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43 Cards in this Set

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  • Back
Are axial and girdle muscles medial or lateral SC?

Are distal limbs/extremities medial or lateral SC?
Axial/Girdle: Medial

Distal Limbs/Extremities: Lateral
Are flexor motorneurons ventral or dorsal SC?

Are extensor motorneurons ventral or dorsal SC?
Flexors - Dorsal

Extenstors - Ventral
Which motoneurons innervate the force generating (extrafusal) muscle fibers?
alpha-motoneurons
Which motoneurons innervate the non-force generating (intrafusal) muscle fibers within the muscle spindle?
gamma-motoneurons
all the motoneurons the innervate a muscle
motoneuron pool
a motoneuron and all its muscle fibers
motor unit
all of the muscles innervated by a single nerve root
mytome
What two events control the force of contraction?
1. Recruitment of motor units (first)

2. Frequency of action potentials
What is the size principle in regards to Recruitment?
smaller motoneurons are recruited first

Why? Smaller motoneurons are more excitable b/c they have a higher Rin

Rin=Rm/A
Which motor units are resistant to fatigue?
Slow motor units: Red/Type I

Fast motor units are fatigue-able: white Type II
Lesions to nerve roots are called what?
radiculopathies
Which spinal nerve has no dorsal root?
C1
What spinal nerve comes out between C5 and C6?
C6
What spinal nerve comes out between C7 and T1?
C8
What spinal nerve comes out between T10 and T11?
T10
If the disc between C3 and C4 herniates which spinal nerve is affected?
C4

In the cervical the spinal nerve the exits the same foramen will be affected. I.E. C4 comes out between C3 and C4.
If the disc between L3 and L4 hearniates, which spinal nerve is affected?
L4

In the lumbar region, the spinal root in the next lowest foramen is affected. I.E. Between L3 and L4, the spinal nerve L3 comes out, so the foramen below this one is affected and thus L4 is in that foramen.
Where are most of the muscle spindles located?
close to the tendons
What do Ia fibers signal ?
both rate of change (bag 1) and magnitude of length (bag2/chain)
What do group II fibers signal?
magnitude and length (bag 2 /chain)

NOT rate of change in length
True or false for each statement:

1. A spindle receives innervation from a single Ia fiber.

2. A spindle receives innervation from a single II fiber.

3. A spindle receives innervation from multiple gamma-motoneurons.

4. A spindle receives innervation from multiple Beta-motoneurons.
all True

dynamic gamma-motoneurons innervate Bag1 fibers. Static gammas innervate a mixture of Bag 2 & chain.

Dynamic B-motoneurons innervate Bag1 fibers. Static B-motoneurons innervate LONG chain fibers only. (Both types have branches that innervate extrafusal fibers)
Stretching the intrafusal sensory fibers results in what?
increase in the frequency of action potentials in the sensory neurons
Choose between phasic, tonic, or both:

1. Group Ia sensory fibers

2. Group II sensory fibers
Ia - both (rate of change and magnitude of length.)

II - only tonic (magnitude of length)
gamma motorneurons do what?
alter the sensitivity (or gain) of the spindle by increasing or decreasing the amount of stretch on the center region of the spindle
Are GTO's in parallel or series with muscle fibers?
series
What fibers transmit tension information/GTO?
Ib fibers
While a Ia spindle fiber is excited w/ passive stretch and inhibited w/ contraction/shortening a GTO Ib fiver is ________ with passive stretch and ________ with contraction and shortening.
While a Ia spindle fiber is excited w/ passive stretch and inhibited w/ contraction/shortening a GTO Ib fiber is EXCITED with passive stretch and EXCITED with contraction and shortening.
How is the stretch reflex elicited?
by tapping on a tendon attached to a muscle
Does tendon tapping active Ib fibers from Golgi tendon organs?
NO
What is the primary function of stretch reflexes?
maintain appropriate lengths of muscles in different postures
What stretch reflex involves C5-6
Biceps
What stretch reflex involves C7-8
Triceps
What stretch reflex involves L3-4
Knee
What stretch reflex involves S1-2?
ankle
What term describes oscillations in muscle contraction in which the muscle alternatively contracts and relaxes rapidly.
Clonus

observed in hyperreflexive states and is causes by sequential stretch reflexes
True or False

Alpha and gamma motoneurons are activated together during most normal movements
TRUE
Which motoneurons have the ability to adjust contraction DURING a movement?
gamma motoneurons
What fibers are involved in the tendon reflex?
Ib fibers
The flexor reflex is elicited by what?
nociceptive stiumulus - activates Adelta and C fibers NOT afferent muscle fibers

excited neurons innvervating flexor alpha motoneurons and inhibits extensors. Therefore the limb flexes away from the stimulus (protective)
What is the purpose of the crossed extensor reflex?
To support a limb during withdrawal
What are Renshaw cells?
a unique type of inhibitory interneuron
What excites a Renshaw cell and then what does it do?
collateral axons of alpha-motoneurons excites Renshaw cells.

The Renshaw cell inhibits the alpha-motoneuron that excited it and may inhibit all homonymous alpha-motoneurons to the same muscle.
In addition to alpha-motoneurons, what else gives input to Renshaw cells?
descending pathways from the brain

purpose: can inhbit muscles that are not needed in the forthcoming movement and reduce inhibition to muscles that will be used.