Neuro - FUNCTIONAL HIERARCHY OF THE MOTOR SYSTEM

Question 1

medio-lateral spacial map of spinal cord: where are the motorneurones that control the proximal shoulder muscles?

Answer 1

medial motorneurones

Question 2

medio-lateral spacial map of spinal cord: where are the motorneurones that control the proximal finger muscles?

Answer 2

(much more) lateral motorneurones

Question 3

how many synapses does the stretch reflex involve? how many neurones?

Answer 3

1 synapse, 2 neurones

Question 4

in which muscles is the stretch reflex found?

Answer 4

all postural muscles (those used to sustain your posture in the gravity field

Question 5

what type of reflex is the patellar tendon?

Answer 5

stretch reflex

Question 6

what type of reflex is knee jerk reflex?

Answer 6

stretch reflex

Question 7

what kind of neurostransmitter is received by the antagonist muscle in stretch reflex?

Answer 7

antagonist neurotransmitter such as Glycine

Question 8

which level is the crucial cord segment for the biceps jerk?

Answer 8

C6

Question 9

which level is the crucial cord segment for the triceps jerk?

Answer 9

C7

Question 10

which level is the crucial cord segment for the patellar tendon reflex?

Answer 10

L4

Question 11

which level is the crucial cord segment for the achilles tendon reflex?

Answer 11

S1

Question 12

which reflexes aren’t monosynaptic?

Answer 12

flexor or withdrawal reflexes (with crossed extension)

Question 13

what happens to the affects part in flexor/ withdrawal reflexes?

Answer 13

it flexes (withdrawal towards the body)

Question 14

what is the flexor reflex a response to?

Answer 14

pain

Question 15

what is the stretch reflex a response to?

Answer 15

stretching of the muscle spindle

Question 16

Y/N- nociceptors branch at a single level

Answer 16

N- several levels, which allows the flexion of all the flexors of the affected limb

Question 17

what other pathways are provoked by the flexor/withdrawal reflex?

Answer 17

• flexion of affected limb
• inhibition of extension muscles of affected limb
• excitation of contralateral extensors (part of crossed extension)
• inhibition of contralateral flexors (part of crossed extension)

Question 18

how do nociceptor fibre’s diameter compare with that of muscle spindle afferent fibres? how does this affect transmission speed?

Answer 18

nociceptors have a smaller diameter, they therefore conduct more slowly

Question 19

which, of the stretch reflex and the flexor-crossed reflex is slowest?

Answer 19

the flexor-crossed reflex

Question 20

what is the Golgi tendon organ reflex?

Answer 20

letting go of a load to heavy to prevent the muscle getting torn

Question 21

what do gamma motor neurones do?

Answer 21

maintain potency of muscle spindles to allow for continuous firing of APs

Question 22

what do alpha motor neurones do?

Answer 22

they contract the muscle when they receive APs from the muscle spindles

Question 23

what does gamma motorneurone activity depend on?

Answer 23

it depends entirely on descending pathways

Question 24

what would be the effect of a disorder causing high activation of gamma motor neurones?

Answer 24

muscles would become extremely resistant to stretch (spastic)

Question 25

when does facilitation occur?

Answer 25

between two instances of the same stimulus (ex: pain fibre inputs)

Question 26

what does facilitation result in?

Answer 26

exaggerated reflex response after a repeated stimulus

Question 27

why does facilitation occur?

Answer 27

the first input will facilitate the action of the muscle spindles by maintaining the alpha motorneurones in a more depolarised state

Question 28

what is the Babinski sign?

Answer 28

extension and not flexion of the toes on stimulation of the plantar skin

Question 29

what is the Babinski sign a consequence of?

Answer 29

corticospinal tract damage

Question 30

what is clonus? (seen in spinal transection patients)

Answer 30

stretch reflex causes oscillatory muscles contraction/relaxation