QUIZ 8

Question 1

a motor neuron pool consists of:

-all of the motor neurons that project to a given muscle
-all of the motor neurons that project to a given limb
-all of the motor neurons within a single segment of spinal cord
-a single motor neuron and all of its afferent interneurons
-a single motor neuron and all of the muscles it innervates

Answer 1

all of the motor neurons that project to a given muscle

Question 2

a specialized motor unit, with an average size of three muscle fibers, controls:

-finger movements
-the large, fast contracting muscles used in sprinting
-postural muscle
-eye muscles

Answer 2

eye muscles

Question 3

which of the following statements about the organization of muscles and motor neurons is false?

-successive stimulation of muscles can produce force levels that build up over time
-the fastest, strongest muscle fibers can produce the most sustained force output
-large motor neurons are recruited only at higher levels of stimulus intensity
-red muscle fibers contract slowly and produce the smallest amount of force

Answer 3

the fastest, strongest muscle fibers can produce the most sustained force output

Question 4

the condition called “fused tetanus” refers to:

-a sustained maximal contraction due to high frequency input to motor unit firing
-lockjaw symptoms resulting from exposure to the tetanus toxin
-the response of single muscle fibers to a single action potential input
-an excessive contraction that results in the fusing together of muscle fibers

Answer 4

a sustained maximal contraction due to high frequency input to motor unit firing

Question 5

group 1a afferents are coiled around ____ fibers

-all extrafusal muscle fibers
-only S-type extrafusal muscle fibers
-both nuclear bag and nuclear chain fibers

Answer 5

both nuclear bag and nuclear chain fibers

Question 6

if the muscle is actively contracted and shortens during voluntary movement, which of the following would you expect to increase their discharge rate?
(select multiple)

-golgi tendon organs
-gamma motor neurons
-muscle spindles
-alpha motor neurons

Answer 6

-golgi tendon organs
-gamma motor neurons
-alpha motor neurons

Question 7

in a stretch reflex with a high gain, a ____ stretch of a muscle would lead to ____ increase in extrafusal muscle tension

-small; a large
-small; no
-large; a small
-large; no

Answer 7

small; a large

Question 8

gamma (γ) motor neuron firing rates are typically high
(select multiple)

-during difficult and precise movements (walking on a narrow beam)
-during voluntary stretching
-during unpredictable conditions (standing on a moving bus)

Answer 8

-during difficult and precise movements (walking on a narrow beam)
-during unpredictable conditions (standing on a moving bus)

Question 9

the flexion-crossed extension reflex would occur in response to which activity?

-holding a box steady as more items are added to it
-coordinating your legs to squat
-stimulation of the mesencephalic locomotor region
-stepping on a sharp object
-a knee tap with a reflex hammer

Answer 9

stepping on a sharp object

Question 10

the local circuits in the spinal cord that are fully capable of controlling the timing and coordination of complex locomotion are called ____

Answer 10

central pattern generators