NationMaster - Encyclopedia: Helix (ear)

An ear is an organ used by an animal to detect sound waves. The term may refer to the entire system responsible for collection and early processing of sound (the beginning of the auditory system), or merely the externally-visible part. Not all animals have ears in the same part of the body. http://www. ... http://www. ... Binomial name Homo sapiens Linnaeus, 1758 Subspecies Homo sapiens idaltu (extinct) Homo sapiens sapiens Human beings define themselves in biological, social, and spiritual terms. ... In botany, an ear is the fruiting body of a grain plant, such as maize or wheat, borne at the end of the stalk. ... This article is about compression waves. ... The auditory system is the sensory system for the sense of hearing. ...

Non-mammalian hearing organs

The mammalian ear

Mammals, including humans, have two ears, one on each side of the head. human ear anatomy I made this myself Iain 05:39 29 Jun 2003 (UTC) version without labels File links The following pages link to this file: Ear Categories: GFDL images ... human ear anatomy I made this myself Iain 05:39 29 Jun 2003 (UTC) version without labels File links The following pages link to this file: Ear Categories: GFDL images ... Orders Subclass Monotremata Monotremata Subclass Marsupialia Didelphimorphia Paucituberculata Microbiotheria Dasyuromorphia Peramelemorphia Notoryctemorphia Diprotodontia Subclass Placentalia Xenarthra Dermoptera Desmostylia Scandentia Primates Rodentia Lagomorpha Insectivora Chiroptera Pholidota Carnivora Perissodactyla Artiodactyla Cetacea Afrosoricida Macroscelidea Tubulidentata Hyracoidea Proboscidea Sirenia The mammals are the class of vertebrate animals characterized by the presence of mammary glands... Binomial name Homo sapiens Linnaeus, 1758 Subspecies Homo sapiens idaltu (extinct) Homo sapiens sapiens Human beings define themselves in biological, social, and spiritual terms. ...

The outer ear is the external portion of the ear. The visible part is called the pinna, or auricle, and functions to collect and focus sound waves. Many mammals can move the pinna in order to focus their hearing in a certain direction, in much the same way that they can turn their eyes. Humans have generally lost this ability. From the pinna, the sound pressure waves move into the ear canal, a simple tube running to the middle ear. This tube amplifies frequencies in the range 3 kHz to 12 kHz. The pinna is the visible part of the ear that resides outside of the head. ... Orders Subclass Monotremata Monotremata Subclass Marsupialia Didelphimorphia Paucituberculata Microbiotheria Dasyuromorphia Peramelemorphia Notoryctemorphia Diprotodontia Subclass Placentalia Xenarthra Dermoptera Desmostylia Scandentia Primates Rodentia Lagomorpha Insectivora Chiroptera Pholidota Carnivora Perissodactyla Artiodactyla Cetacea Afrosoricida Macroscelidea Tubulidentata Hyracoidea Proboscidea Sirenia The mammals are the class of vertebrate animals characterized by the presence of mammary glands... An eye is an organ that detects light. ... Sound pressure p (or acoustic pressure) is the measurement in pascals of the root mean square (RMS) pressure deviation (from atmospheric pressure) caused by a sound wave passing through a fixed point. ... WAVE (WAVE-3) is a local NBC station in Louisville, Kentucky, USA. It is owned by The Liberty Corporation and broadcast from their main studio in downtown Louisville. ... Anatomy of the human ear. ... For an alternative meaning, see ear (botany). ... A kilohertz (kHz) is a unit of frequency equal to 1,000 hertz (1,000 cycles per second). ...

The human ear has ear lobes at the bottom which are vestigial, but are used by many people to provide an attachment point for earrings. The earlobe is usually formed cleft from the side of the face and hangs from the rest of the ear, but occasionally will be found looking fused and "lobeless" due to a recessive gene. The helix is the outer edge of the outer ear[1]. A vestigial organ is an organ whose original function has been lost during evolution. ... Sarmatian silver earrings from the Hermitage Museum. ...

The middle ear includes the eardrum (tympanum or tympanic membrane) and the ossicles, three tiny bones of the middle ear. Their Latin names are the malleus, incus, and stapes, but they are also referred to by their English translations: the hammer, anvil, and stirrup respectively. The tympanum or tympanic membrane, colloquially known as eardrum, is a thin membrane that separates the outer ear from the middle ear. ... The ossicles (also called auditory ossicles) are the three smallest bones in the human body. ... The malleus is hammer-shaped small bone or ossicle of the middle ear which connects with the incus and is attached to the inner surface of the eardrum. ... The incus is the anvil-shaped small bone or ossicle in the middle ear. ... The stapes or stirrup is the stirrup-shaped small bone or ossicle in the middle ear which attaches the incus to the fenestra ovalis, the oval window which is adjacent to the vestibule of the inner ear. ...

Mammals are unique in having three ear bones. The incus and stapes are derived from bones of the jaw, and allow finer detection of sound.

These bones form the linkage between the tympanic membrane and the oval window that leads to the inner ear. The tympanum turns vibrations of air in the ear canal into vibrations of the ossicles. The ossicles in turn transmit the vibrations through the membrane of the oval window into the fluid of the inner ear. The ratio in area between the tympanic membrane and the oval window results in an effective amplication of approximately 14 dB, peaking at a frequency of around 1 kHz. The combined transfer function of the outer ear and middle ear gives humans a peak sensitivity to frequencies between 1 kHz and 3 kHz. The tensor tympani muscle and stapedius muscle of the inner ear contract in response to loud sounds, reducing the transmission of sound to the inner ear. This is called the acoustic reflex. Although it is widely used as a measure of the loudness of sound, the decibel (dB) is more generally a measure of the ratio between two quantities, and can be used to express a wide variety of measurements in acoustics and electronics. ... A transfer function is a mathematical representation of the relation between the input and output of a linear time-invariant system. ... The acoustic reflex is an involuntary muscle contraction that occurs in the middle ear of mammals in response to loud sound stimuli. ...

The middle ear is hollow. If the animal moves to a high-altitude environment, or dives into the water, there will be a pressure difference between the middle ear and the outside environment. This pressure will pose a risk of bursting or otherwise damaging the tympanum if it is not relieved. This is one of the functions of the Eustachian tubes — evolutionary descendants of the gills — which connect the middle ear to the nasopharynx. The Eustachian tubes are normally pinched off at the nose end, to prevent being clogged with phlegm, but they may be opened by lowering and protruding the jaw; this is why yawning helps relieve the pressure felt in the ears when on board an aircraft. Anatomy of the human ear. ... In aquatic organisms, gills are a respiratory organ for the extraction of oxygen from water and for the excretion of carbon dioxide. ... The pharynx is the part of the digestive system of many animals immediately behind the mouth and in front of the esophagus. ... Phlegm is a type of mucus, the sticky fluid secreted by the mucous membranes of animals. ... A dog yawning A yawn is a reflex of deep inhalation and exhalation associated with being tired, with a need to sleep, or from boredom. ...

The inner ear comprises both the organ of hearing (the cochlea) and the labyrinth or vestibular apparatus, the organ of balance located in the inner ear that consists of three semicircular canals and the vestibule. Cross section of the cochlea. ... See also Labyrinth, an article treating the mythical maze that imprisoned the Minotaur. ... See also Labyrinth, an article treating the mythical maze that imprisoned the Minotaur. ... inner ear illustration showing semicircular canal, hair cells, ampulla, cupula, vestibular nerve, & fluid The semicircular canals are three half-circular, interconnected tubes located inside each ear that are the equivalent of three gyroscopes located in three planes perpendicular (at right angles) to each other. ... Vestibule can have the following meanings: A large entrance, reception area, antechamber, or room A small room or passage that connects the outer door of a building to the interior of the building An area in a train where people get on and off. ...

The cochlea (latin for "snail") is a spiralled, hollow, conical chamber of bone filled with perilymph, a fluid medium that receives the sound vibrations transmitted from the air to the oval window through the ear drum and ossicles of the middle ear (see above). Running through its centre is the cochlea duct which contains the spiral organ of Corti, the receptor organ responsible for hearing. The bony cavity of the cochlea is divided into three separate chambers. The scala vestibuli which lies superior to the cochlea duct and abuts the oval window. The scala media which is the membraneous cochlea duct containing endolymph and the organ of Corti, and inferior to the scala media is the scala tympani which terminates at the round window. The two bony chambers (scala vestibuli and scala tympani) both contain perilymph and join together at the cochlear apex, a region called the helicotrema. Separating the scala vestibuli from the scala media is the vestibular membrane and is pretty uninteresting. The basilar membrane separates the scala media from the scala tympani. Sitting on top of the basilar membrane is a cellular layer known as the Organ of Corti, which is lined with hair cells — sensory cells topped with hair-like structures called stereocilia. As the stapes oscillate against the oval window is response to sound, the perilymph within the scala vestibuli also oscillates. For very low frequencies (below 20Hz) the pressure waves propagate along the complete route of the cochlea - up scala vestibuli, around helicotrema and down scala tympani to the round window. Frequencies this low do not activate the organ of Corti and are below the threshold for hearing. Higher frequencies don't propagate to the helicotrema, but are transmitted through the endolymph in the cochlea duct to the perilymph in the scala tympani. This sets the entire basilar membrane into vibrations. The fibres of the basilar membrane are tuned to a certain sound frequency, being short and stiff (responsive to high frequencies) near the oval window and long and floppy (responsive to low frequencies) near the apex of the cochlea. When a region of the basilar membrane resonates, the hair cells in that region send nerve impulses to the brain, which are perceived as a sound of whatever pitch the hair cell is associated with. A very strong movement of the endolymph due to very loud noise may cause hair cells to die. This is a common cause of partial hearing loss, and the reason why anyone near guns or heavy machinery should wear earmuffs or earplugs. Cross section of the cochlea. ... A cross section of the cochlea illustrating the Organ of Corti. ... Hair cells are the sensory cells of the auditory system that are found within the cochleas organ of Corti. ... Stereocilia Stereocilia are mechanosensing organelles of the hair cells which line the Organ of Corti in the cochlea. ... Schematic of an electrophysiological recording of an action potential showing the various phases which occur as the wave passes a point on a cell membrane. ... In the anatomy of animals, the brain, or encephalon, is the supervisory center of the nervous system. ... In music, pitch is the perception of the frequency of a note. ... Earmuffs are objects designed to cover a persons ears for protection. ... An earplug is a piece of protective clothing that is meant to be inserted in the ear canal to protect the wearers hearing from loud noises or the intrusion of water. ...

The vestibular apparatus is filled with the same endolymph as the cochlea, but instead of detecting sound, it detects rotation of the head. If a line is drawn through the middle of each of the three semicircular canals, perpendicular to the plane in which the canal lies, the three lines would be perpendicular. They would represent three axes of rotation. Any rotation could be represented as three simultaneous rotations about the three axes. Rotation is the movement of a body in such a way that the distance between a certain fixed point and any given point of that body remains constant. ... Perpendicular is a geometric term that may be used as a noun or adjective. ... The axis of rotation of a rotating body is a line such that the distance between any point on the line and any point of the body remains constant under the rotation. ...

Diseases and medical conditions of the ear and auditory system

Problems with the ear or auditory processing system in the brain can lead to deafness. In the anatomy of animals, the brain, or encephalon, is the supervisory center of the nervous system. ... The word deaf, can have very different meanings based on the background of the person speaking or the context in which the word is used. ...

Acoustic neuroma (or Vestibular Schwannoma) is a benign tumor of the acoustic nerve (more properly the vestibulocochlear nerve) just after it has left the brainstem, in the pontine angle. ... A balance disorder is a disturbance that causes an individual to feel unsteady, giddy, woozy, or have a sensation of movement, spinning, or floating. ... Barotrauma is physical damage to body tissues caused by a difference in pressure between an air space inside or beside the body and the surrounding gas or liquid. ... Benign paroxysmal positional vertigo (BPPV) is a condition caused by problems in the inner ear. ... Cholesteatomas are benign tumors in cases where a perforation of the eardrum (tympanic membrane) does not heal without surgery, but instead grows through the hole into the middle ear and, if infection develops, results in a cyst-like tumor. ... Otitis media (also known as glue ear) is an inflammation of the middle ear, usually associated with a buildup of fluid. ... Temporary reduction of hearing sensitivity as indicated by the increase of hearing threshold level occurs after exposure to loud sounds. ... Labyrinthitis is a balance disorder that usually follows an upper respiratory tract infection (URI). ... MÃ©niÃ¨reâ€™s disease (or syndrome, since its cause is unknown) was first described by French physician Prosper MÃ©niÃ¨re in 1861. ... Inferior view of a brain with meningitis caused by Haemophilus influenzae. ... In medicine, the neurofibromatoses (singular, neurofibromatosis) are certain genetic disorders of the nervous system. ... In medicine, the neurofibromatoses (singular, neurofibromatosis) are certain genetic disorders of the nervous system. ... Otitis media (also known as glue ear) is an inflammation of the middle ear, usually associated with a buildup of fluid and frequently causes an earache. ... Presbycusis, or age-related hearing loss, is the cumulative effect of aging on hearing. ... This article needs cleanup. ... Tinnitus is a phenomenon of the nervous system connected to the ear, characterized by perception of a ringing or beating sound (often perceived as sinusoidal) with no external source. ... Usher syndrome is a genetic disease causing deaf-blindness. ... ...

Contents

Non-mammalian hearing organs

The mammalian ear

Diseases and medical conditions of the ear and auditory system

See also

External links

Contents

Non-mammalian hearing organs GA_googleFillSlot("encyclopedia_square");

The mammalian ear

Diseases and medical conditions of the ear and auditory system

See also

External links

Non-mammalian hearing organs