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86-485: A sense is a biological system used by an organism for sensation , the process of gathering information about the surroundings through the detection of stimuli . Although, in some cultures, five human senses were traditionally identified as such (namely sight , smell , touch , taste , and hearing ), many more are now recognized. Senses used by non-human organisms are even greater in variety and number. During sensation, sense organs collect various stimuli (such as

172-430: A cell are determined by whether the cell is a eukaryote or prokaryote . Hearing Hearing , or auditory perception , is the ability to perceive sounds through an organ, such as an ear , by detecting vibrations as periodic changes in the pressure of a surrounding medium. The academic field concerned with hearing is auditory science . Sound may be heard through solid , liquid , or gaseous matter. It

258-463: A central point. An example would be when we use parentheses in writing. We tend to perceive all of the words in the parentheses as one section instead of individual words within the parentheses. The Law of Continuity tells us that objects are grouped together by their elements and then perceived as a whole. This usually happens when we see overlapping objects. We will see the overlapping objects with no interruptions. The Law of Past Experience refers to

344-582: A clinical setting, this management is offered by otologists and audiologists . Hearing loss is associated with Alzheimer's disease and dementia with a greater degree of hearing loss tied to a higher risk. There is also an association between type 2 diabetes and hearing loss . Hearing threshold and the ability to localize sound sources are reduced underwater in humans, but not in aquatic animals, including whales, seals, and fish which have ears adapted to process water-borne sound. Not all sounds are normally audible to all animals. Each species has

430-928: A cortical area involved in interpreting sounds that is necessary to understand spoken words. Disturbances (such as stroke or trauma ) at any of these levels can cause hearing problems, especially if the disturbance is bilateral . In some instances it can also lead to auditory hallucinations or more complex difficulties in perceiving sound. Hearing can be measured by behavioral tests using an audiometer . Electrophysiological tests of hearing can provide accurate measurements of hearing thresholds even in unconscious subjects. Such tests include auditory brainstem evoked potentials (ABR), otoacoustic emissions (OAE) and electrocochleography (ECochG). Technical advances in these tests have allowed hearing screening for infants to become widespread. Hearing can be measured by mobile applications which includes audiological hearing test function or hearing aid application . These applications allow

516-456: A definite function. This idea was already present in Antiquity ( Galen , Aristotle ), but the application of the term "system" is more recent. For example, the nervous system was named by Monro (1783), but Rufus of Ephesus (c. 90–120), clearly viewed for the first time the brain, spinal cord, and craniospinal nerves as an anatomical unit, although he wrote little about its function, nor gave

602-401: A group, but we can also perceive three groups of two lines with seven objects in each line. The Law of Closure is the idea that we as humans still see a full picture even if there are gaps within that picture. There could be gaps or parts missing from a section of a shape, but we would still perceive the shape as whole. The Law of Symmetry refers to a person's preference to see symmetry around

688-484: A human), close your eyes (preferably in a dark room) and press gently on the outside corner of one eye through the eyelid. You will see a visual spot toward the inside of your visual field, near your nose.) All stimuli received by the receptors are transduced to an action potential , which is carried along one or more afferent neurons towards a specific area ( cortex ) of the brain . Just as different nerves are dedicated to sensory and motors tasks, different areas of

774-581: A materialistic view of the mind. Some examples of human absolute thresholds for the nine to 21 external senses . Humans respond more strongly to multimodal stimuli compared to the sum of each single modality together, an effect called the superadditive effect of multisensory integration . Neurons that respond to both visual and auditory stimuli have been identified in the superior temporal sulcus . Additionally, multimodal "what" and "where" pathways have been proposed for auditory and tactile stimuli. External receptors that respond to stimuli from outside

860-497: A measure as employing an anechoic chamber , which absorbs nearly all sound. Another means is the use of devices such as earplugs , which are inserted into the ear canal to block noise, or earmuffs , objects designed to cover a person's ears entirely. The loss of hearing, when it is caused by neural loss, cannot presently be cured. Instead, its effects can be mitigated by the use of audioprosthetic devices, i.e. hearing assistive devices such as hearing aids and cochlear implants . In

946-494: A mechanoreceptor. Photoreceptors convert light (visible electromagnetic radiation ) into signals. Chemical stimuli can be interpreted by a chemoreceptor that interprets chemical stimuli, such as an object's taste or smell, while osmoreceptors respond to a chemical solute concentrations of body fluids. Nociception (pain) interprets the presence of tissue damage, from sensory information from mechano-, chemo-, and thermoreceptors. Another physical stimulus that has its own type of receptor

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1032-504: A name to this unit. The enumeration of the principal functions - and consequently of the systems - remained almost the same since Antiquity, but the classification of them has been very various, e.g., compare Aristotle , Bichat , Cuvier . The notion of physiological division of labor, introduced in the 1820s by the French physiologist Henri Milne-Edwards , allowed to "compare and study living things as if they were machines created by

1118-468: A particular color . Visible light is electromagnetic radiation with a wavelength between 380 and 720 nm. Wavelengths of electromagnetic radiation longer than 720 nm fall into the infrared range, whereas wavelengths shorter than 380 nm fall into the ultraviolet range. Light with a wavelength of 380 nm is blue whereas light with a wavelength of 720 nm is dark red . All other colors fall between red and blue at various points along

1204-438: A range of normal hearing for both amplitude and frequency . Many animals use sound to communicate with each other, and hearing in these species is particularly important for survival and reproduction. In species that use sound as a primary means of communication, hearing is typically most acute for the range of pitches produced in calls and speech. Frequencies capable of being heard by humans are called audio or sonic. The range

1290-469: A respective visual system (sense of vision), auditory system (sense of hearing), somatosensory system (sense of touch), olfactory system (sense of smell), and gustatory system (sense of taste). Those systems, in turn, contribute to vision , hearing , touch , smell , and the ability to taste . Internal sensation, or interoception, detects stimuli from internal organs and tissues. Many internal sensory and perceptual systems exist in humans, including

1376-439: A sense, but it is generally regarded as a cognitive (that is, post-sensory) function of the visual cortex of the brain where patterns and objects in images are recognized and interpreted based on previously learned information. This is called visual memory . The inability to see is called blindness . Blindness may result from damage to the eyeball, especially to the retina, damage to the optic nerve that connects each eye to

1462-497: A series of tiny bones to hair-like fibers in the inner ear , which detect mechanical motion of the fibers within a range of about 20 to 20,000  hertz , with substantial variation between individuals. Hearing at high frequencies declines with an increase in age. Inability to hear is called deafness or hearing impairment. Sound can also be detected as vibrations conducted through the body. Lower frequencies that can be heard are detected this way. Some deaf people are able to determine

1548-416: A sound or smell) for transduction , meaning transformation into a form that can be understood by the brain. Sensation and perception are fundamental to nearly every aspect of an organism's cognition , behavior and thought . In organisms, a sensory organ consists of a group of interrelated sensory cells that respond to a specific type of physical stimulus. Via cranial and spinal nerves (nerves of

1634-477: A specific type of stimulus. For example, the general sensation and perception of touch, which is known as somatosensation, can be separated into light pressure, deep pressure, vibration, itch, pain, temperature, or hair movement, while the general sensation and perception of taste can be separated into submodalities of sweet , salty , sour , bitter , spicy, and umami , all of which are based on different chemicals binding to sensory neurons . Sensory receptors are

1720-660: A stimulus is constant and unchanging, perceptual sensory adaptation occurs. During that process, the subject becomes less sensitive to the stimulus. Biological auditory (hearing), vestibular and spatial, and visual systems (vision) appear to break down real-world complex stimuli into sine wave components, through the mathematical process called Fourier analysis. Many neurons have a strong preference for certain sine frequency components in contrast to others. The way that simpler sounds and images are encoded during sensation can provide insight into how perception of real-world objects happens. Perception occurs when nerves that lead from

1806-660: A stronger sense of smell than humans. Some animal species lack one or more human sensory system analogues and some have sensory systems that are not found in humans, while others process and interpret the same sensory information in very different ways. For example, some animals are able to detect electrical fields and magnetic fields , air moisture , or polarized light . Others sense and perceive through alternative systems such as echolocation . Recent theory suggests that plants and artificial agents such as robots may be able to detect and interpret environmental information in an analogous manner to animals. Sensory modality refers to

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1892-410: Is a molecule called propylthiouracil (PROP) that some humans experience as bitter, some as almost tasteless, while others experience it as somewhere between tasteless and bitter. There is a genetic basis for this difference between perception given the same sensory stimulus. This subjective difference in taste perception has implications for individuals' food preferences, and consequently, health. When

1978-428: 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. The loss or impairment of

2064-463: Is a spiral-shaped, fluid-filled tube. It is divided lengthwise by the organ of Corti , which is the main organ of mechanical to neural transduction . Inside the organ of Corti is the basilar membrane , a structure that vibrates when waves from the middle ear propagate through the cochlear fluid – endolymph . The basilar membrane is tonotopic , so that each frequency has a characteristic place of resonance along it. Characteristic frequencies are high at

2150-482: Is attached to the tympanic membrane and articulates with the incus. The incus, in turn, articulates with the stapes. The stapes is then attached to the inner ear , where the sound waves will be transduced into a neural signal. The middle ear is connected to the pharynx through the Eustachian tube , which helps equilibrate air pressure across the tympanic membrane. The tube is normally closed but will pop open when

2236-437: Is based on their location relative to the stimuli. An exteroceptor is a receptor that is located near a stimulus of the external environment, such as the somatosensory receptors that are located in the skin. An interoceptor is one that interprets stimuli from internal organs and tissues, such as the receptors that sense the increase in blood pressure in the aorta or carotid sinus . The cells that interpret information about

2322-489: Is concerned with the nature of perceptual experience and the status of perceptual data , in particular how they relate to beliefs about, or knowledge of, the world. Historical inquiries into the underlying mechanisms of sensation and perception have led early researchers to subscribe to various philosophical interpretations of perception and the mind , including panpsychism , dualism , and materialism . The majority of modern scientists who study sensation and perception take on

2408-428: Is dedicated to the auditory system . The main point is to understand why humans are able to use sound in thinking outside of actually saying it. Relating to auditory cognitive psychology is psychoacoustics . Psychoacoustics is more directed at people interested in music. Haptics , a word used to refer to both taction and kinesthesia, has many parallels with psychoacoustics. Most research around these two are focused on

2494-464: Is described by Steven's power law . Signal detection theory quantifies the experience of the subject to the presentation of a stimulus in the presence of noise . There is internal noise and there is external noise when it comes to signal detection. The internal noise originates from static in the nervous system. For example, an individual with closed eyes in a dark room still sees something—a blotchy pattern of grey with intermittent brighter flashes—this

2580-548: Is encoded or transduced. Multimodality integrates different senses into one unified perceptual experience. For example, information from one sense has the potential to influence how information from another is perceived. Sensation and perception are studied by a variety of related fields, most notably psychophysics , neurobiology , cognitive psychology , and cognitive science . Sensory organs are organs that sense and transduce stimuli. Humans have various sensory organs (i.e. eyes, ears, skin, nose, and mouth) that correspond to

2666-410: Is internal noise. External noise is the result of noise in the environment that can interfere with the detection of the stimulus of interest. Noise is only a problem if the magnitude of the noise is large enough to interfere with signal collection. The nervous system calculates a criterion, or an internal threshold, for the detection of a signal in the presence of noise. If a signal is judged to be above

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2752-462: Is not directly coupled with frequency range. Georg Von Békésy in 1929 identifying sound source directions suggested humans can resolve timing differences of 10μs or less. In 1976 Jan Nordmark's research indicated inter-aural resolution better than 2μs. Milind Kuncher's 2007 research resolved time misalignment to under 10μs. Even though they do not have ears, invertebrates have developed other structures and systems to decode vibrations traveling through

2838-423: Is often multimodal. Multimodality integrates different senses into one unified perceptual experience. Information from one sense has the potential to influence how information from another is perceived. Multimodal perception is qualitatively different from unimodal perception. There has been a growing body of evidence since the mid-1990s on the neural correlates of multimodal perception. The philosophy of perception

2924-414: Is one of the traditional five senses . Partial or total inability to hear is called hearing loss . In humans and other vertebrates, hearing is performed primarily by the auditory system : mechanical waves , known as vibrations, are detected by the ear and transduced into nerve impulses that are perceived by the brain (primarily in the temporal lobe ). Like touch , audition requires sensitivity to

3010-433: Is produced by ceruminous and sebaceous glands in the skin of the human ear canal, protecting the ear canal and tympanic membrane from physical damage and microbial invasion. The middle ear consists of a small air-filled chamber that is located medial to the eardrum. Within this chamber are the three smallest bones in the body, known collectively as the ossicles which include the malleus, incus, and stapes (also known as

3096-591: Is seen into patterns or groups: Common Fate, Similarity, Proximity, Closure, Symmetry, Continuity, and Past Experience. The Law of Common fate says that objects are led along the smoothest path. People follow the trend of motion as the lines/dots flow. The Law of Similarity refers to the grouping of images or objects that are similar to each other in some aspect. This could be due to shade, colour, size, shape, or other qualities you could distinguish. The Law of Proximity states that our minds like to group based on how close objects are to each other. We may see 42 objects in

3182-426: Is temperature, which is sensed through a thermoreceptor that is either sensitive to temperatures above (heat) or below (cold) normal body temperature. Each sense organ (eyes or nose, for instance) requires a minimal amount of stimulation in order to detect a stimulus. This minimum amount of stimulus is called the absolute threshold. The absolute threshold is defined as the minimum amount of stimulation necessary for

3268-522: Is the sensation of potentially damaging stimuli. Mechanical, chemical, or thermal stimuli beyond a set threshold will elicit painful sensations. Stressed or damaged tissues release chemicals that activate receptor proteins in the nociceptors. For example, the sensation of heat associated with spicy foods involves capsaicin , the active molecule in hot peppers. Low frequency vibrations are sensed by mechanoreceptors called Merkel cells , also known as type I cutaneous mechanoreceptors. Merkel cells are located in

3354-430: Is the use of devices designed to prevent noise-induced hearing loss (NIHL), a type of post-lingual hearing impairment . The various means used to prevent hearing loss generally focus on reducing the levels of noise to which people are exposed. One way this is done is through environmental modifications such as acoustic quieting , which may be achieved with as basic a measure as lining a room with curtains , or as complex

3440-494: Is typically considered to be between 20 Hz and 20,000 Hz. Frequencies higher than audio are referred to as ultrasonic , while frequencies below audio are referred to as infrasonic . Some bats use ultrasound for echolocation while in flight. Dogs are able to hear ultrasound, which is the principle of 'silent' dog whistles . Snakes sense infrasound through their jaws, and baleen whales , giraffes , dolphins and elephants use it for communication. Some fish have

3526-489: The cell membrane that mediates a physiological change in a neuron, most often through the opening of ion channels or changes in the cell signaling processes. Transmembrane receptors are activated by chemicals called ligands . For example, a molecule in food can serve as a ligand for taste receptors. Other transmembrane proteins, which are not accurately called receptors, are sensitive to mechanical or thermal changes. Physical changes in these proteins increase ion flow across

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3612-410: The sensory organs (e.g. eye) to the brain are stimulated, even if that stimulation is unrelated to the target signal of the sensory organ. For example, in the case of the eye, it does not matter whether light or something else stimulates the optic nerve, that stimulation will results in visual perception, even if there was no visual stimulus to begin with. (To prove this point to yourself (and if you are

3698-433: The stratum basale of the epidermis . Deep pressure and vibration is transduced by lamellated ( Pacinian ) corpuscles, which are receptors with encapsulated endings found deep in the dermis, or subcutaneous tissue. Light touch is transduced by the encapsulated endings known as tactile ( Meissner ) corpuscles. Follicles are also wrapped in a plexus of nerve endings known as the hair follicle plexus. These nerve endings detect

3784-591: The vestibular system (sense of balance) sensed by the inner ear and providing the perception of spatial orientation ; proprioception (body position); and nociception (pain). Further internal chemoreception - and osmoreception -based sensory systems lead to various perceptions, such as hunger , thirst , suffocation , and nausea , or different involuntary behaviors, such as vomiting . Nonhuman animals experience sensation and perception, with varying levels of similarity to and difference from humans and other animal species. For example, other mammals in general have

3870-416: The "blue" cones predominantly. The relative activation of the three different cones is calculated by the brain, which perceives the color as blue. However, cones cannot react to low-intensity light, and rods do not sense the color of light. Therefore, our low-light vision is—in essence—in grayscale . In other words, in a dark room, everything appears as a shade of gray . If you think that you can see colors in

3956-678: The Central and Peripheral nervous systems that relay sensory information to and from the brain and body), the different types of sensory receptor cells (such as mechanoreceptors , photoreceptors , chemoreceptors , thermoreceptors ) in sensory organs transduct sensory information from these organs towards the central nervous system, finally arriving at the sensory cortices in the brain , where sensory signals are processed and interpreted (perceived). Sensory systems, or senses, are often divided into external (exteroception) and internal ( interoception ) sensory systems. Human external senses are based on

4042-618: 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. Two types of somatosensory signals that are transduced by free nerve endings are pain and temperature. These two modalities use thermoreceptors and nociceptors to transduce temperature and pain stimuli, respectively. Temperature receptors are stimulated when local temperatures differ from body temperature . Some thermoreceptors are sensitive to just cold and others to just heat. Nociception

4128-406: The ability to hear more sensitively due to a well-developed, bony connection between the ear and their swim bladder. This "aid to the deaf" for fishes appears in some species such as carp and herring . Human perception of audio signal time separation has been measured to less than 10 microseconds (10μs). This does not mean that frequencies above 100 kHz are audible, but that time discrimination

4214-567: The air, or “sound”. Charles Henry Turner was the first scientist to formally show this phenomenon through rigorously controlled experiments in ants. Turner ruled out the detection of ground vibration and suggested that other insects likely have auditory systems as well. Many insects detect sound through the way air vibrations deflect hairs along their body. Some insects have even developed specialized hairs tuned to detecting particular frequencies, such as certain caterpillar species that have evolved hair with properties such that it resonates most with

4300-425: The basal entrance to the cochlea, and low at the apex. Basilar membrane motion causes depolarization of the hair cells , specialized auditory receptors located within the organ of Corti. While the hair cells do not produce action potentials themselves, they release neurotransmitter at synapses with the fibers of the auditory nerve , which does produce action potentials. In this way, the patterns of oscillations on

4386-444: The basilar membrane are converted to spatiotemporal patterns of firings which transmit information about the sound to the brainstem . The sound information from the cochlea travels via the auditory nerve to the cochlear nucleus in the brainstem . From there, the signals are projected to the inferior colliculus in the midbrain tectum . The inferior colliculus integrates auditory input with limited input from other parts of

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4472-404: The basis of the type of stimuli they transduce. The different types of functional receptor cell types are mechanoreceptors , photoreceptors , chemoreceptors ( osmoreceptor ), thermoreceptors , electroreceptors (in certain mammals and fish), and nociceptors . Physical stimuli, such as pressure and vibration, as well as the sensation of sound and body position (balance), are interpreted through

4558-414: The basis of three different criteria: cell type , position, and function. Receptors can be classified structurally on the basis of cell type and their position in relation to stimuli they sense. Receptors can further be classified functionally on the basis of the transduction of stimuli, or how the mechanical stimulus, light, or chemical changed the cell membrane potential . One way to classify receptors

4644-451: The body are called exteroceptors . Human external sensation is based on the sensory organs of the eyes , ears , skin , vestibular system , nose , and mouth , which contribute, respectively, to the sensory perceptions of vision , hearing , touch , balance , smell , and taste . Smell and taste are both responsible for identifying molecules and thus both are types of chemoreceptors . Both olfaction (smell) and gustation (taste) require

4730-545: The brain (cortices) are similarly dedicated to different sensory and perceptual tasks. More complex processing is accomplished across primary cortical regions that spread beyond the primary cortices. Every nerve, sensory or motor , has its own signal transmission speed. For example, nerves in the frog's legs have a 90 ft/s (99 km/h) signal transmission speed, while sensory nerves in humans, transmit sensory information at speeds between 165 ft/s (181 km/h) and 330 ft/s (362 km/h). Perceptual experience

4816-439: The brain and is involved in subconscious reflexes such as the auditory startle response . The inferior colliculus in turn projects to the medial geniculate nucleus , a part of the thalamus where sound information is relayed to the primary auditory cortex in the temporal lobe . Sound is believed to first become consciously experienced at the primary auditory cortex . Around the primary auditory cortex lies Wernickes area ,

4902-515: The brain, and/or from stroke ( infarcts in the brain). Temporary or permanent blindness can be caused by poisons or medications. People who are blind from degradation or damage to the visual cortex, but still have functional eyes, are actually capable of some level of vision and reaction to visual stimuli but not a conscious perception; this is known as blindsight . People with blindsight are usually not aware that they are reacting to visual sources, and instead just unconsciously adapt their behavior to

4988-431: The cells or structures that detect sensations. Stimuli in the environment activate specialized receptor cells in the peripheral nervous system . During transduction, physical stimulus is converted into action potential by receptors and transmitted towards the central nervous system for processing. Different types of stimuli are sensed by different types of receptor cells . Receptor cells can be classified into types on

5074-523: The criterion, thus the signal is differentiated from the noise, the signal is sensed and perceived. Errors in signal detection can potentially lead to false positives and false negatives . The sensory criterion might be shifted based on the importance of the detecting the signal. Shifting of the criterion may influence the likelihood of false positives and false negatives. Subjective visual and auditory experiences appear to be similar across humans subjects. The same cannot be said about taste. For example, there

5160-451: The dark, it is most likely because your brain knows what color something is and is relying on that memory. There is some disagreement as to whether the visual system consists of one, two, or three submodalities. Neuroanatomists generally regard it as two submodalities, given that different receptors are responsible for the perception of color and brightness. Some argue that stereopsis , the perception of depth using both eyes, also constitutes

5246-400: The dermis of the skin are examples of neurons that have free nerve endings (1). Also located in the dermis of the skin are lamellated corpuscles , neurons with encapsulated nerve endings that respond to pressure and touch (2). The cells in the retina that respond to light stimuli are an example of a specialized receptor (3), a photoreceptor . A transmembrane protein receptor is a protein in

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5332-423: The detection of a stimulus 50% of the time. Absolute threshold is measured by using a method called signal detection . This process involves presenting stimuli of varying intensities to a subject in order to determine the level at which the subject can reliably detect stimulation in a given sense. Differential threshold or just noticeable difference (JDS) is the smallest detectable difference between two stimuli, or

5418-464: The direction and location of vibrations picked up through the feet. Studies pertaining to audition started to increase in number towards the latter end of the nineteenth century. During this time, many laboratories in the United States began to create new models, diagrams, and instruments that all pertained to the ear. Auditory cognitive psychology is a branch of cognitive psychology that

5504-427: The ear canal toward the eardrum. Because of the asymmetrical character of the outer ear of most mammals, sound is filtered differently on its way into the ear depending on the location of its origin. This gives these animals the ability to localize sound vertically . The eardrum is an airtight membrane, and when sound waves arrive there, they cause it to vibrate following the waveform of the sound. Cerumen (ear wax)

5590-462: The environment can be either (1) a neuron that has a free nerve ending , with dendrites embedded in tissue that would receive a sensation; (2) a neuron that has an encapsulated ending in which the sensory nerve endings are encapsulated in connective tissue that enhances their sensitivity; or (3) a specialized receptor cell , which has distinct structural components that interpret a specific type of stimulus. The pain and temperature receptors in

5676-444: The environment that affect receptor cell membrane potentials. Other stimuli include the electromagnetic radiation from visible light. For humans, the only electromagnetic energy that is perceived by our eyes is visible light. Some other organisms have receptors that humans lack, such as the heat sensors of snakes, the ultraviolet light sensors of bees, or magnetic receptors in migratory birds. Receptor cells can be further categorized on

5762-400: The hammer, anvil, and stirrup, respectively). They aid in the transmission of the vibrations from the eardrum into the inner ear, the cochlea . The purpose of the middle ear ossicles is to overcome the impedance mismatch between air waves and cochlear waves, by providing impedance matching . Also located in the middle ear are the stapedius muscle and tensor tympani muscle , which protect

5848-407: The hearing mechanism through a stiffening reflex. The stapes transmits sound waves to the inner ear through the oval window , a flexible membrane separating the air-filled middle ear from the fluid-filled inner ear. The round window , another flexible membrane, allows for the smooth displacement of the inner ear fluid caused by the entering sound waves. The inner ear consists of the cochlea , which

5934-469: The industry of man." Inspired in the work of Adam Smith , Milne-Edwards wrote that the "body of all living beings, whether animal or plant, resembles a factory ... where the organs, comparable to workers, work incessantly to produce the phenomena that constitute the life of the individual." In more differentiated organisms, the functional labor could be apportioned between different instruments or systems (called by him as appareils ). The exact components of

6020-479: The instrument, the listener, and the player of the instrument. Somatosensation is considered a general sense, as opposed to the special senses discussed in this section. Somatosensation is the group of sensory modalities that are associated with touch and interoception. The modalities of somatosensation include pressure , vibration , light touch, tickle , itch , temperature , pain , kinesthesia . Somatosensation , also called tactition (adjectival form: tactile)

6106-512: The lateral aspect of the head is known as the auricle . At the end of the auditory canal is the tympanic membrane, or ear drum , which vibrates after it is struck by sound waves. The auricle, ear canal, and tympanic membrane are often referred to as the external ear . The middle ear consists of a space spanned by three small bones called the ossicles . The three ossicles are the malleus , incus , and stapes , which are Latin names that roughly translate to hammer, anvil, and stirrup. The malleus

6192-437: The membrane, and can generate an action potential or a graded potential in the sensory neurons . A third classification of receptors is by how the receptor transduces stimuli into membrane potential changes. Stimuli are of three general types. Some stimuli are ions and macromolecules that affect transmembrane receptor proteins when these chemicals diffuse across the cell membrane. Some stimuli are physical variations in

6278-408: The molecular level, visual stimuli cause changes in the photopigment molecule that lead to changes in membrane potential of the photoreceptor cell. A single unit of light is called a photon , which is described in physics as a packet of energy with properties of both a particle and a wave. The energy of a photon is represented by its wavelength , with each wavelength of visible light corresponding to

6364-436: The movement of hair at the surface of the skin, such as when an insect may be walking along the skin . Stretching of the skin is transduced by stretch receptors known as bulbous corpuscles . Bulbous corpuscles are also known as Ruffini corpuscles, or type II cutaneous mechanoreceptors. The heat receptors are sensitive to infrared radiation and can occur in specialized organs, for instance in pit vipers . The thermoceptors in

6450-445: The movement of molecules in the world outside the organism. Both hearing and touch are types of mechanosensation . There are three main components of the human auditory system : the outer ear, the middle ear, and the inner ear. The outer ear includes the pinna , the visible part of the ear, as well as the ear canal , which terminates at the eardrum , also called the tympanic membrane. The pinna serves to focus sound waves through

6536-402: The muscles of the pharynx contract during swallowing or yawning . Mechanoreceptors turn motion into electrical nerve pulses, which are located in the inner ear. Since sound is vibration, 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

6622-711: The sensory organs of the eyes , ears , skin , nose , mouth and the vestibular system . Internal sensation detects stimuli from internal organs and tissues. Internal senses possessed by humans include spatial orientation , proprioception (body position) and nociception (pain). Further internal senses lead to signals such as hunger , thirst , suffocation , and nausea , or different involuntary behaviors, such as vomiting . Some animals are able to detect electrical and magnetic fields , air moisture , or polarized light , while others sense and perceive through alternative systems, such as echolocation . Sensory modalities or sub modalities are different ways sensory information

6708-412: The skin are quite different from the homeostatic thermoceptors in the brain ( hypothalamus ), which provide feedback on internal body temperature. Biological system These specific systems are widely studied in human anatomy and are also present in many other animals. The notion of system (or apparatus) relies upon the concept of vital or organic function : a system is a set of organs with

6794-479: The smallest difference in stimuli that can be judged to be different from each other. Weber's Law is an empirical law that states that the difference threshold is a constant fraction of the comparison stimulus. According to Weber's Law, bigger stimuli require larger differences to be noticed. Magnitude estimation is a psychophysical method in which subjects assign perceived values of given stimuli. The relationship between stimulus intensity and perceptive intensity

6880-483: The sound of buzzing wasps, thus warning them of the presence of natural enemies. Some insects possess a tympanal organ . These are "eardrums", that cover air filled chambers on the legs. Similar to the hearing process with vertebrates, the eardrums react to sonar waves. Receptors that are placed on the inside translate the oscillation into electric signals and send them to the brain. Several groups of flying insects that are preyed upon by echolocating bats can perceive

6966-464: The stimulus. On February 14, 2013, researchers developed a neural implant that gives rats the ability to sense infrared light which for the first time provides living creatures with new abilities, instead of simply replacing or augmenting existing abilities. According to Gestalt Psychology, people perceive the whole of something even if it is not there. The Gestalt's Law of Organization states that people have seven factors that help to group what

7052-451: The tendency humans have to categorize objects according to past experiences under certain circumstances. If two objects are usually perceived together or within close proximity of each other the Law of Past Experience is usually seen. Hearing, or audition, is the transduction of sound waves into a neural signal that is made possible by the structures of the ear . The large, fleshy structure on

7138-584: The transduction of chemical stimuli into electrical potentials. The visual system, or sense of sight, is based on the transduction of light stimuli received through the eyes and contributes to visual perception . The visual system detects light on photoreceptors in the retina of each eye that generates electrical nerve impulses for the perception of varying colors and brightness. There are two types of photoreceptors: rods and cones . Rods are very sensitive to light but do not distinguish colors. Cones distinguish colors but are less sensitive to dim light. At

7224-498: The user to measure hearing thresholds at different frequencies ( audiogram ). Despite possible errors in measurements, hearing loss can be detected. There are several different types of hearing loss: conductive hearing loss , sensorineural hearing loss and mixed types. Recently, the term of Aural Diversity has come into greater use, to communicate hearing loss and differences in a less negatively-associated term. There are defined degrees of hearing loss: Hearing protection

7310-415: The wavelength scale. The three types of cone opsins , being sensitive to different wavelengths of light, provide us with color vision. By comparing the activity of the three different cones, the brain can extract color information from visual stimuli. For example, a bright blue light that has a wavelength of approximately 450 nm would activate the "red" cones minimally, the "green" cones marginally, and

7396-413: The way that information is encoded, which is similar to the idea of transduction . The main sensory modalities can be described on the basis of how each is transduced. Listing all the different sensory modalities, which can number as many as 17, involves separating the major senses into more specific categories, or submodalities, of the larger sense. An individual sensory modality represents the sensation of

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