Chapter 17

Question 1

Subsystem 1:

Answer 1

Lower motor neurons and local circuit neurons in the spinal cord and brainstem.

Question 2

lower motor neurons

Answer 2

innervate the skeletal muscles of the head and body

Question 3

local circuit neurons

Answer 3

receive sensory inputs and descending projections from upper motor neurons

Question 4

functions to commend movement

Answer 4

reflexive or voluntary

Question 5

reflexive movement

Answer 5

sensory neuron to lower motor neuron without involvement of upper motor neuron in the cortex

Question 6

voluntary movement

Answer 6

sensory neuron to upper motor neuron in the cortex and then to lower motor neuron

Question 7

lower motor neurons are in the

Answer 7

ventral horn of the spinal cord gray matter

Question 8

Subsystem II:

Answer 8

Upper motor neurons (UMNs) in brainstem or cerebral cortex

Question 9

Subsystem III:

Answer 9

Basal ganglia; Prepare upper motor neuron circuits for the initiation of the voluntary
movement and suppress unwanted movement (Parkinson’s disease)

Question 10

Subsystem IV:

Answer 10

Cerebellum; Detects and attenuates the difference or “motor error ” between an intended movement and the actual movement (correct motor error)

Question 11

Two upper motor neurons and their function?

Answer 11

Cortical: upper motor neurons are for the initiation of voluntary movements and for skilled movements

Brainstem upper motor neurons are for regulating muscle tone and integrating sensory inputs for postural control

Question 12

Distal muscles are mediated by

Answer 12

lateral LMNs (skilled voluntary movement)

Question 13

proximal muscles are mediated by

Answer 13

medial LMNs (Body posture)

Question 14

What is the somatotopy of LMNs for skilled movement?

Answer 14

UMNs in cortex > lateral LMNs (via lateral interneurons) > lateral (distal) muscles > skilled movement

Question 15

What is the somatotopy of LMNs for postural control and balance?

Answer 15

UMNs in brainstem > medial LMNs (via medial interneurons or directly through medial white matter) > medial (proximal) muscles > postural control and balance.

Question 16

**Definition of motor unit:

Answer 16

Contains one lower motor neuron

Question 17

**Definition of motor pore:

Answer 17

Many lower motor neurons

Question 18

Slow motor units

Answer 18

generate small forces, most resistant to fatigue

Question 19

Fast fatigable motor units

Answer 19

generate large forces, easily fatigued

Question 20

fast fatigue-resistant motor units

Answer 20

resistant to fatigue, medium force

Question 21

The frequency of the action potentials generated by motor neurons also contributes to

Answer 21

the regulation of muscle force and firing rates

Question 22

Stretch reflex circuitry is a negative feedback loop _______

Answer 22

used to maintain muscle length at a desired value.

Question 23

Golgi tendons are most sensitive to _____

Answer 23

increases in muscle tension that arise from muscle contraction.

Question 24

Golgi tendons are mostly insensitive to ____

Answer 24

passive stretch

Question 25

Autogenic inhibition reflex

Answer 25

afferent fibers of Golgi tendon organs terminate on collagen fibers of the tendon.

Question 26

Autogenic inhibition reflex regulates ____

Answer 26

muscle tension to a desired level.

Question 27

Muscle spindles are sensitive to BOTH ____

Answer 27

stretch and contraction of muscle

Question 28

Central pattern generators:

Answer 28

control the timing and coordination of rhythmic movements

biological neural networks that produce rhythmic patterned outputs without sensory feedback and without descending upper motor neuron inputs.