Abstract
The somatosensory system enables organisms to feel, to ache, to chill, and, perhaps most importantly, to know which parts of the body are involved in these sensations. This comprises proprioceptive and cutaneous sensitivity. Somatosensory receptors are distributed throughout the body rather than being concentrated at specialized locations and are able to sense different kinds of stimuli such as pressure against the skin, limb position, distention of the bladder, and body temperature. If a stimulus becomes so strong that it may be harmful, the somatosensory system is also responsible for feeling pain (nociception).
The skin is the largest sensory organ, and a variety of stimuli from the external environment are constantly contacting its surface. These stimuli are sensed by specialized endings of sensory neurons called receptors, which then transmit signals to the spinal cord and brain for interpretation and response. A single stimulus usually activates many receptors, and each receptor is capable of encoding stimulus features such as intensity, duration, and direction. It is the central nervous system (CNS) that interprets the activity of the different receptors involved in the sensation and uses these interpretations to generate coherent perceptions.
In this chapter, the skin as a sensory organ will be discussed and its role in the sense of touch, nonpainful changes of temperature, itch, and pleasant touch.
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Abbreviations
- AM:
-
A-mechanonociceptor
- AMPA:
-
α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor
- ASIC:
-
Acid – sensing ion channel
- ADP:
-
Adenosine diphosphate
- ATP:
-
Adenosine triphosphate
- BC:
-
Basal cell
- BL:
-
Basal lamina
- cAMP:
-
Cyclic adenosine monophosphate
- CF:
-
Cuneate fascicle
- cGMP:
-
Cyclic guanosine monophosphate
- CGRP:
-
Calcitonin gene-related peptide
- CLTM:
-
Tactile fibers
- CN:
-
Clarke’s nucleus
- CNS:
-
Central nervous system
- CT:
-
Unmyelinated fibers
- D:
-
Desmosome
- Deg/ENaC:
-
Degenerin epithelial sodium channel
- DM:
-
Dermal papillae
- DRG:
-
Dorsal root ganglion
- FA:
-
Fast adapting
- FNE:
-
Free nerve endings
- G-protein:
-
Guanine nucleotide-binding protein
- GF:
-
Gracile fascicle
- HFR:
-
Hair follicle root
- IN:
-
Intermediolateral nucleus
- K:
-
Keratinocytes
- MC:
-
Meissner’s corpuscles
- MD:
-
Merkel’s disks
- MEC:
-
Ion channel
- mGluR5:
-
Metabotropic glutamate receptor 5
- ML:
-
Medial lemniscus
- MN:
-
Motor nucleus
- MZ:
-
Marginal zone
- NGF:
-
Nerve growth factor
- NMDA:
-
N-methyl D-aspartate
- NP:
-
Nucleus proprius
- PC:
-
Paccinian corpuscles
- P2X:
-
ATP activated purinergic receptor
- P2Y:
-
G-protein coupled receptor
- PGP:
-
Protein gene product
- PV:
-
Paraventricular nucleus
- RA:
-
Rapidly adapting
- RE:
-
Ruffini’s endings
- SAM:
-
Slowly adapting mechanoreceptor
- SA:
-
Slowly adapting
- SC:
-
Caudal somatosensory area
- SB:
-
Stratum basale
- SG:
-
Substantia gelatinosa
- SP:
-
Substance P (neuropeptide)
- SR:
-
Rostral somatosensory area
- SSC:
-
Somatic sensory cortex
- SI:
-
Primary somatosensory cortex
- SII:
-
Secondary somatosensory cortex
- T:
-
Thalamus
- TREK1:
-
Mechanosensitive potassium channel
- TRP:
-
Transient receptor potential
- UTP:
-
Uridine triphosphate
- VgluT:
-
Vesicular glutamate transporter
- VIP:
-
Vasoactive intestinal peptide
- VP:
-
Ventro posterior nucleus
- VPM:
-
Ventroposterior medial nucleus
- VPLN:
-
Ventral posterior lateral nucleus
Further Reading
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Boulais N, Misery L (2008) The epidermis: a sensory tissue. Eur J Dermatol 18(2):119–127
Bukowska M, Essick GK, Trulsson M (2010) Functional properties of low-threshold mechanoreceptive afferents in the human labial mucosa. Exp Brain Res 201:59–64
Carpenter MB (1976) Human Neuroanatomy. 7th edn. Williams & Wilkins, Baltimore
Denda M, Nakatani M, Ikeyama K, Tsutsumi M, Denda S (2007) Epidermal keratinocytes as the forefront of the sensory system. Exp Dermatol 16:157–161
Dhaka A, Viswanath V, Patapoutian A (2006) TRP ion channels and temperature sensation. Annu Rev Neurosci 29:135–161
Irmak MK (2010) Multifunctional Merkel cells: their roles in electromagnetic reception, finger-print formation, Reiki, epigenetic inheritance and hair form. Med Hypotheses 75:162–168
Koizumi S, Fijishita K, Inoue K, Shigemoto-Mogami Y, Tsuda M, Inoue K (2004) Ca2+ waves in keratinocytes are transmitted to sensory neurons: the involment of extracellular ATP and P2Y2 receptor activation. Biochem J 380:329–338
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Ulmann L, Rodeau JL, Danoux L, Contet-Audonneau JL, Pauly G, Schlichter R (2007) Trophic effects of keratinocytes on the axonal development of sensory neurons in a coculture model. Eur J Neurosci 26(1):113–125
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MartÃn-Alguacil, N., de Gaspar, I., Schober, J.M., Pfaff, D.W. (2013). Somatosensation: End Organs for Tactile Sensation. In: Pfaff, D.W. (eds) Neuroscience in the 21st Century. Springer, New York, NY. https://doi.org/10.1007/978-1-4614-1997-6_27
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DOI: https://doi.org/10.1007/978-1-4614-1997-6_27
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