Lecture 7: Skin Receptors

Question 1

FAIs are located:

Answer 1

Located in the glabrous skin within the dermal papillae

Question 2

Meissner corpuscle morphology:

Answer 2

• Elongated stack of flattened epithelial cells
• Primary afferent terminal waves between the layers, mechanically deforms
• 1 primary afferent can terminate in multiple Meissner corpuscles

Question 3

Firing characteristics of FAIs:

Answer 3

Codes: Velocity of skin, indentation, flutter
Distinct on/off response
Mid-low frequencies (8-64Hz)

Question 4

Where are FAIIs located:

Answer 4

Deep in dermis and in the subcutaneous tissue

Question 5

Pacinian corpuscle morphology:

Answer 5

Onion-like encapsulated receptor
- Made up of many epithelial cell layers which are filled with fluid
- Primary afferent terminal extends centrally within the corpuscle
- 1 primary afferent innervates a single PC

Question 6

Firing characteristics of Pacinian corpuscles:

Answer 6

Codes: acceleration, vibration
Distinct on/off response
No distinct receptive field borders
Sensitive to high frequencies (64-250Hz)

Question 7

Firing characteristics of Merkel Discs:

Answer 7

• Sustained force continue to release neurotransmitter
• Codes: Spatial perception, texture, edges and curvature, pressure
• Edge sensitive
• Sensitive to low frequencies (2-32Hz)
• Irregular discharge

Question 8

Where are Merkel Discs located:

Answer 8

In the basal layer of the epidermis

Question 9

SAI morphology:

Answer 9

• Unencapsulated receptor
• Modified epithelial cell- contains synaptic vesicles

Question 10

To sustain SAI firing, _____ activates _____ Rc

Answer 10

Norepinephrine, B adrenergic

Question 11

Ruffini corpuscle firing characteristics:

Answer 11

• High threshold to indentation
• Sensitive to skin stretch, provides proprioceptive feedback in the direction of skin movement
• Regular discharge
• No distinct field borders
• Sensitive to low frequencies (8Hz)

Question 12

Where are SAIIs located?

Answer 12

Dermis

Question 13

Morphology of Ruffini corpuscles:

Answer 13

• Spindle shaped encapsulated receptor
• Contains collagen fibres which connect to surrounding tissue
• One primary afferent innervates a single Ruffini ending

Question 14

Hand densities of each of the corpuscles:

Answer 14

FAI: 43%
FAII: 13%
SAI: 25%
SAII: 19%

Question 15

Foot densities of each of the corpuscles:

Answer 15

FAI: 48%
FAII: 13%
SAI: 18%
SAII: 21%

Question 16

Why is there singificantly more FAIs in the feet?

Answer 16

• Not as much fine motor control
• More SA in our hands than feet
• Sensitive to slips and respond to that (evolutionary)