week 16: Motor systems L2 Flashcards
proprioception and spinal reflexes control of spinal circuits
proprioception vs exteroception
proprioception: sense of oneself
exteroception: sense of external world
when is the afferent active
when muscle is stretched
(when intrafusal fibres are stretched)
main role of gamma motor neurons
regulate muscle spindle sensitivity by adjusting intrafusal fiber tension, ensuring continous detection of stretch
what happens to muscle spindle sensitivity when gamma motor neuron activity increases
it increases, making muscle spindle more sensitive to small stretches
what happens when gamma MN activity decreases
muscle spindle becomes less sensitive to stretch, useful when body is relaxed and doesn’t need high sensitivity
tendon organs location and function
at junction between muscle and bone
detect excessive muscle tension to prevent tears by inhibiting muscle contraction when overloaded
part of primary feedback
what threshold mechanoreceptors are large diameter afferents associated with
low threshold
rapidly conducting afferents
what threshold mechanoreceptors are small diameter afferents associated with
nocicpetors and thermoreceptors
low conducting afferents
how is condiction velocity corelated to axon diameter
positively
what changes do spindle afferents (gamma) (IA/II) signal in the muscle
length
what changes do golgi tendon afferents signal in the muscle
force
what do joint receptors respond to
extreme flexion and extension
when is a movement at a joint feasible
if one muscle is activated and one inactivated
what two inputs will a reflex always produce
monosynaptic and dysynaptic
what do polysynaptic reflexes involve that monosynaptic dont
interneurons
homonymous reflex
reflexive response occurs in the same muscle that initially receive the stimulus
heteronymous reflex
reflexive response involves a different muscle from the one that initially received stimulus
why can motor neurone not be continuously active
it would not respond to the next stimulus
renshaw cell action
renshaw interneuron is excited by glutamamte from motor neuron and fires AP
renshaw cell rleases glycine or GABA
act on motor neurone
what is a reflex
fast, predictable, automatic response to change in environment or stimulus
monosynaptic reflex pathway
sensory afferent > motor neuron > output
primary spindle (IA) afferents exciting alpha MN of the same muscle
pathway of a polysynaptic reflex:
sensory afferent > interneuron> motor neuron > output
involves golgi tendon (Ib) afferents inhibitng alpha motor neurons of the same muscle via interneurons
reciprocal inhibition
neural mechanism where the activation of one muscle group leads to the inhibition of opposing
allows smooth coordinated movement
is neuronal input needed for reciprocal inhibition
no
happens within spinal circuits maintained by interneuron populations
