Spinal Reflexes Flashcards
ventral horn contains what
motor neurons
what do alpha motor neurons look like
large
prominant cell body
what do alpha motor neurons give rise to
axons that end in skeletal muscle
what do gamma motor neurons look like
smaller
smaller size cell body
what do gamma motor neurons give rise to
axons that run along with alpha motor neurons, terminante in muscle
what do gamma motor neurons innervate
polar ends of intrafusal fibers located insid emuscle spindles
what are muscle spindles
stretch receptors
what do alpha motor neurons innervate
skeletal muscle
spinal reflex reaction
simple stereotyped response to a specific sensory stimulus
where is the cell body of a pseudounipolar neuron located
inside dorsal root ganglia
where is the motor neuron cell body located
ventral body of spinal cord
what does motor neuron form
efferent or motor limb of reflex arc
muscle spindles are unique to what
skeletal muscle
where are intrafusal muscle fibers located
centrally inside the fusiform structure known as muscle spindle
what are the 2 types of intrafusal muscle fibers
nuclear bag fiber, nuclear chain fiber
nuclear bag fiber
have central, noncontractile, bag like strucutre containing many nuclei
what do nuclear bag fibers get innervation
gamma neurons
Ia
II
nuclear chains
have noncontractile component and contractile component
what innervates contractile component of nuclear chain
gamma motor neurons
Ia
II
what innervates extrafusal fibers
alpha motor neurons
pseudounipolar neurons
what do intrafusal fibers receive sensory innervation from
annulospinal endings
reciprocal inhibition
extension of and enhances stretch reflex (can’t have quad. femoris and hamstrings contraction happening at the same time)
autogenic inhibition
enhances stretch reflex, prevent over=contraction of skeletal muscle
flexor (withdrawl, nociceptive) reflex
protects affected limb from noxious stimulus
cross-extension reflex
supports the body and balance as weight is shifted from the affected limb to unaffected limb
muscle stretch reflex
protects muscles from overstretching
functino of gamma motor neuron
maintain muscle tone via gamma loop
function of alpha gamma co-activation
maintains teh sensitivity of the muscle spindles as effective stretch receptors regardless of muscle length
function of alpha gamma co-activation
maintains teh sensitivity of the muscle spindles as effective stretch receptors regardless of muscle length
C fiber
unmyelinated
alphadelta fiber
slightly myelinated
muscle tone
muscle tension
gamme motor neurons are under ______ controle
supraspinal
how is cerebellum involved in coordination of movement
recieve sensory info about orientation and position of body parts
use info to make adjustments to impending movement
produces muscle tone
basal ganglia
inhibit excess muscle tone
what happens if you don’t have gamma motor neurons
intrafusal fibers are ineffective stretch receptors - become slouchy
what happens in a lower motor neuron lesion
gamma and alpha motor neurons are damaged. muscle becomes deneravted
flaccid paralysis of denervated muscle is caused by
no electricle signals from CNS
