Motor units, joint receptors, spinal reflexes and UMNs Flashcards
when muscles work together
synergists
when muscles oppose each other
antagonists
axial muscles control movements of?
trunk
lower motor neurones control..?
contraction of muscles
lower motor neurones consists of 2 types of motor neurones..? which?
alpha and gamma
where do LMNs leave the spinal cord?
in anterior roots
what is a motor unit?
and alpha motor neurone and all the muscle fibres it innervates
what is a motor neurone pool?
COLLECTION OF alpha motor neurones that innervate a single muscle
what is the force of contraction graded by?
frequency of action potential discharge of alpha LMN
the recruitment of additional , synergistic motor units
muscle strength depends on..?
neuromuscular activation
force produced by innervated muscle fibres (fibre size etc)
monosynaptic reflex arc is most prominent in what type of muscle?
extensors
what causes muscle spindle to contract?
gamma LMNS
what makes up the muscle spindle?
intrafusal fibres- nuclear bag fibres and chain fibres
what innervates the muscle spindle?
la afferents- is around the centre of all of them
ll fibres- more slowly conducting flowerspray endings on all of them
where are golgi tendon organs found?
between muscle and tendon
they monitor changes in muscle tension
innervated by lb sensory afferents
where are proprioceptive axons found?
in connective tissue of joint
they respond to change in angle, direction and velocity
prevent excessive flexion or extension
what do inhibitory interneurones mediate?
the inverse myotatic response
reciprocal inhibition between extensors and flexors
what do excitatory interneurones mediate?
flexor reflex- causes limb to flex
crossed extensor relfex- caused limb to extend
what are the 2 types motor pathways?
lateral and ventromedial
what are the 2 types of lateral motor pathway?
corticospinal(main one)
rubrospinal (minor one)
- what pathway helps hold you upright and deals with balance and posture
- and controls head and neck movement
ventromedial pathways
VESTIBULOSPINAL TRACTS
- lateral
- medial
cell bodies reside in superior colliculus which gets input from retina and visual cortex
axons decussate in dorsal tegmental decussation and descend close to midline as the tectospinal tract
tectnospinal tract
pontine (medial) RETICULOSPINAL TRACT
arise from brain stem and descend ispilaterally
enhances anti gravity reflexes
helps maintain a standing posture
medullary (lateral) RETICULOSPINAL TRACT
arise from brainstem
descend bilaterally
opposes action of medial tract (pontine)
