Term
|
Definition
| Detect sound, and can discriminate between a wide range of sound frequencies |
|
|
Term
|
Definition
| Detect the body’s orientation and movement in space. Detects whether the body’s vertical horizontal, upside down, tilted, accelerating, decelerating, or rotating |
|
|
Term
| the tilt of the head with respect to the direction of gravity |
|
Definition
| the ear structures involved are the utricle and the saccule |
|
|
Term
| Linear acceleration and decelaration |
|
Definition
| again, the ear structure involved are the utricle and saccule |
|
|
Term
|
Definition
| the ear structures involved are the semicircular canals |
|
|
Term
|
Definition
| the utricle, saccule and semicircular canals are grouped together under the name Vestibular apparatus |
|
|
Term
|
Definition
-The receptor cells in the are all hair cells, whether they are found in the cochlea or the vestibular apparatus.
-Hair cells are mechanoreceptors with stiff, hair-like processes projecting from one end. They are stimulated when these processes are bent to one side |
|
|
Term
| The tips of these hair-like structures are always embedded in a gelatinous material |
|
Definition
-In the cochlea, this material makes up the tectorial membrane
-In the semicircular canals this material constitutes the cupula
-In the utricle and saccule it is called the otolithic membrane because it contains calcium carbonate crystals called otoliths that make it heavier. |
|
|
Term
| In every part of the ear... |
|
Definition
| the cells are stimulated when there is relative movement between the hair cell and the gelatatinous material in which the tips of its hairs are embedded. This relative movement bends hair-like processes |
|
|
Term
|
Definition
|
|
Term
| Head tilt and linear acceleration and deceleration |
|
Definition
| detected in the utricle and saccule |
|
|
Term
|
Definition
| detected in the semicircular canals |
|
|
Term
|
Definition
| The brain receives information from the utricle, saccule, semicircular canals and cochlea via a sensory ganglion and the VIII cranial nerve |
|
|
Term
| Gelatinous “membrane" (Vestibular; Cochlea) |
|
Definition
Vestibular - otolithic (utricle, saccule) cupula (semicircular canals)
Cochlea - tectorial |
|
|
Term
|
Definition
| consist of an outer, funnel-like flap called the auricle or pinna, and an S-shped called the external auditory meatus. |
|
|
Term
|
Definition
| helps localized sounds as we turn our heads. As noted in a previous lecture, the epithelium of the external auditory meatus contains ceruminous glands that secret a waxy substance |
|
|
Term
|
Definition
| eardrum, or tympanic membrane |
|
|
Term
| The cavity of the middle ear |
|
Definition
is filled with air, and contains three little bones (auditory ossicles) known as the:
-hammer (malleus),
-anvil (mincus)
-stirrup (stapes) |
|
|
Term
|
Definition
| opening to the inner ear has a membranous covering that separates the airfilled middle ear from the liquid-filled cochlea in the inner ear |
|
|
Term
|
Definition
| in response to sound waves that travel down the external auditory meatus. The auditory ossicles assembly vibrates in turn, and the footplate of stapes vibrates against the oval window, so transmitting the sound waves to the liquids of the inner ear. |
|
|
Term
|
Definition
| Two small skeletal muscles are attached to the ossicles. One is the tensor tympani, which inserted into the malleus, and the other is the stapedius, which is inserted into the stapes. The muscles operate in the tympanic reflex, or attenuation reflex, which is a response to loud sound and makes the brigde of ossicles more rigid. |
|
|
Term
| Function of the ear muscles |
|
Definition
-Muscles contract in response to loud sounds, making the bridge of ossicles more rigid and reducing the effectiveness of the ossicles in transmitting loud sounds to the inner ear (attenuation reflex, tympanic reflex). This protects the auditory apparatus from damage.
-The attenuation reflex also masks out low-frequency sounds in loud enviroments, so that we can concentrate on the sounds of voice communication, which are at higher frequencies.
-Both muscles are activated at the same time that the brain activates the voice the mechanism, which decreases our hearing sensitivity to our speech.
-An addition function of the tensor tympani muscle is to maintain a steady pull on the eardrum, keeping it taut |
|
|
Term
|
Definition
| Connects the air-filled cavity of the middle ear with the pharynx is a tube. This helps to equalize the air pressure in the middle ear with that of the atmosphere. The function of this system is particularly noticeable when ascending in an air craft. |
|
|
Term
|
Definition
| Contains the vestibular apparatus (semicircular cals, utricle, Saccule) and the Cochlea |
|
|
Term
|
Definition
| the equipment of the inner ear is housed in a bony labyrinth carved out of the temporal bone |
|
|
Term
|
Definition
| interconnected membranes and canals in the inner ear |
|
|
Term
|
Definition
| The space between the membranous labyrinth and the walls of the bony labyfinth is filled perilymph, which is almost identical with cerebrospinal fluid. The interior of the membranous labyrinth is filled with endolymph |
|
|
Term
| The cochlea is partitioned into three tubes |
|
Definition
Scala vestibuli
Scala media
Scala tympani |
|
|
Term
|
Definition
| Filled with perilymph. One end of the scala vestibuli is sealed off by the oval window. |
|
|
Term
| Scala media (cochlear duct) |
|
Definition
| The composition of endolymph is similar to intracellular fluid in that it has high concentration of potassium ions and a very low concentration of sodium ions |
|
|
Term
|
Definition
| Filled with perilymph. the round window seals off one end of the scala tympani |
|
|
Term
| Reinssner’s membrane (= the vestibular membrane) |
|
Definition
| The thin and flexible, seperates the scala vestibuli from the scala media. |
|
|
Term
|
Definition
| Separates the scala media from the scala tympani. On the surface of the basilar membrane lies the organ of Corti, which contains the auditory receptor cells, or hair cells. There are actually two types of hair cell, called inner and outer hair cells |
|
|
Term
| Sound waves are transmitted in the ear as follows |
|
Definition
1. Sound waves tramitted throung the outside air and the air in the external auditory meatus make the tympanic membrane (eardrum) vibrate.
2. The vibration of the tympanic membrane are transmitted via the malleus, incus and stapes to the oval window.
3. Vibration of the oval window causes vibration of the perlymph in the scala vestibuli
4. Sound vibration are transmitted through Reissner’s membrane and then through the endolymph of the scala media.
5. the sound waves transmitted through the endlyph of the scala media set up a resonating wave of vibration in the basilar membrane ( this results in stimulation of the hair cells in the Organ of Corti)
6.The perilymph in the scala tympani picks up these vibrations, transmitting them back to the round window, which is in contact with the air-filled cavity of the middle ear. So, when the oval window moves in, the round window moves out, and vice versa. The helicotrema facilities the equalization of pressure between the scala vestibuli and scala tympani |
|
|
Term
| The basilar membrane and resonance in the Cochlea |
|
Definition
| Different part sound frequencies, enabling us to distinguish them |
|
|
Term
|
Definition
| Contains a meshwork of stiff, collagen fibers. These fibers have different lengths and thicknesses. They are fixed at one end to the bony central structure of the cochlea, and are free at their other ends. The fibers in the basilar membranes can vibrate the reeds of a harmonica. The short, stiff ones are near the oval window and vibrate in response to low frequencies. |
|
|
Term
|
Definition
| The organ of corti sits on the basilar membrane, and is the receptor organ that generates nerve impulses in response to vibration of the basilar membrane |
|
|
Term
| How do cells detect the vibrations of the basilar membrane? |
|
Definition
| The tips of their stereocilia are emedded in a gelatinous immovable “membrane” called the tectorial membrane, which projects out from a bony shelf of the cochlea |
|
|
Term
|
Definition
| When the basilar membrane moves upwards in response to sound vibrations, the stereo cilia are bent in one direction because of their attachment to the immovable tectorial membrane. This bending of the stereocilia causes the hair cells to depolarize, producing a generator potential |
|
|
Term
|
Definition
| The hair cell is not a true neuron, and has no dendrites or axon. However, the dendrites of sensory neurons that have their cell bodies in the spiral ganglion make a synaptic connection with the hair cells |
|
|
Term
| When hair cells are depolarized |
|
Definition
| it is believed that the hair cells release a neurotransmitter that depolarizes the afferent nerve endings that form synapses with them. The cell bodies of these sensory nerves lie in a ganglion called the spiral ganglion (this ganglion is similar to a dorsal root ganglion). The axons of the neurons in the spiral ganglion make up the cochlear branch of the vestibulocochlear (VIII) cranial nerve |
|
|
Term
|
Definition
| The utricle and saccule -the otolith organs- each contain small patch of hair cells and supporting cells in a sensory area called macula |
|
|
Term
|
Definition
| the hairs of the hair cells are in contact with the otolithic membrane. The otolithic membrane is a sheet of gelatinous material, made twice as dense as endolymph because it contains many small carbonate crystals - statoconia or otoliths (ear stones) |
|
|
Term
| In summary, the utricle and saccule |
|
Definition
| are important in detecting movements such as falling or accelerating in an automobile, and are the sensory structures involved in maintaining balance when standing still or walking. |
|
|
Term
|
Definition
| there are three semicircular canals. Two of the semicircular canals stand vertically at right angles to each other, and the other is horizontal. In other words, they represent all three planes in space. |
|
|
Term
|
Definition
| Each ampulla of each semicircular canal houses sense organ called crista ampullaris or just crista Each crista is composed of groups of hair cells and supporting cells |
|
|
Term
| Cupula: Semicircular canals |
|
Definition
| As in the maculae, the hair cells extend upwards into a gelatinous mass. In this case, the mass is called cupula The cupula dors not contain otholiths. In fact, it has the same specific gravity as endolymph and, unlike the otolithic, membranes of the utricle and saccule, it is not affected by gravity. |
|
|
Term
| Comparison of the cupula with the otolithic membrane |
|
Definition
| The cupula projects into the endolymph of the semicircular canal, and is deflected by movements of the endolymph caused by head rotation. unlike the otolithic membrane in the utricle and saccule, gravity has no effect on the cupula, because the cupula lacks otoliths that would make it heavier than the endolymth in which it floats and sways |
|
|
Term
| Vestibular ganglion & Spiral ganlion |
|
Definition
| The hair cells of the vestibular system have synaptic contract with the dendrites of bipolar neurons with cell bodies in the vestibular ganglion. The axons of these neurons and the axons of neurons in the spiral ganglion (associated with the cochlea) together make up the vestibulocochlear nerve (cranial nerve VIII) |
|
|
Term
|
Definition
| proprioceptors in the joints of the neck inform the neurons in the vestibular nuclear complex of the position of the head as it relates to the rest of the body. The information can be transmitted to the cerebellum |
|
|
Term
| Proprioceptive Information |
|
Definition
| Tells us about the relative position of other body parts (such as bending and extension of the limbs, bending of truck) is also important for the maintenance of balance |
|
|
Term
| Exteroceptive Information |
|
Definition
| such as presure sensation from the soles of the feet, can tell you whether the wight is distributed equally between the two feet, and whether the weight is forwad or backward on the feet. |
|
|
Term
|
Definition
| can also be important, because movement of the body shifts the position of an image on the retina. It is interesting that a person with lesion in thir vestibular apparatus can still maintain their balance provided that their eyes are open and provided that they move slowly. If the close their eyes, they loose balance and fall over |
|
|
