receptors

Free nerve endings

Unmyelinated terminal fibers, no capsule

Superficial dermis; some enter epidermis

Cold, heat, touch, noxious stimuli

Hair follicle receptors

Unmyelinated endings around hair roots

Around hair roots

Detect hair movement

Merkel (tactile disk)

Nerve fiber expands into disk attached to Merkel cell

Below epidermis (glabrous skin)

Sustained touch / pressure

Meissner corpuscle

Oval, thin capsule, lamella-like core

Dermal papillae (glabrous skin)

Fine touch

Vater-Pacini corpuscle

Capsule with concentric lamellae, intermediate zone, central core

Subcutaneous tissue

Vibration (not constant pressure)

Golgi-Mazzoni corpuscle

Same as Pacini but smaller

Subcutaneous tissue

Mechanical stimuli

Krause end bulbs

Thin round capsule with nerve network

Dermal papillae

Mechanical stimuli

Ruffini end organs

Elongated capsule, branched nerve fiber in collagen

Deep dermis

Stretch / sustained pressure

Vater-Pacini corpuscles

Periosteum, joints, tendons, fascia

Mechanical stimuli

Ruffini end organs

Joint capsule

Mechanical stimuli

Golgi tendon organ

Muscle–tendon junction

Inhibits somatomotor neurons → prevents excessive contraction

Type

Stretch receptor

Structure

Intrafusal fibers in connective tissue capsule

Location

Skeletal muscle (parallel to extrafusal fibers)

Motor supply

γ (gamma) motor fibers

Function

Maintains muscle tone (opposes relaxation)

Nuclear bag fibers

Clustered nuclei (bag shape), two contractile ends

Nuclear chain fibers

Nuclei in single chain, two contractile ends

Primary (annulospiral)

AIa

Middle of intrafusal fibers

Secondary (flower-spray)

AII

Above and below primary endings

Chemoreceptors

Detect chemical composition changes

Baroreceptors

Detect pressure changes

Osmoreceptors

Detect osmotic pressure changes