Phys - Motor Reflexes Flashcards Preview

Maddy - Neuro II - tracks > Phys - Motor Reflexes > Flashcards

Flashcards in Phys - Motor Reflexes Deck (42)
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1

what part of the CNS controls the placing and hopping reactions

cortex

2

describe the placing reaction

example: cat putting paws in weight bearing mode when you hold is over a counter

3

describe the hopping reaction

the hop you do when someone pushes you to the side

4

what part of the CNS controls the righting reflex

brainstem/midbrain

5

what part of the CNS controls the suckle reflex

brainstem/midbrain

6

what part of the CNS controls the yawn reflex

brainstem/midbrain

7

what part of the CNS controls stretch (myotatic reflex)

spinal cord

8

what part of the CNS controls golgi tendon reflex

spinal cord

9

compare the level of organization from the CNS between a reflex and volitional motion

reflex: any CNS level, does not require cortex for most
volitional: requires cortical and subcortical involvement

10

compare the circuitry between reflex and volitional movement

reflex: fixed
volitional: variable depending on motion

11

purpose of the myotatic reflex (stretch)

contracting of a stretched muscle to protect muscle from tearing

12

where are the extrafusal and intrafusal fibers of the muscle spindle

intrafusal: within the capsule
extrafusal: the fibers that make up the bulk of the muscle

13

describe the sensory portion of a muscle spindle

- not contractile
- sensitive to length
- consists of nuclear bag fiber and nuclear chain fiber

14

what innervates the nuclear bag and nuclear chain of the muscle spindle (primary afferent)

1a fibers

15

describe 1a fibers

large, myelinated, fast
- innervates sensory portion of muscle spindle (nuclear bag and chain)

16

what are 1a fibers sensitive to

length of muscle and rate at which the length is changing

17

what do group 2 fibers innervate

secondary afferent parts of muscle spindle (only the nuclear chain)

18

what are group 2 fibers sensitive to

only the length of muscle (not the rate of change in length)

19

compare group 1a fibers and group 2 fibers

group 1a: heavily myelinated, faster, low threshold
group 2: smaller diameter, less myelin, still fast but not as fast

20

what innervates the motor portion of the muscle spindle (intrafusal contractile elements)

gamma motorneuron

21

how does the motor portion of the muscle spindle affect the sensory portion

motor portion controls the length of the sensory portion (and its sensitivity)

22

how does contraction of the intrafusal fibers affect length of muscle spindle and length of sensory portion

does not change the length of the muscle spindle but shortens the intrafusal fibers which stretches the sensory portion, increasing sensitivity of the 1a and group II fibers to stretch

23

compare structures of alpha and gamma motor neurons

alpha: large, heavily myelinated
gamma: slightly smaller, slower, still fast though

24

compare function of alpha and gamma motor neurons

alpha: innervates skeletal muscle (extrafusal fibers) --> leads to direct motion
gamma: innervates intrafusal fibers --> does NOT lead to direct motion

25

where do the 1a fibers synapse after leaving the muscle spindle

directly onto alpha motor neuron innervating the stretched muscle

26

after the 1a fibers synapse onto the alpha motor neurons, what occurs

the motoneuron causes contraction of muscle to relieve the stretch and the 1a fiber's discharge rate returns to normal

27

when the 1a fiber synapses onto the alpha motor neuron, it causes contraction of that muscle that was being stretched. Describe how this contraction also causes stretching in the antagonist muscle

the 1a fiber also synapses onto an interneuron that inhibits the contraction of the antagonist muscle, causing it to relax and thus stretch
(inhibition is mediated by GABA)

28

what reflex protects muscles from damage due to excessive force

golgi tendon organ

29

describe the appearance of a golgi tendon organ reflex

a sudden relaxation of a contracted muscle to prevent from damage

30

what innervates the golgi tendon organ

1b fibers