Chapter 9: The Somatic Sensory System: Touch and Propioception

1. Where would the cell body of a sensory neuron that transmits touch information from the cheek to the central nervous system be located?
a. Ganglion alongside the brainstem
b. Nucleus inside the brainstem
c. Ganglion alongside the spinal cord
d. Nucleus inside the spinal cord
e. Ganglion immediately underneath the skin of the cheek

Answer: a

2. Which feature is characteristic of the pseudounipolar neurons of the somatosensory system?
a. Central and peripheral components of the fibers are of a similar length
b. Thick fibers that enables fast signal transduction
c. Fibers with particularly high myelin content
d. Continuous fibers, with the cell body attached by a single process
e. Multiple dendrites

Answer: d

3. Afferent fibers that lack specialized receptors at their terminals detect which type of stimuli?
a. Touch
b. Vibration
c. Pressure
d. Pain
e. Itch

Answer: d

4. Which afferent fibers have the largest diameter?
a. Ia sensory afferents from the muscles
b. Ia sensory afferents from the skin
c. Aβ sensory afferents from the skin
d. A and C fibers that conduct temperature information
e. A and C fibers that conduct pain information

Answer: a

5. The _______ is inversely proportional to the density of the fibers supplying an area.
a. diameter of the afferent fiber
b. size of the receptive field
c. speed of conduction
d. average stimulus strength
e. distance between an area and the central nervous system

Answer: b

6. On which body part would the two-point discrimination threshold be shortest?
a. Thigh
b. Foot
c. Arm
d. Thumb
e. Ear

Answer: d

7. Rapidly adapting fibers are most likely to provide information about the _______ of a stimulus.
a. shape
b. weight
c. texture
d. movement
e. temperature

Answer: d

8. Which type of somatosensory afferents transmit information from touch mechanoreceptors to the central nervous system?
a. Ia
b. II
c. Aβ
d. Aδ
e. C

Answer: c

9. Which afferents have the highest spatial resolution?
a. Merkel afferents
b. Meissner afferents
c. Pacinian afferents
d. Ruffini afferents
e. Pain afferents

Answer: a

10. Meissner afferents account for about _______ of the mechanosensory innervation of the human hand.
a. 10%
b. 25%
c. 40%
d. 75%
e. 90%

Answer: c

11. Merkel afferent fibers convey information about which variable(s)?
a. Motion detection
b. Temperature
c. Proprioception
d. Shape and texture
e. Subtle vibrations

Answer: d

12. The longitudinal lanceolate endings do not respond to
a. deflection of the hair by strokes on the skin.
b. movement of air over the skin surface.
c. sensual touch.
d. gentle caress.
e. pain.

Answer: e

13. A dermatome is an area innervated by
a. fibers of the cells from a single dorsal root ganglion.
b. the axon of a single neuron.
c. fibers from one spinal cord segment.
d. fibers with similar properties.
e. fibers of the cells from a single nucleus in the brain stem.

Answer: a

14. Which component of the musculoskeletal system is responsible for force-production?
a. Muscle spindle
b. Intrafusal muscle fiber
c. Extrafusal muscle fiber
d. Sensory afferents
e. Connective tissue capsule

Answer: c

15. Which sensation would be affected if group II sensory afferents in a limb were rendered dysfunctional due to a mutation?
a. Velocity of limb movement
b. Direction of limb movement
c. Touch to the limb
d. Static position of the limb
e. Change in muscle length

Answer: d

16. Which role do γ motor neurons play in the function of a muscle spindle?
a. They improve the accuracy of the reported sensory information by innervating extrafusal fibers.
b. They improve the accuracy of the reported sensory information by innervating intrafusal fibers.
c. They enhance the force of muscle contraction by innervating extrafusal fibers.
d. They enhance the force of muscle contraction by innervating intrafusal fibers.
e. They coordinate the contraction of extrafusal and intrafusal fibers.

Answer: b

17. Muscles in which region would most likely have the lowest density of muscle spindles?
a. Tongue
b. Extraocular
c. Hand
d. Neck
e. Leg

Answer: e

18. Joint receptors are important to perception which information?
a. Joint position near the limits of normal range of motion
b. Joint movement
c. Finger position near the limits of normal range of motion
d. Finger movement
e. Limb position and movement

Answer: c

19. The axons of the medial lemniscus synapse with neurons of the
a. primary sensory cortex.
b. thalamus.
c. gracile nucleus.
d. cuneate nucleus.
e. dorsal root ganglion.

Answer: b

20. Tactile information from the face to the central nervous system follows which pathway?
a. Cutaneous receptors, trigeminal ganglion, pons, VPL of thalamus, ipsilateral cortex
b. Cutaneous receptors, trigeminal ganglion, trigeminal brainstem complex, VPL of thalamus, contralateral cortex
c. Cutaneous receptors, cranial nerve V, trigeminal brainstem complex, VPM of thalamus, contralateral cortex
d. Cutaneous receptors, dorsal root ganglion, trigeminal brainstem complex, VPM of thalamus, ipsilateral cortex
e. Cutaneous receptors, dorsal root ganglion, dorsal column nuclei, VPM of thalamus, cortex

Answer: c

21. Where are the bodies of the cells that innervate proprioceptors of the face located?
a. Cervical dorsal root ganglia
b. Thoracic dorsal root ganglia
c. Trigeminal ganglia
d. Mesencephalic trigeminal nucleus
e. Principal nucleus

Answer: d

22. Organization in which region of the brain is represented as a complete somatotopic map?
a. Primary somatosensory cortex SI
b. Brodmann's area 1
c. Brodmann's area 2
d. Secondary somatosensory cortex SII
e. Hypothalamus

Answer: a

23. Refer to the figure.



Activity of which cortical area(s) depend(s) on the projections from other cortical areas?
a. Secondary somatosensory cortex only
b. Brodmann's areas 1 and 2 only
c. Brodmann's areas 3a and 3b
d. Secondary somatosensory cortex and Brodmann's areas 1 and 2
e. Parietal areas 5 and 7

Answer: d

24. Functional reorganization in the brain
a. occurs at all ages, all of the time.
b. occurs after nerve damage, amputation, and skill training.
c. results in a temporary loss of sensory input.
d. occurs only during the first ten years of life.
e. occurs only in the cortex.

Answer: b

1. What change could improve the two-point discrimination of a region of skin?

Answer: An increase in the density of innervation and reduction of the receptive field size

2. What is a somatosensory receptive field?

Answer: The surface area over which stimulation results in a significant change in the rate of action potentials of a particular neuron.

3. What is proprioception? Name three kinds of proprioceptors.

Answer: Proprioception is the ability to sense the position of the body and limbs in space. Muscle spindles, Golgi tendon organs, and joint receptors are types of proprioceptors.

4. Where are the gracile and cuneate tracts located, and what information do they convey?

Answer: The gracile tract lies in the medial dorsal column of the spinal cord and conveys information from the lower limbs; the cuneate tract lies in the lateral dorsal column of the spinal cord and conveys information from the upper limbs, trunk, and neck.

14. The _______ of the trigeminal _______ conveys facial tactile information in much the same way that the dorsal column nuclei transmit lower body tactile information.
a. principal nucleus; complex
b. spinal nucleus; complex
c. ophthalmic branch; nerve
d. mandibular branch; nerve
e. maxillary branch; nerve

Answer: a