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NEURO > Functional hierarchy of motor control > Flashcards

Functional hierarchy of motor control Flashcards

1
Q

what is responsible for direct control of muscles

A

a motoneurones

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2
Q

where do reflexes occur

A

autonomously at each segmental spinal level

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3
Q

what are higher order reflexes and what do they control

A

spinal reflexes that have been integrated at the brainstem nucleii

involve trunk and limb muscles

control posture and balance

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4
Q

what do the brainstem nucleii control

A

cerebral cortex
basal ganglia
cerebellum

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5
Q

what are the 4 systems that control movement

A

descending control pathways
basal ganglia
cerebellum
local spinal cord and brainstem circuits

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6
Q

what do lower motor neurones do

A

innervate muscles, initiate reflexes, voluntary movements

all at the SPINAL LEVEL

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7
Q

what do LMN lesions cause

A

flaccid paralysis and muscle atrophy

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8
Q

what do upper motor neurones do

A

synapse with lots of lower circuit neurones and REGULATE a motoneurone activity

in the BRAINSTEM OR CORTEX

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9
Q

what do UMN lesions cause

A

spasticity, paralysis, spastic paralysis

if corticospinal lesion = weakness not paralysis

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10
Q

how is the spatial map of the body in the spinal cord arranged

A

medio-laterally

eg proximal shoulder = medial motoneurones
eg finger muscles = lateral motoneurones

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11
Q

what input does the spinal cord receive

A

descending input via neurones in the brainstem

direct cortical input from the corticospinal/pyramidal tracts

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12
Q

where does sensory input enter

A

at all levels

spinal cord, brainstem and cortex

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13
Q

what is the sensory input at the spinal cord

A

proprioception, touch, pain

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14
Q

what is the sensory input at the brainstem

A

balance from the vestibular system

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15
Q

what is the sensory input at the cortex

A

visual, olfactory, auditory, emotional, intellectual

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16
Q

what does damage to sensory inputs at the spinal cord cause

A

paralysis as if the motoneurones were damaged

17
Q

what is a reflex arc

A

the nerve pathway involved in reflex action

18
Q

what is the stretch reflex

A

simplest form of reflex - involves a sensory nerve, a motor nerve and the synapse between them

in every muscle in the body e.g. patellar tendon reflex

19
Q

what happens during the stretch reflex

A
  1. initial stimulus - muscle stretch in spindles
  2. excitatory afferent impulse - stretch receptor to spinal cord
  3. excitatory efferent impulse to a motoneurone - causes contraction of stretched muscle
  4. inhibitory efferent impulse to antagonist muscle - dampened action - reciprocal inhibitio
20
Q

what spinal levels can different reflexes test for

A

biceps jerk = C6
triceps jerk = C7
patellar tendon = L4
achilles tendon = S1

21
Q

what can reflexes help detect

A

level of spinal cord damage

impaired reflex areas = areas of nerve damage

22
Q

what must you be sure to do when testing reflexes

A

distract patient to avoid voluntary influence

23
Q

what is the flexor (withdrawal) reflex

A

polysynaptic and protective reflex that uses info from pain receptors (nociceptors) to withdraw the body away from painful stimuli

24
Q

what is the flexor-crossextensor reflex

A

when painful stimuli very large - larger response from flexor reflex
e.g. move whole arm and side of body away

if that is the only action - loss of balance - can fall

so when flexor response is large in ipsilateral side of body - cross extensor action of the contralateral side of the body occurs to maintain balance
e.g. move right side back - extend left leg to balance

25
Q

what are the steps that occur in the flexor-crossextensor reflex

A
  1. increased sensory APs from stimulated nociceptors
  2. excitatory afferent impulse to spinal cord
  3. excitatory efferent impulse to flexor muscles
  4. inhibitory efferent impulse to extensors
  5. excitatory interneurones cross spinal cord to excite contralateral extensors
  6. inhibitory interneurones cross spinal cord to inhibit contralateral flexors 7. sensory info ascends to brain
26
Q

why is the flexor reflex slower than the stretch reflex

A

nociceptor fibres smaller that spindle afferents - conduct more slowly

27
Q

how does a heavy load affect muscle spindles

A

causes them to stretch - causes a reflex contraction to restore arm position

28
Q

how does an excessively heavy load affect the muscle spindles

A

causes them to over stretch - causes activation of the golgi tendon organ reflex - causes muscle to relax as a protective mechanism

29
Q

what can cause spastic muscles

A

high gamma motoneurone activation of muscle spindles - muscles can’t stretch easily (?over contraction of muscles)

30
Q

what are the clinical relevances of reflexes

A

assess the integrity of the spine

spinal level localisation of problem - reflexes occur above but not below problem

31
Q

what is facilitation

A

when the larger the pain stimulus - the greater the spinal spread - so the larger the response

occurs between similar and diverse fibres e.g. between pain fibres
e.g. between pain fibres and spindle fibres

32
Q

how does facilitation work

A

pain fibre input acts to facilitate muscle spindles by maintaining a motoneurons in a more depolarised state = larger response

33
Q

what is Babinskis sign and how is it elicited

A

toes fanning up and out (extension) when

stroking of the lateral aspect of the sole of the foot

34
Q

what is the normal response to stroking the underside of the foot

A

toes curl in - flexion

35
Q

when is Babinskis sign seen

A

damage or disruption to CS tract

<1 year old infant - motor system not fully developed

after en epileptic seizure - transient cortical function disruption

36
Q

what are the effects of spinal transection

A

immediate sensory and autonomic effects

  • decreased sensation
  • decreased bowel, bladder and sexual function
37
Q

what is spinal shock

A

loss of supra spinal excitation

38
Q

what can be seen in spinal shock

A

loss of reflexes for 2-6 weeks
gradual return
exagerated reflexes

39
Q

what is clonus

A

stretch causes oscillatory muscle contration and relaxation

NEURO (51 decks)

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