Neuro - FUNCTIONAL HIERARCHY OF THE MOTOR SYSTEM Flashcards
medio-lateral spacial map of spinal cord: where are the motorneurones that control the proximal shoulder muscles?
medial motorneurones
medio-lateral spacial map of spinal cord: where are the motorneurones that control the proximal finger muscles?
(much more) lateral motorneurones
how many synapses does the stretch reflex involve? how many neurones?
1 synapse, 2 neurones
in which muscles is the stretch reflex found?
all postural muscles (those used to sustain your posture in the gravity field
what type of reflex is the patellar tendon?
stretch reflex
what type of reflex is knee jerk reflex?
stretch reflex
what kind of neurostransmitter is received by the antagonist muscle in stretch reflex?
antagonist neurotransmitter such as Glycine
which level is the crucial cord segment for the biceps jerk?
C6
which level is the crucial cord segment for the triceps jerk?
C7
which level is the crucial cord segment for the patellar tendon reflex?
L4
which level is the crucial cord segment for the achilles tendon reflex?
S1
which reflexes aren’t monosynaptic?
flexor or withdrawal reflexes (with crossed extension)
what happens to the affects part in flexor/ withdrawal reflexes?
it flexes (withdrawal towards the body)
what is the flexor reflex a response to?
pain
what is the stretch reflex a response to?
stretching of the muscle spindle
Y/N- nociceptors branch at a single level
N- several levels, which allows the flexion of all the flexors of the affected limb
what other pathways are provoked by the flexor/withdrawal reflex?
- 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)
how do nociceptor fibre’s diameter compare with that of muscle spindle afferent fibres? how does this affect transmission speed?
nociceptors have a smaller diameter, they therefore conduct more slowly
which, of the stretch reflex and the flexor-crossed reflex is slowest?
the flexor-crossed reflex
what is the Golgi tendon organ reflex?
letting go of a load to heavy to prevent the muscle getting torn
what do gamma motor neurones do?
maintain potency of muscle spindles to allow for continuous firing of APs
what do alpha motor neurones do?
they contract the muscle when they receive APs from the muscle spindles
what does gamma motorneurone activity depend on?
it depends entirely on descending pathways
what would be the effect of a disorder causing high activation of gamma motor neurones?
muscles would become extremely resistant to stretch (spastic)
when does facilitation occur?
between two instances of the same stimulus (ex: pain fibre inputs)
what does facilitation result in?
exaggerated reflex response after a repeated stimulus
why does facilitation occur?
the first input will facilitate the action of the muscle spindles by maintaining the alpha motorneurones in a more depolarised state
what is the Babinski sign?
extension and not flexion of the toes on stimulation of the plantar skin
what is the Babinski sign a consequence of?
corticospinal tract damage
what is clonus? (seen in spinal transection patients)
stretch reflex causes oscillatory muscles contraction/relaxation
