Lecture 11 - Cutaneous Receptors

Question 1

Cutaneous Receptors

Answer 1

A type of sensory detector in the skin

4 types of receptors located in the non hairy or GLABROUS skin.

They are classified based on field size and responses to skin indentation

Question 2

Mechanotrandsduction

Answer 2

The process where mechanical energy is turned into a voltage change in sensory afferent neurons

Turning mechanical energy into AP (electrical energy).

Action potential threshold is reached by the amount of force on cutaneous receptors which causes sodium to enter the cell

Question 3

Cutaneous Receptive field

Answer 3

A cutaneous RECEPTIVE FIELD is the region of the skin that is capable of evoking action potentials in a given cutaneous afferent

Question 4

Merkel Cell (SA1)

Answer 4

Slowly Adapting, Type 1

Superficial, not that deep into the skin. Has the cell and a nerve attached

-Irregular disc charge when stimulated (uneven spacing on rastor clot)
- Highly sensitive to edges and curvature
- Moderatley Low threshold (30)

slowly adapting when stimulated, will fire AP whole time (while stimulated)

Ex: holding a phone

Question 5

Messiner Corpuscles (FA1)

Answer 5

Fast Adapting, Type 1

Superficial, not that deep into the skin. Sensory end and there is a myelinated axon

• Codes for velocity of skin indentation across the skin (rate of indentation change)
• 40% of innervation in the hand
• sensitive to low frequency vibration (constant change) 30-50 hz
• Low threshold of 6
• As indentation is growing, AP is firing but when held at constant force is will stop firing

Ex: Holding a glass, slip/grip detection

Question 6

Ruffini Endings (SA2)

Answer 6

Slow adapting, Type 2

Deep into skin. Has collagen fibers that are nerves endings that come together

-NOT IN NON HUMAN PRIMATES (ex: monkey)
-Firing AP hold
- Very sensitive to skin stretch
- High threshold of indentation (300)

Ex: Holding a baseball, skin stretch

Question 7

Pacinian Corpuscles (FA2)

Answer 7

Fast adapting, type 2

Sensory information, Lowest/Most indentation

-Codes for acceleration, change in indentation rate
-picks up super high frequencies (50-500hz)
- Extremely low threshold of 0.08
- AP fired at discharge

Ex: blind person walking cane, feeling vibrations

Question 8

How Cutaneous Receptors are categorized

Answer 8

Type 1 = superficial/surface
Type 2 = deep

Slow adapting vs fast adapting

Question 9

Order of indentation (fastest to slowest)

Answer 9

Pancinian Corpuscles = 0.08
Messiner Corpuscles = 6
Merkel Cell = 30
Ruffini Ending = 300

Question 10

Type 1 vs Type 2

Answer 10

-Type 1 field is smaller then type 2 field
-Type 1, for one axon has many cells/corpuscles
- Type 2 is 1:1 ratio. Type 1 many hotspot, type 2 one
- Tip of the finger has high concentrations of Type 1 while type 2 is spread out on hand

Question 11

Vibration sensitivity - constant change

Answer 11

• These receptors are very sensitive to
  alternating inputs, such as those seen
  during mechanical vibration
• Can fire along with vibrations up to
  approximately 400 Hz (1 action potential every 2.5 ms cycle of vibration!)
• Found in skin, joint capsules, and digestive system.

The HIGHER the vibration frequency the more sensitive to indentation (lower threshold)

Question 12

Spatial code

Answer 12

Spacial fields and axons don’t move

The CNS can determine the location of stimuli based on which afferents
specifically are active…