Neuro Anatomy -- Lab 17 Ear and Vestibular System

Utricle

F

Saccule

G

Endolymph

fluid within the scala media & the vestibular apparatus

Perilymph

fluid within the scala vestibuli & scala tympani

Semicircular canals

A

• Horizontal Canal

• Anterior Canal

• Posterior Canal

Horizontal canal

D

Anterior canal

B

Posterior canal

C

Most common canal for otoliths to be displaced in with BPPV

Common crus

D

Most common route for otoliths to enter the canals in BPPV

Ampulla

E

expanded region on one end of each semi-circular canal

Contains cristae ampullaris organs

Cupula

A

gelatinous mass within the cristae ampullaris

Same density as endolymph, making rotational acceleration non-gravity sensitive

Cristae Ampullaris

C

Sensory organs contained within the ampulla of the semi-circular canals

Sensitive to rotational/angular movements

non-gravity dependent

Otolithic membrane

D

Gelatinous mass of the macula

otoliths make the macula gravity sensitive

Macula

Sensory Organs contained in the utricle and saccule

Sensitive to linear acceleration

A - utricle -- horizontal

B - Saccule -- vertical

Gravity dependent

Vestibular ganglion

8 & 9

Collection of 1st order sensory neuron cell bodies coming from the vestibular apparatus

CN VIII (vestibulocochlear n.)

7 & 10

Combined sensory nerve coming from the vestibule and cochlia

Carrying efferent sensory information of hearing and balance

Vestibular nuclei complex

Blue and green nuclei

Deep to vestibular area

Reticular formation

in tegmentum of midbrain, pons, and medulla

Vestibulospinal tract

Involuntary

Proximal > Distal

Posture > Muscle Tone

Medial VST: head on body

Lateral VST: body vs gravity

Pathway:

• Cell body in Vestibular Nuclei Complex (pons & medulla)

• Bilateral projections

• Anterior funiculus

• interneuron in spinal cord

• medial / anterior aspects of ventral horn

Secondary somatosensory cortex

S2

Cerebellum

Flocculus

Nodulus

Flocculonodular lobe

Vermis

Outer Ear

• Auricle

• External acoustic meatus

• Tympanic membrane

Auricle

External auditory meatus

Tympanic membrane

Middle Ear

• Pharyngotympanic (Eustachian) tube

• Ossicles

- Malleus

- Incus

- Stapes

Pharyngotympanic (Eustachian) tube

C

Malleus

B

Incus

A

Stapes

E

Sits in the oval window

Inner Ear (Auditory portion)

• Cochlea

• Scala Vestibuli

• Scala Media

• Scala Tympani

• Basilar membrane

• Vestibular membrane

• Organ of Corti

• Tectorial membrane

• Hair cells

Cochlea

4

Scala Vestibuli

9

Connected to oval window

where sound waves travel first in the cochlea

contains perilymph

Scala Media

3

where the organ of corti resides

contains endolymph

Scala Tympani

10

connected to round window

where sound waves travel second in the cochlea

contains perilymph

Basilar membrane

6

b/w scala media and scala tympany

directly connected to the organ of corti

Vestibular membrane (Reissner's Membrane)

1

b/w the scala vestibuli and the scala media

Organ of Corti (spiral organ)

Sensitive to sound waves

Tectorial membrane

2

gelatinous mass of in the organ of corti

Spiral ganglion

8

cell bodies of the cochlear nerve located throughout the cochlea near the organ of corti

Cochlear Nerve

Hair cells

sensory receptors located in the:

• organ of corti

• cristae apullaris

• macula

Types:

• Stereocilia

• Kinocilia

Stereocilia

located in the:

• organ of corti

• cristae apullaris

• macula

Kinocilia

located in the:

• cristae apullaris

• macula

Stereocilia toward kinocilia => excitatory

Stereocilia away from kinocilia => inhibitory

Inferior colliculus

5

Medial geniculate body

1

Primary auditory cortex

Transverse temporal gyrus