The Cutaneous Senses

Question 1

What are cutaneous senses?

Answer 1

Based on mechanoreceptors in the skin for touch/tactile perception, vibration, texture, shape, warmth, cold, itch, and pain

Question 2

What is proprioception?

Answer 2

Sensing position of the body and limbs

Question 3

What is kinesthesis?

Answer 3

Sensing movement of the body and limbs

Question 4

What is haptic perception?

Answer 4

Coordination of tactile and kinesthetic sensation

Question 5

What is vestibular sense?

Answer 5

Balance/spatial orientation due to semicircular canals and vestibular sacs

Question 6

What are some characteristics of the skin?

Answer 6

Heaviest organ
Range of thickness
May by glabrous or hairy
Neural structures at the epi/dermal boundary are believed to be receprots

Question 7

What is the outer layer of the skin called?

Answer 7

The epidermis
The surface is called the corneum

Question 8

What is the inner layer of the skin called?

Answer 8

The dermis

Question 9

What is specificity theory?

Answer 9

One mechanoreceptor type proposed for each basic sensation

Question 10

What do Ruffini endings detect?

Answer 10

Warmth

Question 11

What do Krause end bulbs detect?

Answer 11

Cold

Question 12

What to Meissner corpuscles detect?

Answer 12

Touch

Question 13

What do free nerve endings detect?

Answer 13

Pain

Question 14

What touch blend leads to detection in something wet?

Answer 14

Even pressure, cold

Question 15

What touch blend leads to the detection of something oily?

Answer 15

Weak pressure, warm, movement

Question 16

What is punctate sensitivity?

Answer 16

If there is a receptor under the skin at a location, there must be sensitivity to the associated sensation

Question 17

What is microneurography?

Answer 17

Use an electrode to find a nerve fibre that is triggered by a particular stimulus

Question 18

What is histology?

Answer 18

Trace the fibre back to the receptor

Question 19

What are the problems with determining the nature of fibers?

Answer 19

Self-dissection shows no correlation between structure and sensations, restest impossible
Skin transmits kinetic and thermal energy over a distance from the point of stimulation - many receptors affect by any stimulus
Cornea only has free nerve endings but all four sensations
Sensory spots changed over time

Question 20

What is the thermal grill illusion?

Answer 20

Simultaneous presentation of separate warm and cold stimuli = painfully hot

Question 21

What is pattern theory?

Answer 21

The pattern of neural impulses from a number of receptors corresponds to a particular sensation
Assumed that receptors differ in structure, but not in function
The same receptor can yield two different kinds of sensations, depending on the intensity of activation

Question 22

What is stimulus preference?

Answer 22

Intermediate approach
Each sensation arises from the firing of a number of receptor types tuned to different aspects of a stimulus

Question 23

What do the Pacinian corpuscles do?

Answer 23

The corpuscle around the nerve fibre acts to absorb sustained pressure
Fibre itself only stimulated at onset or offset of stimulus

Question 24

What is the spinothalamic pathway?

Answer 24

Smaller nerve fibres synapse in the spinal cord
Ascends via the spinal cord and brainstem to the thalamus
Projects to the anterior cingulate cortex, and insular cortex. and primary somatosensory cortex
Carries primarily temperature and pain information

Question 25

What is the medial lemniscal pathway?

Answer 25

Larger, longer nerve fibres synapse in the medulla Ascends via medial lemniscus to the thalamus Projects to the primary somatosensory cortex Conveys touch and proprioceptive information

Question 26

What is the evoked potential method?

Answer 26

Electrodes on the scape measure cortical activity Different skin loci are stimulated until activity produced at electrode Very time-consuming

Question 27

What is stimulation during open brain surgery?

Answer 27

Stimulate the cortex at a low voltage to produce sensations in awake patients to not damage vital parts of the brain

Question 28

How is the somatosensory cortex organized?

Answer 28

Somatotopic organization, adjacent points on the skin have adjoining cortical representations Touch represented in somatosensory cortex as a homunculus

Question 29

What is touch?

Answer 29

Constant pressure

Question 30

What is vibration?

Answer 30

Changing pressure

Question 31

Where does soft touch go?

Answer 31

To the insular cortex where emotion is processed Plays a role in development, social cooperation, and affiliation

Question 32

What is proxemics?

Answer 32

Zones of personal space Distances between people depend on the nature of social interaction

Question 33

What is public distance?

Answer 33

For public speaking Over 3.5 m

Question 34

What is social distance?

Answer 34

For interaction with strangers and acquaintances 1.2-3.5 m

Question 35

What is personal distance?

Answer 35

For interactions with friends and family 45-120 cm

Question 36

What is intimate distance?

Answer 36

For whispering, touching, or embracing intimate partners 15-45 cm

Question 37

What is oxytocin?

Answer 37

A hormone synthesized in the hypothalamus and stored in the pituitary gland Involved in contractions and lactation Release at orgasm

Question 38

What is the absolute touch threshold?

Answer 38

Hair pushed into skin until hair bends Each bends with a different amount of force Use stronger hairs until absolute threshold is established

Question 39

What is the difference threshold for touch?

Answer 39

Two-point threshold Smallest separation between two points on the skin that can be perceived

Question 40

What does actively handling an object aid in?

Answer 40

Identification

Question 41

What do exploratory procedures do?

Answer 41

Provide information on different stimulus features

Question 42

What can we determine with lateral motion and contour following?

Answer 42

Texture

Question 43

What can we determine with pressure?

Answer 43

Hardness

Question 44

What can we determine with static contact?

Answer 44

Temperature

Question 45

What two fibres are temperature encoded by?

Answer 45

Warm fibres = 30-48 degrees Cold fibres = 20-45 degrees

Question 46

What is paradoxical cold?

Answer 46

A hot stimulus produces the sensation of cold due to activation of cold fibres

Question 47

What is physiological zero?

Answer 47

Temperature at which receptors have become adapted Perception of temperature is relative to this point

Question 48

What is pain?

Answer 48

An unpleasant sensory or emotional experience associated with actual or potential tissue damage

Question 49

What is nociception?

Answer 49

The neural encoding of impending or actual tissue damage

Question 50

What are nociceptors?

Answer 50

Receptors for noxious stimuli Peptide substance P is released from C fibres

Question 51

What do A-delta fibres transmit?

Answer 51

Sharp, pricking pain

Question 52

What do C fibres transmit?

Answer 52

Burning, throbbing pain

Question 53

What is double pain?

Answer 53

Sharp pain followed by dull pain

Question 54

What is congenital insensitivity to pain with anhidrosis?

Answer 54

Rare congenital insensitivity disorder Cannot feel pain Complete absence of A-delta and C fibers; normal sensation of touch in A-beta fibres

Question 55

Where is the substantia gelatinosa?

Answer 55

In the spinal cord

Question 56

Where are transmission cells found?

Answer 56

In the spinothalamic pathway

Question 57

What are L-fibers?

Answer 57

Large diameter axons from mechanoreceptors

Question 58

What are S-fibers?

Answer 58

Small diameter axons from nociceptors

Question 59

What does activity in L-fibers do?

Answer 59

Closes the gate Activates the SG so that T is inhibited and there is no pain signal

Question 60

What does activity in S-fibers do?

Answer 60

Opens the gate Activates the SG so that T is excited and a pain signal is sent

Question 61

How does rubbing reduce pain?

Answer 61

By activating A-beta fibers

Question 62

What is TENS?

Answer 62

Transcutaneous Electrical Nerve Stimulation Small electrical current activates A-beta fibers Inhibits pain signals

Question 63

How might pain signals be attenuated?

Answer 63

This may be due to endogenous opioids Inhibit Substance P

Question 64

What is naloxone?

Answer 64

Narcotic antagonist Wipes out the effects of placebo and acupuncture, but not hypnosis

Question 65

What is synesthesia?

Answer 65

The involuntary physical experience of a cross-modal association in which stimulation of one sensory modality reliably causes a perception in one or more different senses

Question 66

What are the characteristics of synesthesia?

Answer 66

Responses are generic and unelaborated One-way projections Idiosyncratic

Question 67

What are one-way projections in relation to synesthesia?

Answer 67

A synesthete who sees colours when hearing spoken words does not necessarily hear words when viewing colours

Question 68

What are the two theories of synesthesia?

Answer 68

More connections Less inhibition

Question 69

What was found about colour synesthetes in an fMRI?

Answer 69

Their V4 activates in response to spoken words but not when viewing coloured surfaces

Question 70

What might synesthesia reveal?

Answer 70

Aspects of top-down processing, the binding problem, sensory integration, and conscious experience