Motor 1

Question 1

describe the hierarchy of the motor system

Answer 1

highest: cerebral cortex
middle: brain stem
lowest: spinal cord

Question 2

the final common pathway for movements

Answer 2

a motoneurones in spinal cord

Question 3

upper motor neurones

Answer 3

connect cerebrum and brain stem with spinal cord

Question 4

lower motor neurones

Answer 4

connect cranial nerve nuclei in brainstem and spinal cord with muscles

Question 5

white matter

Answer 5

tracts of axons carrying information to and from the brain

• ascending: sensory information to the brain
• descending: carry commands to motor neurons

Question 6

grey matter

Answer 6

sensory and motor nuclei

Question 7

list the white matter tracts

Answer 7

lateral

• corticospinal
• rubrospinal

ventromedial

• medullary recticulospinal
• pontine reticulospinal
• vestibulospinal
• tectospinal

Question 8

function of lateral tracts

Answer 8

control voluntary movements

axons from cortex

• CST
• RST

Question 9

functions of medial tracts

Answer 9

control posture and locomotion

axons from brainstem

• VS: stabilises head and neck
• TS: ensures eyes remain stable as body moves
• reticulospinal tracts: reflexly maintain balance and body position

Question 10

describe the lower motor neurone distribution

Answer 10

medial ventral horn (posture and balance)
- innervate axial and proximal limb muscles

lateral ventral horn (voluntary movements)
- innervate distal limb muscles

Question 11

describe sensory inputs at all levels

Answer 11

spinal cord: proprioceptors, touch, pain

brainstem: vestibular system informs about balance

cortical level: visual, olfactory, auditory, emotional, intellectual cues

Question 12

spinal cord reflexes

Answer 12

simple building blocks for movement

brainstem nuclei control spinal reflexes and integrate them into higher order reflexes that control posture and balance

Question 13

describe stretch reflex

Answer 13

muscle stretch stimulates muscle spindles

activates sensory 1a afferent nerves firing of APs

causes muscle contraction and muscle shortens to previous length

Question 14

describe inverse stretch reflex

Answer 14

muscle contracts and shortens which pulls on the tendon

activates sensory 1b afferent nerves firing of APs

muscle inhibited and relaxes rapidly

Question 15

describe flexor/withdrawal reflex

Answer 15

polysynaptic and protective

ipsilateral flexion and contralateral extension in response to pain

Question 16

can reflexes be overridden

Answer 16

yes from voluntary input from CNS

descending voluntary excitations of a motoneurones overrides inhibition from GTOs and maintains muscle contraction

Question 17

what is the clinical relevance of reflexes

Answer 17

assesses integrity of the whole spinal cord circuit

help spinal level localisation of a problem

Question 18

primary motor cortex

Answer 18

pre-central gyrus or area 4

Question 19

pre motor areas

Answer 19

area 6

contains:

• premotor area
• supplementary motor area

Question 20

where are somatotopic maps of the body located

Answer 20

human cortex

• pre motor area: innervates proximal motor units
• supplementary motor area: innervates distal motor units

Question 21

describe the process of making decisions

Answer 21

areas 5 & 7 (prefrontal and parietal cortex): involved in decidint which actions/movements to take

area 6: axons converge here and plan how to carry this out

area 4: doing the action

Question 22

decision making neurones

Answer 22

PMA (area 6) neurones fire APs one second before a movement occurs

Question 23

mirror neurones

Answer 23

PMA (area 6) also fire when others make the same specific movement

allows understanding of actions/intentions of others

Question 24

when do PMA (area 6) neurones fire

Answer 24

movement is made

movement is imagined

movement is done by someone else

Question 25

deciding the direction of a movement

Answer 25

each neurone has a preferred direction but the responses of all neurones are combined to produce a population vector

Question 26

feedback mechanisms controlling movement

Answer 26

change in body position

rapid compensatory feedback messages from brainstem vestibular nuclei to spinal cord motor neurones

correct postural instability

Question 27

feedforward mechanisms

Answer 27

before movements begin

brainstem reticular formation nuclei initiate feedforward anticipatory adjustments

to stabilise postural instability

Question 28

basal ganglia motor loop

Answer 28

a loop of information cycles from the cortex through the thalamus and basal ganglia and back to the cortex (SMA)