week 16: Motor systems L3

Question 1

what threshold and receptor type are large diameter, rapidly conducting afferents associated with

Answer 1

low threshold mechanoreceptors

Question 2

what receptor type are small diameter, low conducting afferents associated with

Answer 2

nociceptors and thermoreceptors

Question 3

how is conduction velocity related to axon diameter

Answer 3

positvely correlated

Question 4

what do joint receptors respond to

Answer 4

extreme flexion and extension

Question 5

why do reflexes always have a monosynaptic and dysnaptic component

Answer 5

monosynaptic component ensures speed
dysnptic component fine tunes response by inhibiting antagonist or recruiting additional motor units

Question 6

what event is stretch always

Answer 6

IA

Question 7

how is motor output often affected in disease

Answer 7

affects way motor neurons fire

Question 8

what are the 5 primary descending pathways

Answer 8

reticulospinal
vestibulospinal
rubrospinal
tectospinal
corticospinal

Question 9

what are monamines and what release them

Answer 9

neuromodulators released by slow motor pathways (involving reticulospinal, vestibulospinal, dopaminergic systems)
modulate excitability of neurons, makes them high or low threshold

Question 10

corticospinal

Answer 10

precise voluntary control of distal muscles

Question 11

rubrospinal function

Answer 11

facilitates flexor muscles of upper limb, some role in motor control

Question 12

rubrospinal origin, decussation and target

Answer 12

red nucleus
midbrain (immediately after leaving red nucleus)
cervical spinal cord

Question 13

corticospinal origin and target

Answer 13

primary motor cortex
spinal cord and motor neurons

Question 14

reticulospinal tract function

Answer 14

controls posture, locomotion and muscle tone

Question 15

reticulospinal tract origin, decussation and target

Answer 15

reticular formation (pons and medulla)
mostly ipsilateral, some bilateral projections
axial and proximal limb muscles

Question 16

vestibulospinal tract function

Answer 16

maintains balance, posture and head stabilisation

Question 17

vestibulospinal origin, decussation and target

Answer 17

vestibular nuclei (brainstem)
lpsilateral (lateral tract)
bilateral (medial tract)

spinal motor neurons controlling extensors

Question 18

tectospinal function

Answer 18

reflexive head, neck and eye movements in response to visual, auditory and somatosensory stimuli

Question 19

tectospinal origin, decussation and target

Answer 19

superior colliculus

midbrain

cervical spinal cord

Question 20

what part of the corticospinal tract stays ipsilateral

Answer 20

anterior corticospinal
10%

Question 21

what part of the corticospinal tract decussate and where

Answer 21

lateral corticospinal
medullary pyramids

Question 22

what type of movements does lateral corticospinal tract control

Answer 22

contralateral

Question 23

what is the reticular formation

Answer 23

network of interconnected nuclei in brainstem

connects to cortex, spinal cord, cerebellum

regulate arousal, motor control, autonomic functions and reflexes

Question 24

what is the basal ganglia

Answer 24

group of subcortical nuclei involved in motor control, movement initiation, habit formation
modifies movement indirectly
deep within forebrain
connected to thalamus, cortex and brainstem

Question 25

2 roles of basal ganglia in motor control

Answer 25

regulates movement by modulating motor cortex activity facilitates desired movements and inhibits undesired movements

Question 26

inputs of the basal ganglia

Answer 26

main input site: striatum (caudete and putamen nucleus) from: cerebral cortex substantia nigra pars compacta thalamus

Question 27

basal ganglia outputs

Answer 27

ventroanterior and ventrolateral areas of thalamus feeds to motor cortex (motor modulation) second output from SNpr to superior colliculus (eye and head movement)

Question 28

hyperkinesia

Answer 28

excessive movement e.g Huntington's disease

Question 29

hypokinesia

Answer 29

limited movement e.g Parkinson's disease

Question 30

role of GPi and GPe

Answer 30

regulate motor signals

Question 31

STN

Answer 31

role in modulating movement via excitatory input

Question 32

SN

Answer 32

contains dopamine producing neurons that modulate striatum

Question 33

how does the basal ganglia work to allow or supress movement

Answer 33

modulates inhibition levels

Question 34

what does the direct pathway of basal ganglia do

Answer 34

inhibits GPi, less inhibition on thalamus, more movement

Question 35

what does the indirect pathway of the basal ganglia do

Answer 35

excited GPi, more inhibition on thalamus, less movement

Question 36

what does cerebellum keep track of

Answer 36

real time, monitors sensory inputs, from every source, monitors real time feedback

Question 37

what does basal ganglia remember

Answer 37

what was good and beneficial, does not keep track of what is happening real time, reward prediction mechansim