The cutaneous senses

Question 1

What four problems are caused by losing the sense of touch?

Answer 1

Prone to injuries
Difficulty interacting with the environment
Difficulty moving
Difficulty with sexual activity

Question 2

What three functions characterize the somatosensory system?

Answer 2

Cutaneous senses - responsible for touch and pain
Proprioception - ability to sense the positions of the body and limbs
Kinesthesis - ability to sense the movement of the body and limbs

Question 3

Identify the two layers of the skin

Answer 3

Epidermis - outer layer of dead skin cells

Dermis - inner layer containing mechanoreceptors

Question 4

Identify the four mechanoreceptors by function and type

Answer 4

Merkel receptor (SA1) - slowly adapting fibres; fine detail, shape, texture
Meissner corpuscle (RA1) - rapid adapting fibres; controlling handgrip, preceiving motion across skin
Ruffini cylinder (SA2) - slowly adapting fibres; perceiving stretching of skin
Pacinian corpuscle (RA2) - rapid adapting fibres; sensing rapid vibrations and fine texture

Question 5

Which two receptors are located closer to surface of skin? Which two receptors are located deeper in the dermis?

Answer 5

Shallow - Merkel and Meissner

Deeper - Ruffini and Pacinian

Question 6

Identify and describe the two nerve fibre pathways

Answer 6

Medial lemniscal pathway - large fibres carrying signals related to proprioception and perceiving touch
Spinothalamic pathway - smaller fibres carrying signals related to pain and temperature

Question 7

Describe the pathway of cutaneous neurons

Answer 7

Mechanoreceptors –> spinal chord/dorsal root –> ventrolateral nucleus in thalamus –> somatosensory receiving area (S1) and secondary somatosensory cortex (S2) in parietal lobe

Question 8

Homunculus

Answer 8

Body map of somatosensory cortex depicting locations of sensory areas for different body parts

Question 9

Which body parts take up a disproportionately large area of the homunculus?

Answer 9

Fingers (necessary to detect details in touch)

Question 10

Give an example of how experience-dependent plasticity is observed in humans

Answer 10

Violin players having greater than normal cortical representation for fingers of left hand

Question 11

Two-point threshold

Answer 11

Experimental technique to detect the minimum detectable separation of two objects applied to skin

Question 12

Grating acuity

Answer 12

Experimental technique to indicate the narrowest detectable grating spacing of object applied to skin

Question 13

Which receptor types are used to detect fine texture and detail

Answer 13

Merkel receptor (SA1)
Pacinian corpuscle (RA2)

Question 14

Surface texture

Answer 14

The visual and tactile quality of a surface created by peaks and valleys

Question 15

Duplex theory of perception

Answer 15

Perception of texture depends on both spatial cues and temporal cues

Question 16

Spatial cues

Answer 16

Relatively large surface elements, such as bumps and grooves, that can be felt both when the skin moves across the surface elements and when it is pressed onto the elements

Question 17

Temporal cues

Answer 17

Smaller surface elements felt by moving the skin across surface; responsible for perception of fine texture

Question 18

Active touch

Answer 18

Person actively exploring an object

Question 19

Passive touch

Answer 19

Touch by which an object is pressed into stationary skin

Question 20

Haptic perception

Answer 20

Perception by which three-dimentional objects are explored with the fingers and hand

Question 21

Exploratory procedure

Answer 21

Identifying an object by movements of hands and fingers on object

Question 22

What are the four exploratory procedures?

Answer 22

Lateral motion
Contour following
Enclosure
Pressure

Question 23

Somatosensory cortical responding is affected by which three factors?

Answer 23

Neuron specialization
Conscious attention
Visual attention

Question 24

Where are centre-surround cortical neurons located?

Answer 24

Ventral posterior nucleus and somatosensory cortex

Question 25

Neurons in the somatosensory cortex can take on which two specialties?

Answer 25

Centre-surround orientation

Specialized movements/orientations

Question 26

What are the three types of pain?

Answer 26

Inflammatory
Neuropathic
Nociceptive

Question 27

Pain matrix

Answer 27

Subcortical: thamalmus, hypothalamus, limbic system
Cortical: Insula, anterior cingulate, prefrontal cortex