Chapter 12: The Somatic Sensory System

Question 1

Enables body to feel, ache, sense temperature and pressure (communication to external world)

Answer 1

somatic sensation

Question 2

somatic sensation is responsible for ()

Answer 2

touch and pain

Question 3

unique characteristics of the somatic sensory system (compared to other senses)

Answer 3

1. receptors are found all over the body
2. responds to multiple (at least 4) types of stimuli

Question 4

somatic sensation responds to the ff. stimuli

Answer 4

1. touch
2. temperature
3. pain
4. body position

Question 5

types of skin

Answer 5

hairy and glabrous (i.e. hairless: palm)

Question 6

Most somatosensory receptors are () -> Present in unmyelinated axon branches sensitive to stretching, bending, pressure or vibration

Answer 6

mechanoreceptors

Question 7

Specialized structures of mechanoreceptor nerve endings

Answer 7

Pacinian corpuscles
Ruffini’s endings
Meissner’s corpuscles
Merkel’s disks

Question 8

mechanoreceptor nerve ending structures that have small receptive fields (only a few millimeters wide)

Answer 8

Meissner’s corpuscles and Merkel’s disk

Question 9

mechanoreceptor nerve ending structures that have large receptive fields (an entire finger or half of palm)

Answer 9

Pacinian corpuscles and Ruffini’s endings

Question 10

mechanoreceptor nerve ending structure: most sensitive to vibration of about 200-300 Hz

Answer 10

Pacinian corpuscles

Question 11

mechanoreceptor nerve ending structure: respond best around 50 Hz.

Answer 11

Meissner’s corpuscles

Question 12

The selectivity of a mechanoreceptive axon depends primarily on the ().

Answer 12

structure of its special ending

Question 13

Larger onion-like capsules allow for increased ()

Answer 13

adaptivity

Question 14

• Onion shells (corpuscles) have () in response to pressure on the structure

Answer 14

viscous fluid-filled structures that flow

Question 15

For striped corpuscles, adaptation is ()

Answer 15

slow -> slow AP

Question 16

Mechanoreceptors have (myelinated/unmyelinated) axon terminals.

Answer 16

unmyelinated

Question 17

() convert mechanical force into a change of ionic current.

Answer 17

Mechanosensitive ion channels

Question 18

Mechanical stimuli may trigger release of ().

Answer 18

second messengers

Question 19

mechanosensitive ion channels can be sensitive to one of the ff. types of stimuli

Answer 19

1. stretching of lipid membrane
2. Force Applied to Extracellular Structures
3. Deformation and Stress on Cell’s Cytoskeleton

Question 20

Minimum distance for specific tissues for the successful discrimination of 2 points

Answer 20

Two-Point Discrimination

Question 21

smaller 2-point discrimination -> (higher/lower) density of mechanoreceptors, (larger/smaller) receptive field size

Answer 21

higher, smaller

Question 22

types of primary afferent axons (axon fibers) in the somatic sensory system

Answer 22

A(alpha), A(beta), A(delta), C

Question 23

() fibers mediate pain, temperature, and itch

Answer 23

C

Question 24

() fibers mediate touch sensation

Answer 24

A(beta)

Question 25

spinal nerves within four divisions of spinal cord

Answer 25

spinal segments

Question 26

()—one-to-one correspondence with spinal segments

Answer 26

Dermatomes

Question 27

Divisions of spinal gray matter: ()

Answer 27

dorsal horn, intermediate zone, ventral horn

Question 28

The neurons that receive sensory input from primary afferents: () (mostly in the dorsal horns)

Answer 28

second-order sensory neurons

Question 29

A(beta) axons get branched to connect with the: - (1) for rapid and unconscious reflexes) - (2) for perception and judgments about the stimuli

Answer 29

1. second-order sensory neurons 2. brain

Question 30

The pathway serving touch is called the ().

Answer 30

dorsal column-medial lemniscal pathway

Question 31

From (), the somatic sensory system of one side of the brain is concerned with sensations originated from the other side of the body. (contralateral)

Answer 31

medial lemniscus

Question 32

Somatosensory information from face is supplied by the (1), which enter the brain at the (2)

Answer 32

1. large trigeminal nerves 2. pons

Question 33

also called S1/area 3b; Lesions here impair somatic sensation

Answer 33

primary sensory cortex

Question 34

the primary sensory cortex receives dense inputs from the ()

Answer 34

VP nucleus of the thalamus

Question 35

The thalamic inputs to S1 terminate mainly in layer ().

Answer 35

4

Question 36

S1 neurons with similar inputs and responses are () that extend across the cortical layers.

Answer 36

stacked vertically into columns

Question 37

(): usually evoked for the amputees by stimulating skin regions whose somatotopic representation border those of the missing limb.

Answer 37

Phantom limb sensation

Question 38

the () cortex is involved in somatic sensation, visual stimuli, movement planning, attentiveness

Answer 38

posterior parietal

Question 39

Damage to posterior parietal areas causes neurological disorders: (examples)

Answer 39

1. agnosia 2. neglect syndrome

Question 40

(): the inability to recognize objects even though simple sensory skills seem to be normal

Answer 40

Agnosia

Question 41

(): a part of the body or a part of the world is ignored or suppressed.

Answer 41

Neglect syndrome

Question 42

(): a sensory neuron with free nerve ending that responds to damaging or potentially damaging stimuli (distinct from the path taken by mechanoreceptors) 

Answer 42

Nociceptors

Question 43

()—feeling of sore, stinging, aching, throbbing sensations

Answer 43

Pain

Question 44

()—sensory process that provides signals that trigger pain

Answer 44

Nociception

Question 45

ion channels on nociceptors can be opened by: - direct stimulation (1) - indirect stimulation (2)

Answer 45

1. Direct and strong mechanical stimulation, temperature extremes, oxygen deprivation, chemicals 2. Indirect substances released by damaged cells

Question 46

examples of substances that indirectly open ion channels on nociceptors

Answer 46

1. proteases, ATP, K+ 2. Histamine

Question 47

kininogen cleaved -> () : increase ionic conductances, stimulates nociceptors

Answer 47

bradykinin

Question 48

Types of nociceptors—most are (1), but show (2) in their responses to different stimuli

Answer 48

1. polymodal nociceptors 2. selectivity

Question 49

(): tissues that have been already damaged are unusually sensitive to additional stimuli

Answer 49

Hyperalgesia

Question 50

primary hyperalgesia occurs at ()

Answer 50

within area of damaged tissues

Question 51

Surrounded damaged area may become supersensitive as well

Answer 51

secondary hyperalgesia

Question 52

() (from the enzymatic breakdown of lipid membrane) induces hyperalgesia.

Answer 52

Inflammation soup, including Bradykinin, and Prostaglandins

Question 53

(1), a peptide produced by the nociceptors causes vasodilation and (2) release from the mast cells -> One cause of secondary hyperalgesia.

Answer 53

1. Substance P 2. histamine

Question 54

TRPV1 (transient receptor potential V1) as a () receptor

Answer 54

capsaicin

Question 55

() can be activated by several natural pain inducers as well as high temperature

Answer 55

TRPV1 (transient receptor potential V1)

Question 56

There are more TRPs that regulate many different pain stimuli as well -> () as cold detection

Answer 56

TRPM8

Question 57

Disagreeable sensation that induces desire or reflex to scratch; Usually brief, minor annoyance—can become chronic, debilitating condition

Answer 57

Itch

Question 58

Since Aδ and C fiber have different rates of action potential conduction velocities, the activation of skin nociceptors produces ()

Answer 58

two distinct perceptions of pain

Question 59

two distinct perceptions of pain -> First pain by (1) and second pain by (2) fiber

Answer 59

1. Aδ 2. C

Question 60

() -> signals from actual source have same paths as signals from other sources -> brain is confused and identifies source incorrectly

Answer 60

Referred pain

Question 61

angina as an example of referred pain

Answer 61

Source is from lack of oxygen in heart, but pain is felt in upper chest wall

Question 62

The neurotransmitter of the pain afferents: ()

Answer 62

glutamate

Question 63

Within the spinal cord, there is (): cause the phenomenon of referred pain

Answer 63

mixing of information from nociceptors in skin and viscera

Question 64

Touch and pain pathways differ: Nerve endings in the skin

Answer 64

specialized structures for touch vs free nerve ending for pain

Question 65

Touch and pain pathways differ: Diameter of axons

Answer 65

large Aβ vs small Aδ or C fiber

Question 66

touch sensation is (faster/slower) than pain sensation

Answer 66

faster

Question 67

Touch and pain pathways differ: Connections in spinal cord

Answer 67

Touch—ascends ipsilaterally - Decussation further up in brain Pain—ascends contralaterally - Decussation in spinal cord

Question 68

decussation in the touch pathway occurs specifically at ()

Answer 68

medial lemniscus

Question 69

The pathway serving pain is called the ()

Answer 69

spinothalamic pathway

Question 70

in the spinothalamic pathway, axons of the second-order neurons () and ascend through the spinothalamic tract running along the ventral surface of the spinal cord.

Answer 70

immediately decussate

Question 71

The relay of nociceptive signals by the projection neuron is gated by the activity of an ().

Answer 71

inhibitory interneuron

Question 72

If the large sensory neuron is activated concurrently, the interneurons inhibit the pain signals from reaching spinothalamic tract

Answer 72

gate theory of pain

Question 73

(): Electrical stimulation of PAG in the midbrain cause a profound pain insensitivity by depressing activity of nociceptive neurons.

Answer 73

descending regulation

Question 74

() - area in midbrain involved in descending regulation

Answer 74

periaqueductal gray matter (PAG)

Question 75

() are highly concentrated in areas that process nociceptive information, where they suppress nociceptive signal transduction.

Answer 75

Opioid or endorphin receptors

Question 76

() channels are involved in detecting temperature

Answer 76

Thermoreceptor TRP

Question 77

Thermoreceptors also have adaptations to ()

Answer 77

continuous stimulation

Question 78

Sudden () generate most intense neural and perceptual responses to temperature

Answer 78

changes in quality of stimulus

Question 79

Organization of temperature pathway is similar to the ()

Answer 79

pain pathway

Question 80

Cold receptors coupled to () fibers

Answer 80

A(delta) and C

Question 81

Hot receptors coupled to ()

Answer 81

C fibers