receptor

=Receptor=

toc Read here about the general act of resonance or reception and how it relates to ideas of scale. Receptors are significant in scale research as they are both the medium by which we perceive the world, and they have built-in scaling capabilities.

=Overview= A receptor is an entity able to respond to an external stimulus and transmit a signal. The term may refer to a technological tool or instrument, or biological cell or organ. Many biological receptors operate logarithmically, the inverse of exponentially, enabling a broad range of resonance while sacrificing linear accuracy. From the evolutionary or survival perspective, logarithmic sensation is very valuable, as generally it is important for organisms to respond to stimuli in a wide range of levels, from very low levels, to very high levels, while the accuracy of the estimation of differences at high levels of stimul]] us is much less important. This logarithmic capability may result from the physical form of the receptor.

Two examples:
 * Loudness and frequency of sound are perceived logarithmically, enabling even very faint stimuli to resonate with our aural sensory fabric and enable human perception. The logarithmic receptor is physically enabled by the spiral form of portions of the aural sensory fabric.
 * brightness of visual stimuli is perceived by humans as a linear increase, rather than an exponential increase. The logarithmic receptor is enabled by the tree-like branching structure of the nerve bundle connecting the cortex to the retina.

=Biological reception=

List Of Biological Receptors
A biological organ that both resonates with an event in the outside world, and make such resonance accessible to conscious report, apperception. Most receptor names are coined from the suffix –receptor and a prefix distinguishing the receptor’s activity.

A comprehensive list of biological receptors, being receptors that have been identified as part of biological, living creatures:
 * Electroreceptor, coulombic forces.
 * Salinity
 * Baroreceptors measured in pascals (Pa)
 * Chemoreceptor or chemosensor, transduces a chemical signal into an action potential.
 * Hydroreceptor, humidity
 * Mechanoreceptors, respond to mechanical stress or mechanical strain.
 * Nociceptors respond to damage to body tissues leading to pain perception.
 * Osmoreceptors respond to the osmolarity of fluids where they contribute to fluid balance in the body.
 * Photoreceptors respond to light via phototransduction.
 * Proprioceptors provide a sense of position.
 * Thermoreceptors respond to temperature, either heat, cold or both.
 * Electromagnetic receptors respond to electromagnetic waves
 * Equilibriocepors allow an organism to sense body movement, direction, and acceleration, and to attain and maintain postural equilibrium and balance.
 * Chronoception is a brain-originated experience that results from the comparison in memory of other sensory data.
 * Polariceptors respond to polarization, a property of certain types of waves that describes the orientation of their oscillations.
 * Interoceptor is a receptor that works internally, on behalf of an autonomic system that largely operates outside of conscious control.

Electricity (electro-)
Electroreceptors respond to coulombic forces. Biological receptors: Ampullae of Lorenzini function primarily as electroreceptors as they can respond to electric fields, measured in Coulombs (C).

Salt (Salinity)
Salinity receptors detect the percentage of salt in a solute. Biological receptors: Ampullae of Lorenzini may also respond to changes in salinity, frequently reported in mass per volume (mg/L) or parts mols of salt per million mols of solution (ppm); this is not a consensus view.

Pressure (baro-)
Baroreceptors measure changes in pressure. Biological receptors: Baroreceptors respond to pressure in blood vessels, measured in pascals (Pa) though people’s blood pressure is usually expressed in terms of the systolic pressure over diastolic pressure (mmHg), for example 140/90. Baroreceptors can be divided into two categories: high-pressure arterial baroreceptors and low-pressure baroreceptors (also known as cardiopulmonary or volume receptors); the latter are in large systemic veins.

Chemical (Chemo-)
Chemoreceptors detects certain chemical stimuli in the environment by enacting a mediated reaction to electron fine structure. The chemoreceptor, or chemosensor, transduces a chemical signal into an action potential. Biological receptors: There are two main classes of the chemosensor: direct and distance. Examples of distance chemoreceptors are olfactory receptor neurons in the olfactory system, neurons in the vomeronasal organ that detect pheromones. Examples of direct chemoreceptors include taste buds in the gustatory system, carotid bodies and aortic bodies that detect changes primarily in oxygen and CO2. Chemoreceptors may rely on sensory cellular antennae that coordinate a large number of cellular signaling pathways.

Water content (hydro-)
Hydroreceptors respond to changes in humidity, or the mass of dissolved water vapor per cubic meter of total moist air measured in gram per cubic meter (g/m^3).

Stress Or Strain (Mechano-)
Mechanoreceptors respond to mechanical stress or mechanical strain. A mechanoreceptor is a sensory receptor that responds to mechanical pressure or distortion.

Biological receptors: There are four main types in the glabrous skin of humans (called cutaneous mechanoreceptors): Pacinian corpuscles, Meissner's corpuscles, Merkel's discs, and Ruffini corpuscles. Responsiveness in mechanoreceptors is divided into adaptation speeds slow, medium and rapid. There are also mechanoreceptors in hairy skin, and the hair cells in the cochlea are the most sensitive mechanoreceptors, transducing air pressure waves into nerve signals sent to the brain. In the periodontal ligament, there are some mechanoreceptors that allow the jaw to relax when biting down on hard objects; the mesencephalic nucleus is responsible for this reflex. Mechanoreception may also originate with sensory cellular antennae that coordinate a large number of cellular signaling pathways, sometimes coupling the signaling to ciliary motility or alternatively to cell division and differentiation. States of neuropathic pain, such as hyperalgesia and allodynia, are also directly related to mechanosensation. A wide array of elements are involved in the process of mechanosensation, many of which are still not fully understood.

Pain (noci-)
Nociceptors respond to damage by facilitating the experience of pain. Biological receptors: Nociceptors respond to nerve-damage or damage to tissue. Nociceptors respond to damage to body tissues leading to pain perception. The peripheral terminal of the mature nociceptor is where the noxious stimuli are detected and transduced into electrical energy. The three types of nocireceptors are cutaneous (skin), somatic (joints and bones) and visceral (body organs). Pain is registered in the anterior cingulate gyrus of the brain. The main function of pain is to warn us about dangers.

Osmosis (Osmo-)
Osmoreceptors respond to the osmolarity of fluids where they contribute to fluid balance in the subsystem under measurement. Biological receptors: Osmoreceptors respond to the osmolarity of fluids (such as in the hypothalamus) where they contribute to fluid balance in the body. Osmoreceptors can be found in several structures, including the organum vasculosum of the lamina terminalis (OVLT) and the subfornical organ (SFO).

Light (photo-)
Photoreceptors respond to light.

Biological receptors: A photoreceptor cell is a specialized type of neuron found in the eye's retina that is capable of phototransduction. The great biological importance of photoreceptors is that they convert light (electromagnetic radiation) into signals that can stimulate biological processes. More specifically, photoreceptor proteins in the cell absorb photons, triggering a change in the cell's membrane potential. The entire process by which light initiates a sensory response is called visual phototransduction. Visual phototransduction is a process by which light is converted into electrical signals in the rod cells, cone cells and photosensitive ganglion cells of the retina of the eye. The visual cycle is the biological conversion of a photon into an electrical signal in the retina. This process occurs via G-protein coupled receptors called opsins which contain the chromophore 11-cis retinal. 11-cis retinal is covalently linked to the opsin receptor via a Schiff base forming a retinylidene protein. When struck by a photon, 11-cis retinal undergoes photoisomerization to all-trans retinal which changes the conformation of the opsin GPCR leading to signal transduction cascades which causes closure of a cyclic GMP-gated cation channel, and hyperpolarization of the photoreceptor cell. Following isomerization and release from the opsin protein, all-trans retinal is reduced to all-trans retinol and travels back to the retinal pigment epithelium to be "recharged". It is first esterified by lecithin-retinol acyltransferase (LRAT) and then converted to 11-cis retinol by the isomerohydrolase RPE65. The isomerase activity of RPE65 has been shown, but it is still uncertain whether it also acts as a hydrolase. Finally, it is oxidized to 11-cis retinal before traveling back to the rod outer segment where it can again be conjugated to an opsin to form a new, functional visual pigment (rhodopsin).

Position (Proprio-)
Proprioceptors provide a visceral sense of position. Biological receptors: Proprioception is the sense that indicates whether the body is moving with the required effort, as well as where the various parts of the body are located in relation to each other. Kinesthesia is another term that is often used interchangeably with proprioception, though use of the term "kinesthesia" can place a greater emphasis on motion. Proprioception and kinesthesia are seen as interrelated and there is considerable disagreement regarding the definition of these terms. Some of this difficulty stems from Sherrington's original description of joint position sense (or the ability to determine exactly where a particular body part is in space) and kinesthesia (or the sensation that the body part has moved) under a more general heading of proprioception. The inner ear’s sense of balance, for example, is alternately grouped with one or the other. For example, when a cat walks, its flexors and extensors constantly send kinematic messages to the brain.

Heat (thermo-)
Thermoreceptors respond to temperature, either heat, cold or both. A thermoreceptor is a sensory receptor, or more accurately the receptive portion of a sensory neuron, that codes absolute and relative changes in temperature, primarily within the innocuous range. In the mammalian peripheral nervous system warmth receptors are thought to be unmyelinated C-fibres (low conduction velocity), while those responding to cold have both C-fibers and thinly myelinated A delta fibers (faster conduction velocity).[1] The adequate stimulus for a warm receptor is warming, which results in an increase in their action potential discharge rate. Cooling results in a decrease in warm receptor discharge rate. For cold receptors their firing rate increases during cooling and decreases during warming. Some cold receptors also respond with a brief action potential discharge to high temperatures, i.e. typically above 45°C, and this is known as a paradoxical response to heat. The mechanism responsible for this behavior has not been determined. Ampullae of Lorenzini may also respond to changes in temperature, measured in degrees Kelvin or celcius (K, or C); such receptivity, if it occurs, is transduced as an electrical signal; this is not a consensus view. A special form of thermoreceptor is found in some snakes, the viper pit organ and this specialized structure is sensitive to energy in the infrared part of the spectrum. Temperature is measured in degrees Kelvin or Celcius (K or C).

Electromagnetic Radiation
Electromagnetic receptors respond to electromagnetic waves. See light (photo-).

Balance (equilibrio-)
Equilibriocepors are a special class of mechanoreceptor that respond to forces in such a way as to allow an organism to sense body movement, direction, and acceleration, and to attain and maintain postural equilibrium and balance. The organ of equilibrioception is the vestibular labyrinthine system found in both of the inner ears. Technically this organ is responsible for two senses of angular momentum acceleration and linear acceleration (which also senses gravity), but they are known together as equilibrioception. The vestibular nerve conducts information from sensory receptors in three ampulla that sense motion of fluid in three semicircular canals caused by three-dimensional rotation of the head. The vestibular nerve also conducts information from the utricle and the saccule which contain hair-like sensory receptors that bend under the weight of otoliths (which are small crystals of calcium carbonate) that provide the inertia needed to detect head rotation, linear acceleration, and the direction of gravitational force. The vestibular nerve conducts information from sensory receptors in three ampulla that sense motion of fluid in three semicircular canals caused by three-dimensional rotation of the head. The vestibular nerve also conducts information from the utricle and the saccule which contain hair-like sensory receptors that bend under the weight of otoliths (which are small crystals of calcium carbonate) that provide the inertia needed to detect head rotation, linear acceleration, and the direction of gravitational force.

Time (Chrono-)
Chronoceptors have not been shown to exist; instead, chronoception is a brain-originated experience that results from the comparison in memory of other sensory data.

Polarization (polari-)
Polariceptors respond to polarization, a property of certain types of waves that describes the orientation of their oscillations. Electromagnetic waves, such as light, and gravitational waves exhibit polarization; acoustic waves (sound waves) in a gas or liquid do not have polarization because they are longitudinal, the direction of vibration and direction of propagation being the same. In a solid medium, however, sound waves can be transverse. In this case, the polarization is associated with the direction of the shear stress in the plane perpendicular to the propagation direction. This is important in seismology.

Internal (Intero-)
Interoceptor is a receptor that works internally, on behalf of an autonomic system that largely operates outside of conscious control. Its many examples can be summarized as stretch receptors in organs, skin receptors that respond to vasodilation in the skin such as blushing, and receptors lining the digestive tract from esophagus to rectum.

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.

=Links and References=

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