Week 5 Flashcards
Describe Merkel Cells
- superficial (SA1); slow adapting to continual stimuli
- highly sensitive to edges and curvature
- cells wedged along border of the dermis
- small receptive fields with multiple hotspots
- moderately low threshold to indentation (30μm)
- 0-100 Hz (however, most sensitive to 5 Hz)
- irregular discharge when stimulated
Describe Meissner corpuscles
- superficial (FA1); fast adapting reactive to change stimuli
- stack of flattened disks in the dermis just below epidermis
- stroking velocity or motion across skin
- small receptive fields with multiple
- ~40% of innervation in the hand
- low threshold to indentation (6 μm)
- sensitive to low frequency vibration (most sensitive to 40-50 Hz but range 1-300 Hz)
What do Merkel Cells detect?
highly sensitive to edges and curvature
What is the receptive field of a merkel cell?
small receptive field with multiple hotspots
What percentage of the hand’s cutaneous mechanoreceptors do the merkel cells make up?
~25%
What is the threshold and frequency of merkel cells?
- moderately low threshold: 30 μm
- frequency 0-100 Hz (most sensitive to 5 Hz)
What do meissner corpuscles detect?
stroking velocity or motion across the skin
- important for grip control
What is the receptive field of the Meissner corpuscle like?
small receptive fields with multiple hotspots
What percentage of the hand’s cutaneous mechanoreceptors do meissner corpuscles make up?
~40% of innervation in the hand
What is the threshold and frequency of meissner corpuscles?
- low threshold to indentation (6 μm)
- low frequency vibration 1-300 Hz (most sensitive to 40-50 Hz)
What do ruffini endings detect?
Skin stretch
What is the receptive field of ruffini endings like?
large receptive fields with only one hotspot
What percentage of the hand’s cutaneous mechanoreceptors do ruffini endings make up?
~20 % of innervation in the hand
What is the threshold and frequency of ruffini endings?
- high threshold to indentation (300 μm)
- low frequency: 0.5 -
What type of afferent axon innervates the Merkel, Messiner, Pecinians, and Ruffinis?
Aβ
Describe the cutaneous mechanoreceptors from superficial to deep
Meissner, merkel, ruffini, pacinian
Describe ruffini endings
- Deep (SA2): slow adapting to continuous stimuli
- branched fibers inside a cylindrical capsule
- large receptive fields with only one hotspots
- ~20% of innervation in the hand
- low threshold to indentation (300 μm)
- low frequency: 0.5 - ???
Where are merkel cells usually found?
at the tips of our fingers
Which cutaneous mechanoreceptors are slow adapting? Which are fast adapting?
SA = Merkel, Ruffini
FA = Meissner, Pacinain
What does it mean if the mechanoreceptor has a low frequency?
Do not need to press hard for them to detect stimulus
What do Pacinian Corpuscles detect?
vibration through an object
What is the receptive field of Pacinian corpuscles?
large receptive fields with only one hotspot
What percentage of the hand’s cutaneous mechanoreceptors do pacinian corpuslces make up?
~15% of innervation in the hand
What is the threshold and frequency of pacinian corpuscles?
- extremely low threshold (0.08 μm)
- pick up high frequencies (300-400 Hz) - 200 Hz
Describe the Pacinian Corpuscles
- Deep (FA2); fast adapting
- vibration through an object
- onion-like capsule located deep in the skin
- large receptive fields with only one hotspot
- ~15% of hand innervation
- extremely low threshold (0.08 μm)
- pick up high frequencies (300-400 Hz) - 200 Hz
When are pacinian corpuscles used in the real world?
- very sensitve to alternating inputs, such as those seen during mechanical vibration
- high-frquency complex vibrations are elicited in the skin when scanning textures
- allowing us to distinguish microscopic differences in texture
