Week 7: Movement Flashcards
What is Moravec‘s Paradox?
- discovery by AI and robotics researches
- High-level reasons requires very little computation
- Low-level sensorimotor skills require enormous computational resources
How many muscles do humans have?
Over 600
how can muscles be categorised?
Posture vs manipulation muscles
What muscles are under voluntary control?
Skeletal muscles
what muscles are not under voluntary control?
Cardiac muscles
Smooth muscles (e.g. peristaltic)
What are Tendons?
Bind muscle to bone
what are Ligaments?
Bind bone to bone
What are Antagonists? (Muscles)
While one Muscle is extended the antagonistic muscle is flexed and vice versa
What are the different type of motor neurons?
Upper motor neurons: originating in the cortex
Lower motor neurons: originating in spine and Innervate muscle
What is a motor unit?
Multiple muscle fibres that are innervated by one motor neuron
through what neurons passes the activation of muscles?
Lower motor neurons
-relationship between muscle fibres and motor neurons
- every muscle fibre is only innervated by one motor neuron (sparse mapping)
- One motor neuron can innervate multiple muscle fibres (motor unit)
how do motor neurons act?
They induce acetylcholine transmission in neuromuscular synapse (action potential) → changes length and tension of muscle fibre
What is the difference between the dorsal and ventral spinal cord?
Dorsal = sensory
Ventral = motor
What is a monosynaptic reflex?
- lower motor neuron directly connects to sensory neuron in spinal cord
- No cortical involvement
- E.g. patellar reflex
what is the patellar reflex?
Doctor raps knee → quadricep is stretched
→ stretch triggers receptors in muscle spindle to fire
→ sensory signal is transmitted through dorsal root of spinal cord and directly activates an alpha motor neuron to contract the quadricep
- the stretch reflex helps maintain stability of the limb following an unexpected perturbation
What are polysynpatic reflexes?
- complex coordination between sensory and motor neurons by interneurons at level of spinal cord
- E.g. pain in one leg leads to stabilisation by the other leg
what are interneurons?
modulate reflex loop
What are Spinal „pattern generators“?
- study to determine whether movement can be produces without top-down input to the spinal dort (cat on treadmill)
- Disconnect spinal cord from brain
- Cut dorsal root fibres
- Spinal cord can perform locomotion by itself
what are the different types of handedness and how likely are they?
- right dominant (~90%)
- Left dominant (~8%)
- Cross-dominant or mixed (~1%)
- Ambidextrous (~1%)
What is the Hierarchy of cortical control?
Area 6: Movement sequences
Area 4: Movement primitives
Posterior parietal cortex (area 5 and 7): sensory motor integration
S1: Somatosensory feedback
Cerebellum: motor learning/ fine-tuning/ coordination
What is part of the central motor system?
- pyramidal tract (because it goes through medullary pyramids)
- Brainstem: cranial nerves for critical reflexes
- Substantia nigra
- Basal ganglia: selection and initiation of actions
What are the principles of organization in the motor system?
- antagonism
- Somatotopy
- Contralaterality
- Closed-loop control
What does the hierarchical motor System look like?
Premotor and supplementary motor cortex regions
→
Motor Cortex
→
brainstem
→
Spinal cord
→
Output signals to muscles
- signals that descend down spinal cord trigger movement → motor efferent
- Copies of these signals that loop around in recurrent circuits in the CNS hold an efferent copy of the motor command → can use this to compare whether outcome of a movement is the same is intended movement
What is an Effector?
A part of the body that can move
What is Antagonism?
Antagonist pairs of muscles: one for flexing, the other for extending
What is Contralaterality?
Left hemisphere M1 controls right side of the body and vice versa
What is Somatotopy?
- electrical stimulation causes movement or jitter
- Overrepresentation (hands, mouth)
- Motor „homunculus“
- Representation corresponds to importance of action
What is closed-loop motor control vs open loop control?
Open loop = ballistic movement, no control over movement trajectory
Closed loop = guided movement, monitored and updated in real time and not only unidirectional command from M1 to muscles
What is the hierarchical control of action?
Action selection is performed at multiple levels
- conceptual: broad goal of behaviour
- Response system: selection of action to achieve conceptual goal
- Motor implementation: activation of the exact muscles in the right order
