Motor Systems 1

Front 1

topographical organization of ventral horn LMNs
1. flexor muscles
2. extensor muscles
3. paravertebral muscles and proximal limbs
4. distal limbs

Back 1

1. posterior
2. anterior
3. medial
4. lateral

Front 2

Golgi tendon organs
1. location
2. measure
3. path of information flow

Back 2

1. in tendons near junction with muscle
2. muscle tension
3. GTO > Ib fibers > V horn inhibitory interneuron > inhibits alpha motor neuron > stop contraction of extrafusal fibers

Front 3

Ib fibers
What are they?
What do they carry?

Back 3

large-diameter, heavily myelinated fibers with high conduction velocity
-carry info from GTOs to SC

Front 4

inverse myotatic reflex (autogenic inhibition)

Back 4

interneuron excited by GTO, inhibit alpha motor neurons sypplying the same muscle innervated by the GTO

Front 5

Neuromuscular spindles
1. what are they?
2. location
3. what do they measure

Back 5

small encapsulated fusiform bundles of specialized myocytes
-located within the muscle among other muscle cells
-changes in muscle length, and the rate of those changes

Front 6

2 structural types of intrafusal fibers and 2 phsiologic subtypes

Back 6

structural: nuclear bag fibers and nuclear chain fibers
physiologic: static (sensitive to changes in muscle length) and dynamic (sensitive to rate of chang)

Front 7

2 classes of sensory axons supplying equatorial (non-contractile) region of intrafusal fibers

Back 7

-group Ia fibers: heavily myelinated, high conduction velocity
-group II fibers: smaller, myelinated fibers, slower conduction

Front 8

group Ia fibers
1. what do they innervate?
2. describe terminal branches
3. myelination and conduction speed

Back 8

1. all intrafusal fibers (dynamic and static)
2. primary/annulospiral: wrap around equatorial region of intrafusal fibers in a spiral fashion
3. heavily myelinated; fast conduction

Front 9

group II fibers
1. what do they innervate?
2. describe terminal branches
3. myelination and conduction speed

Back 9

1. static intrafusal fibers
2. secondary/flow-spray: clusters of thin, radiating braches near end of nuclear zone
3. small, myelinated; slow conduction

Front 10

innervation of intrafusal muscle fibers (2 types)

Back 10

1. dynamic gamma MNs: innervate dynamic nuclear bag fibers
2. static gamma neurons: innervate static nuclear bag and nuclear chain fibers

Front 11

alpha vs. gamma MNs
1. target
2. size
3. conducation speed

Back 11

1. extrafusal vs. intravusal
2. larger vs. smaller
3. faster vs. slower

Front 12

isolated muscle prep
1. passive stretch
2. isotonic contaction
3. isometric contraction

Back 12

1. stretch applied; no alpha or gamma stimulation
2. constant load; stretch and alpha stimulation applied producing contraction
3. constant length; alpha stimulation applied, but no changes in length

Front 13

Alpha-Gamma coactivation
1. what happens?
2. what does its purpose?

Back 13

1. when UMNs signal alpha MNs to contract, parallel signals are sent to gamma MNs causing intrafusal fibers to contract too
2. prevents muscle spindle from becoming slack and inactive

Front 14

Gamma loop
1. what happens?
2. important for...

Back 14

1. gamma MNs activated > intrafusal contract > stretches muscle spindle > Ia fibers fire > alpha MN activated > extrafusal contraction
2. maintenance of muscle tone

Front 15

The muscle stretch (myotatic) reflex
1. describe synapse
2. path of impulse

Back 15

1. one synapse (monosynaptic) b/n Ia fibers and alpha MN
2. tap tendon > Ia fiber > alpha motor neuron > extrafusal fibers of same muscle

Front 16

reciprocal inhibition of myotatic reflex

Back 16

Ia fibers synapse with inhibitory glycinergic interneurons that inhibit alpha MN supplying anatagonist muscles

Front 17

Flexor (Withdrawl/Nociceptive) Reflex

Back 17

A-delta and C fibers for synapse with...
1. excitatory interneurons that supply ipsi flexor mmm
2. inhibitory interneurons that supply ipsi extensor mm
-results in withdrawl of body part from source of injury

Front 18

Crosssed Extension Reflex

Back 18

A-delta and C fibers carry nociceptive input to interneurons that project to contralateral ventral horn
1. cause excitation of contralateral extensor mm
2. cause inhibition of contralateral flexor mm

Front 19

Neurotransmitters
1. excitatory interneurons
2. inhibitory interneurons

Back 19

1. glutamine
2. glycine