Physiological Basis of Motor Control Flashcards
(38 cards)
1
Q
Movement arises from the interaction of what 3 internal systems
A
- Cognitive system
- Perception Systems
- Action systems
2
Q
What steps in the movement process are each system responsible for
A
- Perceptual/Cognitive systems: sensing -> perceiving -> interpreting -> conceptualizing
- Cognitive/Action systems: conceptualizing -> strategizing -> activating -> executing
3
Q
What are the steps to creating movement and their components responsible
A
- Sensing: peripheral receptors
- Perceiving: 1º & 2º sensory cortices
- Interpreting: higher level sensory processing areas inn the parietal, occipital, & temporal lobes
- Conceptualization: prefrontal cortex & other higher level association areas
- Strategy/Plan: supplementary motor cortex basal ganglia/cerebellum (BG/CB)
- Activation: 1º motor cortex basal ganglia/cerebellum (BG/CB)
- Execution: motor neurons & muscles/joints
4
Q
Describe hierarchical processing
A
- higher level of CNS are concerned with abstract processing of information & lower levels bring in/send information
- Perceptual system from sensing to interpreting
- Action system from planing to execute specific response
5
Q
Describe parallel processing
A
- the same signal might reach different brain structures simultaneously for processing (divergent) but different purposes
- Example: basal ganglia and cerebellum sharing information to motor cortex at same time
6
Q
Describe spinal cord connections
A
- hierarchically, ‘lowest level employees’ respond to sensory inputs & follow ‘orders’ from action systems
- involved in initial signal reception & final execution of in/voluntary movements (final common pathway)
- connections from different motor areas (motor cortex, premotor areas, brain stem) descend down to modulate spinal level responses
7
Q
Examples of basic/simple signal processing of spinal cord connections
A
- spinal reflexes
- basic flex/ext of muscles
8
Q
Describe brain stem connections
A
- ‘Middle management’: contain important control centers (sensory and motor) for postural control & locomotion
- Receives inputs from head/neck, vestibular, & visual systems, sends somewhat processed signals to sensory/perceptual centers
- contain motor nuclei for descending motor pathways to neck/face/eyes & extrapyramidal pathways (but not the corticospinal pathways) also receives modulating info from cortical structures, cerebellum, spinal cord
9
Q
What anatomy is included in the brainstem
A
- pons
- midbrain
- medulla
10
Q
Describe cerebellar connections
A
- ‘back-channel’ needed for comparing & calibrating movements
- receives inputs of ongoing movements (specially postural control-related movements) from spinal cord (feedback mechanism), outputs go to cortex to adjust ongoing movements
- important center for coordination and balance during movement control
- helps generate smooth coordinated movements by modulating force and sequence: receives info from cortex (for planning refining movements), compares planned movement commands to its consequences from ‘past experience’, refines planned movement & communicates back to cortex via brainstem, prior to execution of movement (feedforward mechanism)
11
Q
Describe thalamus connections
A
- the ‘doorkeeper to the boardroom’
- acts as a junction, a rely center for signal processing
- processes almost all sensory info coming from spinal cord pathways
- outputs are carried forward to different parts of the cortex
12
Q
Describe basal ganglia connections
A
- involved in higher order motor planning for coordinated movements
- receives inputs from many areas of cerebral cortex
- sends output back to motor cortex via thalamus
13
Q
Describe cerebral cortex connections
A
- highest executive level of motor control hierarchy
- direct control of voluntary movements by controlling motor neurons via corticospinal/corticobulbar pathways
- interacts with premotor/SMA (supplementary motor area) to form motor plan/strategy
14
Q
Advantages of having hierarchical and parallel control
A
- makes the motor control system dynamic, flexible, and resilient
- sufficient info to respond accurately
- one system can take over functions if tasks /environments require it
- can suppress unnecessary responses
- certain amount of functional recovery possible using alternate pathways after injury to one system
15
Q
Somatosensory components within perception system in order
A
- Incoming info sensed from environment
- Activation of the somatosensory receptors
- Type/intensity/area of sensation
- Info sent up towards the CNS to attach meaning for interpretation
16
Q
What information do muscle spindles detect
A
- info about muscle tone
- state of muscle contraction
- proprioception
- spatial awareness
17
Q
Information from muscle spindle used during motor control
A
- hierarchical and parallel pathways ii stretch reflex arcs
- response ca be modulated by transcortical/functional reflexes that comes under cortical control
18
Q
Describe the Golgi tendon organ reflex in motor control
A
- inhibitory disynaptic reflex
- inhibits its own muscle & activates the antagonistic muscle
- joint & cutaneous receptors contribute to reflex
19
Q
Describe cutaneous receptors
A
- take part in spinal level info processing for motor control
- flexor withdrawal ca be modulated by higher centers depending on task & context (inhibited consciously to prevent injury)
- flexor withdrawal reflex = limb flexes to protect itself which elicits crossed-extension reflex
- light diffuse stimulus elicits placing reaction = limb extends
20
Q
What role does the spinal cord play in motor control
A
- acts as a conduit
- participates in both perception & action systems
21
Q
Effect of somotaosensory information on spinal CPGs (central pattern generators)
A
- cutaneous inputs can modulate gait in different ways
- spinalized cats were able to walk after T12 spinal cord transection with brushing stimulus on paw
22
Q
Role of primary somatosensory cortex
A
- where afferent info from sensory receptors are processed to provide ‘us’ perception
- perceptions of movement of body parts in space or objects in environment that interact with our body
23
Q
Define perception
A
- making sense of the ‘senses’
24
Q
Role of sensory association areas
A
- provide higher levels of perception of movements
- cross-model processing: info from muscle spindles, joint receptors, cutaneous receptors, etc. are integrated to give accurate info about limb movements
- different sets of neurons process different features of movement in parallel (amplitude or direction)
- responsible for combined cortical sensations: 2-point discrimination, stereognosis, and graphesthesia
- spread across all lobes of the brain
- participate in more complex cross-modal processing (somatosensory, visual, auditory) to provide holistic context of the sensory experience through more abstract cognitive processes (interpreting, conceptualizing)
25
Clinical relevance of sensory association areas
- damage to parietal areas may lead to spatial perceptual problems: not recognize objects or drawings, complete neglect of contralateral side causing agnosia, claim that side is not theirs, may want to leave hospital due to being unaware of they problem
26
Define agnosia
- lack of awareness of sensation or perception
27
What cognitive areas do sensory association areas talk to
- Cognitive areas associated with memory, attention, judgement, motivation, and emotion to plan for strategies to deal with perceptions
28
Motor components within action system in order
- Motor planning areas
- Execute movement plan through primary motor cortex
- Descending motor pathways specify muscles (amplitude, timing, force)
- Modify/refine movement if needed
29
Components of the motor system
- Primary motor cortex (M1)
- 2 motor planning areas: Supplemental motor cortex (SMA) and premotor cortex
- Subcortical structures: basal ganglia & cerebellum to plan/coordinate movements
- Spinal cord & peripheral neuromuscular system
30
Primary motor cortex (M1) connections
- one-to-one connection (somatotopy) to the level of single motor neuron in spinal cord
- convergent & divergent parallel pathways are possible: one cortical site can connect to a bunch of motor neurons & one muscle can also be connected to many neurons in a cortical site
- important for recovery after injuries
31
Motor cortex encodes motor plans
- Motor cortical neurons have directional preference: maximally activate with specific movements and activates less optimally with others
- movement is controlled by neurons where the sum total of vectors of those neurons could predict direction & amplitude of movement
- same set of neurons are not always used for a particular directional movement (picking up an object vs hand gesture)
32
Clinical relevance of motor cortex encoding motor plans
- different pathways/connections exist which brings specificity of task
- training one particular movement doesn't automatically transfer to other tasks
- we need to train tasks to improve motor control not just joint movements
33
Role of the supplemental motor area
- involved with controlling internally generated movements, learned motor programs, but can transfer those programs to primary motor cortex (M1) after extensive training
- anticipated movements
34
Role of the premotor area
- controls movements activated by external stimuli (visual cues)
- 2 pathways from parietal-occipital areas to premotor area to control reaching & grasping
35
Describe reaching pathway
- from parietal-occipital lobe to dorsal premotor area uses visual info to locate object to control reaching
36
Describe grasping pathway
- from dorsal extrastriate area of occipital lobe to ventral premotor area uses visual info to judge shape, size, of object to control grasping
37
Functional roles of basal ganglia for movement control
- planning of internally generated movements
- initiate movements without external stimuli
38
Functional roles of cerebellum for movement control
- movements triggered by external stimuli
