Senses are the physiological capacities within organisms In biology, an organism is any contiguous living system . In at least some form, all organisms are capable of response to stimuli, reproduction, growth and development, and maintenance of homoeostasis as a stable whole. An organism may either be unicellular (single-celled) or be composed of, as in humans, many trillions of cells grouped into that provide inputs for perception In philosophy, psychology, and cognitive science, perception is the process of attaining awareness or understanding of sensory information. The word "perception" comes from the Latin words perceptio, percipio, and means "receiving, collecting, action of taking possession, apprehension with the mind or senses.". The senses and their operation, classification, and theory are overlapping topics studied by a variety of fields, most notably neuroscience Neuroscience is the scientific study of the nervous system. Traditionally, neuroscience has been seen as a branch of biology. Nevertheless, it is currently an interdisciplinary science that involves other disciplines such as psychology, computer science, mathematics, physics, philosophy, and medicine. As a result, the scope of neuroscience has, cognitive psychology Cognitive psychology is a discipline within psychology that investigates the internal mental processes of thought such as visual processing, memory, thinking, learning, feeling, problem solving, and language (or cognitive science Cognitive science is the interdisciplinary study of how information, e.g., concerning perception, language, reasoning, and emotion, is represented and transformed in the brain. It consists of multiple research disciplines, including psychology, artificial intelligence, philosophy, neuroscience, learning sciences, linguistics, anthropology,), and philosophy of perception The philosophy of perception is concerned with the nature of sensory and perceptual experience, the status of what is given in such experience, and in particular with how beliefs or knowledge about the world can be accounted for and justified on that basis. The nervous system The nervous system is an organ system containing a network of specialized cells called neurons that coordinate the actions of an animal and transmit signals between different parts of its body. In most animals the nervous system consists of two parts, central and peripheral. The central nervous system contains the brain, spinal cord, and retina has a specific sensory system A sensory system is a part of the nervous system responsible for processing sensory information. A sensory system consists of sensory receptors, neural pathways, and parts of the brain involved in sensory perception. Commonly recognized sensory systems are those for vision, hearing, somatic sensation , taste and olfaction (smell). In short, senses or organ, dedicated to each sense.

Definition

There is no firm agreement among neurologists as to the number of senses because of differing definitions of what constitutes a sense. One definition states that an exteroceptive sense is a faculty by which outside stimuli are perceived.^[1] The traditional five senses are sight, hearing, touch, smell and taste, a classification attributed to Aristotle Aristotle (384 BC – 322 BC) was a Greek philosopher, a student of Plato and teacher of Alexander the Great. His writings cover many subjects, including physics, metaphysics, poetry, theater, music, logic, rhetoric, politics, government, ethics, biology, and zoology. Together with Plato and Socrates (Plato's teacher), Aristotle is one of the most.^[2] Humans are considered to have at least five additional senses that include: nociception Nociception is defined as "the neural processes of encoding and processing noxious stimuli." It is the afferent activity produced in the peripheral and central nervous system by stimuli that have the potential to damage tissue. This activity is initiated by nociceptors, (also called pain receptors), that can detect mechanical, thermal or (pain); equilibrioception Equilibrioception or sense of balance is one of the physiological senses. It helps prevent humans and animals from falling over when walking or standing still (balance); proprioception Proprioception , from Latin proprius, meaning "one's own" and perception, is the sense of the relative position of neighbouring parts of the body. Unlike the exteroceptive senses by which we perceive the outside world, and interoceptive senses, by which we perceive the pain and movement of internal organs, proprioception is a third and kinaesthesia Proprioception , from Latin proprius, meaning "one's own" and perception, is the sense of the relative position of neighbouring parts of the body. Unlike the exteroceptive senses by which we perceive the outside world, and interoceptive senses, by which we perceive the pain and movement of internal organs, proprioception is a third (joint motion and acceleration); sense of time When asked to place the time of a past event, people have a systematic tendency to recall that recent events occurred farther back in time and distant events occurred more recently (forward telescoping) than is actually the case; thermoception Thermoception or thermoreception is the sense by which an organism perceives temperature. In larger animals, most thermoception is done by the skin.[citation needed] The details of how temperature receptors work is still being investigated. Mammals have at least two types of sensor: those that detect heat and those that detect cold (i.e (temperature differences); and possibly an additional weak magnetoception Magnetoception is the ability to detect a magnetic field to perceive direction, altitude or location. This sense plays a role in the navigational abilities of several animal species and has been postulated as a method for animals to develop regional maps (direction)^[3], and six more if interoceptive senses (see other internal senses below) are also considered.

One commonly recognized categorisation for human senses is as follows: chemoreception A chemoreceptor, also known as chemosensor, is a sensory receptor that transduces a chemical signal into an action potential. Or, more generally, a chemosensor detects certain chemical stimuli in the environment; photoreception A photoreceptor, or 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 as cells they convert light (electromagnetic radiation) into the beginning of a chain of biological processes. More specifically, the photoreceptor absorbs; mechanoreception A mechanoreceptor is a sensory receptor that responds to mechanical pressure or distortion. There are four main types in the glabrous skin of humans: Pacinian corpuscles, Meissner's corpuscles, Merkel's discs, and Ruffini corpuscles. There are also mechanoreceptors in the hairy skin, and the hair cells in the cochlea are the most sensitive; and thermoception Thermoception or thermoreception is the sense by which an organism perceives temperature. In larger animals, most thermoception is done by the skin.[citation needed] The details of how temperature receptors work is still being investigated. Mammals have at least two types of sensor: those that detect heat and those that detect cold (i.e. This categorisation has been criticized as too restrictive,^{[by whom?]} however, as it does not include categories for accepted senses such as the sense of time When asked to place the time of a past event, people have a systematic tendency to recall that recent events occurred farther back in time and distant events occurred more recently (forward telescoping) than is actually the case and sense of pain Pain is an unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage. It is the feeling common to such experiences as stubbing a toe, burning a finger, putting iodine on a cut, and bumping the "funny bone".

Non-human animals may possess senses that are absent in humans, such as electroreception Electroreception, sometimes called electroception, is the biological ability to perceive electrical impulses. It is particularly common among aquatic creatures since salt water is a much more efficient conductor than air. It is used for electrolocation and for electrocommunication. There are no known cases of mimicry involving electroreception, and detection of polarized light Polarization is 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 the direction of vibration and direction of propagation are the same.

A broadly acceptable definition of a sense would be "A system that consists of a group of sensory cell types that responds to a specific physical phenomenon, and that corresponds to a particular group of regions within the brain where the signals Within evolutionary biology, signalling theory is a body of theoretical work examining communication between individuals. The central question is when organisms with conflicting interests should be expected to communicate "honestly". Mathematical models in which organisms signal their condition to other individuals as part of an are received and interpreted." Disputes about the number of senses typically arise around the classification of the various cell types and their mapping A mind map is a diagram used to represent words, ideas, tasks, or other items linked to and arranged around a central key word or idea. Mind maps are used to generate, visualize, structure, and classify ideas, and as an aid to studying and organizing information, solving problems, making decisions, and writing to regions of the brain.

Senses

Sight

Sight Visual perception is the ability to interpret information and surroundings from the effects of visible light reaching the eye. The resulting perception is also known as eyesight, sight, or vision . The various physiological components involved in vision are referred to collectively as the visual system, and are the focus of much research in or vision is the ability of the brain and eye to detect electromagnetic waves Electromagnetic radiation is a phenomenon that takes the form of self-propagating waves in a vacuum or in matter. It comprises electric and magnetic field components, which oscillate in phase perpendicular to each other and perpendicular to the direction of energy propagation. Electromagnetic radiation is classified into several types according to within the visible range of (light Light is electromagnetic radiation of a wavelength that is visible to the human eye . In physics, the term light sometimes refers to electromagnetic radiation of any wavelength, whether visible or not) and, in some cases, determine between varying colors, hues, and brightness. There is some disagreement as to whether this constitutes one, two or three senses. Neuroanatomists generally regard it as two senses, given that different receptors are responsible for the perception of colour (the frequency of photons of light) and brightness (amplitude/intensity - number of photons of light). Some argue^{[citation needed]} that stereopsis Stereopsis is the process in visual perception leading to the sensation of depth from the two slightly different projections of the world onto the retinas of the two eyes. The differences in the two retinal images are called horizontal disparity, retinal disparity, or binocular disparity. The differences arise from the eyes' different positions in, the perception of depth, also constitutes a sense, but it is generally regarded as a cognitive (that is, post-sensory) function of brain to interpret sensory input and to derive new information. The inability to see is called blindness Blindness is the condition of lacking visual perception due to physiological or neurological factors.

Hearing

Hearing Hearing is one of the traditional five senses. It is the ability to perceive sound by detecting vibrations via an organ such as the ear. The inability to hear is called deafness or audition is the sense of sound Sound is a travelling wave that is an oscillation of pressure transmitted through a solid, liquid, or gas, composed of frequencies within the range of hearing and of a level sufficiently strong to be heard, or the sensation stimulated in organs of hearing by such vibrations perception. Since sound is vibrations propagating through a medium such as air, the detection of these vibrations, that is the sense of the hearing, is a mechanical sense because these vibrations are mechanically conducted from the eardrum through a series of tiny bones to hair-like fibers in the inner ear The inner ear is innermost part of the vertebrate ear. It consists of the bony labyrinth, a system of passages comprising two main functional parts: which detect mechanical motion of the fibers within a range of about 20 to 20,000 hertz The hertz is the SI unit of frequency defined as the number of cycles per second of a periodic phenomenon. One of its most common uses is the description of sine wave, particularly those used in radio and audio applications,^[4] with substantial variation between individuals. Hearing at high frequencies declines with age. Sound can also be detected as vibrations conducted through the body by tactition. Lower frequencies than that can be heard are detected this way. The inability to hear is called deafness Hearing impairment or deafness refers to conditions in which individuals are fully or partially unable to detect or perceive at least some frequencies of sound which can typically be heard by members of their species. Use of the term impaired implies that deafness presents an inherent disadvantage to an animal, a view that is rejected within the.

Taste

Taste Taste is a form of direct chemoreception and is one of the traditional five senses. It refers to the ability to detect the flavor of substances such as food, certain minerals, and poisons. In humans and many other vertebrate animals the sense of taste partners with the less direct sense of smell, in the brain's perception of flavor. In the West, or gustation is one of the two main "chemical" senses. There are at least four types of tastes^[5] that "buds" (receptors) on the tongue The tongue is a group of muscles on the floor of the mouth that manipulates food for mastication. It is the primary organ of taste, as much of the upper surface of the tongue is covered in papillae and taste buds. It is sensitive and kept moist by saliva, and is richly supplied with nerves and blood vessels. In humans a secondary function of the detect, and hence there are anatomists who argue^{[citation needed]} that these constitute five or more different senses, given that each receptor conveys information to a slightly different region of the brain^{[citation needed]}. The inability to taste is called ageusia Ageusia is the loss of taste functions of the tongue, particularly the inability to detect sweetness, sourness, bitterness, saltiness, and umami (the taste of monosodium glutamate). It is sometimes confused with anosmia - a loss of the sense of smell. Because the tongue can only indicate texture and differentiate between sweet, sour, bitter, salty,.

The four well-known receptors detect sweet, salty, sour, and bitter, although the receptors for sweet and bitter have not been conclusively identified. A fifth receptor, for a sensation called umami Umami, also referred to as savoriness, has been proposed as one of the basic tastes sensed by specialized receptor cells present on the human and animal tongue. Umami is a loanword from Japanese meaning "good flavor" or "good taste" (noun). In English, however, "brothy", "meaty", or "savory" have, was first theorised in 1908 and its existence confirmed in 2000^[6]. The umami receptor detects the amino acid Amino acids are molecules containing an amine group, a carboxylic acid group and a side chain that varies between different amino acids. These molecules contain the key elements of carbon, hydrogen, oxygen, and nitrogen. These molecules are particularly important in biochemistry, where this term refers to alpha-amino acids with the general formula glutamate, a flavour commonly found in meat and in artificial flavourings such as monosodium glutamate.

Note: that taste is not the same as flavour Flavor or flavour is the sensory impression of a food or other substance, and is determined mainly by the chemical senses of taste and smell. The "trigeminal senses", which detect chemical irritants in the mouth and throat as well as temperature and texture, is also very important to the overall Gestalt of flavor perception. The flavor; flavour includes the smell of a food as well as its taste.

Smell

Smell Olfaction is the sense of smell. This sense is mediated by specialized sensory cells of the nasal cavity of vertebrates, and, by analogy, sensory cells of the antennae of invertebrates. Many vertebrates, including most mammals and reptiles, have two distinct olfactory systems - the main olfactory system, and the accessory olfactory system (mainly or olfaction is the other "chemical" sense. Unlike taste, there are hundreds of olfactory receptors, each binding to a particular molecular feature. Odor molecules possess a variety of features and thus excite specific receptors more or less strongly. This combination of excitatory signals from different receptors makes up what we perceive as the molecule's smell. In the brain, olfaction is processed by the olfactory system The olfactory system is the sensory system used for olfaction, or the sense of smell. Most mammals and reptiles have two distinct parts to their olfactory system: a main olfactory system and an accessory olfactory system. The main olfactory system detects volatile, airborne substances, while the accessory olfactory system senses fluid-phase. Olfactory receptor neurons An olfactory receptor neuron, also called an olfactory sensory neuron, (OSN) is the primary transduction cell in the olfactory system in the nose Physically a nose is an organ on the face. Anatomically, a nose is a protuberance in vertebrates that houses the nostrils, or nares, which admit and expel air for respiration in conjunction with the mouth. Behind the nose is the olfactory mucosa and the sinuses. Behind the nasal cavity, air next passes through the pharynx, shared with the differ from most other neurons in that they die and regenerate on a regular basis. The inability to smell is called anosmia Anosmia /ænˈɒzmi.ə/ is a lack of functioning olfaction, or in other words, an inability to perceive odors. Anosmia may be either temporary or permanent. A related term, hyposmia, refers to a decreased ability to smell, while hyperosmia refers to an increased ability to smell. Some people may be anosmic for one particular odor. This is called &. Some neurons in the nose are specialized to detect pheromones A pheromone is a secreted or excreted chemical factor that triggers a social response in members of the same species. Pheromones are chemicals capable of acting outside the body of the secreting individual to impact the behavior of the receiving individual. There are alarm pheromones, food trail pheromones, sex pheromones, and many others that.^{[citation needed]}

Touch

Touch The somatosensory system is a diverse sensory system comprising the receptors and processing centres to produce the sensory modalities such as touch, temperature, proprioception , and nociception (pain). The sensory receptors cover the skin and epithelia, skeletal muscles, bones and joints, internal organs, and the cardiovascular system. While, also called tactition The somatosensory system is a diverse sensory system comprising the receptors and processing centres to produce the sensory modalities such as touch, temperature, proprioception , and nociception (pain). The sensory receptors cover the skin and epithelia, skeletal muscles, bones and joints, internal organs, and the cardiovascular system. While or mechanoreception, is a perception resulting from activation of neural receptors, generally in the skin including hair follicles, but also in the tongue, throat, and mucosa. A variety of pressure receptors respond to variations in pressure (firm, brushing, sustained, etc.). The touch sense of itching caused by insect bites or allergies involves special itch-specific neurons in the skin and spinal cord.^[7] The loss or impairment of the ability to feel anything touched is called tactile anesthesia. Paresthesia is a sensation of tingling, pricking, or numbness of the skin that may result from nerve damage and may be permanent or temporary.

Balance and acceleration

Balance, equilibrioception, or vestibular sense is the sense which allows 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 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.

Temperature

Thermoception is the sense of heat and the absence of heat (cold) by the skin and including internal skin passages, or rather, the heat flux (the rate of heat flow) in these areas. There are specialized receptors for cold (declining temperature) and to heat. The cold receptors play an important part in the dogs sense of smell, telling wind direction, the heat receptors are sensitive to infrared radiation and can occur in specialized organs for instance in pit vipers. The thermoceptors in the skin are quite different from the homeostatic thermoceptors in the brain (hypothalamus) which provide feedback on internal body temperature.

Kinesthetic sense

Proprioception, the kinesthetic sense, provides the parietal cortex of the brain with information on the relative positions of the parts of the body. Neurologists test this sense by telling patients to close their eyes and touch the tip of a finger to their nose. Assuming proper proprioceptive function, at no time will the person lose awareness of where the hand actually is, even though it is not being detected by any of the other senses. Proprioception and touch are related in subtle ways, and their impairment results in surprising and deep deficits in perception and action.^[8]

Pain

Nociception (physiological pain) signals near-damage or damage to tissue. The three types of pain receptors are cutaneous (skin), somatic (joints and bones) and visceral (body organs). It was previously believed that pain was simply the overloading of pressure receptors, but research in the first half of the 20th century indicated that pain is a distinct phenomenon that intertwines with all of the other senses, including touch. Pain was once considered an entirely subjective experience, but recent studies show that pain is registered in the anterior cingulate gyrus of the brain.^[9]

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