BMS11004 WEEK 11 - WEDNESDAY

Question 1

what do simple reflexes involve

Answer 1

local circuit control of spinal motor neurons by spinal sensory neurons

Question 2

what motor neuron initiates all movements from skeletal muscles

Answer 2

lower motor neurons

Question 3

what neurons control upper motor functions

Answer 3

upper motor neurons

Question 4

what does somatotopically mapped mean in motor cortex

Answer 4

correlate site of stimulation with location of muscle contraction, showing topographic maps

Question 5

how is lower and upper body represented on somatotopic map

Answer 5

lower body = medially
upper body = laterally
proportions reflect density of innervation, behavioural signif

Question 6

what do axial muscles control

Answer 6

trunk movement

Question 7

what do proximal muscles control

Answer 7

shoulder, elbow, pelvis, knee movement

Question 8

what do distal muscles control

Answer 8

hands, feet, digits movement

Question 9

what do lower motor neurons in ventral horn of spinal cord do

Answer 9

innervate striated muscle to control movement

Question 10

define motor unit

Answer 10

motor neuron and all muscle fibres it innervates

Question 11

define motor neuron pool

Answer 11

all motor neurons that innervate single muscle

Question 12

explain the organisation of motor pools in spinal cord

Answer 12

grouped in rod-shaped clusters, extends over several vertebrae segments

Question 13

what is corticospinal tract (CST) important for

Answer 13

control of voluntary movement
position of CST neurons in cortex reflex where it projects to in SC

Question 14

what are main inputs of cortex

Answer 14

to stellate cells in layer IV

Question 15

what are main outputs to cortex

Answer 15

layers III, V, VI

Question 16

explain the projections of corticospinal tract axons controlling distal muscles

Answer 16

axons cross midline in “pyramidal decussation” in medulla, project contralaterally in spinal cord and synapse onto lateral lower motor neuron circuits

Question 17

what do ventromedial pathways control

Answer 17

controls posture

Question 18

what do vestibulospinal, tectospinal and reticulospinal tracts (part of ventromedial pathway) control

Answer 18

vestibulospinal= head balance, turning, input from vestibular systems
tectospinal= orientating response, input from visual system via superior colliculus
reticulospinal= antigravity reflex

Question 19

name the 3 tracts making up ventromedial pathway

Answer 19

vestibulospinal, tectospinal, reticulospinal

Question 20

what is role of upper motor neurons of motor cortex when projecting contralaterally via corticospinal tract

Answer 20

initiate complex voluntary movement, muscles for precise limb movement (mostly hands)

Question 21

what is role of upper motor neurons of motor cortex when projecting via corticobulbar tract to the hypoglossal nucleus in brainstem

Answer 21

movement of tongue

Question 22

name an overall function of upper motor neurons in brainstem

Answer 22

maintain posture and balance

Question 23

where are upper motor neurons in brianstem mostly located

Answer 23

reticular formation, vestibular nucleus, superior colliculi

Question 24

what does ipsilaterally mean?

Answer 24

on same side of body

Question 25

where do upper or lower motor neurons synapse onto?

Answer 25

upper= onto lower motor neurons
lower= onto muscle fibres

Question 26

explain anticipatory feedforward mechanism

Answer 26

adjust body posture to compensate for generated forces when lever is lifted

Question 27

apply feedforward mechanism to indirect cortical control of lower motor neurons for voluntary movement

Answer 27

anticipation of movement activate indirect projections to axial muscle, via reticular formation
direct to spinal cord via corticospinal tract

Question 28

how does mirror therapy work for phantom limb pain

Answer 28

reorganise/integrate the mismatch between proprioception and visual feedback of non-limb
mirror neurons in somatosensory and motor cortex fire when act and observe an action

Question 29

what can mirror therapy be used in aside from phantom limb pain

Answer 29

complex regional pain syndrome, post-stroke

Question 30

give another name for motor neuron disease

Answer 30

amyotrophic lateral sclerosis

Question 31

define motor neuron disease

Answer 31

degenerative disease of motor neurons, muscle atrophy, sclerosis (hardening) of lateral spinal cord (degeneration in axons in CST)

Question 32

name symptoms of lower MND

Answer 32

muscle paresis, weakness, paralysis
lost muscle tone, lost stretch reflex
severe muscle atrophy

Question 33

what do individuals with lower MND die from

Answer 33

lung dysfunction from atrophy of intercostal muscles

Question 34

name symptoms of upper MND

Answer 34

muscle weakness
spasticity -increase muscle tone, failed modulation of stretch reflex
hyperactive reflex
lost fine movement

Question 35

what do individuals with upper MND die from

Answer 35

loss of input to bulbar muscles- tongue, pharynx via corticobulbar tract

Question 36

what could MND potentially be due to?

Answer 36

excitoxicity (overstimulated by glutamate = cell deaths)
vicious cycle of glutamate release in hypoxia (post-cardiac arrest, stroke or trauma)

Question 37

what drug could work for MND but give issues of this

Answer 37

glutamate blocker, but only delays by few months

Question 38

explain the 10% link of MND to genetics

Answer 38

mutation in genetic encoding of SOD1- enzyme picking up free radicals accumulating in metabolically active cells.