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FN Unit 2 > #16 Neuromotor System > Flashcards

#16 Neuromotor System Flashcards

1
Q

Motor Cortex Inputs, Outputs

A
  • Gives rise to corticobulbar and corticospinal tracts
  • Input:
    • Premotor cortex
    • Ventrolateral thalamus
  • Output: (via Corticobulbospinal tracts)
    • Local circuit neurons (CPGs)
    • Motor neuron pools
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2
Q

Premotor Cortex Input, Output

A
  • Planning, executing, directing voluntary movements
  • Consistes of premotor area (PMA) and supplementary motor area (SMA)
  • Input:
    • Non-motor cortical areas
    • Ventral anterior thalamus
  • Output:
    • Motor cortex
    • Basal ganglia
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3
Q

Non-Motor Cortical Areas, Input, and Output

A
  1. Visual Cortex: Visual guidance of movements
  2. Parietal Cortex: Integrates visual, proprioceptive, and mechanosensory signals
  • Input:
    • Premotor cortex
  • Output:
    • Premotor cortex
    • Basal ganglia
    • Cerebellum
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4
Q

Side Loop Structures

A
  • Basal Ganglia
  • Cerebellum
  • Thalamus
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5
Q

Basal Ganglia Function, Input, Output

A
  • Side Loop structure
  • Initiates movements, suppresses non-synergistic movements, “chunks” element into action sequences (muscle memory for patterns of movement)
    • Consolidation of procedural memory
    • Activation of internally generated movements
    • Automation of movements
  • Input:
    • Non-motor cortical areas
    • Premotor cortex
  • Output:
    • Ventral anterior thalamus
    • Pedunculopontine nucleus (PPN)
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6
Q

Cerebellum Function, Input, Output

A
  • Side Loop structure
  • Coordinates movements and corrects error in performance (move smoothly, accurately)
  • Input:
    • Non-motor cortical areas
    • Brainstem UMNs
    • Proprioceptive feedback
  • Output:
    • Ventrolateral thalamus
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7
Q

Thalamus Input, Output

A
  • Input:
    • Basal ganglia
    • Cerebellum
  • Output:
    • Premotor cortex
    • Motor cortex
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8
Q

Brainstem Components

A
  1. Brainstem UMNs: Extrapyramidal pathways adjust tone
  2. Pedunculopontine Nucleus: midbrain locomotor center activates spinal pattern generators for stepping/locomotion
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9
Q

Brainstem UMN Function, Input, Output

A
  • Extrapyramidal pathways adjust tone (partial contraction of a muscle) and posture
  • Input:
    • PPN
    • Cerebellum
  • Output: via reticulospinal & vestibulospinal path?
    • Local circuit neurons (CPGs)
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10
Q

Pedunculopontine Nucleus Function, Input, Output

A
  • Midbrain locomotor center activates spinal pattern generators for stepping/locomotion
  • Input:
    • Basal ganglia
  • Output:
    • Brainstem UMNs
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11
Q

Local Circuit Neurons

A

?

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12
Q

Motor Neuron Pools

A

?

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13
Q

Skeletal Muscles Function, Input, Output

A
  • Move the body
  • Input:
    • Motor neuron pools
  • Output:
    • Proprioceptive feedback
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14
Q

Proprioceptive Feedback Function, Input, Output

A
  • Sensory consequences of movement
  • Input:
    • Skeletal muscles
  • Output:
    • Cerebellum
    • Local circuit neurons (CPGs)
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15
Q

Types of Muscle Spindle Stretchable Fibers

A
  1. Nuclear chain fibers: deformation signals info about static length of muscle
  2. Nuclear bag fibers: deformation encodes rate of change of muscle length
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16
Q

2 Muscle Spindle Afferent Types

A
  1. Type Ia
    • Wrap around both types of fibers (nuclear chain AND bag) to provide info to CNS about muscle length and velocity
    • Dynamic, fast-adapting, fast-conducting
    • Involved in monosynaptic (deep tendon) reflex
  2. Type II
    • Only innervate nuclear chain fibers, so only signal muscle length
    • Static, slower-adapting, active during steady state
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17
Q

Types of Motor Neurons and Where their Axons End

A
  • Alpha: axons end in motor end plates of contractile muscle units
  • Gamma: axons end in contractile end portions of muscle spindles
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18
Q

Premotor Area Function, Input, Output

A
  • Input:
    • Parietal cortex (PC) - sensory
    • Dorsolateral prefrontal cortex (DLPFC) - cognitive
    • Supplementary motor cortex (SMA) - cognitive
    • Basically, integrates “where is the world” (parietal) and “what do I want to do about it?” (DLPFC)
  • Projects mainly to the primary motor cortex (M1) which is responsible for control of individual muscles via the corticospinal system
  • Forms part of a neural network that integrates sensory and cognitive info into goal-directed actions
  • Is involved in planning and preparing movements in response to external cues, particularly visual cues
  • Also represents “ownership” of the limbs and perception of their movements (sense of agency)
19
Q

Side Loop Structures & Function

A
  • Basal Ganglia: initiates movement
  • Cerebellum: coordinates movement & corrects errors
  • Thalamus: relay center
20
Q

Brainstem Components & Functino

A
  • Brainstem UMNs
    • Partial contraction of muscles for tone, posture
  • Pedunculopontine Nucleus
    • Activation of locomotion pattern generators
21
Q

Functional Effector Groups & Function

A
  • Local Circuit Neurons
    • CPGs in reticular core
  • Motor Neuron Pools
    • LMNs innervating whole muscles for contraction
  • Skeletatl muscles
  • Proprioceptive feedback
22
Q

Pyramidal vs Extrapyramidal

A
  • Pyramidal: corticospinal tract because it decussates in the pyramids
  • Extrapyramidal: all other descending motor systems
23
Q

Alpha Motor Neurons: Distal vs Proximal

A
  • Distal muscles: AMNs receive
    • Pyramidal (lateral corticospinal tract) input
    • Fine control
  • Proximal/Axial muscles: AMNs receive
    • Extrapyramidal (vestibulospinal, reticulospinal, tectospinal) input
24
Q

Motor Unit

A

Single alpha motor neuron + extrafusal muscle fibers (that the AMN innervates)

25
Q

Extrafusal muscle fiber

A
  • Standard skeletal muscle fiber innervated by AMN
  • Generate tension by contracting, thereby moving skeletal muscles
  • As opposed to intrafusal muscle spindles embedded wihthin the muscle fiber
26
Q

Contractile force of a motor unit

A

force-generating capability of muscle fiber types (slow or fast twitch)

x

of fibers innervatd by the alpha motor neuron

27
Q

Fast vs slow twich

A
  • Slow twitch: contracts for longer periods of time, but lower force
  • Fast twitch: contracts quickly/powerfully, but fatigues very quickly
  • Important in determining the contractile force of a motor unit ( x # of fibers innervated by AMN)
28
Q

Rate Code

A
  • Rate of action potential generation
  • Increased rate code = increased muscle force of up to 4x
29
Q

Size Principle

A
  • With increasing strength of input, motor neurons in a motor pool are recruited from smallest size to largest
    • Because smaller neurons are easier to depolarize
  • Small neurons innervate slow-twitch fibers = postural control
  • Medium neurons innervate fast-twitch, fatigue resistant fibers = normal movement
  • Large neurons innervate fast-twitch, fatigable fibers = burts of movement
30
Q

Motor Pool

A
  • Collection of all motor neurons (motor units) that innervate a single muscle
  • Arranged in columns
  • Somatotopically organized:
    • Dorsal: flexor
    • Ventral: extensor
    • Medial: axial/proximal (ex: trunk)
    • Lateral: distal (ex: hand)
31
Q

Biceps Brachii nerve & SC levels

A
  • Musculocutaneous nerve of brachial plexus
  • Motor pool locates in C5-C6
32
Q

Intrafusal Muscle Fibers

A

Proprioceptive muscle spindles embedded in parallel with muscle fibers

33
Q

Muscle Spindle Function

A
  • Respond to muscle stretch
  • Afferent: report back to DRG
  • Facilitate maintance of muscle tone
    • Muscle tone = partial contraction of extrafusal muscle fibers
34
Q

Muscle Spindle Fiber Types

A
  1. Nuclear chain fibers
    • Signal static muscle length
  2. Nuclear bag fibers
    • Signal rate of change (velocity) [of muscle length]
35
Q

Muscle Spindle Ending Types

A
  • Type Ia
    • Provide info to CNS about muscle length AND velocity
      • So, wrap around both nuclear chain and nuclear bag types.
    • Dynamic, fast-adpating, fast-conducting
  • Type II
    • Provide info to CNS about muscle length only
      • So,w rap around nuclear chain fibers only
    • Static, slower-adapting (though also fast-conducting)
    • Active during steady state after change in muscle length
36
Q

Alpha, Gamma motor neurons end on…

A
  • Alpha: motor end plants of contractile muscle units
    • EXTRAFUSAL
  • Gamma: contractile end portions of muscle spindles
    • INTRAFUSAL
    • Keep muscles taut
37
Q

Propriospinal Neurons

A
  • Are made of yoked sensory and motor neurons
  • Constitute circuit pattern generators (CPGs)
  • Live in reticular core/intermediate zone of SC
  • Project axons across different levels of SC
  • Every alpha, gamma motor neuron is engaged by many propriospinal interneurons
38
Q

Central Pattern Generators

A
  • Generate patterns of rhythmic activity (even in absence of external feedback or supraspinal control)
    • Supraspinal input = corticospinal, rubrospinal, vestibulospinal
  • Live in SC intermediate zone/reticulare core
  • Are made of propriospinal interneuons (=yoked sensory, motor (both alpha and gamma) neurons
  • Input: peripheral sensory fibers, supraspinal neurons
  • Output: mostly inhibitory to alpha and gamma motor neurons
39
Q

SC Intermediate Zone

A
  • AKA reticular core
  • Home of CPGs
    • Home of propriospinal interneurons
40
Q

Types of CPG Movement

A
  1. Voluntary: volitional and fractionated movements
  2. Stereotypic: hard-wired from birth like grasping, walking, crawling
  3. Postural: automatic corrections, based on cerebellum and control of gamma motor neurons to increase tone
41
Q

Premotor Area

A
  • Part of premotor cortex
  • Heavily influences M1
  • Also has some direct influence over SC via corticospinal tract
  • Involved in planning and preparing movements in response to external cues, particularly visual
  • Integrates the following inputs:
    • Parietal cortex = sensory
    • Dorsolateral prefrontal cortex = cognitive
    • Supplementary motor area = cognitive
42
Q

Supplementary Motor Area

A
  • Part of the premotor cortex
  • Appears to be involved in internally generated movements
  • Heavily influence M1
43
Q

Medulla, Pons Reticular Formation Function

A
  • Contain interneuons which interact with moro neurons in brainstem tegmentum
  • Regulate stereotypic movements of the head:
    • Swallowing
    • Respiration
    • Coughing
    • Vomiting
    • Chewing

FN Unit 2 (11 decks)

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