Mechanoreception

1
Mechanoreception
Diverse

• Balance Acceleration (equilibrioception)
• Body Awareness (proprioception)
• Internal Stretch Receptors (ex. bladder, blood
  vessels)
• Internal Touch/Pressure Receptors (ex. pharynx)
• Thermoreception
• Cutaneous Mechanoreceptors
• Nocioceptors

2
Cutaneous Mechanoreceptor Types
Skin Type Depth Adaptation Modality Modality
Skin Type Depth Adaptation Touch Pressure
Pacinian Corpuscles Glabrous and Hairy Deep Rapid Light Vibration
Meissners Corpuscles Glabrous Surface Rapid Light Vibration
Merkels Disk Glabrous Surface Slow Crude Pressure
Ruffini Corpuscles Hairy Deep Slow Crude Pressure
Hair Follice Receptors Hairy Deep Rapid Light Neither
Pacinian Corpuscle
Hair Follicle Receptor
Merkels Disk
Ruffini Ending
Mechanical Displacement
3

• Hair follice receptors.
• Light Touch Meissners Corpuscle
• Strong Pressure Merkels Disk
• Pain Nociceptors
• Heat/Cold Thermoreceptors, some Nociceptors

4
Nociception

• Primarily detect pain.
• Free Nerve Endings, Wide Dynamic Range
  receptors
• Only known polymodal receptors. Also receive
• Hot, cold
• Warm, cool (similar receptors, distinct pathways)
• Chemoreception
• Complicated.
• Many exceptions.
• Poorly understood.

5
Pacinian Corpuscles

• In joints, organs.
• Rapidly adapting responds briefly to begining
  and end of stimulus
• Detects pressure change, esp. vibrations
• Up to centimeters away
• Responds best to sinusoidal vibrations w/ narrow
  frequency range.
• Low pass filter
• Result of onion-shaped structure

6
Meissners Corpuscles

• Highly concentrated in areas sensitive to light
  touch.
• Fingertips, lips, tongue, soles, genitals
• Located surface of the skin
• ? highly sensitive
• ? Limited. Must physically be touching.

7
Merkels Disk

• Slow adaption because of rigid structure.
• Sustainable response 30 min. in humans
• Irregular firing in sustained.
• Large receptive field.
• Small, sharp pressure fast firing rate.
• Large, flat pressure slow rate
• Located in hairless skin and in hair follices.
• Not in skin surrounding follicle.

8
Ruffini Ending

• Only in glabrous skin
• Sensitive to skin streching.
• Contributes to fine motor control.
• Contributes significantly to finger positioning.

9
Mechanosensory Homunculus
Somatosensory area of human cortex
Postcentral Gyrus of Parietal Lobe

• Topographic map of skin receptors.

• Size of area of receptors

Receives projections from Skin receptors ?
spinal nerve Face / Mouth ? trigeminal nerve