Sensory Receptors - Nerve Endings
Overview
Major Sensory Receptor Types
There are six major forms of sensory receptors (from superficial to deep*):
- Free nerve endings
- Merkel cells
- Meissner corpuscles
- Ruffini corpuscles & Krause end bulbs
- Pacinian corpuscles
Major Classes of Sensory Receptors
- There are three major classes of sensory receptors:
- Mechanoreceptors detect mechanical deformation
- Nociceptors detect pain
- Thermoreceptors detect temperature
Sensory Receptors by Location within the skin
EPIDERMIS
Free nerve endings
- Unmyelinated nerve endings.
- Detect pain and temperature.
BASAL EPIDERMIS
Merkel cells
- Discs at the ends of unencapsulated nerve fibers.
- Detect tactile sensation: light touch/hair movement.
SUPERFICIAL DERMIS
Meissner corpuscles (aka tactile corpuscles)
- Elliptical shaped.
- Lie perpendicular to the epidermis, within the dermal papillae.
- Detect light touch; hence, "tactile corpuscle".
DERMIS
Ruffini corpuscles
- Detect pressure.
Krause end bulbs
- Detect pressure and low-frequency vibration.
DEEP DERMIS & HYPODERMIS
Pacinian corpuscles (aka lamellated corpuscles)
- Pacinian corpuscles are large and oval-shaped with a very characteristic concentric, lamellated histological appearance.
- They are encapsulated mechanoreceptors that detect touch, pressure, vibration.
- Capsule distortion works to amplify the signal of a mechanical stimulus.