Deck 23: Touch, Pain, and Texture Sensation

Question 1

What morphological feature distinguishes between Pacinian and Ruffini receptors on one hand and Meissner and Merkel receptors on the other?

A) Pacinian and Ruffini structures tend to be larger than Meissner and Merkel structures.
B) Pacinian and Ruffini structures respond to mechanical stimuli, whereas Meissner and Merkel's structures do not.
C) Pacinian and Ruffini structures are more sensitive to mechanical stimuli than Meissner and Merkel's structures are.
D) Pacinian and Ruffini receptors are encased in a capsule, whereas Meissner and Merkel's receptors are not.
E) Pacinian and Ruffini receptors are also sensitive to changes in temperature, whereas Meissner and Merkel receptors are not.

Answer 1

A

Question 2

Which two receptors tend to lie deeper in the skin?

A) Pacinian and Merkel
B) Pacinian and Meissner
C) Pacinian and Ruffini
D) Merkel and Meissner
E) Merkel and Ruffini

Answer 2

C

Question 3

Which receptors tend to adapt slowly to compression on the skin?

A) Pacinian and Merkel
B) Pacinian and Meissner
C) Pacinian and Ruffini
D) Merkel and Meissner
E) Merkel and Ruffini

Answer 3

E

Question 4

Which receptors will be stimulated when tickled?

A) Pacinian
B) Meissner and free nerve endings
C) Ruffini endings
D) Merkel disks
E) Ruffini and free nerve endings

Question 5

Which two receptors tend to lie relatively close to the surface of the skin?

A) Pacinian and Merkel
B) Pacinian and Meissner
C) Pacinian and Ruffini
D) Merkel and Meissner
E) Merkel and Ruffini

Question 6

Besides Meissner Corpuscles, which receptor will be affected by local anesthetics?

A) Pacinian
B) Merkel
C) Ruffini
D) Nociceptors
E) Free nerve endings

Question 7

When a hair is pulled out of the skin, it is painful. Which kind of receptor is stimulated?

A) Pacinian
B) Merkel and free nerve endings
C) Ruffini and free nerve endings
D) Free nerve endings
E) Meissner

Question 8

How long will it take for an action potential to reach the spinal cord if a receptor neuron's skin receptors were in the toe? Assume that action potentials travel at a rate of 80 m/s and that the distance to be travelled is 0.6 m.

A) 0.5 milliseconds
B) 1 millisecond
C) 7.5 milliseconds
D) 15 milliseconds
E) 48 milliseconds

Question 9

What part of the long receptors make synaptic contact with the secondary neurons that extend into the brain?

A) The somas in the dorsal root ganglion
B) The axon hillock
C) The part that enters the spinal cord dorsal horn
D) The part that enters the spinal nerve
E) The part that enters the spinal cord intermediate zone

Question 10

The sensitivity of long receptors in the skin of various body parts in the periphery are determined by the

A) size of their receptive fields
B) number of terminal axons at the receptor
C) length of the axon between the receptor and the dorsal root ganglion
D) length of the axon between the dorsal root ganglion and spinal cord
E) number of somas in the dorsal root ganglion

Question 11

Microneurography can be used to map sensory receptive fields all over the body. Specifically, this technique can determine their

A) relative size.
B) number of receptors contained therein.
C) depth (how far under the skin it extends).
D) number of neighboring receptive fields.
E) innervation density.

Question 12

Microneurography can be used to map sensory receptive fields all over the body. This is a well-known way to diagnose and evaluate

A) multiple sclerosis.
B) Parkinson's disease.
C) cerebral meningitis.
D) spinal cord injury.
E) traumatic brain injury.

Question 13

Besides the ability to provide verbal feedback, using microneurography on humans offers which other advantage over that if using other animals?

A) Human skin is more sensitive than that of other animals.
B) Humans have a smaller surface area (skin)-to-volume ratio.
C) Human skin is thinner than that of other animals
D) Humans have little-to-no hair, the presence of which will confound the findings obtained in microneurography and must be shaved off if using other animals.
E) Ultimately, the goal is to be able to map the sensory receptive fields in humans; other animals are used when using humans is ethically, morally or legally inappropriate.

Question 14

Which nerve fibers will conduct action potentials the fastest?

A) Wide diameter, heavily myelinated
B) Wide diameter, thinly myelinated
C) Narrow diameter, heavily myelinated
D) Narrow diameter, thinly myelinated
E) Any diameter, not myelinated

Question 15

Suppose the Aδ fibers send action potentials at 10 m/sec and the unmyelinated C fibers sends them at 2 m/sec. How much time will elapse between first pain and second pain upon accidently dropping a heavy brick on your toe? Assume a total distance of 1.2 m from toe to spinal cord to somatosensory cortex.

A) 25 milliseconds
B) 100 milliseconds
C) 120 milliseconds
D) 480 milliseconds
E) 600 milliseconds

Question 16

Although probably impossible to experiment with, a person is surprised by being struck with equal force in the face by two other people: one familiar (a loved one) and one complete stranger. The pain felt by the struck person is seems greater if (s)he is struck by the familiar person than if struck by the complete stranger. This subjective difference in sensation of these two identical forces is processed by the

A) primary somatosensory cortex.
B) secondary somatosensory cortex.
C) somatosensory association cortex.
D) anterior cingulate cortex.
E) central sulcus.

Question 17

The placebo effect seems to work primarily through the

A) anterior cingulate cortex.
B) somatosensory cortex.
C) thalamus.
D) brainstem.
E) insular cortex.

Question 18

What might be one possible reason or scenario in which the placebo treatment does not work in relieving pain?

A) Prior knowledge or awareness of the placebo effect
B) Overwhelming subjective feelings about the severity of the pain resulting from a serious injury, such as from an amputation
C) When enough anesthetics are used
D) When insufficient anesthesia is used
E) When only topical anesthetics are used

Question 19

Blockade of µ-opioid receptors is correlated with suppression of activity in the anterior cingulate and insular cortices. This can be experimentally confirmed by administration of a µ-opioid receptor

A) antagonist and subsequent visualization via fMRI.
B) antagonist and simultaneous visualization via fMRI.
C) agonist, such as morphine, followed by visualization via fMRI.
D) antagonist, accompanied by administration of a µ-opioid receptor agonist, such as morphine, and simultaneous visualization via fMRI.
E) antagonist, accompanied by administration of a µ-opioid receptor agonist, such as morphine, followed by visualization via fMRI.

Question 20

Although a surface topographic map of the sensory inputs is used to illustrate the disproportionate amount of somatosensory cortex devoted to whiskers, it is more valid to evaluate the underlying cortical ________ of such input.

A) density
B) organization
C) depth
D) volume
E) activity

Question 21

In rats and mice, a single whisker projects to

A) a single neuron in the somatosensory cortex.
B) a single barrel of neurons in the somatosensory cortex.
C) a single cluster of neurons in the somatosensory cortex.
D) a single chain of neurons in the somatosensory cortex.
E) the somatosensory cortex indiscriminately throughout.

Question 22

Receptive fields of the whiskers on the snout of rats and mice are

A) large and overlapping.
B) small and overlapping.
C) large and nonoverlapping.
D) small and nonoverlapping.
E) absent.

Question 23

Rats and mice tend to use their whiskers to explore their environment in a way that is analogous, albeit much more extensively, to the way humans use their

A) arms and legs.
B) hands.
C) fingers.
D) feet.
E) toes.

Question 24

A rat who has lost a couple of whiskers in an environmental mishap will

A) die, because intact whiskers are absolutely essential for survival.
B) recover, because the surviving surrounding whiskers will grow longer to compensate for the lost ones.
C) recover, because the surviving surrounding whiskers will grow thicker wider shafts to compensate for the lost ones.
D) recover, because all the surviving whiskers will become compensate sensory function for that of the lost ones.
E) recover, because the surviving surrounding whiskers' receptive fields will compensate by taking over the cortical vacancies left by the lost ones.

Question 25

What is probably the signal that causes the firing of action potentials from the trigeminal nerve when a whisker is deflected?

A) Neurotransmitter binding to its GPCR
B) Hormone binding to its GPCR
C) Mechanically gated ion channel
D) Cyclic nucleotide (cAMP)-activated ion channel
E) Mechanical stretch of the skin, resulting in pulling on the whisker shaft

Question 26

With respect to the cortical layers (I - VI) of the primary somatosensory cortex of rats and mice, barrels are arranged

A) in a parallel fashion.
B) perpendicular to each other.
C) at a 30^⸰ angle.
D) at a 60^⸰ angle.
E) randomly.

Question 27

Where is the highest concentration of whisker barrels in the mouse primary somatosensory cortex?

A) Layer I
B) Layer II
C) Layer III
D) Layer IV
E) Layer V

Question 28

A single whisker stimulates a

A) single cortical layer.
B) single cortical barrel.
C) cortical layer and the immediate layers above and below it.
D) cortical barrel and the immediate barrels next to it.
E) single cortical layer and cortical barrel.

Question 29

The ability of rats to learn among different textures provides evidence that

A) rats and mice tend to use their forepaws just as often as they do their whiskers to learn about their environment.
B) rats and mice tend to use their forepaws more often than they use their whiskers to learn about their environment.
C) the whisker-to-brain innervation is highly plastic and adapts to the environmental demands (e.g., different textures).
D) the whisker-to-brain innervation requires that (nearly) all whiskers be intact in order for the rat to learn and successfully navigate his environment.
E) the whisker-to-brain innervation is active only when the whiskers are deflected by some solid texture.

Question 30

When discriminating among different textures, the amount of neuronal firing by sensory receptor neurons is proportional to the

A) novelty of the texture object.
B) natural nature of the texture (e.g., dirt vs. an artificial texture, e.g., metal).
C) size of the textured object.
D) shape of the textured object.
E) roughness of the texture object.

Question 31

A stroke that results death of two-thirds of the neurons of the fingers/hand area of the somatosensory cortex would result in

A) permanent inability to feel sensation in the contralateral fingers/hand.
B) permanent inability to feel sensation in the ipsilateral fingers/hand.
C) temporary inability to feel sensation in the contralateral fingers/hand, provided the patient undergoes regular physical therapy of the affected hands and fingers.
D) temporary inability to feel sensation in the ipsilateral fingers/hand, provided the patient undergoes regular physical therapy of the affected hands and fingers.
E) complete paralysis of the contralateral side of the body.

Question 32

What can be expected to occur in the event of a stroke in an area of the somatosensory cortex if no palliative nor restorative therapies are undertaken (e.g., physical therapy)?

A) Those affected neurons will die and glial scarring will gradually fill in the area.
B) Those affected neurons will die, but neighboring neurons will gradually restore function spontaneously.
C) Some of those affected neurons will die, depending on the extent of their damage and glial scarring will gradually fill in the area.
D) Those affected neurons will re-grow and re-establish their original connections.
E) Glial scarring will rapidly develop, thereby inhibiting any attempt of surviving neurons to recuperate.

Question 33

What is the most likely reason for the somatosensory cortex representing the fingers and hands being so large, but that representing the toes and feet being so small?

A) The skin of the feet and toes are much thicker, and therefore, less sensitive than the skin on the palms of your hands and fingers.
B) The feet have evolved to be less sensitive, and therefore, the area of somatosensory cortex that is served by them, has likewise shrunk since humans started wearing shoes.
C) The amount of cortex representing the two distal limbs are actually equivalent, when you consider the part that represents the feet is hidden within the sagittal fissure.
D) The amount of cortex representing the two distal limbs are actually equivalent, when you consider that the homunculus does not only comprised of cortical surface area, but rather, cortical volume, because the cortex is organized into columns.
E) It is impossible to answer this question with significant certainty.

Question 34

What part of the primary somatosensory cortex receives the densest thalamocortical projections?

A) Fingers and hands
B) Face
C) Trunk
D) Legs
E) Toes and feet

Question 35

Which of the following body parts has the smallest receptive field?

A) Fingers and hands
B) Face
C) Trunk
D) Legs
E) Toes and feet

Question 36

The homunculus has a particularly large cortical area devoted to the face, especially the mouth. This is because it receives dense projections from the

A) trigeminal cranial nerve (V),
B) thalamus.
C) internal capsule.
D) parietal cortex.
E) spinal cord.

Question 37

Which area on the human body is analogous to whiskers on rats and mice in terms of function, innervation density and cortical magnification?

A) Finger tips
B) Hands
C) Lips
D) Eyelids
E) Toes

Question 38

The main stimulus for the ability to discriminate between coarse and fine surfaces is

A) pressure.
B) temperature.
C) vibration.
D) movement.
E) shape.

Question 39

Perception of rough texture is correlated with firing rate of action potentials by

A) slowly adapting Pacinian receptors.
B) quickly adapting Pacinian receptors.
C) Meissner's receptors.
D) slowly adapting Merkel's receptors.
E) quickly adapting Merkel's receptors.

Question 40

The main difference in protocol in having experimental subjects discriminate between rough and smooth surfaces is that they must

A) be exposed to the rough texture first.
B) be exposed to the smooth texture first.
C) move their finger(s) over the rough texture.
D) move their finger(s) over the smooth texture.
E) wear a glove on the contralateral hand.

Question 41

Explain why sitting too long, especially on a hard surface, will eventually be painful.

Question 42

Explain how Pacinian receptors are involved in proprioception and why this is important.

Question 43

Compare a generic hair in the body of a mammal to a highly specialized hair, such as a whisker found in the snout of a rat or mouse.

Question 44

Besides conveying somatosensory impulses of touch, pain, pressure, etc. from the periphery, what do dorsal root ganglion cells also mediate?

Question 45

If electrical circuits were embedded in the skin of an artificial limb to help amputees feel and manipulate, what must happen for this to be successful?

Question 46

How could the mapping of human sensory receptive fields be useful in diagnosing spinal cord injury?

Question 47

Explain how opiate receptors can bind both endorphins and opiates, such as morphine.

Question 48

In pain transmission, how does the medial system affect the lateral system?

Question 49

Cite a piece of evidence that shows that rats trust their whiskers more than their eyes to navigate a novel environment.

Question 50

Outline the pathway that input takes from whisker to cortex in rats and mice.

Question 51

Discuss the neurons that comprise the barrel cortex in rats and mice.

Question 52

After a rat runs its whiskers over a novel surface a number of times, it will decide what to do about it. For example, if a narrow pipe, the kind found in the plumbing of an old building, the rat will decide whether to enter it. How does the rat arrive at this decision?

Question 53

Would you expect the homunculus for touch to be different from that for pain? Why or why not?

Question 54

You are measuring resolution on your lab partner's body (resolution is the ability to discriminate one point from two closely-spaced points when poked with a compass on the skin, without the subject looking, of course). Suppose the two compass points are 5 mm apart. Why does your partner perceive this to be one point when poked on his back, but perceives it to be two points when poked on his upper lip?

Question 55

Explain why it is advantageous to activate slowly adapting receptors when reading Braille.