Reticular Formation

Stereocilia

Hair cells

Transverse Fibres Basilar Membrane

Basilar membrane Supporting cells ^Spiral lamina Afferent nerve fibers

"Spiral ganglion Efferent nerve fibers

As basilar membrane moves up, hairs are deflected outward, causing ¿e, depolarization of hair cells and increased firing of afferent nerve fibers ®||g|\|

Figure 2.34 Cochlear Receptors

The cochlea transduces sound into electrical signals. This is accomplished by the hair cells, which depolarize in response to vibration of the basilar membrane. The basilar membrane moves in response to pressure changes imparted on the oval window of the cochlea in response to vibrations of the tympanic membrane.

Acoustic area of temporal lobe cortex

Acoustic area of temporal lobe cortex

Reticular Formation Location

Dorsal acoustic stria Reticular formation Trapezoid body Intermediate acoustic stria Superior olivary complex

Figure 2.35 Auditory Pathways

The cochlea transduces sound into electrical signals. Axons convey these signals to the dorsal and ventral cochlear nuclei, where it is tonotopically organized. Following a series of integrated relay pathways, the ascending pathway projects to the thalamus (medial geniculate bodies) and then the acoustic cortex in the transverse gyrus of the temporal lobe, where information is tonotopically represented (low, middle, and high tones).

Vestibular ganglion _

Vestibular and cochlear divisions of vestibulocochlear n Maculae Saccule Utricle

Cochlear duct (scala media)

B. Section of crista

Opposite wall of ampulla Gelatinous cupula Hair tufts Hair cells Nerve fibers Basement membrane

A. Membranous labyrinth

A. Membranous labyrinth

Membranous Labyrinth

Superior semicircular canal

Cristae within ampullae

Horizontal semicircular canal

Posterior semicircular canal

Otoconia Kinocilium

C. Section of macula

Otoconia

Gelatinous otolithic membrane Hair tuft -Hair cells Supporting cells Basement membrane Nerve fibers

Kinocilium Stereocilia

Basal body

D. Structure and innervation of hair cells

Kinocilium

Stereocilia

Myelin sheath

Kinocilium

Kinocilium Stereocilia

Basal body

D. Structure and innervation of hair cells

Kinocilium

Stereocilia

Hair cell (type I)

Supporting cells

Afferent nerve calyx

Efferent nerve ending

Basement membrane

Hair cell (type II)

Supporting cell

Efferent nerve endings

Afferent nerve endings

Myelin sheath

Myelin sheath

Figure 2.36 Vestibular Receptors

The vestibular apparatus detects movement of the head in the form of linear and angular acceleration. This information is important for the control of eye movements so that the retina can be provided with a stable visual image. It is also important for the control of posture. The utricle and saccule respond to linear acceleration, such as the pull of gravity. The three semicircular canals are aligned so that the angular movement of the head can be sensed in all planes. The sensory hair cells are located in the maculae of the utricle and saccule and in the cristae within each ampullae.

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