Deck 55: Motor Functions of the Spinal Cord; the Cord Reflexes

Question 1

The stretch reflex initiated by tapping on the patellar tendon causes muscle contraction by which of the following mechanisms?

A)Activation of type Ia sensory fibers
B)Activation of type Ib sensory fibers
C)Activation of gamma motor neurons
D)Activation of inhibitory interneurons

Answer 1

A

Question 2

A Golgi tendon organ is most likely to sense which of the following?

A)Fine touch
B)Length
C)Pressure
D)Tension
E)Vibration

Answer 2

D

Question 3

Which of the following is most likely to increase the sensitivity of the stretch reflex?

A)Cutting dorsal root fibers associated with muscle in which stretch reflex is being examined
B)Increasing activity of medullary reticular nuclei
C)Bending head forward
D)Increased activity in fusimotor (gamma motor neuron) system

Answer 3

D

Question 4

Assuming all sensory, motor, and reflex neuronal pathways are intact, skeletal muscle contraction can be caused by stimulation of which of the following?

A)Type 1a sensory nerve endings
B)Type 1b sensory nerve endings
C)Neurons in ventromedial hypothalamus
D)Preganglionic parasympathetic vagal nerves

Question 5

The dynamic response of the muscle spindle receptor can best be described as which of the following?

A)An increase in the activity of the nuclear chain fibers as a result of the change in length of the muscle fiber
B)An increase on activity of the group II sensory afferents in response to the rate of change in length of the muscle fiber
C)A decrease in the activity of the group 1a sensory afferents in response to a change in length of the muscle fiber
D)An increase in the activity of the muscle spindle receptor that is proportional to the rate of change in length of the muscle fiber

Question 6

Type 1a afferents innervate which of the following types of receptors in the muscle spindle apparatus?

A)Nuclear chain fibers
B)Static nuclear bag
C)Dynamic nuclear bag fibers
D)All of the above

Question 7

The sensitivity of the stretch reflex can be altered by which of the following?

A)Activity in the olivocerebellar tract
B)Simultaneous stimulation of primary motor cortex and supplemental motor area of cortex
C)Activity of pontine reticular nuclei
D)Activity of corticospinal tract

Question 8

What is the function of the Golgi tendon organ?

A)To sense the length of the muscle tendon in which it is located
B)To provide the cerebellum with feedback information concerning which motor impulses have arrived at the anterior motor neurons of the spinal cord
C)To transmit muscle stretch information to higher brain centers
D)To sense muscle tension and equalize the contractile force exerted by groups of muscle fibers in a muscle

Question 9

In a muscle spindle receptor, which fiber is responsible for the dynamic response?

A)Extrafusal muscle fiber
B)Static nuclear bag fiber
C)Nuclear chain fiber
D)Dynamic nuclear bag fiber

Question 10

Type II sensory afferents from the muscle spindle receptor are attached to which of the following structures?

A)Extrafusal muscle fiber
B)Dynamic nuclear bag fiber
C)Nuclear chain fiber
D)Gamma S fiber

Question 11

Following Questions :A 30-year-old man with bare feet steps on a broken bottle with his right foot. His right leg immediately lifts while his left leg extends before he can consciously react to the pain. Use this information to answer the next two questions.
Which of the following best describes the type of reflex arc and sensory receptor for this reflex?

Question 12

Activation of a type 1b sensory neuron is most likely to have which of the following effects?

A)Contraction of muscle fiber associated with this neuron
B)An initiation of a complex spike output signal
C)Central nystagmus
D)Inhibition of muscle contraction in muscle fiber associated with this neuron

Question 13

Which of the following is true regarding stimulation of type II sensory fibers innervating a muscle spindle?

A)Will inhibit muscle contraction
B)Will activate an inhibitory interneuron in the anterior horn of the spinal cord and lead to inhibition of Golgi tendon response
C)Will activate a gamma motor neuron connected to the muscle containing the spindle receptor
D)Will activate an alpha motor neuron connected to the muscle containing the spindle receptor

Question 14

Assuming all sensory, motor, and reflex pathways are intact, muscle contraction can be caused by stimulation of which of the following types of neurons?

A)Alpha motor neurons
B)Gamma motor neurons
C)Type 1a sensory endings from a nuclear bag fiber
D)All of the above

Question 15

Under normal conditions, activation of which of the following can lead to muscle contraction?

A)Free nerve endings
B)Type Ia sensory fibers
C)Nuclear chain fibers
D)All of the above

Question 16

Following Questions :A 30-year-old man with bare feet steps on a broken bottle with his right foot. His right leg immediately lifts while his left leg extends before he can consciously react to the pain. Use this information to answer the next two questions.
Which of the following best describes the name of this reflex?

A)Walking reflex
B)Stretch reflex
C)Patellar tendon reflex
D)Golgi tendon reflex
E)Flexor withdrawal reflex