Functional Hierarchy of the Motor System

Question 1

What allows direct control of muscle

Answer 1

Motor neurones in the spinal cord

in the final common path

Question 2

Where doe reflex occur

Answer 2

Autonomously at each segmental spinal levels

Question 3

Where does input to trunk and limbs arise from

Answer 3

Vestibulospinal and reticulospinal tracts

Question 4

What is the function of the basal ganglia in the motor system

Answer 4

Gating proper initiation of movement

Question 5

What is the function of the cerebellum in motor system

Answer 5

Sensory motor coordination of ongoing movement

-refinement

Question 6

What is the function of the cerebral cortex in the motor system

Answer 6

Planning, initiating and directing voluntary movements

Question 7

What is the function of brainstem in the motor system

Answer 7

Controls spinal reflexes and integrates them into higher order reflexes controlling posture and balance

Question 8

What controls the brainstem nuclei and stimulates voluntary movement

Answer 8

Cerebral cortex
(motor cortex, premotor and supplementary motor areas)

Basal ganglia

Cerebellum

Question 9

What four system control movement

Answer 9

Descending control pathway (motor cortex and brainstem)

Basal ganglia

Cerebellum

Local spinal cord and brainstem circuits

Question 10

Where are the Lower motor neurones found and what is their function

Answer 10

at spinal levels directly innervate muscles to initiate reflex and voluntary movements

Question 11

What is the result of lower motor neurones lesions

Answer 11

Flaccid paralysis

muscle atrophy - as no longer metabolically active

Question 12

What is the function of the upper motor neurones

Answer 12

synapse with multiple lower circuit neurones to regulate  motoneurone activity

Question 13

Where are upper motor neurones located

Answer 13

Brainstem or cortex

Question 14

What do the upper motor neurones from the cortex control

Answer 14

Spatiotemporal skilled movement

Question 15

Lesion is upper motor neurones in the cortex causes

Answer 15

Spasticity, some paralysis, may be transient

Question 16

Lesion specifically in the brainstems posture -regulating pathway causes

Answer 16

Spastic paralysis

Question 17

Lesion in the Corticospinal tract (cortex) result in

Answer 17

weakness (paresis), rather than paralysis

Question 18

What does it mean that there is a spatial map of the body musculature in the spinal cord

Answer 18

Muscles closer to the trunk (shoulders) are more medial motor neurones and muscle located further away from the trunk (fingers) are lateral motor neurones

Question 19

How does body musculature in the spinal cord refer to arms and legs

Answer 19

Medio-laterally

Question 20

How does the spinal cord receive descending input

Answer 20

via neurons in the brainstem AND direct cortical input via Corticospinal / Pyramidal tract.

Question 21

How does ascending sensory input enter the spinal cord

Answer 21

at any level and in the from of proprioceptors, touch, pain etc

Question 22

Why and How does the sensory input reach brainstem

Answer 22

via the vestibular system to inform about balance

Question 23

What occurs when sensory input is at the level of the cortex

Answer 23

We make movements in response to visual, olfactory, auditory, emotional, intellectual cues

Question 24

If their is damage to sensory input at spinal level what can occur

Answer 24

paralysis as if the motoneurones themselves had been damaged

Question 25

What is the affect of sensory neuropathy

Answer 25

Loose all proprioception (lost sense of body in time and space and motor control so effectively paralysed)

Question 26

How does sensory neuropathy occur

Answer 26

autoimmune attack on sensory neurones in the dorsal root ganglia cause loss of large myelinated fibres

Question 27

What occurs in the stretch reflex

Answer 27

Initial stimulus causes the muscle to stretch and stimulates muscle spindles afferent Impulses from muscle spindle acting as stretch receptor travel to spinal cord via dorsal route efferent/motor impulses leave via ventral route and travel to to alpha motor neuones leading to contraction of the stretched muscle resulting in extension whilst efferent impulses travel to antagonist muscle and cause relation (= reciprocal inhibition)

Question 28

``` What is the crucial cord segment in the biceps jerk tricep jerk patellar tendon Achilles tendon reflex ```

Answer 28

C6 C7 L4 S1

Question 29

What is the significance of testing reflexes

Answer 29

Helps to detect level of spinal cord damage Impaired reflexes indicate areas of nerve damage

Question 30

In spinal cord damages where can reflects be evoked

Answer 30

Above spinal cord damage

Question 31

How do you avoid voluntary influencing of reflex response

Answer 31

Distract patient

Question 32

What occurs in the process of the flexor (withdrawal) reflex

Answer 32

Uses information from pain receptors (nociceptors) in skin, muscle and joint and through a polysynaptic and protective process to withdraw body away from painful stimulus and toward the body =ipsilateral flexion in response to pain

Question 33

What is activated by the nociceptive fibres that controls all the flexor muscle of the affected limb

Answer 33

activate interneurones in spinal cord segment which in turn activates α motoneurones

Question 34

In the flexor withdrawal reflex if you withdraw the limb and do nothing else, you would fall over, so what additional process occurs to prevent this

Answer 34

The Contralateral limb extends - maintain an upright postures by extending the limb to bear body weight

Question 35

How does the contralateral limb extend

Answer 35

By excitatory interneurones crossing the spinal cord

Question 36

What is the affects of increase sensory AP from nociceptors

Answer 36

Increases activity of the flexor muscle of the affected part Inhibits the antagonist extensors Excite contralateral extensors Inhibit contralateral flexors

Question 37

How does sensory information ascend to the brain

Answer 37

Via the contralateral spinothalamic tract

Question 38

What is the two reasons the flexor crossed extensor reflex far slower than the stretch reflex

Answer 38

The process has several interneurones in the pathways each with a small synaptic delay (slow down process) Nociceptive fibres have smaller smaller than muscle spindle afferents (conduct more slowly)

Question 39

What occurs in the golgi tendon reflex

Answer 39

There is an excessive load on muscle, activates GTO reflex Neurones from golgi tendon organ flies, motor neurone is inhibited causing the muscle to relax and release the load in an aim to protect the arm

Question 40

How do you maintain contraction of the GOT reflex if you are holding something important and heavy

Answer 40

Reflexes are over-ridden consciously by Descending voluntary excitation of motoneurones overriding the inhibition from the GTOs

Question 41

Where does a motor neurones receive its synpases

Answer 41

Many are from descending cortical excitatory and inhibitory inputs, with continual integration of EPSPs and IPSPs

Question 42

How is the stretch reflex over-ridden

Answer 42

strong descending inhibition hyperpolarizes α-motoneurones and the stretch reflex can not be evoked.

Question 43

Where do the muscle spindles get their motor innervation

Answer 43

Gamma motor neurones innervating both poles of the intrafusal pathway and maintain spindles sensitivity t stretch

Question 44

What occurs with high gamma motoprneruone activation of spindle fibres

Answer 44

Muscles become extremely resistant to stretch and become spastic

Question 45

What is the clinical relevance of the stretch reflex

Answer 45

reflexes can be evoked above, but not below given level may localise a problem eg. segmental trauma to the spine.

Question 46

Why does a more painful stimulus give a larger response

Answer 46

Due to facilitation which increases the effects of sensory inputs

Question 47

How do pain fibres input facilitate the action of muscle spindles

Answer 47

By maintaining the alpha motor neurones in a more depolarised state

Question 48

What can mild cutaneous stimulation provoke (give an example)

Answer 48

Flexor reflex | eg mild stoking of the sole of your foot causes plantar flexion - downward curling of big toe)

Question 49

What is it called when the toe extends and doesn't flex (fans up and out)

Answer 49

Babinskis sign

Question 50

What is the cause of Babinskis sign

Answer 50

Damage or disruption to the Corticospinal tract (upper motor leison) meaning their is an imbalance between extensor and flexor reflexes

Question 51

Where else is babinskis sign seen in

Answer 51

Seen in children < 1 year old motor system not fully developed After epileptic seizures - transient cortical function disruption

Question 52

What is the affect does spinal transection (complete tear of spinal cord) have on the function of higher centres in maintaining normal reflexes

Answer 52

immediate sensory and autonomic effects - loss of sensation; loss of bowel, bladder and sexual regulation

Question 53

What Occurs in spinal shock

Answer 53

Loss of supraspinal excitation (no control from higher centres) hyporeflexia, as all reflexes below the point of injury are not evoked This lasts 2-6 weeks - then gradual return of reflexes

Question 54

What is the second stage of symptoms seen after spinal shock

Answer 54

Reflexes return Reflexes are exaggerated = hyperflexia - Light touch provokes powerful withdrawl - extensor reflex support body weight briefly Clonus

Question 55

Define clonus

Answer 55

stretch causes oscillatory muscle contraction/relaxation