Control of movement Flashcards
What are 3 major sensory inputs that control muscles?
-visual input (position)
-vestibular input (balance)
-proprioceptive input (position)
Name some proprioceptors involved in the spinocerebellar pathway
-muscle spindles - muscle length and rate of length change
-golgi tendon organ- tension in muscles
Name some proprioceptors involved in the dorsal column pathway
-skin
-Pacinian corpuscle-pressure and vibration
-ruffini endings- tension and stretch
-joints
-kinaesthetic receptors-Pacinian receptors,ruffini endings, limb position and rate of position change
What are each of the spinal pathways in control of?
-spinocerebellar- unconscious proprioception
dorsal column- fine touch, vibration, conscious proprioception
spinothalamic- temp/ course touch/ pain
Define proprioceptive deafferentation
process by which you loose the afferent proprioceptive info coming in from your body through your spine- you loose the info going into the CNS
How might the immune system be involved in proprioceptive deafferentation?
-triggered autoimmune process
-viral infection
-target and destroy their own proprioceptive afferents
-immune system destroys and removes proprioceptive first order neurons
-info cant reach the CNS
What are some targets for proprioceptive info?
1-somatosensory cortex and associated areas (early cognition)
2-primary motor cortex (initiation of motor control)
3-pre motor cortex (develops pattern of movement)
4-basal ganglia (scaling and action selection)
5-cerebellum ( refinement of motor control)
6-brain stem nuclei(refinement of motor control)
7-spinal cord (spinal reflex hoops)
Where is the vestibular system?
-inner ear
-moves when the head moves- senses acceleration/movement
What does an accelerometer do?
records motion, movement, acceleration
What is the vestibular system comprised of?
- 3 semi circular canals
-otolith organs
-scarpa’s ganglion
fluid filled
What is the function of the semi circular canals?
angular acceleration
What is the function of the otolith organs?
utricle-horizontal acceleration
saccule-vertical acceleration
What is the function of Scarpa’s ganglia?
-a series of sensory nerve cell bodies receiving info from the semi circular canals, utricle, saccule and carries the info via the vestibular nerve up to the brain stem.
what is the difference between kinocilia and stereocilia?
kinocilia is tallest and stereocilia is shorter
embedded in a gel and attached apically to the hair cell
-want to move with the head
-move them away from each other hair cell hyperpolarises
-move them close together the hair cell with depolarise
What are otoliths?
-dense made out of calcium carbonate
-like pebbles- embedded in gel
-Have inertia due to significant mass
What is the ampullae?
-vectoral measurement
-swellings at the base of the semi-circular canal filled with endolymph
-contains hair cells which are embedded in gel called cupula
Where are vestibular nuclei found?
brain stem
By nuclei we mean they are concentrations of nerve cells that act as computational areas
What are the 4 main outputs of the vestibular nuclei?
-oculomotor complex- contribution to control of eye muscles
-Contribution to control of limb extensors- balance/posture
-to cervical spinal cord- adjustment of head
-Balance info sent to the cerebellum
Name some problems liked to vestibular apparatus damage
1-vertigo- deterioration of input to vestibular nuclei. False sensation of movement
2-Balance disorders-deterioration of input to vestibular nuclei. postural and tonal feed to LMN
3-Lack of coordination-deterioration of input to cerebellum via vestibular nuclei
4-bouncing vision-deterioration of input to oculomotor nuclei. Head/neck and eye coordination
Where is visual and proprioceptive info integrated?
posterior parietal cortex
What is the dorsal visual stream?
occipital lobe to sensory associative areas
What is the ventral visual stream?
insula and temporal lobe memory areas
What happens when there is a loss of visual sense?
1-loss of a major proprioceptive sense
2-reliance on other proprioceptive modalities
3-much more severe difficulties if other senses impaired
describe the control of movement model
1-descending pathways-UMN
2-motor cortex-planning, voluntary movements (basal ganglia)
3-brainstem motor pathways-basic movement and postural control (cerebellum)
4- interneurons-reflex coordination or lower alpha motor neurons
leads to skeletal muscles
What is the function of basal ganglia?
-interact in a 2 way manner
-check and monitor and adjust the basic processes produced in motor areas of the cerebellum
Name some key structures in the basal ganglia
-caudate nucleus
-putamen
-Globus pallidus
-subthalamic nucleus
-substantia Nigra
What is the internal capsule ( in side the basal ganglia) ?
white brain matter- connectivity highway of axons
these axons travel from higher brain centres through the internal capsule down to the brain stem into the spine to carry motor info. Sensory info is coming back the other way
What do the 5 nuclei in the basal ganglia work to control?
-scaling (how big our movements are)
-action selection (selecting appropriate actions over inappropriate actions for the moment you are in)
What are the key inputs to basal ganglia and motor feedback loop?
-parietal association cortex
-somatosensory cortex
-primary motor cortex
-frontal and prefrontal cortices
receives sensory and a copy of the motor control plan to be executed
How does the basal ganglia talk to the other neurons to control movement?
-not directly
-feedback loop from basal ganglia to motor areas
-monitors sensory and motor info from the rest of the brain helps to make decisions on scaling and action selection
What is the function of the amygdala?
emotional dimension of movement control
what is the direct pathway of the basal ganglia model?
sustains and promotes desired behaviours
What is the indirect pathway of the basal ganglia model?
inhibits undesired behaviours
Describe the relevance of the substantia nigra
-heavily pigmented dark areas associated with the production of dopamine
dopamine is released from the substantia nigra to certain areas of the basal ganglia
-facilitates direct pathway-select appropriate motor commands
-inhibits the indirect pathway - inhibits inappropriate motor commands
What are some impacts when there is a loss of dopamine from SN?
-Bradykinesia- action selection inhibited
-festinating gait- scaling issue-parkinsonian gait
-tremor- more distant relationship to action selection and scaling
- rigidity- increased tone in LMNs
How do basal ganglia influence motor activity?
-action selection( facilitates/suppresses movements )
-establishes background patterns of movement, control, and adjust posture during voluntary movements
-regulate scale/intensity of motor output
What are three functional divisions of the cerebellum?
-vestibulocerebellum
-spinocerebellum
-corticocerebellum
What is the function of the vestibulocerebellum?
-balance
-connections with the vestibular system
-connections with vestibular nuclei
What is the function of the spinocerebellum?
-posture
-muscle tone
-inputs from proprioceptors
-outputs to motor centres in brainstem
What is the function of the corticocerebellum?
-coordination
-motor learning
-inputs from motor cortex
-outputs to motor cortex via thalamus
Describe the link between the cerebellum and motor control
-compares actual movement with intended and predicted movement
-reduces errors via output to motor cortex and brain stem
cortical/reticular links- no direct links to LMNs
What are some consequences of cerebellar lesions?
-balance and posture problems
-ataxia-abnormal/uncoordinated movements
-asynergia-difficulty creating fluid movements
-dysmetria-cant judge distance or scale
-scanning speech- uncoordinated development of speech
-decomposition of movements
