neuromuscular reflexes Flashcards
what are the two types of muscle fibers?
Extrafusal and intrafusal
Extrafusal muscle fibers
- bulk of skeletal muscle fibers
-responsible for force generation
-innervated by α motor neurons
intrafusal muscle fibers
- responsible for detecting changes in muscle length
-innervated by γ motor neuron and sensory afferents
what two groups of sensory afferents innervate intrafusal muscle fibers
group Ia and II
where do sensory afferents from intrafusal fibers relay information to ?
α motor neurons in the spinal cord
what do reflex arcs (stretch reflex) consist of ?
- sensory receptors
- sensory afferents (group Ia and II)
- interneurons in the spinal cord
-motor efferents ( α motor neurons)
describe the knee jerk stretch (myotatic) reflex
1) muscle is stretched and group Ia afferent fibers in the muscle spindle fire
2) the afferent fibers synapse α motor neurons in the spinal cord
3) α motor neurons induce contraction of skeletal muscle
4) muscle returns to resting length and firing frequency of group Ia decreases.
function of the Golgi tendon organ
It gauges the force generated by a muscle by measuring the tension in its tendon
what does the Golgi tendon organ consist of ?
group 1b axons
where do the Golgi tendon organs sit
-at the junction between skeletal muscle fibers and tendon encapsulated in collagen matrix
- aligned in series with extrafusal muscle fibers
what triggers action potentials in the Golgi tendon organ?
when tension develops in the muscle the collagen fibers surrounding the nerves squeeze and distort the nerve-endings triggering an action potential
give an example of a Golgi tendon (inverse myotic) reflex
clasp knife
describe Golgi tendon (inverse myotatic) reflex
1) muscle contracts and extrafusal fibers shorten stimulating Golgi tendon organ
2)group 1b afferents start firing and send sensory info to the inhibitory interneurons that synapse in the spinal cord
3)inhibitory interneurons synapse on the α motor neurons
4)muscle returns to resting length and firing frequency of group Ib decreases
example of flexion withdrawal reflex
stubbing your toe or touching something hot
during flexion-withdrawal reflex what happens to the muscles on the same side as the stimuli
flexors are contracted and extensors are relaxed
during flexion-withdrawal reflex what happens to the muscles on the opposite side to the stimuli
flexors are relaxed and extensors are contracted
