Transduction / Receptors
Receptors
STIMULUS |
RECEPTOR |
LOCATION |
ADAPTATION |
|
Mechanoreception | ||||
Touch, pressure |
Free nerve
ending |
Hair root |
Small |
Variable |
Steady pressure, texture |
Merkel
receptor |
Superficial |
Slow |
|
Flutter,
stroking |
Meissner corpuscle |
Rapid |
||
Vibration |
Pacinian
corpuscle |
Deep |
Large |
Extremely rapid |
Stretch |
Ruffini
ending |
Slow |
||
Thermoreception | ||||
Cold |
Free nerve
ending |
Superficial |
Small |
Rapid |
Warm |
||||
Nociception | ||||
Thermal |
Free nerve
ending |
Superficial |
Small |
Rapid |
Mechanical |
Large |
Slow |
||
Polymodal (esp. chemical) |
Large |
Slow |
-
discriminative touch receptors (Meissner and Pacinian corpuscles, as well as Merkel discs and Ruffini endings) have specialized secondary structures that give them their physiological properties (e.g., it is the onion-like connective tissue lamellae that enable Pacinian corpuscles to respond to vibration)
- in the table, the various receptors within each submodality are sorted by receptive field size
- among touch/pressure receptors, superficial sensations are well-localized, while deep sensations are not
- temperature is well-localized, and these receptors (whether nociceptive or not) adapt rapidly
- other types of nociception are not well localized and their receptors slowly adapt
- another way to think about discriminative touch receptors is to sort them according to speed of adaptation rather than receptive field size:
- Meissner and Pacinian corpuscles, which encode flutter and vibration, adapt rapidly (they'll respond when something first touches your skin)
- Merkel discs and Ruffini endings, which encode steady pressure and stretch adapt slowly (they'll continue to respond if something stays in contact with your skin)