N36

Question 1

Local circuitry

Answer 1

LMN and local circuit interneurons that receive proprioceptive information and info from higher centers

Question 2

Descending systems from motor cortices

Answer 2

UMN–>(interneurons)–>LMN for initiation and planning of voluntary movement

Question 3

Cerebellum and basal ganglion

Answer 3

no direct access to motor neurons, control movement via regulation of UMN

Question 4

Interneurons

Answer 4

integrate inputs from higher centers, peripheral receptors, other interneurons (final determination of which neurons are activated)

Question 5

Central Pattern Generators (CPG)

Answer 5

interconnected interneurons that generate rhythmic outputs (timing sequence of activation and inhibition)

Question 6

Spinal cord transection can still walk because

Answer 6

CPG of interneurons

Question 7

Alpha motor neurons innervate

Answer 7

innervate extrafusal fibers that generate force

Question 8

Alpha motor neurons receive input from

Answer 8

descending motor pathways and reflex circuits

Question 9

Gamma motor neurons innervate

Answer 9

intrafusal fibers (no force)

Question 10

Gamma motor neurons receive input from

Answer 10

descending motor pathways and reflex circuits

Question 11

muscle spindles and stretch receptors monitor

Answer 11

Absolute muscle length and rate of change of muscle length (kinesthesia, locomotion, muscle tone)

Question 12

Structure of muscle spindles

Answer 12

deep in belly, nuclear chain and nuclear bag fibers

Question 13

Afferent innervation of muscle spindles

Answer 13

Primar endings: Ia, innervate chain and bag fibers are sensitive to the onset of muscle stretch
Secondary endings: II, innervate chain fibers and are sensitive to absolute length (slow adapting)

Question 14

Efferent innervation of muscle spindles

Answer 14

GAMMA motor neurons

Question 15

How can the CNS control the sensitivity of spindles to stretch?

Answer 15

by contracting the intrafusal muscle fibers

Question 16

Stretching =

Answer 16

stretches the intrafusal fibers and activates the muscle spindle stretch receptors

Question 17

Contracting =

Answer 17

extrafusal contraction, slows the rate of stretch receptor activation

Question 18

alpha-gamma coactivation

Answer 18

Too much contraction of extrafusal fibers (alpha) causes intrafusal fibers to contract (gamma) to maintain information on muscle length

Question 19

Golgi tendon organs monitor

Answer 19

tension (muscle length, load, and degree of fatigue)

Question 20

Golgi tendon organs location

Answer 20

junction of tendon and muscle

Question 21

Golgi tendon organs innervation

Answer 21

Ib unmyelinated and intertwined with collagen fibers

Question 22

Golgi tendon organs tension monitoring system

Answer 22

connected to extrafusal fibers and contraction causes tension and firing, causing inhibition of contracting muscle and activation of antagonistic muscle

Question 23

Muscle spindle and golgi tendon

Answer 23

muscle spindles fire when the muscle is stretched (muscle length and dynamic change in length) and golgi tendons fire when muscle is contracted (tension)

Question 24

Unmyelination of Ia, Ib, II

Answer 24

gait impairment, errors in positioning and force

Question 25

Spinal reflexes are

Answer 25

Fast, automatic, predictable

Question 26

Mytotatic reflex

Answer 26

stretch receptors activated when extrafusal, intrafusal, and muscle spindles are stretched causing muscle activation

Question 27

Autogenic excitation

Answer 27

Monosynaptic, Ia muscle spindle afferent –> alpha motor neuron of the homonymous muscle (excitation and contraction)

Question 28

Synergistic Activation

Answer 28

Ia afferent –> alpha motor neurons of synergistic muscles causing excitation and contraction

Question 29

Reciprocal Innervation

Answer 29

Ia afferents –> excitatory connection on an inhibitory interneuron of alpha motor neuron to antagonistic muscle (polysynaptic)

Question 30

Negative Feedback Control Loops

Answer 30

maintain stability of system by returning it to a “set-point” or dampening the oscillations in a perturbed system (muscle spindles and golgi tendons)

Question 31

Recurrent Inhibition

Answer 31

produced by Renshaw cells which acts to decrease the activity of a motor neuron

Question 32

Renshaw cells

Answer 32

alpha motor neuron collateral branches innervate them and upon activation, they release inhibitory glycine to decrease the firing rate

Question 33

Tetanus

Answer 33

inhibits the release of glycine from Renshaw cells, inhibition cannot occur and overexcitation occurs in alpha motor neurons

Question 34

Strychine

Answer 34

poison that binds glycine receptors and causes tetanic contractions

Question 35

Reciprocal inhibition

Answer 35

relaxation of antagonistic muscles to enhance speed and efficiency

Question 36

Co-contraction

Answer 36

prime mover and antagonist muscles both contract to stiffen joint (precision and joint stability)

Question 37

Tendon reflex

Answer 37

golgi tendon –> Ib afferent –> inhibitory interneurons –> inhibition of alpha motor neurons (relaxation)

Question 38

another name for tendon reflex

Answer 38

autogenic inhibition (also excites antagonistic muscles)

Question 39

Flexion reflex

Answer 39

sensory input –> flexion of ipsilateral limb –> inhibition of ipsilateral extensors (and opposite for contralateral limb)

Question 40

Crossed extension reflex

Answer 40

input causes flexion of ipsilateral limb and extension of contralateral limb via

Question 41

Flexor withdrawal reflex

Answer 41

protective reflex that results in flexion away from a noxious stimuli

Question 42

Local sign

Answer 42

modification of the reflex response so that it reflects the area being stimulated