Motor Control: Reflexes

Question 1

What are the cortical reflexes

Answer 1

Placing and Hopping Reaction

Question 2

What are the brainstem/midbrain reflexes

Answer 2

Vestibular
righting reflex
suckle
yawn
eye/head movements

Question 3

What are the spinal reflexes

Answer 3

stretch
golgi tendon
crossed extensor

Question 4

What requires cortical and subcortical involvement

Answer 4

Volitional motion

Question 5

What is the appearance of a myotactic reflex

Answer 5

contraction of stretched muscle

Question 6

What is a myotatic reflex initiated by

Answer 6

muscle spindle

Question 7

What components are found in a muscle spindle

Answer 7

afferent and efferent components

Question 8

What forms the bulk of the muscle

Answer 8

extrafusal fibers

Question 9

What are characteristics of a sensory portion of a muscle spindle

Answer 9

Not contractile, sensitive to length, have two sensors.

Question 10

What do Ia fibers innervate

Answer 10

nuclear bag and nuclear chain

Question 11

What is the Ia fiber sensitive to

Answer 11

length of muscle, and how fast the length is changing

Question 12

What are characteristics of the Secondary Afferent

Answer 12

smaller, myelinated Group II fiber
only nuclear chain
sensitive to length of muscle

Question 13

What is innervated by a gamma motorneuron

Answer 13

Intrafusal contractile elements

Question 14

What is the purpose of a gamma motorneuron

Answer 14

control length of sensory portion

Question 15

Within spinal cord, what does the Ia fiber synapse to

Answer 15

alpha motorneuron innervating stretched muscle

Question 16

How is the antagonist muscle relaxed during a reflex

Answer 16

Ia afferent interacts with interneuron that inhibits alpha motorneuron of antagonist muscle

Question 17

What is the appearance of a golgi tendon reflex

Answer 17

abrupt relaxation of contracted muscle to protect it from damage. Is polysynaptic

Question 18

What type of fiber is the golgi tendon reflex

Answer 18

Ib fiber to spinal cord

Question 19

What do recovery of reflexes come from

Answer 19

axonal sprouting below level of transection, or expression of phenotypes that are self activating

Question 20

What causes decerebrate posturing

Answer 20

loss of all structures rostral to pons (caudal to red nucleus)

Question 21

What causes rigidity

Answer 21

continual activation of alpha-motorneurons, maintains muscle contraction

Question 22

What causes spasticity

Answer 22

Continual activation of gamma motorneurons, which contracts intrafusal muscle and lengthen nuclear bag/chain

Question 23

What is the characteristic movement of rigidity

Answer 23

resists motion in all directions

Question 24

what is the characteristic movement of spasticity

Answer 24

resists movement in a given direction

Question 25

What is the function of the brainstem facilitatory region

Answer 25

makes muscle spindle more senstitive by activating gamma neurons. Spontaneously active.

Question 26

What ist he function of the brainstem inhibitory region

Answer 26

makes muscle spindle less sensitive by inhibiting gamma motorneurons, which requires activation from cortical regions

Question 27

What does decorticate posturing look like

Answer 27

flexion of upper limb joints, extension of lower limbs, dependent on head position

Question 28

What causes flexion of upper limbs in decorticate posturing

Answer 28

disinhibition of red nucleus and its control of UE flexors

Question 29

What causes extension of lower limbs in decorticate posturing

Answer 29

disinhibition of reticulospinal and vestibulospinal pathways

Question 30

What is decorticate posturing commonly associated with

Answer 30

strokes in vicinity of internal capsule