Exam 4 Review:  Chapter 15:  Inner Ear - Static & Dynamic Equilibrium

vestibular apparatus - The functional components of the membranous labyrinth involved in the sensations of static and dynamic equilibrium are a system of thin-walled intercommunicating tubes and ducts situated within the petrous part of the temporal bone at the base of the skull; there are five vestibular structures, each containing a specialized mechanoreceptor, a maculae, within the utricle and saccule, and a cristae within the ampullae of the superior, horizontal, and posterior semicircular canals.


vestibule - The central cavity of the bony labyrinth of the ear containing the functional components of the membranous labyrinth involved in the sensations of static equilibrium which are two vestibular structures, each containing a specialized mechanoreceptor, a maculae, within the utricle and saccule.

saccule - The smaller of the two membranous sacs in the vestibule of the inner ear; it contains a specialized mechanoreceptor, a maculae, for the detection of static equilibrium.

utricle - The larger of the two membranous sacs in the vestibule of the inner ear; it contains a specialized mechanoreceptor, a maculae, for the detection of static equilibrium.

static equilibrium - The special sense which interprets the position of the head permitting the CNS to maintain stability and posture when the head and body are not moving; it is detected by mechanoreceptors in the vestibule of the inner ear, the utricle and saccule, which each contain a macula with the receptors for static equilibrium; when the head moves with reference to gravity, the otolithic membrane shifts and the mechanoreceptors (hair cells) in the macula detect this movement and send the information along the vestibular nerve to the brain for interpretation ("which way is up").

maculae -  The specialized mechanoreceptors within the utricle and saccule for the detection of static equilibrium; they make use of hair cells to detect movements of the otolithic membrane; the nerve impulses thus generated are transmitted along the vestibular branch of cranial nerve VIII to the CNS.

otolithic membrane - The gelatinous covering of macula of the utricle and saccule of the vestibular apparatus which has many crystals of calcium carbonate (otoconia or otoliths); their movements in response to changes in the position of the head with reference to gravity stimulate the hair cells to send nerve impulses to the CNS which are interpreted as information about static equilibrium.




dynamic equilibrium - The special sense which interprets balance when one is moving, or at least the head is moving; the semicircular canals contain the receptors for dynamic equilibrium; within each semicircular canal is a complex mechanoreceptor called a crista ampullaris which contains the mechanoreceptors (Hair cells) for dynamic equilibrium; when the perilymph in one of the semicircular canals moves, the hair cells in the crista ampullaris are stimulated to send nerve impulses to the brain; this advises the brain of whether or not a person has their balance during body movements or if their body is in motion, e.g, riding in a car or turning one's head from side to side.

semicircular canals - The functional components of the membranous labyrinth, a series of three interconnected perilymph-filled tubes with enlarged ends, involved in the sensations of dynamic equilibrium; the contain the cristae ampullaris which detect acceleration in the three perpendicular planes (superior, horizontal, and posterior); these accelerometers make use of hair cells similar to those on the organ of Corti, but these hair cells detect movements of the fluid in the canals caused by angular acceleration about an axis perpendicular to the plane of the canal; tiny floating particles aid the process of stimulating the hair cells as they move with the fluid; the nerve impulses thus generated are transmitted along the vestibular branch of cranial nerve eight to the CNS.

ampulla - The dilation or expanded end of each of the semicircular canals of the vestibular apparatus which contains the specialized mechanoreceptor structure, the crista, which detect acceleration in the planes of the canal; these accelerometers make use of hair cells to detect movements of the fluid in the canals caused by angular acceleration about an axis perpendicular to the plane of the canal; the nerve impulses thus generated are transmitted along the vestibular branch of cranial nerve eight to the CNS.

crista ampullaris - Within the ampulla of each semicircular canal is a complex mechanoreceptor structure, the crista ampullaris;  the ampulla has a ridge covered by neuroepithelium consisting of sensory hair cells and supporting cells; the hair cells attached to a gelatinous mass, the cupula,  which rests on top of the crista ampularis; when the perilymph in one of the semicircular canals moves, the hair cells in the crista ampullaris are stimulated to send nerve impulses to the brain; this advises the brain of whether or not a person has their balance during body movements or if their body is in motion, e.g, riding in a car.

vestibular nerve - The division of the vestibulocochlear (eighth) cranial nerve which conducts sensory information regarding static and dynamic equilibrium from the vetibular apparatus of the inner ear to the various centers of the CNS which process and integrate that information with visual and proprioception.

Identify and describe:

 

1. the location and site of transduction, including cellular components, for the sensations of:

 

e) equilibrium:  within the vestibular apparatus:  there are five vestibular structures, each containing a specialized mechanoreceptor (site of transduction), a maculae, within the utricle and saccule, and a cristae within the ampullae of the superior, horizontal, and posterior semicircular canals.