex
Group of brainstem and mid brain nuclei
To the eye muscles
Move the head and know how to move our eyes in relation to each other
Vestibular nuclei: output targets - extensor muscles
Lower motor neurones
Lower limbs
Balance, posture and muscle tone
Vestibular nuclei: output targets - cervical spinal cord
Adjustment of the head
Awareness of how to control the muscles of the neck
Have the head at an angle
Vestibular nuclei: output targets - cerebellum
Balance
Smooth movements
Embed information about how to react to movement
Problems linked to vestibular apparatus damage
Dizziness and vertigo
Balance disorders
Lack of coordination
‘Bouncing’ vision
Problems linked to vestibular apparatus damage: dizziness and vertigo
Deterioration of input to vestibular nerve
False sensation of movement
Problems linked to vestibular apparatus damage: balance problems
Deterioration of input to vestibular nerve
Postural and tonal feed to lower motor neurones
Problems linked to vestibular apparatus damage: lack of coordination
Deterioration of input to cerebellum via vestibular nuclei
Problems linked to vestibular apparatus damage: ‘bouncing’ vision
Deterioration of input to oculomotor nuclei
Head, neck and eye coordination
Visual input
Integrated at the posterior parietal cortex
Dorsal visual stream
Ventral visual stream
Visual input: dorsal visual stream
From occipital lobe to sensory associative areas, motor cortex, posterior parietal cortex and somatosensory cortex
Visual input: ventral visual stream
From occipital lobe to insula and temporal lobe memory areas
Loss of visual sense
Loss of major proprioceptive sense
Reliance on other proprioceptive modalities
Much more severe difficulties if other senses are impaired
Basal ganglia
Deep and dark areas
Caudate nucleus
Putamen
Globus
Pallidus
Subthalamic nucleus
Substantial nigra
Basal ganglia: internal capsule
White matter - connectivity highway
Axons travel from higher brain area through the internal capsule and through brainstem to the spine
Motor information
Sensory information
Basal ganglia: amygdala
Scaling - how big the movements are, tiny or huge
Action selection - appropriate actions above inappropriate actions
Inputs to basal ganglia: onto caudate nucleus
From parietal association cortex
From frontal and prefrontal cortices
Inputs to basal ganglia: onto putamen
From somatosensory cortex
From primary motor cortex
Basal ganglia: motor feedback loop
Receives information and works out if the movements are appropriate and in the right scale
Decision
Monitoring sensory and motor information
Feedbacks to cortices to improve movements if necessary
Model of basal ganglia function: direct pathway
Sustains and promotes the desired behaviour
Sends feedback to motor cortex that the plan is appropriate
So the movements will happen
Model of basal ganglia function: indirect pathway
Inhibits undesired pathways
Sends inhibitory feedback to the motor cortex that the plan is inappropriate
So the movements will not happen
Substantia nigra
Releases dopamine
Facilitates direct pathway - selects initiates appropriate motor commands
Inhibits inappropriate motor commands
Substantia nigra: loss of dopamine
Movements to be inhibited or cannot start intended movements
Effect on scaling
Parkinson’s disease
Bradykinesia - action selection inhibited
Festinating gait - scaling issues
Tremor - action selection and scaling
Rigidity - increased tone in lower motor neurones
How do basal ganglia influence motor activity
Action selection
Establish background patterns of movement
Control and adjust posture during voluntary movements
Regulate scale and intensity of motor output
Cerebellum
Receives information from sensory and motor cortices
Regulatory control of motor output
Perfection of movement
Automatic sense of motor control system
Functional divisions of cerebellum
Vestibulocerebellum
Spinocerebellum
Corticocerebellum
Functional divisions of cerebellum: Vestibulocerebellum
Balance
Connections with vestibular system
Connections with vestibular nuclei
Feedbacks to motor control system and adjust movements
Functional divisions of cerebellum: Spinocerebellum
Posture
Muscle tone
Inputs from proprioceptors
Outputs to motor centres in brainstem
Adjust motor output
Functional divisions of cerebellum: Corticocerebellum
Coordination
Motor learning
Inputs from motor cortex
Outputs to motor cortex via thalamus
Wider cortex of brain
Feedback loop
Cerebellum: motor control
Comparator
Compares actual movement with intended and predicted movements
Reduces errors
Cortical and reticular links but no direct links to lower motor neurones
Cerebellar lesions
Problem with balance and posture
Ataxia - presence of abnormal and uncoordinated movements
Asynergia - difficulty creating fluid movements
Dysmetria - undershoot or overshoot, cannot judge distance or scale
Scanning speech - uncoordinated development of speech
Decomposition of movement - component motions, move in stages
