Topic 11: The Cutaneous Senses

Question 1

Why are conditions that result in losing the ability to feel things dangerous?

Answer 1

Absence of the warning signals provided by touch and pain.

Question 2

What makes it difficult to interact with the environment with the loss of an ability to feel things?

Answer 2

Loss of feedback

Question 3

Sense of our body’s position and the movement of our
limbs

Answer 3

Proprioception

Question 4

Describe the case of Ian Waterman

Answer 4

Suffered complications from a viral infection that damaged sensory neurons from his neck down

As a result, he was completely unable to sense the position of his limbs and also lost the sense of touch

Couldn’t feel his body; used inappropriate amounts of force

Question 5

Ability to perceive sensations based on the stimulation of receptors in the skin

Answer 5

Cutaneous senses

Question 6

Enables us to perceive the properties of surfaces including details, texture, and shape

Answer 6

Sense of touch

Question 7

Heaviest organ in humans, and one of the largest by
total surface area

Answer 7

Skin

Question 8

Describe the role of skin in maintaining regular bodily functions

Answer 8

Gives us information about the external environment, prevents body fluids from escaping, and protects us by keeping bacteria, chemical agents, and dirt from getting inside

Question 9

What are the two different kinds of human skin?

Answer 9

Hairy skin: Hair follicles
Glabrous skin: No hair follicles

Question 10

Where is glabrous skin found?

Answer 10

Areas most sensitive to touch and the parts we use to explore our environment (Palms, feet, lips, tongue)

Question 11

Outer layer of dead skin cells

Answer 11

Epidermis

Question 12

Receptors that respond to mechanical stimulation of the skin

Answer 12

Mechanoreceptors

Question 13

Where are the mechanoreceptors located?

Answer 13

In the epidermis and dermis

Question 14

Which two mechanoreceptors are located close to the surface of the skin?

Answer 14

Merkel receptors

Meissner corpuscles

Question 15

Merkel receptors and Meissner corpuscles have — receptive fields

Answer 15

Small

Question 16

Describe the firing and adaptation of Merkel receptors

Answer 16

Fires continuously, as long as the stimulus remains present

It adapts slowly to stimulation, so it is a slowly-adapting fiber (SA1)

Question 17

Merkel rceptors are associated with the perception of…

Answer 17

Fine details, texture, and shape

Question 18

Describe the firing and adaptation of Meissner corpuscles

Answer 18

Fires only when the stimulus is first applied, and again when it is removed

Adapts rapidly to stimulation, so it is a rapidly-adapting fiber (RA1)

Question 19

Meissner corpuscles are associated with…

Answer 19

Perceiving motion across the skin

Question 20

What are the two mechanoreceptors located deeper in the skin?

Answer 20

Ruffini cylinders

Pacinian corpuscles

Question 21

Ruffini cylinders and Pacinian corpuscles have — receptive fields then mechanoreceptors located closer to the surface of the skin

Answer 21

Larger

Question 22

Describe the firing and adaptation of Ruffini cylinders

Answer 22

Fire continuously, as long as the stimulus remains present

Adapts slowly to stimulation, so it is also a slowly-adapting fiber (SA2)

Question 23

Ruffini cylinders are associated with…

Answer 23

The perception of skin stretching

Question 24

Describe the firing and adaptation of Pacinian corpuscles

Answer 24

Fire only when the stimulus is first applied, and again when
it is removed

Adapts rapidly to stimulation, so it is also a rapidly-adapting fiber (RA2)

Question 25

Pacinian corpuscles are associated with...

Answer 25

Perceiving vibrations and fine texture

Question 26

Why is the somatosensory system unique compared to the other sensory systems?

Answer 26

Sensory receptors are distributed throughout the body Signals need to travel long distances to reach the brain

Question 27

Brings signals from all over the body from the skin to the brain

Answer 27

Spinal cord

Question 28

How many segments does the spinal cord have?

Answer 28

31

Question 29

Bundle of fibers through which the segments of the spinal cord receive signals

Answer 29

Dorsal roots

Question 30

What are the two major pathways through which signals are sent to the brain after they enter the spinal cord?

Answer 30

The medial lemniscal pathway The spinothalamic pathway

Question 31

Carries signals for proprioception, pressure and fine touch

Answer 31

Medial lemniscal

Question 32

Carries signals about pain, irritation, itchiness, and temperature

Answer 32

Spinothalamic

Question 33

Describe the pathway of signals from the mechanoreceptors to the brain

Answer 33

Signals travel through one of the two spinal cord pathways Signals pass through the thalamus End at the contralateral primary somatosensory cortex (S1)

Question 34

How is S1 organized?

Answer 34

A map that corresponds to to the different locations of the body (homunculus)

Question 35

Which portion of S1 is associated with sensations on the lips and face?

Answer 35

Lower portion

Question 36

Which portion of S1 is associated with sensations on the hands and feet?

Answer 36

Higher portion

Question 37

Which areas of the body correspond to disproportionately large sections in S1?

Answer 37

Areas that we typically use to explore the environment (hands, tongue, feet, etc.)

Question 38

How can perceiving details be studied?

Answer 38

Tactile acuity

Question 39

The smallest amount of detail that can be detected on the skin

Answer 39

Tactile acuity

Question 40

Tactile acuity differs based on...

Answer 40

Location and type of skin

Question 41

Describe the typical results of a two-point threshold (sensitivity) test

Answer 41

Glabrous skin = detect 2 points until about 3mm apart Hairy skin = only detect 2 points until about 2-5cm apart

Question 42

Test of tactile acuity in which the narrowest spacing possible to detect is identified

Answer 42

Grating acuity

Question 43

Test of tactile acuity involving identifying shapes and patterns in the absence of visual cues

Answer 43

Shape perception

Question 44

What are three tests of tactile acuity?

Answer 44

Two-point threshold (sensitivity) test Grating acuity Shape perception

Question 45

How do mechanoreceptors relate to perceiving detail?

Answer 45

Firing pattern closely correlates to the details on the surface

Question 46

Which mechanoreceptor is associated with the perception of fine details?

Answer 46

Merkel receptors

Question 47

Parts of the body sensitive to detail are likely to have more ---

Answer 47

Merkel receptors

Question 48

Describe the relationship between the brain and the size of the receptive fields on the skin

Answer 48

The smaller the receptive field, the better the detail acuity

Question 49

Explain how smaller receptive fields lead to the perception of more details

Answer 49

When two points are hit in an area with small receptive fields, the two points would hit different fields whereas when this happens in an area with large receptive fields, two points would only hit the same field (overlapping point in the brain)

Question 50

Which mechanoreceptors respond best to vibrations?

Answer 50

Pacinian corpuscles

Question 51

Explain how Pacinian corpuscles respond to vibrations

Answer 51

The corpuscles contain many layers with fluid in between Constant pressure moves the fluid only once and therefore the neuron only fires once, but vibrations cause the fluid to constantly move causing the neuron to keep firing

Question 52

The physical, tactile surface of an object created by its peaks and valleys

Answer 52

Surface texture

Question 53

Theory describing that our perception of a texture depends on spatial and temporal cues

Answer 53

Duplex theory of texture perception

Question 54

Provided by large surface elements, like bumps and grooves, that can be felt when the skin is resting on a surface

Answer 54

Spatial cues

Question 55

Provide information through vibrations and only occur when one moves across a surface

Answer 55

Temporal cues

Question 56

Spatial = perception of --- textures, temporal = perception of --- textures

Answer 56

Course, fine

Question 57

How do different textures get represented differently in our brains?

Answer 57

Each texture seemingly causes a unique pattern of neurons to fire

Question 58

Touch in which a person is actively exploring an object, typically by using the fingers and hands for humans

Answer 58

Active touch

Question 59

Occurs when touch stimuli are applied to the skin, and the person simply “receives” it

Answer 59

Passive touch

Question 60

Perceptual process in which three-dimensional objects are explored

Answer 60

Haptic perception

Question 61

List the systems involved in haptic perception and their roles

Answer 61

Somatosensory system – detecting touch, temperature, texture, etc. Motor system – moving your hands and fingers Visual system – perceiving the visual details of the object Cognition – thinking about the meaning of all this information

Question 62

How long does it take people to accurately identify most common objects?

Answer 62

1-2 seconds

Question 63

How do people accomplish object identification?

Answer 63

Through the use of exploratory procedures that differ depending on the quality they are trying to judge

Question 64

Give six examples of exploratory procedures

Answer 64

Lateral motion Pressure Enclosure Contour following Static contact Unsupported holding

Question 65

Deficits in tactile perception and detail perception by touch resulting from damage to S1

Answer 65

Weakened stereognosis

Question 66

The complete inability to recognize objects by touch alone resulting from damage to S1

Answer 66

Astereognosis