Spinal Cord and Movement 2: Reflexes Lec19 Flashcards
(42 cards)
Extrafuscal (normal) muscle fibers are innervated by
α motor neurons

Intrafuscal (muscle spindle / stretch receptors) fibers are innervated by
γ motor neurons
and by Type Ia and Type II sensory neurons
Spindles are arranged in ___ with extrafuscal muscle fibers
parallel
what do γ motor neurons affect?
only spindle stiffness, not contraction
Muscle spindles send stretch signals via
type Ia and type II neurons:
Type ___ central (bag) region
Ia:
type ___ fire intensely at onset of stretch,
! then slows down.
1a
type II firing is at what rate
static, increases linearly with increasing strethc
Stretch reflex?
muscle spindle senses stretch --\> spinal cord --\> original (homonymous) and synergist (heteronymous) muscles excited and anatagonist inhibited to counter perturbation
during stretch reflex, the Antagonist
muscle is___
inhbhited by interneruons
Contraction response:
when extrafuscal muscle contracts,____fire to
shorten intrafuscal fibers
the γ motor neurons
why do the the γ motor neurons fire during contraction response?
to shorten the intrafusal fibers and to keep them sensitive
Golgi Tendon Organs (GTO) only fire when muscle ___
actively contracts
muscle spindle cares about ___
length
golgi tendon cares about ___
tension
holgi tendon organs are receptors are ___ fibers
Type Ib
golgi tendon organ receptors arranged in ____ with extrafuscal muscle fibers
series
muscle spindle is the only afferent that ___
receives a nerve supply
difference between gamma motor neurons and alpha MN?
gamma has a smaller soma and a lower conduction velocity
____ motor.. innervate intrafusal not at center point
but lower down
gamma
____ contraction makes the muscle spindle more sensitive to stim.
intrafusal
sensory receptors on intrafusal fibers
type 1a and II
___ receptor fires with stretch from distal muscle spindle
type II
biceps and brachialis are examples of
agonists





