Ear Flashcards
What is human hearing range?
20hz-20,000hz
What is the function of the outer ear?
Collects sound
What is the function of the middle ear?
Transmits sound
What is the function of the inner ear?
Converts sound into neural impulses.
Give the components of the outer ear.
Auricle, external auditory canal, tympanic membrane
Give the components of the middle ear.
Hammer, anvil, stirrup
Give the components of the inner ear.
Semicircular canals, oval window, cochlea
Where is the middle ear?
Temporal bone of the skull
Which nerve innervates the middle ear?
CN IX : Glossopharyngeal
What connects the middle ear to the pharynx?
Eustachian tube. This exposes the middle ear to atmospheric pressure.
What causes a difference in pressure between the middle and outer ear?
Changes in altitude
Vibrations of the tympanic membrane transmit to the inner ear via which bones?
Ossicles (smallest bones in body) which have synovial joints:
Malleus
Incus
Stapes
Is the cochlear air or fluid filled?
Fluid filled
What membrane lies between the middle and inner ear?
Oval window
Which muscles in the middle ear control the amount of energy transmitted to the inner ear?
Tensor tympani
Stapedius
Which nerve innervates tensor tympani?
CN V, V3
Mandibular branch of trigeminal nerve
Which nerve innervates stapedius?
CN VII
Facial nerve
Which bone does tensor tympani attach to?
Malleus
Which bone does stapedius attach to?
Stapes
Which membranous tube divides the cochlear lengthwise?
Cochlear duct
Contains sensory receptors
What fluid does the cochlea duct contain?
Endolymph: high K+, low Na+
What structures lie above and below the cochlear duct?
Above: Scala vestibuli
Below: Scala tympani
Briefly outline the path of sound transmission in the ear.
External acoustic meatus > Tympanic membrane > Ossicles > Oval window >
Scala vestibuli > Cochlear duct > Organ of Corti
What are the receptor cells on the Organ of Corti called?
Hair cells. They are mechanoreceptors that have stereo-cilia. There are inner and outer hair cells.
What is the function of inner hair cells?
Stereo-cilia extend into the endolymph. They convert pressure waves caused by movement of cochlear fluid into receptor potentials.
What is the function of outer hair cells?
Stereo-cilia are embedded in overlying tectorial membrane. They mechanically alter its movement to sharpen frequency tuning.
What are the spiral ganglion and where do they lie?
These are the cell bodies of cochlear nerve fibres. They lie within the cochlea.
Briefly outline the pathway of neural transmission in hearing.
Cochlear nerve > Second order neurones in pons > Superior olivary nucleus > Inferior colliculus of midbrain > Inferior branchium nerve fibre > Medial geniculate body of thalamus > Internal capsule > Primary auditory cortex of temporal lobe
What region of the temporal lobe surrounds the primary auditory cortex?
Wernicke’s area
What happens if Wernicke’s area is damaged?
Wernicke’s area processes language in the brain. If damaged, the patient will not be able to understand speech and their speech will be incomprehensible.
What nerve is the cochlear nerve a branch of?
CN VIII
Vestibulocochlear nerve
What does I’M Auditory stand for?
Inferior colliculus, Medial geniculate body, for Auditory information
What is Bell’s palsy?
Acute unilateral inflammation of facial nerve. Results in pain behind the ear, paralysis of facial muscles and failure to close eye.
What is the vestibular apparatus?
Found in the inner ear. A series of endolymph-filled membranous tubes.
What are the two sac swellings in the vestibular apparatus?
Utricle and saccule.
How many semicircular canals does the vestibular apparatus contain?
Three
What is the function of the semicircular canals?
They detect angular acceleration during rotation of the head.
How is glutamate linked to the direction of stereo-cilia movement?
Each hair cell receptor has one direction of maximum glutamate release. When bent in one direction, the receptor cell depolarises. When bent in the opposite direction, the receptor cell hyperpolarises.
What is nystagmus?
Rapid jerky movement of the eyes. Caused by damage to semicircular canals on one side.
What is the function of the utricle and saccule?
They provide information about linear acceleration of the head and changes in head position in relation to gravity.
How do the hair cells in the utricle stand?
They point straight up when the body is standing. They respond when the head is tipped away from the horizontal plane.
How do the hair cells in the saccule stand?
They project at right angles to those of the utricle. They respond when you move from lying down to a standing position.
What are otoliths?
Calcium carbonate crystals in a gelatinous substance that cover stereo-cilia.
Briefly outline the usage of vestibular information.
- Control of eye movement. In spite of head movement, eyes can remain fixed on the same point.
- Reflex mechanisms of maintaining upright posture and balance
- Conscious awareness of the position and acceleration of the body i.e. proprioception.
