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Physio > Pt13 Central Control Of Movement > Flashcards

Pt13 Central Control Of Movement Flashcards

1
Q

What are the 2 forms movement can be divided into?

A
  1. Flexor muscles
    -learned, voluntary, conscious, skilled
    -discrete contraction of few muscle groups
    -distal to spinal cord
  2. Extensor muscles
    -postural, antigravity, subconscious, involuntary
    -long term contraction of lg group of muscles
    -located closer to spinal cord (proximal & axial)
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2
Q

How are the 2 types of movements controlled?

A

by the nervous system
-FLEXORS: lateral system (lateral funiculus) of lower & upper motor neurons
>UMN tracts inhibitory to extensors, facilitatory to flexor
>corticospinal
>rubrospinal
>medullary reticulospinal
-EXTENSORS: medial system (ventral funiculus) of neurons & tracts
>UMN tract inhibitory to flexors, facilitatory to extensors
>pontine reticulospinal
>vestibulospinal

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3
Q

What is the organization of the CNS structures that control movement?

A
  1. Simple movement/movement patterns
    -caudal regions of CNS
  2. Complex/skilled patterns
    -rostral regions of CNS
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4
Q

What is voluntary movement directed by?

A

-primary motor cortex
-initiated by CC
>cerebellum
>basal nuclei
>spinal cord
>brainstem

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5
Q

Describe the higher level VS lower level motor system hierarchy.

A
  1. Higher order: action, sequence of actions, coordination of activity of limbs
    >CC, cerebellum, basal nuclei
  2. Lower order: force & velocity of muscles, changes in posture
    >LMN, brain stem, spinal cord
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6
Q

Describe the spinal cords role in movement control.

A

-contain alpha LMN innervating skeletal muscle
-interneurons & complex neural circuits = spinal reflexes
-low level commands = generate forces on muscle groups
>LMN can recruit more motor units or increase freq of AP to control amount of force on muscle
># of muscle fibers innervated by LMN decreases as need for fine control of muscle increases

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7
Q

How is posture maintained by the motor system?

A
  1. Tonic excitatory bias to motor circuits that excite extensor muscles (antigravity)
    stretch reflex = contracts extensor muscles whenever stretched by postural changes
  2. Modulate stretch reflex circuits
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8
Q

Describe the gamma loop.

A

CNS modulates stretch reflex & muscle tone by modulating the gamma loop
-higher motor center via reticulospinal tract activates gamma motor neuron innervating the muscle spindle
-causes increase in firing of sensory fibers
-excitation of alpha motor neuron innervating the extensor muscle = contraction

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9
Q

Describe the relationship between postural support & the stretch reflex.

A

-the quads, hock extensor muscles, & hepaxial & hypaxial muscles stretched by gravity = reflex stimulated contraction & posture support

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10
Q

Describe what walking depends on.

A

-know initial starting position & force applied to limb
-proprioceptive info by golgi tendon & muscle spindles (also imp for spinal reflexes - motor control)
-walking = extension & flexion via spinal cord reflexes
>stretch reflex -> (muscle spindle) contracts muscle being stretched
>inverse stretch reflex -> (golgi tendon) relaxes muscle being tensioned
>withdrawal/flexor reflex -> (proprioceptive & nonproprioceptive receptors) flexion of limb being stimulated
modulated by cortex

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11
Q

Describe the crossed-extensor reflex.

A

-0.2-0.5s after stimulus = withdrawal reflex in one limb & opposite limb extends
-works in coordination with withdrawal reflex to avoid loss of balance when limb is flexed
-balance & body posture maintains anytime limb is flexed
-physiological when walking but pathological during neuro exam = UMN lesion

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12
Q

Describe the positive supportive reaction.

A

-pressure in footpad causes limb to extend against pressure applied to foot
-complex circuit in interneurons
-keeps animal from falling to that side

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13
Q

Describe why muscle tone is important.

A

-maintains posture
-support for joints to stabilize their position
-muscle resistance to being stretched
-regulated by local spine reflexes (muscle spindle/golgi tendon) & by higher levels of brain (gamma loop)
-muscle tone examined in neuro exam via the extensor tone
-apply pressure to palmer/plantar surface of pelvic/thoracic limbs
-animals should flex when pressure is applied
>extensor tone increase (rigid/hypertonic) = UMN lesion - inhibition from UMN is lost
>tone is decreased (flaccid/hypotonic) = LMN lesion = direct control from LMN is lost

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14
Q

Describe what the reflex circuitry within the spinal cord is based on.

A

-stepping & oscillation between extension/flexion & weight bearing/non weight bearing = based on reflex circuitry within cord

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15
Q

Describe the neuronal networks of the CNS.

A

-produce oscillatory outputs
-control rhythmical motor activity
-dependent on groups of spinal interneurons
>locomotion, scratching, chewing, barking
>’central pattern generators’
>excitatory/inhibitory neurons
*CPG’s of locomotion & scratching = neuronal circuit in spinal cord intumescence (spinal cord reflexes)
*control centers that initiate & terminate the rhythmical activity = brainstem

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16
Q

Where does sensory input for the reflexes come from?

A

-muscle spindle
-golgi tendon
-joints
-tactile receptors
>integration of input in spinal cord causes inhibition/excitation of LMNs
—in same/opposite limb or limbs of other girdle
activity of muscles of trunk, neck & tail = interlinked

17
Q

Describe proprioceptive input.

A

-proprioceptive input to forebrain = conscious awareness of posture & movement
-coordination of motor activity
-activates reflexes & sends sensory info to cerebellum

18
Q

Describe the LMN & UMN of the muscle activity in the body.

A

-LMN = stimulated/inhibited by both reflex connections & input from UMN
-UMN = initiate, modify, terminate muscle activity
*extrapyramidal tract [brainstem] = (quadruped) gait & movement
*pyramidal tract [corticospinal] = voluntary skilled movement

19
Q

What are the 2 major descending motor system pathways from brain to spinal cord?

A
  1. Brainstem UMN pathway ‘extrapyramidal’
    -4 diff tracts
  2. Corticospinal ‘pyramidal’
    -motor cortex & cord
20
Q

What is the major role of the medial pathways?

A

-maintain body subconsciously in an upright position against the pull of gravity
-control of axial & proximal extensor muscles
>bilateral control
>prevent from falling to ground

21
Q

Describe the vestibulospinal (medial).

A
  1. Vestibulospinal
    -regulate antigravity muscle tone
    -sensory info from vestibular system (acceleration of head)
    -body position
    -disturbances of balance
22
Q

Describe reticulospinal tract. (Medial)

A

-antigravity muscle tone
-speed & rhythm of walking
-consciousness
-pain perception, respiration, circulatory

23
Q

Describe the tectospinal tract. (Medial)

A

-reflex orientation of head toward environmental stimuli (rapid reflex movement of eyes)
-axons project at the upper cervical regions of spinal cord (muscles that move the head)
-process visual, auditory, somatosensory info about position of stimuli
coordinate head & eyes so gaze is fixed on stimulus

24
Q

Describe the main function of the lateral brainstem pathway.

A

-controls distal limb muscles associated with movement
-rubrospinal tract
>unilateral control of muscles (flexors with skilled movements)
>input from higher levels of motor system + cerebellum (synchronizes muscle by fine tuning movement initiated by the corticospinal tract)
>motor cortices influence indirectly the spinal LMNs

25
Q

Describe the Palpebral reflex.

A

-coordinated by brainstem
-CN V trigeminal
-CN VII facial
-eye & vestibular apparatus
-reflex organized at brainstem without control from other levels of motor system
-brainstem receives direct input from sensory organs in face & head

26
Q

Describe the corticospinal tract.

A

-from CC to spinal cord
-skilled voluntary movement (derived from synaptic termination pattern of axons)
-decussation of axons at ventral surface of medulla
>lesion to motor cortices on one side of body effects the voluntary movement of distal flexor musculature on opposite side of body
-axons bypass brainstem motor pathway to cord & premotor neurons of spinal cord
>contact alpha motor neuron directly
>corticospinal neuron controls smaller #s of alpha neurons
>increases dependence of actions of diff muscles
—move individual fingers instead of all together

27
Q

What is cerebellums role in muscle activity?

A

-coordinates agonistic (tensed) & antagonistic (relaxed) muscle activity
-permits posture
-creates movement that occurs at the correct rate, range, force

28
Q

Describe the cerebellum & posture.

A

-extensors
-contraction/relaxation muscle used for posture (at rest & during movement)
-failure to establish a posture prevents normal coordinated movement
cerebellum doesn’t initiate movement, the motor cortex does for voluntary movement

29
Q

Describe the cerebellum during movement.

A

-coordinates initiation of movement, the movement itself, & termination of movement
-during movement, proprioceptive input from body informs cerebellum how much movement occurred, how fast, and how forceful
-cerebellum compares the achieved movement with the planning info received about that movement
-determines when correct range of movement is achieved & when the action should be terminated

30
Q

Describe voluntary learned movement planning.

A

-occurs in executive motor planning areas of brain
-integration/interpretation areas associated with sensory receiving areas
>visual cortex
>somatosensory cortex
-memory & behavior centers

31
Q

Describe what the cerebellum does with planned movement.

A

-establishes appropriate postural platforms
-feeds back to motor planning centers to inform them the posture has been made
-executive centers then:
>direct pyramidal & extrapyramidal tracts
>movement is initiated

32
Q

Describe ataxia.

A

-inability to coordinate position of head, trunk, limbs
-incoordinated movements
-localizes lesions in NS

33
Q

Describe vestibular ataxia.

A

-head tilt, leaning, rolling, circling, strabismus, nystagmus peripheral CN XIII [vestibular]
-mental status change (ex. Somnolence) & proprioceptive deficits (knuckling) central [brainstem & cerebellum]

34
Q

Describe cerebellum ataxia.

A

-dysmetria / hypermetria
-inability to control rate & range of stepping movements
-head & body tremors, intentional tremors, wide pelvis limb stance & gait
pure cerebellar ataxia doesn’t show conscious proprioceptive deficits = differentiates from proprioceptive ataxia

35
Q

Describe proprioceptive or sensory ataxia.

A

-spinal cord diseases (white matter)
-NO head tremor/tilt
-dysfunction of sensory tracts carrying unconscious proprioception
>dorsal, ventral, cranial spinocerebellar tracts, cuneocerebellar tract
-truncal sway (wobbliness) & abnormal limb stance & gait
-abduction, abduction of limbs crossing as they walk

Physio (35 decks)

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