whats the difference between the inner and outer hair cells of cochlea?
414049
The presence of two types of hair cells, the inner and outer hair cells, in the organ of Corti was appreciated nearly a 100 years ago but the function of the two has only become clear in the last 20 years. The first clue that they might play different roles in hearing came about 40 years ago as the result of a painstaking anatomical investigation which revealed that most of the nerve fibers that carry information to the brain contact only the inner hair cells. This meant that most the information about the acoustic world reached the brain via the inner hair cells. What then was the role of outer hair cells which are over three times more numerous? The mystery was compounded by the discovery that neural fibers originating from neurons deep in the brain, which send information back to the hair cells, only touch outer hair cells. It was later determined that outer hair cell stereocilia are firmly embedded in the overlying tectorial membrane while inner hair cell sterocilia make only a tenuous connection. The outer hair cells are located near the center of the basilar membrane where vibrations will be greatest while the basilar membrane is anchored under the inner hair cells (see Figure 5). These observations suggest that the movement of stereocilia and the resulting modulation of their ionic currents is likely to be greater for outer hair cells than for inner hair cells. Several studies that had examined the inner ears of deaf people shortly after they died demonstrated that outer hair cells were required for hearing. It was clear that the inner hair cells served to transmit information to the brain but the role of the outer hair cells remained a mystery. \n\nThe mechanical vibrations of the organ of Corti had been analyzed by engineers since the 1940s. Their analysis was able to explain the frequency selectivity originally measured by von Bekesy in cochlea obtained from cadaver ears. It was known at the time that the measured frequency selectivity and the frequency selectivity computed from the engineering analysis did not approach the frequency selectivity of the human hearing or the frequency selectivity that could be measured from individual nerve fibers. Shortly after WW2 an American astrophysicist who had worked on radar during the war suggested that the frequency selectivity of the cochlea could be enhanced if a source of mechanical energy were present in the cochlea. His suggestion was largely ignored until several engineering groups in the late 70s rediscovered the potential benefits of this hypothetical energy source. They were forced to consider the possible existence of this "cochlear amplifier" when improved measures from living (as opposed to dead) ears revealed that the mechanical frequency selectivity in the living ear began to approach that of human hearing. The concept that a source of mechanical energy exists in the cochlea appeared validated when in the late 70s it was discovered that sound is produced by the inner ear. These sounds can be measured by placing a sensitive microphone in the ear canal. They were called otoacoustic emissions and they are now routinely measured in the clinic to assess hearing. Their discovery was amazing for sensory physiology because it was equivalent to finding that light comes out of the eye (which has never been observed). Within five years it was discovered that the outer hair cell could be made to elongate and shorten by electrical stimulation. The function of the outer hair cell in hearing is now perceived as that of a cochlear amplifier that refines the sensitivity and frequency selectivity of the mechanical vibrations of the cochlea.
691277
outer layer: cell wall\ninner layer: cell membrane\ninside:\ncytoplasm, mitochondria, nucleus, chloroplast (all enclosed with membranes), endoplasmic reticulum, ribosoms, vacuoles (which contains various pigments depending upon the cell type and species), dictysomes.
431489
vestibulocohlear & auditory & acoustic & eighth * 8th. the vibration of air molecules sets up sound waves that are transmitted to the outer ear, the middle ear, the inner ear, the ear drum and the small bones of the ears. Small nerve fibers from the vestibulocochear nerve(or auditory nerve or acoustic nerve or 8th cranial nerve) transmitt the stimuli to the brain where it is interpreted as hearing. Small fibers from the vestibular portion of this nerve are located in the semicircular canal of the inner ears and control equiibrium.
135640
Vibrations in air --> external auditory meatus (duct) lets vibrating air pass --> tympanic membrane vibrates --> hammer (malleus) moves --> anvil (incus) moves --> stirrup (stapes) moves --> oval fenestra (opening into inner ear)--> endolymphatic fluid vibrates --> three parallel ducts that form the cochlea: vibrations travel through vestibular channel --> apex --> tympanic channel (vestibular and tympanic channel surround the cochlear channel or Corti organ) --> membrane of round window vibrates. \nVibrations stimulate different parts of the Organ of Corti --> Auditory nerve (VII cranial nerve pair) --> medulla oblonga at the base of the brain. \n\nConfused? Try reading this while watching these:\nMammalian ear (from the BBC, with great animations)\nhttp://www.bbc.co.uk/science/humanbody/body/factfiles/hearing/hearing.shtml\nInner ear\nhttp://pages.cpsc.ucalgary.ca/~mario/npr/courses/cpsc601/homeworks/ear.jpg\nhttp://www.wadalab.mech.tohoku.ac.jp/images/inner_ear2.jpg
842289
In what respect?\nYet more general questions asked by inquisitive ... erm.... well... I shall try to answer...\n\nThey are both substancial collections of atoms... formed into molecules... mostly water though a fair number of hydrocarbons and amino acids, among other similar structures. \nThey're both animal cells...  presumably human animal cells in this case... That means they have a cell membrane, nucleus, mitochondria and various smaller organelles.\n\nAside from that, we have the specifics of those cells:\nThey're both rather skinny for one thing... lengthy and skinny. Neurones... i.e. nerve cells.... can however be easily as long as the entire length of your forearm... and yet thinner than most cells. Sperm are very much smaller than that. \n\nFeature-wise... nerve cells have dentrites... branching extensions of the cell membrane... at each end. These are to connect to other neurones and transmit signals between them. The signals are transferred through the cell itself along the axon... which is the long, thin bit in the middle.... by means of an ionic differential gradient between potassium and sodium ions. In almost all cases, neurones will be found in bundles (since they're so thin) to cover a wide area and send as much data as possible to and from the brain.\nThere are different kinds of neurones that serve different functions.... in particular motor neurones (which transmit data from the brain to the body)  ... well... whatever the opposite ones... sensory neurones maybe... (which, by whatever name, transmit data from the sensory organs to the brain)... and interneurones... which join the others together inbetween.  As I recall, the neurones in the brain are of different types again, but I don't know the slightest thing about those.\nAnyhow... I don't think I can tell you much more about nerve cells.\n\n\nSperm on the other hand... are male gametes.... produced in vast numbers at very little bodily expense per cell. Each one is basically just a haploid nucleus (one copy of each chromosome) with a flagellum (a 'tail' to propel the cell forward) and just enough cytoplasm and mitochondria to power it for a short journey. They are generated at quite an alarming rate in the testes.... and their entire purpose is to be ejaculated into the female reproductive system and propel themselves forcefully and rather erratically to an awaiting ovum.... Eventually, of the ones that reach the ovum (most die along the way due to the corrosive substances which coat the inside of the uterus), one will get chemically accepted by the larger cell and allowed to fuse the cytoplasms together. The nuclei will then fuse into a single diploid (2 of each chromosome) nucleus.... and the newly fertilised cell will begin to divide.  Note however that while the nucleus of the sperm is allowed to fuse with the nucleus of the ovum... the mitochondria that are in the sperm will be destroyed by the new host cell.... hence all the mitochondria you will ever have are near-identical copies of your mother's ones (not perfect copies since mutations can and will occur between generations).\n\n\nRight... I've had enough of answering this question now...\nOff to other things.
1047759
Cells have openings on their outer membrane - ion pumps. The pumps regulate the concentration of sodium and potassium ions in the cell. The difference in ions in and out of the cell creates an electric potential across the membrane allowing a nerve impulse to propagate along its length. Jens C. Skou won the 1997 Nobel Prize for work in this area. Several ion pumps have now ben described.
382596
Good Question!  And The answer is this: Located in the middle ear, the stapedius is a miniscule 1.27 millimeters in length.  It controls the tiniest bone in the body, the stapes or stirrup bone. The stapes and two other bones conduct sound vibrations through the middle ear. The stapedius is innervated by the facial nerve. \n\nHope this answers your Question.
499411
inside the inner ear,there are 3 semicircular canals,uttricles,succulus and cochlea which are collectively called MEMBRANEOUS LABYRINTH..\nthe space around membranous labyrinth contains a fluid called PERILYMPH while  inside it is another fluid called ENDOLYMH..the 3 semicircular canals,uttricles and succulus are required for maintaining balance and posture..\nthe former responses to changes in direction while latter to changes in posture.\nany defect in these causes dizziness and loss of balance.\n\ni hope it shud be clear to you..
269469
Sound travels in waves like light or heat does, but unlike them, sound travels by making molecules vibrate. So, in order for sound to travel, there has to be something with molecules for it to travel through. On Earth, sound travels to your ears by vibrating air molecules. In deep space, the large empty areas between stars and planets, there are no molecules to vibrate. There is no sound there.
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an immature cell is a newly born cell which was just produced by the process of cell division.it differentiates and matures to form certain kind of cell to perform it's specific function.\nfor example in animals, an immature cell consisting of all the cell organelles, but as u know that the cells in each tissue in an animal's body is so different.thus the immature cell differentiates or develops and takes the form of the cell that is need in the particular tissue.\nsee, a neuron,the nerve cell that is,doesn't have a centriole because the mature neuron cells don't need them as mature neuron cells don't divide,and that is the reason why when one has a head injury,its hard to recover.\ntake for instance an RBC in the blood tissue doesn't have a nucleus while WBCs have differently shaped nucles having lobes or in the shape of kidney etc.\nso this means each tissue has a different cell.hence the immature cells have to develop themselves as per the need of the body.\nsame thing happens in the plant cell . just that the tissues are entirely different from that of the animal's and here in plant cell an immature cell has the ability to divide,called meristematic cell.these cells after the growth of the plant becomes mature,differentiate and form permanent non dividing cells.\nthese permanent cell again de-differentiates for the secondary growth in the plant and starts dividing again.\neach tissue of the plant body has different types of cells...\n\nand chondroblasts are the same in the case of animals.\nthese are cells found in the cartilage tissue.these are immature cells which develops to form mature chondrocytes.\nnote : the cartilage tissue is mostly connected to the areolar connective tissue for the nourishment of the chondrocytes present in the cartilage as the cartilage doesn't have a blood supply but the connective tissue does.and the chondroblasts are the immature cells present in the connective tissue which moves to the cartilage tissue and forms a part of the cartilage as chondrocytes.
464632
(1) The Sound is a  physical phenomenon that stimulates the sense of hearing. \n(2) In human beings, hearing takes place whenever vibrations of frequencies between about 15 and 20,000 hertz reach the inner ear.\n(3)  The hertz (Hz) is a unit of frequency equalling one cycle per second. Such vibrations reach the inner ear when they are transmitted through air, and the term sound is sometimes restricted to such airborne vibrational waves. Modern physicists, however, usually extend the term to include similar vibrations in liquid or solid media. Sounds of frequencies higher than about 20,000 hertz are called ultrasonic
494099
same:   both have a lipid bi-layer membrane.  Both have Peripheral and integral membrane proteins.\n\nDifference:  single celled normally have cilia or flagella, single celled macrophage whereas multicelled normally don't.  Multicelled handle disease better.
911107
To protect the inner ear from invading particles and moisture protection keeping the eardrum (much like the contact lens solution) from drying out and causing discomfort......\n\nYour sister,\nGinger
543036
The periderm is the outer bark of a tree.The periderm is a secondary tissue that replaces epidermis in roots and stems, and which consists of phellem, phellogen, and phelloderm (it includes dead tissues). while the inner bark is called the phloem,It conducts usable food from the leaves to the cambium to nourish it or to storage areas in the wood (it includes living tissues)and consists of  of alternating wedges of sieve tube tissue and radial parenchyma, most of the former crushed by secondary growth.
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Snakes have internal ears.Although these are not as well developed, they can sense ground vibrations.\n\nHearing: Snakes can hear but this sense is not as well-developed as its other senses.Snakes don't have external ears or even a middle ear. They only have a small bone (columella) which connects the jaw bone to the inner ear canals. These inner ear canals work superbly as the snake moves in three dimensions! A snake picks up sound through the skin which passes on to this jaw bone.There are also indications that the lung may act as a sound receptor.\nTongue is used for detecting chemicals in the air
127487
The cerumen glands. See the reference.
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I assume you are asking about cell membranes, but the answer should generally hold for anything.  The inner face of a cell membrane is negative relative to the outer face-this is the polarity of the cell, and in neurons, for example, its about 60 millivolts (mv).  Anything that causes more negative ions to enter the cell, or more positive ions to leave the cell will cause this to be greater, so for example, movement of (negatively charged) chlorine ions into the cell will make the inside of the cell more negative, and thus hyperpolarized.  On the other hand, anything that would cause a loss of negative ions from the inside to outside the cell, or entry of positive ions into the cell, would cause the inside of the cell to be more positive, closer to the outside of the cell, thus depolarizing it, because it gets rid of the relative polarity of the cell.  Ill give you some specific real examples- activation of chlorine channels are hyperpolarizing, and inhibition of sodium channels are as well.  Activation of sodium channels or inhibition of chlorine channels are depolarizing.  Other important ions that control the polarity are potassium and calcium.