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What are extrafusal muscle fiber?

skeletal muscle fiber- contains all contractile elements.


What are intrafusal muscle fibers

Sits inside extrafusal fibers. The muscle spindle and all of its components parts-sit parallel to the extrafusal fibers. (Static nuclear bag, dynamic nuclear bag, nuclear chain).


What are the Golgi Tendon Organs (GTO)?

Sit between muscle and tendon. located in the musculotendinous junction and are situated in series with the extrafusal fibers


What do the extrafusal muscle fibers contain?

motor neurons-Alpha motor neuron


what do the intrafusal muscle fibers contain?

motor neurons-gamma motor neuron-can control motion based on info. to the brain.
sensory neurons-Ia and II-provides info to the brain.


what do GTOs contain?

Sensory Neurons-Ib


What do the intrafusal muscle fibers and GTO provide together?

static muscle length- what is the length of the muscle
rate of length of change-this is how fast we move
force the muscle can generate


What does the fusimotor system and Gamma loop do?

participates in stretch reflexes (muscle spindle only) sends proprioceptive info to the CNS regarding movement and position of body segments
helps to regulate muscle contraction under the influence of descending motor pathways as well as afferent feedback
Is fine motor control


Where are muscle spindles found in greatest abundance?

In muscles capable of intricate contractile activity


What is typically in a muscle spindle?

one dynamic nuclear bag fiber
one static nuclear bag fiber
five nuclear chain fibers


What are the different categories of the sensory nerve fibers?

Groups Ia-primary sensory (annulospiral)
Group II- secondary sensory (flowerspray)


Where does Groups Ia of the sensory nerve fibers come from?

All three components of the muscle spindle.


Where does group II of the sensory nerve fibers come from?

only from the static nuclear bag and nuclear chain of the muscle spindle.
from the Golgi tendon organ


What happens to the intrafusal muscle fibers when they are stretched?

primary and secondary afferents fire


What are secondary afferents of the intrafusal muscle fibers more sensitive to?

steady-state stretch and reports the length of muscle to the CNS


When do primary afferents in intrafusal muscle fibers discharge more?

during length changing stretch and report length of muscle as well as rate of change to the CNS.


What are three important things to know about the gamma motor neurons or fusimotor fibers?

nerve fivers that form the efferent or motor supply to the muscle spindle
dynamic gamma motor neurons innervate the dynamic nuclear bag
static gamma motor neurons innervate the static nuclear bag and the nuclear chain


Which part of the gamma motor neurons is the contractile element?

the ends


which part of the gamma motor unit is the sensory?

the middle


Where does the gamma motor neuron innervate?

the contractile regions of the nuclear bag and chain


What does the gamma motor neuron do?

contracts and shortens the intrafusal fibers at its ends thereby stretching the central nuclear region.
the input regulates the sensitivity of the spindle


Where is the Golgi tendon organ located?

between the muscle and the tendon-sits parallel


Where does the Golgi tendon organ sit in series with?

15-20 extrafusal fibers


what is the Golgi tendon inervated by?

Ib afferent nerve fiver (only sensory, not motor)


What is the Golgi tendon organ sensitive to?

changes in tension in the muscle and particularly sensitive to active muscle contractions and therefore monitors muscle contraction.


When does the Golgi tendon organ fire?

fires steadily during passive lengthening


What does the Golgi tendon monitor?

monitors muscle contraction
rate of tension change in an isotonic activation
signals the amount of tension in an isometric activation.


What causes autogenic inhibition of the Golgi tendon organ?

high levels of excitation of the Ib nerve fiver


What is autogenic inhibition?

self generated inhibitory process


What does the Golgi tendon organ protect?

the integrity of the musculotendinous complex