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Stereocilia (inner Ear)
In the inner ear, stereocilia are the mechanosensing organelles of hair cells, which respond to fluid motion in numerous types of animals for various functions, including hearing and balance. They are about 10–50 micrometers in length and share some similar features of microvilli.Caceci, T. VM8054 Veterinary Histology: Male Reproductive System. http://education.vetmed.vt.edu/Curriculum/VM8054/Labs/Lab27/Lab27.htm (accessed 2/16/06). The hair cells turn the fluid pressure and other mechanical stimuli into electric stimuli via the many microvilli that make up stereocilia rods.Alberts, B., Johnson, A., Lewis, J., Raff, M., Roberts, K. and Walter, P. (2002) The Molecular Biology of the Cell. Garland Science Textbooks. Stereocilia exist in the auditory and vestibular systems. Morphology Resembling hair-like projections, the stereocilia are arranged in bundles of 30-300. Within the bundles the stereocilia are often lined up in several rows of increasing height, similar to a stairca ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Stereocilia Of Frog Inner Ear
Stereocilia (or stereovilli or villi) are non-motile apical cell modifications. They are distinct from cilia and microvilli, but are closely related to microvilli. They form single "finger-like" projections that may be branched, with normal cell membrane characteristics. They contain actin. Stereocilia are found in the vas deferens, the epididymis, and the sensory cells of the inner ear. Structure Stereocilia are cylindrical and non-motile. They are much longer and thicker than microvilli, form single "finger-like" projections that may be branched, and have more of the characteristics of the cellular membrane proper. Like microvilli, they contain actin and lack an axoneme. This distinguishes them from cilia. They do not have a Basal body at their base since they do not contain microtubules. They may or may not be covered by a glycocalyx coating. They have no fixed arrangement, different to the structure present in kinocilium. Function Stereocilia are found in: *the vas defe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Endolymph
Endolymph is the fluid contained in the membranous labyrinth of the inner ear. The major cation in endolymph is potassium, with the values of sodium and potassium concentration in the endolymph being 0.91 mM and 154 mM, respectively. It is also called ''Scarpa's fluid'', after Antonio Scarpa. Structure The inner ear has two parts: the bony labyrinth and the membranous labyrinth. The membranous labyrinth is contained within the bony labyrinth, and within the membranous labyrinth is a fluid called endolymph. Between the outer wall of the membranous labyrinth and the wall of the bony labyrinth is the location of perilymph. Composition Perilymph and endolymph have unique ionic compositions suited to their functions in regulating electrochemical impulses of hair cells. The electric potential of endolymph is ~80-90 mV more positive than perilymph due to a higher concentration of K compared to Na. The main component of this unique extracellular fluid is potassium, which is ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tectorial Membrane (cochlea)
The tectoria membrane (TM) is one of two acellular membranes in the cochlea of the inner ear, the other being the basilar membrane (BM). "Tectorial" in anatomy means forming a cover. The TM is located above the spiral limbus and the spiral organ of Corti and extends along the longitudinal length of the cochlea parallel to the BM. Radially the TM is divided into three zones, the limbal, middle and marginal zones. Of these the limbal zone is the thinnest (transversally) and overlies the auditory teeth of Huschke with its inside edge attached to the spiral limbus. The marginal zone is the thickest (transversally) and is divided from the middle zone by Hensen's Stripe. It overlies the sensory inner hair cells and electrically-motile outer hair cells of the organ of Corti and during acoustic stimulation stimulates the inner hair cells through fluid coupling, and the outer hair cells via direct connection to their tallest stereocilia. Structure The TM is a gel-like structure containing ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Saccule
The saccule is a bed of sensory cells in the inner ear. It translates head movements into neural impulses for the brain to interpret. The saccule detects linear accelerations and head tilts in the vertical plane. When the head moves vertically, the sensory cells of the saccule are disturbed and the neurons connected to them begin transmitting impulses to the brain. These impulses travel along the vestibular portion of the eighth cranial nerve to the vestibular nuclei in the brainstem. The vestibular system is important in maintaining balance, or equilibrium. The vestibular system includes the saccule, utricle, and the three semicircular canals. The vestibule is the name of the fluid-filled, membranous duct that contains these organs of balance. The vestibule is encased in the temporal bone of the skull. Structure The saccule, or sacculus, is the smaller of the two vestibular sacs. It is globular in form and lies in the recessus sphæricus near the opening of the vest ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Utricle (ear)
The utricle and saccule are the two otolith organs in the vertebrate inner ear. They are part of the balancing system (membranous labyrinth) in the vestibule of the bony labyrinth (small oval chamber). They use small stones and a viscous fluid to stimulate hair cells to detect motion and orientation. The utricle detects linear accelerations and head-tilts in the horizontal plane. The word utricle comes . Structure The utricle is larger than the saccule and is of an oblong form, compressed transversely, and occupies the upper and back part of the vestibule, lying in contact with the recessus ellipticus and the part below it. Macula The macula of utricle (macula acustica utriculi) is a small (2 by 3 mm) thickening lying horizontally on the floor of the utricle where the epithelium contains vestibular hair cells that allow a person to perceive changes in latitudinal acceleration as well as the effects of gravity; it receives the utricular filaments of the acoustic nerve. Th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Otoconia
An otolith ( grc-gre, ὠτο-, ' ear + , ', a stone), also called statoconium or otoconium or statolith, is a calcium carbonate structure in the saccule or utricle of the inner ear, specifically in the vestibular system of vertebrates. The saccule and utricle, in turn, together make the ''otolith organs''. These organs are what allows an organism, including humans, to perceive linear acceleration, both horizontally and vertically (gravity). They have been identified in both extinct and extant vertebrates. Counting the annual growth rings on the otoliths is a common technique in estimating the age of fish. Description Endolymphatic infillings such as otoliths are structures in the saccule and utricle of the inner ear, specifically in the vestibular labyrinth of all vertebrates (fish, amphibians, reptiles, mammals and birds). In vertebrates, the saccule and utricle together make the ''otolith organs''. Both statoconia and otoliths are used as gravity, balance, movement, and d ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ampullary Cupula
The ampullary cupula, or cupula, is a structure in the vestibular system, providing the sense of spatial orientation. The cupula is located within the ampullae of each of the three semicircular canals. Part of the crista ampullaris, the cupula has embedded within it hair cells that have several stereocilia associated with each kinocilium. The cupula itself is the gelatinous component of the crista ampullaris that extends from the crista to the roof of the ampullae. When the head rotates, the endolymph filling the semicircular ducts initially lags behind due to inertia. As a result, the cupula is deflected opposite the direction of head movement. As the endolymph pushes the cupula, the stereocilia is bent as well, stimulating the hair cells within the crista ampullaris. After a short time of continual rotation however, the endolymph's acceleration normalizes with the rate of rotation of the semicircular ducts. As a result, the cupula returns to its resting position and the hair cel ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Crista Ampullaris
The crista ampullaris is the sensory organ of rotation. They are found in the osseous ampullae, ampullae of each of the semicircular canals of the inner ear, meaning that there are three pairs in total. The function of the crista ampullaris is to sense angular acceleration and deceleration. Background The inner ear comprises three specialized regions of the membranous labyrinth: the vestibular sacs – the utricle (ear), utricle and saccule, and the semicircular canals, which are the vestibular organs, as well as the cochlear duct, which is involved in the special sense of Hearing (sense), hearing. The semicircular canals are filled with endolymph due to its connection with the cochlear duct via the saccule, which also contains endolymph. It also contains an inner membranous sleeve that lines the semicircular canals. The canals also contain the crista ampullaris. The hair cell, receptor cells located in the semicircular ducts are innervated by the eighth cranial nerve, the vestib ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hyperpolarization (biology)
Hyperpolarization is a change in a cell's membrane potential that makes it more negative. It is the opposite of a depolarization. It inhibits action potentials by increasing the stimulus required to move the membrane potential to the action potential threshold. Hyperpolarization is often caused by efflux of K+ (a cation) through K+ channels, or influx of Cl– (an anion) through Cl– channels. On the other hand, influx of cations, e.g. Na+ through Na+ channels or Ca2+ through Ca2+ channels, inhibits hyperpolarization. If a cell has Na+ or Ca2+ currents at rest, then inhibition of those currents will also result in a hyperpolarization. This voltage-gated ion channel response is how the hyperpolarization state is achieved. In neurons, the cell enters a state of hyperpolarization immediately following the generation of an action potential. While hyperpolarized, the neuron is in a refractory period that lasts roughly 2 milliseconds, during which the neuron is unabl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Afferent Nerve Fiber
Afferent nerve fibers are the axons (nerve fibers) carried by a sensory nerve that relay sensory information from sensory receptors to regions of the brain. Afferent projections ''arrive'' at a particular brain region. Efferent nerve fibers are carried by efferent nerves and ''exit'' a region to act on muscles and glands. In the peripheral nervous system afferent and efferent nerve fibers are part of the somatic nervous system and arise from outside of the spinal cord. Sensory nerves carry the afferent fibers to enter into the spinal cord, and motor nerves carry the efferent fibers out of the spinal cord to act on skeletal muscles. In the central nervous system non-motor efferents are carried in efferent nerves to act on glands. Structure Afferent neurons are pseudounipolar neurons that have a single process leaving the cell body dividing into two branches: the long one towards the sensory organ, and the short one toward the central nervous system (e.g. spinal cord). The ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Depolarization
In biology, depolarization or hypopolarization is a change within a cell, during which the cell undergoes a shift in electric charge distribution, resulting in less negative charge inside the cell compared to the outside. Depolarization is essential to the function of many cells, communication between cells, and the overall physiology of an organism. Most cells in higher organisms maintain an internal environment that is negatively charged relative to the cell's exterior. This difference in charge is called the cell's membrane potential. In the process of depolarization, the negative internal charge of the cell temporarily becomes more positive (less negative). This shift from a negative to a more positive membrane potential occurs during several processes, including an action potential. During an action potential, the depolarization is so large that the potential difference across the cell membrane briefly reverses polarity, with the inside of the cell becoming positively char ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Kinocilium
A kinocilium is a special type of cilium on the apex of hair cells located in the sensory epithelium of the vertebrate inner ear. Anatomy in humans Kinocilia are found on the apical surface of hair cells and are involved in both the morphogenesis of the hair bundle and mechanotransduction. Vibrations (either by movement or sound waves) cause displacement of the hair bundle, resulting in depolarization or hyperpolarization of the hair cell. The depolarization of the hair cells in both instances causes signal transduction via neurotransmitter release. Role in hair bundle morphogenesis Each hair cell has a single, microtubular kinocilium. Before morphogenesis of the hair bundle, the kinocilium is found in the center of the apical surface of the hair cell surrounded by 20-300 microvilli. During hair bundle morphogenesis, the kinocilium moves to the cell periphery dictating hair bundle orientation. As the kinocilium does not move, microvilli surrounding it begin to elongate and form ac ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
