Spinal Cord and Movement 2: Reflexes Lec19

Question 1

Extrafuscal (normal) muscle fibers are innervated by

Answer 1

α motor neurons

Question 2

Intrafuscal (muscle spindle / stretch receptors) fibers are innervated by

Answer 2

γ motor neurons
and by Type Ia and Type II sensory neurons

Question 3

Spindles are arranged in ___ with extrafuscal muscle fibers

Answer 3

parallel

Question 4

what do γ motor neurons affect?

Answer 4

only spindle stiffness, not contraction

Question 5

Muscle spindles send stretch signals via

Answer 5

type Ia and type II neurons:

Question 6

Type ___ central (bag) region

Answer 6

Ia:

Question 7

type ___ fire intensely at onset of stretch,

! then slows down.

Answer 7

1a

Question 8

type II firing is at what rate

Answer 8

static, increases linearly with increasing strethc

Question 9

Stretch reflex?

Answer 9

muscle spindle senses stretch --\> spinal cord --\> original (homonymous)
 and synergist (heteronymous) muscles excited and anatagonist inhibited to counter perturbation

Question 10

during stretch reflex, the Antagonist

muscle is___

Answer 10

inhbhited by interneruons

Question 11

Contraction response:

when extrafuscal muscle contracts,____fire to
shorten intrafuscal fibers

Answer 11

the γ motor neurons

Question 12

why do the the γ motor neurons fire during contraction response?

Answer 12

to shorten the intrafusal fibers and to keep them sensitive

Question 13

Golgi Tendon Organs (GTO) only fire when muscle ___

Answer 13

actively contracts

Question 14

muscle spindle cares about ___

Answer 14

length

Question 15

golgi tendon cares about ___

Answer 15

tension

Question 16

holgi tendon organs are receptors are ___ fibers

Answer 16

Type Ib

Question 17

golgi tendon organ receptors arranged in ____ with extrafuscal muscle fibers

Answer 17

series

Question 18

muscle spindle is the only afferent that ___

Answer 18

receives a nerve supply

Question 19

difference between gamma motor neurons and alpha MN?

Answer 19

gamma has a smaller soma and a lower conduction velocity

Question 20

____ motor.. innervate intrafusal not at center point
but lower down

Answer 20

gamma

Question 21

____ contraction makes the muscle spindle more sensitive to stim.

Answer 21

intrafusal

Question 22

sensory receptors on intrafusal fibers

Answer 22

type 1a and II

Question 23

___ receptor fires with stretch from distal muscle spindle

Answer 23

type II

Question 24

biceps and brachialis are examples of

Answer 24

agonists

Question 25

triceps and biceps are

Answer 25

anatagonists

Question 26

increased load about the elbow causes rotation

–> spindle in biceps are stretched –>

afferents sent to spinal cord activating the

Answer 26

biceps motor neurons

Question 27

when an anatagonist muscle is inhibited it is by a

Answer 27

1a inhibitory interneuron

Question 28

correction is ____ perturbation

Answer 28

resisting

Question 29

if you ___ of a spindle it becomes silent

Answer 29

reduce

Question 30

when alpha motor neuron is activated without ___ you get silent

Answer 30

gamma MN

Question 31

golgi tendon reflex involves the ___ interneuron

Answer 31

1b

Question 32

in golgi tendon reflex action

1b interneuron does what

Answer 32

excites the anatgonist muscle

inhibits the agonist muscle

Question 33

Flexion-crossed-extension reflex:

if one limb reflexively withdraws, the limb across the midline ____ to keep you balanced.

Answer 33

extends

Question 34

Central pattern generators are defined as neurons that

Answer 34

produce coordinated movements in the absence of higher inputs

Question 35

in cats & humans central pattern generators are for ___ movements

Answer 35

stepping

Question 36

central pattern generators are activated by (2)

Answer 36

2. stim of Mesencephalic Locomotor Region
3. noradrenergic inputs

Question 37

if one limb reflexively withdraws, theipsilateral limb ____ to keep you balanced.

Answer 37

flexes

Question 38

central pattern input can be modified by

Answer 38

training

Question 39

with emg demonstration Low amplitude action potentials…could mean

Answer 39

lost neurons

Question 40

its difficult to activate a nerve AP with direct electrical stimulation but easy to

Answer 40

monitor or record

Question 41

emg – Can only recruit a few motor units…suggests a

Answer 41

partial problem

Question 42

emg – Spontaneous, non-rhythmic activity…suggests

Answer 42

dennervated muscle