event whose occurrence ends something; "his death marked the ending of an era"; "when these final episodes are broadcast it will be the finish of the show" (同)conclusion, finish
the end of a word (a suffix or inflectional ending or final morpheme); "I dont like words that have -ism as an ending" (同)termination
any bundle of nerve fibers running to various organs and tissues of the body (同)nervus
control of your emotions; "this kind of tension is not good for my nerves"
A free nerve ending (FNE) or bare nerve ending, is an unspecialized, afferent nerve fiber sending its signal to a sensory neuron. Afferent in this case means bringing information from the body's periphery toward the brain. They function as cutaneous nociceptors and are essentially used by vertebrates to detect pain.
Contents
1Structure
2Types
2.1Rate of adaptation
2.2Modality
2.3Fiber types
3References
4External links
Structure
Free nerve endings are unencapsulated and have no complex sensory structures. They are the most common type of nerve ending, and are most frequently found in the skin. They mostly resemble the fine roots of a plant. They penetrate the dermis and end in the stratum granulosum. FNEs infiltrate the middle layers of the dermis and surround hair follicles.
Types
Free nerve endings have different rates of adaptation, stimulus modalities, and fiber types.
Rate of adaptation
Different types of FNE can be rapidly adapting, intermediate adapting, or slowly adapting. A delta type II fibers are fast-adapting while A delta type I and C fibers are slowly adapting.[1][2]
Modality
Free nerve endings can detect temperature, mechanical stimuli (touch, pressure, stretch) or danger (nociception). Thus, different free nerve endings work as thermoreceptors, cutaneous mechanoreceptors and nociceptors. In other words, they express polymodality.
Fiber types
See also: Sensory fiber types
The majority of Aδ (A delta) fibers (group III) and C (group IV) fibers end as free nerve endings.
References
^Rolf-Detlef Treede, Richard A.Meyer, Srinivasa N.Raja, James N.Campbell. Evidence for two different heat transduction mechanisms in nociceptive primary afferents innervating monkey skin. J Physiol 1995;483:747-758
^Churyukanov M, Plaghki L, Legrain V, Mouraux A (2012). "Thermal detection thresholds of Aδ- and C-fibre afferents activated by brief CO2 laser pulses applied onto the human hairy skin". PLoS ONE. 7 (4): e35817. doi:10.1371/journal.pone.0035817. PMC 3338467. PMID 22558230.
External links
MacIver M, Tanelian D (1993). "Free nerve ending terminal morphology is fiber-type-specific for A delta and C fibers innervating rabbit corneal epithelium". J Neurophysiol. 69 (5): 1779–83. PMID 8509835.
Gray's s233
Nociception: Transduction. From the University of Utah.
Hada R (1990). "[Difference in responses of free nerve endings and Ruffini-type endings innervating the cat mandibular periosteum to square wave pressure stimuli, ramp mechanical stimuli and triangular vibrations]". Shikwa Gakuho. 90 (2): 161–80. PMID 2135092.
Textbook in Medical Physiology And Pathophysiology: Essentials and clinical problems. Copenhagen Medical Publishers. 1999 - 2000
Cleland C, Hayward L, Rymer W (1990). "Neural mechanisms underlying the clasp-knife reflex in the cat. II. Stretch-sensitive muscular-free nerve endings". J Neurophysiol. 64 (4): 1319–30. PMID 2258749.
Somatosensory System from Dr. Daley of North Carolina Wesleyan College.
v
t
e
Sensory receptors
Touch
Mechanoreceptor
Vibration
Lamellar corpuscle
Light touch
Tactile corpuscle
Pressure
Merkel nerve ending
Stretch
Bulbous corpuscle
Pain
Free nerve ending
Nociceptors
Temperature
Thermoreceptors
Proprioception
Golgi organ
Muscle spindle
Intrafusal muscle fiber
Nuclear chain fiber
Nuclear bag fiber
Other
Hair cells
Baroreceptor
Authority control
TH: H3.11.06.0.00002
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a macroscopic cordlike structure of the body, comprising a collection of nerve fibers that convey impulses between a part of the central nervous system and some other body region. See Appendix 2-6 and see color plates. Depending ...