Neuro: 3.01 - Motor Systems - Overview

Front 1

What is the relationship between the sensory and motor system pathways?

Back 1

Very similar except flipped "backward"

Front 2

What is the route of information through the sensory system?

Back 2

- Information enters at receptors
- Transformed into neural signals
- Ascends through neural pathways (tracts) to cortex
- Generates internal representation of world

Front 3

What is the route of information through the motor system?

Back 3

- Begins in cortex with internal representation of desired movement
- Programming starts in cortex through lower levels of CNS
- Information converted to contractile force in muscles

Front 4

What are the characteristics of motor control?

Back 4

- Hierarchical - small/simple elements at spinal cord, more integrated/complex at higher levels (cortex and brainstem)
- Parallel - redundant
- "Final Common Pathway" - motor neuron that controls movement

Front 5

What influences the Final Common Pathway?

Back 5

- Higher motor commands / different levels
- Sensory input

Front 6

What are the three major components and levels of control of the motor system?

Back 6

1. Spinal cord/motor neurons (bottom)
2. Brainstem
3. Cortex (top)

Front 7

What structures modulate the cortex, brainstem, and spinal cord components of the motor system?

Back 7

Subcortical Structures:
- Basal Ganglia
- Cerebellum

Front 8

What structure is a relay station for information?

Back 8

Thalamus

Front 9

What does the thalamus relay information between?

Back 9

- Basal ganglia --> Cortex
- Cerebellum --> Cortex

Front 10

What are the components of the Basal Ganglia?

Back 10

- Caudate Nucleus
- Putamen
- Globus Pallidus
- Substantia Nigra
- Subthalamic Nucleus

Front 11

What are the two types of spinal cord neurons related to the motor system?

Back 11

- Lower motor neurons
- Interneurons

Front 12

Location of lower motor neurons? Function?

Back 12

- Cell bodies in ventral horn
- Project to muscles
- Ultimately cause muscle contraction and execute movement
- Final Common Pathway of motor system

Front 13

Somatotopy of lower motor neurons?

Back 13

- Medial innervate Proximal muscles controlling balance, posture, movement of trunk
- Lateral innervate Distal muscles controlling limbs and digits

Front 14

Where are interneurons located? Function?

Back 14

- Start in intermediate zone
- Segmental interneurons project within a single spinal cord level
- Propriospinal interneurons that transmit info between multiple spinal cord levels; project to motor neurons
- Form circuits that help connect and coordinate motor neurons

Front 15

What is the function of the brainstem in the motor pathway?

Back 15

Modulates the action of spinal motor circuits

Front 16

What are the two types of (motor) neurons in the brainstem?

Back 16

- Lower motor neurons - directly innervating muscles in head and face
- Upper motor neurons - send axons down to spinal cord and modulate spinal cord (lower motor neurons and interneurons)

Front 17

Where are the cell bodies of lower motor neurons that control the extraoccular muscles?

Back 17

Occulomotor nucleus in brainstem

Front 18

Where are the cell bodies of lower motor neurons that control the tongue?

Back 18

Hypoglossal nucleus in brainstem

Front 19

Where are the cell bodies of lower motor neurons that control facial expression?

Back 19

Facial nucleus in brainstem

Front 20

What pathways do the upper motor neurons that are descending from the brainstem pass through?

Back 20

Medial and Lateral Descending Brainstem Pathways (Tracts)

Front 21

What are the Medial Brainstem Pathways?

Back 21

- Reticulospinal: from reticular formation to spinal cord
- Vestibulospinal: from vestibular nuclei to spinal cord
- Tectospinal: from tectum (superior colliculus) to spinal cord

Front 22

Where do the reticulospinal, vestibulospinal, and tectospinal tracts pass? What do they innervate?

Back 22

- Begin at brainstem at respective locations
- Descend in medial ventral white matter
- Terminate in ventromedial area of ventral spinal cord
- Influence axial/proximal muscles

Front 23

What do the reticulospinal, vestibulospinal, and tectospinal tracts control?

Back 23

Basic postural control upon which cortical motor areas can organize more highly differentiated movement

Front 24

What are the Lateral Brainstem Pathways?

Back 24

Rubrospinal Tract (main one): Red nucleus to spinal cord

Front 25

Where does the rubrospinal tract pass? What does it innervate?

Back 25

- Starts at red nucleus in brainstem
- Descends in dorsolateral white matter
- Terminates in dorsolateral area of ventral spinal cord
- Influences motor neurons controlling distal muscles of limbs

Front 26

What does the rubrospinal tract control?

Back 26

Modulate goal-directed limb movements like reaching and manipulating

Front 27

What is the function of the cerebral cortex in the motor system? What kind of neurons?

Back 27

- Modulates action of motor neurons in brainstem and spinal cord (top of hierarchy)
- Gives us ability to organize complex motor acts and execute fine movements w/ precision
* Via Upper Motor Neurons

Front 28

What are the major areas of cerebral cortex involved in motor control?

Back 28

- Primary Motor Cortex (red, #4)
- Premotor Cortex (orange, #6)
- Supplementary Motor Area (purple, #6)

Front 29

What is the function of the Primary Motor Cortex?

Back 29

- Executes commands to motor neurons
- Controls individual finger movements
- Coordinates force and direction of movements
- Contains somatotopic map of body

Front 30

What does electrical stimulation of discrete spots on the primary motor cortex cause?

Back 30

Movement of specific body parts on opposite side

Front 31

What is the function of the Premotor Cortex?

Back 31

- Integrates motor movements w/ sensory input (especially visual system)
- Coordinates complex sequences of movement (motor learning)

Front 32

What is the function of the Supplementary Motor Area?

Back 32

- Important for internally-driven, will-driven movements
- Formulate an intention to make a movement

Front 33

What is the role of the Primary Somatosensory Cortex (S1) to the motor system?

Back 33

Regulates incoming sensory information from dorsal horn of spinal cord (from medial lemniscus and anterolateral tracts)

Front 34

What is the role of the Posterior Parietal Complex in the motor system?

Back 34

- Helps localize where object is with respect to body
- Helps motor system reach in right direction for an object

Front 35

What changes the blood flow in the cerebral cortex (related to motor system)?

Back 35

- Simple movements (A)
- Complex movements (B)
- Mental rehearsal of complex movements (C)

Front 36

What area is important for planning and learning complex, internally-generated movements?

Back 36

Supplementary Motor Area

Front 37

What changes in blood flow occur after a simple movement (flex left index finger)?

Back 37

Increased blood flow to right hemisphere (opposite side) in primary motor cortex

Front 38

What changes in blood flow occur after a complex movement (touch each finger of left hand to thumb)?

Back 38

- Increased blood flow to right hemisphere (opposite side) in primary motor cortex
- Increased blood flow also to supplementary motor area (both sides)

Front 39

What changes in blood flow occur after mentally rehearsing a complex task (touch each finger of left hand to thumb)?

Back 39

- Increased blood flow to supplementary motor area (both sides)
- No increased blood flow to primary motor cortex

Front 40

What are the two descending pathways by which the cerebral cortex acts on motor neurons? Functions?

Back 40

- Lateral corticospinal tract / Pyramidal system (through dorsolateral white matter to lateral ventral horn) - contralateral limb, digits; goal-directed reaching
- Ventral corticospinal tract (through ventromedial white matter to medial ventral horn) - neck, trunk muscles; postural control

Front 41

What is the importance of having parallel motor pathways between the cortex and spinal cord (corticospinal tracts) and brainstem and spinal cord (brainstem tracts)?

Back 41

- When cortical, brainstem, or spinal cord lesions occur, alternative pathways can partially compensate and carry out motor tasks such that the person can still have basic motor functions
* Gives flexibility and plasticity after injury

Front 42

What is the somatotopic organization of the primary motor cortex?

Back 42

- Feet and legs most medial
- Face and tongue most lateral
(Motor is more fragmented than somatosensory)

Front 43

What is the importance of having a hierarchical arrangement of the motor system?

Back 43

- Reflexes are fast and automatic
- Cognitive motor activities take more time, energy, and neural processing
- Preserved for more complicated tasks

Front 44

What are the three general types of movement?

Back 44

- Reflex movements
- Automatic postural adjustments
- Voluntary movements

Front 45

What kind of movement is mediated by "reflex movements"?

Back 45

- Simple, involuntary, unconscious coordinated patterns of muscle contraction and relaxation evoked by peripheral stimuli
- Involves spinal cord, motor neurons, and sensory neurons
-

Front 46

Why are "Reflex Movements" important?

Back 46

- Higher level motor control systems make use of simple reflex circuitry to coordinate muscles during complex, purposeful movements
- Reflexes are tested clinically to diagnose level of lesions/damage

Front 47

What kind of movement is mediated by "automatic postural adjustments"?

Back 47

- More complex, more flexible than simple reflexes
- Involves brainstem, spinal cord, motor neurons
- Descending motor pathways from brainstem to motor neurons make a compensatory shift in mass to maintain balance following input from vestibular system

Front 48

What system conveys information about your posture to your brain?

Back 48

Vestibular system (inner ears) in midbrain

Front 49

How does the context play into the automatic postural adjustment movement?

Back 49

If you are holding onto a rail while the boat rocks the motor pathway induces a smaller shift than if you were not holding anything

Front 50

What is the function of voluntary movements?

Back 50

- Purposeful acts / goal-directed
- Very flexible
- Involve cerebral cortex, brainstem, spinal cord, and motor neurons

Front 51

How do you improve your voluntary movements w/ practice?

Back 51

Nervous system learns to anticipate and correct for environmental obstacles

Front 52

What is the cost of voluntary movement relative to the other types of movement?

Back 52

- Response time is much longer than for reflexes
- Additional processing time and energy is required by multiple inputs from higher order CNS structures