somatic motor system

Question 1

upper motor neuron cell body location

Answer 1

motor cortex

midbrain/brainstem centers

Question 2

motor cortex

Answer 2

upper motor neuron
voluntary movements (planning & precise control, somatic expression of emotional states)

Question 3

midbrain/brainstem centers

Answer 3

upper motor neuron

1. superior colliculus
2. vestibular nuclei
3. reticular formation

Question 4

superior colliculus

Answer 4

head & eye coordination

Question 5

vestibular nuclei

Answer 5

body posture & position

head & eye movements

Question 6

reticular formation

Answer 6

body posture & position

regulation of muscle tone

Question 7

lower motor neuron cell body location

Answer 7

motor nuclei of cranial nerves

ventral horn of the SC in rexed lamina IX

Question 8

motor unit

Answer 8

a single alpha motor neuron and the muscle fibers it innervates

Question 9

motor neuron pool for a muscle

Answer 9

• all alpha motor neurons innervating this muscle

- each alpha motor neuron innervates muscle fibers of only one muscle

Question 10

somatotopic organization of motor neuron pool in SC

Answer 10

each motor neuron pool is grouped together into a rod shaped cluster that runs parallel to the long axis of the SC and shows somatotropin organization

• axial musculature - medially
• distal musculature - laterally

Question 11

2 types of lower motor neurons

Answer 11

alpha motor neurons

gamma motor neurons

Question 12

alpha motor neurons

Answer 12

• innervate extrafusal muscle fibers (striated)

- muscle contraction & forces needed for posture & movement

Question 13

gamma motor neurons

Answer 13

• innervate specialized intrafusal muscle fibers

- regulate the sensory input

Question 14

myotatic reflex

Answer 14

stretch or knee jerk reflex
monosynaptic reflex
negative feedback loop

Question 15

myotatic reflex:

tapping the tendon causes

Answer 15

muscle spindles stretching

Question 16

myotatic reflex:

input received via

Answer 16

proprioceptor afferent with body in the DRG

Question 17

myotatic reflex:

synapses with

Answer 17

alpha motor neurons in the ventral horn

Question 18

myotatic reflex:

alpha motor neurons innervates

Answer 18

extrafusal muscle fibers, causes contraction

Question 19

myotatic reflex:

excitatory pathway for ____________ muscles and an inhibitory pathway for _____________ muscles

Answer 19

synergistic
antagonist

**inhibitory pathway via an inhibitory interneuron

Question 20

golgi tendon organ reflex

Answer 20

inverse myotatic

protects the muscle and tendon against excessive stress

Question 21

golgi tendon organ reflex:

stress on the tendon causes

Answer 21

activation of golgi tendon organ

Question 22

golgi tendon organ reflex:

input received via

Answer 22

proprioceptor afferent with body in the DRG

Question 23

golgi tendon organ reflex:

synapses with

Answer 23

1) inhibitory interneuron in the ventral horn

2) inhibition of alpha motor neuron

Question 24

golgi tendon organ reflex:

alpha motor neurons innervates

Answer 24

inhibition of extrafusal muscle fibers, causes relaxation

Question 25

golgi tendon organ reflex:

increase in muscle/tendon __________ results in rapid relaxation of the contracting muscle

Answer 25

tension

Question 26

flexion reflex

Answer 26

initiated by noxious stimuli (nociceptors)

polysynaptic reflex

Question 27

two major components of flexion reflex

Answer 27

ipsilaterally
contralaterally
**each engaging at least one local circuit neuron

Question 28

flexion reflex:

ipsilaterally

Answer 28

activation of alpha motor neurons to flexors and inhibition of alpha motor neurons to extensors
*flexion reflex - withdrawal

Question 29

flexion reflex:

contralaterally

Answer 29

activation of alpha motor neurons to extensors and inhibition of alpha motor neurons to flexors
*crossed extension reflex - postural support