Sensory receptor 569437 222713214 2008-06-30T19:19:04Z 74.230.42.56 /* Structure */ {{portalpar|Neuroscience|Neuro logo.png}} In a [[sensory system]], a '''sensory receptor''' is a structure that recognizes a [[stimulus (physiology)|stimulus]] in the internal or external environment of an [[organism]]. In response to stimuli the sensory receptor initiates [[sensory transduction]] by creating [[graded potential]]s or [[action potential]]s in the same cell or in an adjacent one. ==Functions== The [[sensory receptor]]s involved in taste and smell contain [[receptor (biochemistry)|receptors]] that bind to specific chemicals. [[Odor receptor]]s in [[olfactory receptor neuron]]s, for example, are activated by interacting with molecular structures on the [[odor]] molecule. Similarly, [[taste]] receptors (gustatory receptors) in [[taste bud]]s interact with chemicals in food to produce an [[action potential]]. Other receptors such as [[mechanoreceptor]]s and [[photoreceptor]]s respond to physical stimuli. For example, [[photoreceptor cell]]s contain specialized proteins such as [[rhodopsin]] to [[transduction (physiology)|transduce]] the physical energy in light into electrical signals. Some types of mechanoreceptors fire action potentials when their membranes are physically stretched. The sensory receptor functions as the first component in a sensory system. Sensory receptors respond to specific stimulus modalities. The stimulus modality to which a sensory receptor responds is determined by the sensory receptor's [[adequate stimulus]]. The sensory receptor responds to its stimulus modality by initiating sensory transduction. This may be accomplished by a net shift in the initial states of a receptor(see a picture of these putative states [http://www.bio-balance.com/Receptor2.htm] with the biophysical description - link [http://www.bio-balance.com/Graphics.htm]). ==Classification== ===by adequate stimulus=== A sensory receptor's adequate stimulus is the stimulus modality for which it possesses the adequate [[sensory transduction]] apparatus. Adequate stimulus can be used to classify sensory receptors: *[[Ampullae of Lorenzini]] respond to [[electric fields]], salinity, and to temperature, but function primarily as electroreceptors *[[Baroreceptor]]s respond to pressure *[[Chemoreceptor]]s respond to chemical stimuli *[[Hydroreceptor]]s respond to changes in humidity *[[Mechanoreceptor]]s respond to [[mechanical stress]] or [[mechanical strain]] *[[Nociceptor]]s respond to damage to body tissues leading to pain perception *[[Osmoreceptor]]s respond to the [[osmolarity]] of fluids (such as in the hypothalamus) *[[Photoreceptor]]s respond to light *[[Proprioceptor]]s provide the sense of position *[[Thermoreceptor]]s respond to temperature, either heat, cold or both ===by location=== Sensory receptors can be classified by location: *[[Cutaneous receptor]]s are sensory receptors found in the dermis or epidermis. *[[Muscle spindle]]s contain mechanoreceptors that detect stretch in muscles. ===by morphology=== Somatic sensory receptors near the surface of the skin can usually be divided into two groups based on morphology: *[[Free nerve endings]] characterize the [[nociceptor]]s and [[thermoreceptor]]s and are called thus because the terminal branches of the neuron are unmyelinated and spread throughout the [[dermis]] and [[Epidermis (skin)|epidermis]]. *[[Encapsulated receptor]]s consist of the remaining types of cutaneous receptors. Encapsulation exists for specialized functioning. ==Innervation== {{Main|Sensory fiber types}} Different sensory receptors are innervated by different types of [[nerve fibers]]. Muscles and associated sensory receptors are innvervated by type I and II sensory fibers, while [[cutaneous receptors]] are innervated by Aβ, Aδ and C fibers. ==See also== *[[Sense]] *[[Sensory neuron]] *[[Proprioception]] *[[Receptor theory]] ==External links== * {{MeshName|Sensory+Receptors}} {{Sensory_system}} [[Category:Sensory receptors]] [[id:Reseptor indra]] [[bg:Рецептор]] [[es:Receptor sensorial]] [[fr:Récepteur sensoriel]] [[he:קולטן תחושתי]] [[it:Recettore sensoriale]] [[hu:Receptor]] [[mk:Рецептор]] [[sl:Čutilni receptor]] [[sr:Чулна ћелија]] [[zh:感受器]]