Table 1 – Sensory Receptors for Proprioception (correction to table for Update on Proprioception, JDMS, 13(2)2009)
Receptor
Axon Size
Class
Shape
Location
Firing Threshold &
Deformation Source
Adaptive Properties
& Effect
Musculotendinous
Muscle Spindles
Intrafusal Fibers
Large
myelinateda
Ia
Fusiform “Bag”
Scattered distribution, 3-10 fibers in
parallel with 1 extrafusal muscle fiberc
Velocity-sensitive
Rapid changes in muscle lengthb
II
Fusiform
“Chain”
Capsular
In parallel with extrafusal muscle fibersc
Golgi tendon
organs
Medium
myelinated
Large
myelinated
Low,
Quick stretch and
Maintained (Tonic) stretch
Higher than Ia
Tonic stretch
Low, <1gm tendon tension,
Active contraction mainly
High Threshold, signal tension
changes
Very low,
Movement, not constant joint
position
Slow-adapting
Higher than I, extremes of joint
range, passive more than active
Variable, highly contextdependent
Slow-adaptingd
Joint Afferents
Golgi-like
receptors
Pacinian
Ruffini
Free Nerve
Endings
Ib
I
Medium
myelinated
II
Medium
myelinated
Small,
myelinated
III
IV
(Adelta
& C)
In series with 1 GTO per 10-20 collagen
fibers of tendon
Joint ligaments
Onion-shaped,
concentric
layers of
corpuscle
Spindle-shaped
capsular ending
Branching, noncapsular
Deep layer joint capsules
Deep layers in skin, joint capsules,
ligaments, & tendons
Superficial layers of skin, joint capsule
Slow-adapting, static or sustained muscle
lengths
Accurate sampling of active muscle tension and
velocity of change of tension, less responsive to
passive stretch
Rapidly-adapting, high sensitivity to vibration
& tissue displacement
Tissue damage, coarse touch, Paine
a. Neural diameter (large, small) and myelination is significant in conduction velocity. The larger, myelinated fibers conduct faster.
b. Intrafusal fibers do not add appreciably to the force of muscle contraction, but change in their tension level via the gamma
motor system and impact significantly on their sensitivity to muscle length changes.purves
c. The ratio of muscle spindles to muscle fibers varies with the type of muscle. Larger muscles that generate coarser movements
(e.g., superficial back muscles) have fewer spindles compared with extraocular muscles or intrinsics of the hand that require greater sensitivity
and accuracy for precise movements of the head and for manipulation, respectively. puves
d. While not much is understood about joint afferents (which also occur in skin), Pacinian and Ruffini afferents presumably respond to tracking of motion and position (of
fingers), while Merkel cell afferents and Meissner corpuscles (which appear only in skin) are more responsive to shape and pattern detail, as evidenced in research on Braille
readers’ finger afferents, providing ‘stereognosis”.phillips,et al, 1990
e. Note that with any abnormal (repetitive, continuous, overly-forceful) input, any receptor can become a “nociceptor” and signal pain.
Compiled by Glenna Batson, PT, DSc, MA, Associate Professor, Department of Physical Therapy, Winston-Salem State University, batsong@wssu.edu
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