Spinal Reflexes

Question 1

while spinal reflexes can be modulated by supraspinal control, they largely function as reliable input-output functions that do not require ( )

Answer 1

volition

Question 2

reflexes happen where?

Answer 2

at spinal level

Question 3

3 different “I need a drink” pathways

Answer 3

1) conscious desire to move
2) unconscious control of movement
3) reflexes

Question 4

what participate in reflex function?

Answer 4

1) sensory afferents
2) spinal interneurons
3) motoneurons

Question 5

muscles have what types of sensors?

Answer 5

both length and force sensors (muscle spindles and Golgi tendon organ and associated fibers)

Question 6

the sensitivity of muscle spindles can be maintained over a range of muscle lengths by activation of the spindle’s ( ) fibers via ( )

Answer 6

• intrafusal

- gamma motoneurons

Question 7

monosynaptic and disynaptic spinal reflexes are mediated through ( )

Answer 7

muscle afferents

Question 8

simplest of muscle afferent spinal reflexes

Answer 8

stretch/myotactic reflex

Question 9

stretch/myotactic reflex: a short stretch of the muscle’s spindles results in a synchronous volley of activity in ( ) and ( ) afferents that in turn causes that muscle’s motoneurons to be activated in a ( ) reflex arc

Answer 9

• group Ia and group II

- two neuron, monosynaptic reflex arc

Question 10

the activation of a muscle’s stretch receptors also usually leads to activation of ( ) innervating synergist muscles

Answer 10

motoneurons

Question 11

muscle spindle afferent fibers

Answer 11

group Ia and II

Question 12

golgi tendon afferent fibers

Answer 12

group Ib

Question 13

muscle spindle activation on motoneurons of anatagonist muscle reflex: the same muscle afferents synapse on a population of interneurons called ( ) that then synapse on ( ) to prevent them from being activated

Answer 13

• Ia inhibitory interneurons

- antagonist motoneurons

Question 14

the stretch reflex can be mimicked using

Answer 14

electrical stimulation (the Hoffman reflex)

Question 15

golgi tendon: when too much force happens, motoneurons of the activated muscle are ( ) and motoneurons of antagonist muscles are ( )

Answer 15

• inhibitied

- activated

Question 16

Ib inhibitory interneurons recieve not only afferent input but also ( )

Answer 16

supraspinal input

Question 17

motoneurons have ( ) in addition to their main axon that reaches the muscle and thes activate inhibitory Renshaw cells that then synapse back on the activated motoneurons to limit their activity

Answer 17

collateral branches

Question 18

Renshaw cells are also conntect to ( ) through other interneurons so that the activity in one group of motoneurons eventually leads to their own inactivation and the easier activation of their antagonists

Answer 18

antagonist muscle motoneuron pools

Question 19

interneurons of spinal cord also receive non-muscle afferent input that participates in reflexes that, in the case of the flexor reflex/crossed extensor reflex, coordinates activity within motoneurons located where?

Answer 19

on both sides of the spinal cord

Question 20

the stepping on nail reflex is mediated through multiple levels of interneurons and is therefore ( )

Answer 20

polysynaptic

Question 21

there are also ( ) connections to coordinate activity between different levels of the spinal cord

Answer 21

intra-spinal

Question 22

intra-spinal connections allow for ( ) across motoneuron pools of the entire arm or leg but also of arms with legs or limbs with trunk muscles for certain motor tasks

Answer 22

coordination

Question 23

there is circuitry for locomotion located in the ( ) of the spinal cord and this is connected to similar circuitry in the cervical enlargement so that arm swing and stepping may be coordinated

Answer 23

lumbar enlargement

Question 24

intra-spinal connections make up the ( )

Answer 24

fasciculus proprius

Question 25

neural circuits within the spinal cord that permit the coordination bw flexors and extensors

Answer 25

stretch reflex and reciprical inhibition

Question 26

movements across multiple joints and between right and left limbs

Answer 26

crossed extensor reflex

Question 27

if you lose medial frontal lobe, where would be the deficit?

Answer 27

?

Question 28

can a single neuron control only one motor unit?

Answer 28

no, it can control multiple

Question 29

what are made up of neural circuits that can carry out rhythmic locomotion?

Answer 29

central pattern generators (CPGs)

Question 30

how are the functions of interneurons for CPGs different than the functions for Ia interneurons or Renshaw cells?

Answer 30

CPG interneurons are not as well identified as the others

Question 31

stepping can be initiated in rhythm generaor interneurons in the isolated spinal cord using ( ) but it can also be initiated from a collection of supraspinal sites as well

Answer 31

afferent input or drugs

Question 32

afferent input, descending signals from supraspinal centers and drugs can also change the ( ) of stepping through these rhythm generator interneurons

Answer 32

speed and pattern