Ch. 16-5

Summarize how the utricle and saccule monitor equilibrium.

Both the macula utricle and the saccule contain receptor cells that monitor the position of the head. This aspect is the sense of static equilibrium

Otoliths

Calcium carbonate crystals of the macula

Summarize the key events in the pathway for hearing.

1. Sound waves vibrate the tympanic membrane 2. Auditory ossicles vibrate. Pressure is amplified. 3. Pressure waves created by the stapes pushing on the oval window move through fluid in the scala vestibuli. 4a. Sounds with frequencies below hearing travel through the helicotrema and do not excite hair cells. 4b. Sounds in the hearing range go through the cochlear duct, vibrating the basilar membrane and deflecting hairs on inner hair cells.

Describe the bony labyrinth and the parts within the internal ear.

A cavity in the petrous part of the temporal bone consisting of a system of twisting channels that has three parts. Consist semicircular canals, the vestibule, and the cochlea.

Membranous ampulla

Description Swelling corresponding bony ampulla

Crista ampullaris

Description: Contain receptor cells that measure rotational acceleration of the head Function: Sense angular acceleration and deceleration

Scala vestibuli

Description: Continuous with the vestibule near the base of the cochlea where it abuts the oval window. Filled with perilymph Function:

Scala tympani

Description: Ends at the round window at the base of the cochlea. Filled with perilymph Function:

Ampulla

Description: Expansion at the end of the 3 semicircular canal.

Semicircular duct

Description: Inside each semicircular canal Function: Contain the sensory receptors for turning movements of the head.

Cupula

Description: Jellylike mass that resembles a pointed cap. Basal part of the hair cells synapse with fibers of the vestibular nerve.

Cochlear duct (scala media)

Description: Part of the membranous labyrinth that contains the sensory receptors for hearing. Filled with endolymph It lies between the scala vestibuli and scala tympani. Function:

Vestibular membrane

Description: The "roof" of the cochlear duct, separating it from the scala vestibuli Function:

Basilar membrane

Description: The floor of the cochlear duct consists of the osseous spiral lamina plus an attached sheet of fibers. Function:

Hair cells

Description: The hairlike sensory receptors for sound, which are embedded in the basilar membrane of the cochlea; synapse with sensory fibers of vestibular nerve.

Stereocilia

Description: The inner hair cells are arranged linearly. Function:

Spiral organ

Description: The tall epithelium consists of columnar supporting cells and one row of inner and three rows of outer hair cells, which are the receptor cells. Function:

Semicircular canals

Description: Three tiny, fluid-filled tubes in your inner ear Function: Help keep balance

Saccule

Description: lower membranous sac that has hair cells in a gelatinous membrane with tiny crystals of calcium carbonate called otoliths;gravity pulls on otoliths and bends hair cells as position of head changes.

Macula

Description: spot of sensory epithilieum cells within the macula of utricle and saccule to monitor the position of the head

Utricle

Description: upper membranous sac that has hair cells in a gelatinous membrane with tiny crystals of calcium carbonate called otoliths

Endolymph and Perilymph.

Endolymph the membranous labyrinth is filled with a clear fluid. Perilymph the external to the membranous labyrinth, the bony labyrinth is filled with another clear fluid; continuous with w/ spinal fluid that fills subarachnoid space.

Cochlea

Membranous labyrinth: Cochlear duct Functions of membranous labyrinth: Hearing

Semicircular canals

Membranous labyrinth: Semicircular ducts Functions of membranous labyrinth: Equilibrium: rotational (angular) acceleration of the head.

Vestibule

Membranous labyrinth: Utricle and saccule Functions of membranous labyrinth: Equilibrium: static equilibrium and linear acceleration of the head.

Where is perilymph located within the cochlea?

Perilymph fills the cavities of the bony labyrinth of the cochlea, the scala vestibuli, and the scala tympani.

The endolymph-filled cochlear duct (scala media) lies between two perilymph-filled chambers named ______ and ______

Scala Vestibuli and Scala tympani

Describe the membranous labyrinth and the parts found within the internal ear.

Series of membrane-walled sacs and ducts that fit loosely within the bony labyrinth and more or less follow its contours. Parts are found: Semicircular ducts, inside each semicircular canal; contain sensory receptors for turning head movements. Utricle and saccule, both in the vestibule; Receptors that monitor position of head located in the membranous labyrinth. Cochlear duct located within the cochlea contains sensory receptors for hearing.

Which sensory receptors monitor stationary head position and linear movements of the head? Where are these receptors located?

The maculae of the utricle and the saccule monitor stationary head position and linear acceleration.

What is the difference between the membranous labyrinth and the bony labyrinth of the internal ear?

The membranous labyrinth is a continuous series of membranous sacs and ducts filled with endolymph that contain the sensory receptors for hearing and equilibrium. The bony labyrinth is the cavity within the petrous portion of the temporal bone that surrounds the membranous labyrinth.

Where in the cochlear duct is each of these membranes located: vestibular membrane, the basilar membrane, the tectorial membrane? Vibrations in which membrane stimulate the hair cells of the spinal organ?

The vestibular membrane forms the roof of the cochlear duct The basilar membrane forms the floor Tectorial membrane sits atop the sensory hair cells. Vibrations in the tectorial membrane stimulate the hair cells of the spinal organ.

Vestibular nerve

Vestibular division of vestibulocochlear nerve

Summarize how the semicircular ducts monitor equilibrium.

When the head start to rotate, the endolymph in the semicircular duct lags behind at first, pushing on the cupula and bending the hairs. As hairs bend, the hair cells depolarize and change the pattern of impulses carried by vestibular nerve fibers to the brain.

Otolith membrane

a jellylike disc that contains heavy crystals of calcium