EAR AND HEARING Flashcards
What is the ear involved in
Hearing and Balance
Which parts of the ear are involved in hearing
Outer ear
Middle ear
Inner ear (Cochlea )
What makes up the outer ear
- Pinna, is moved by muscles)
- External acoustic meatus
- Tympanic membrane
Which 5 muscles move the pinna and what are they innervates by
- Rostral
-dorsal
-caudal - ventral
- intrinsic
All innervates by CN 7 (Facial)
Describe the external acoustic meatus
- l shaped the ending in eardrum
- contains glads which produce earwax
Describe the tympanic membrane
Also known as ear drum
Covered by epithelium on outside and mucous membrane on inside
Describe the middle ear
Is an air filled space in the temporal bone containing ossicles which transfer tympanic membrane vibrations to the inner ear
Name the ossicles in the middle ear
Malleus
Incus
Stapes
What does the Eustachian tube do
Connects the ear an mouth and is an air pressure equaliser
Describe the inner ear
Is found in the temporal bone and is made up of the cochlea, vestibular and semi circular canals
Describe the cochlea
- 3 fluid filled canals = upper, middle and lower
- sensory cells sit on the basilar membrane
What is the upper and lower canals of the cochlea filled with
Perilymph
What is the middle canal of the cochlea filled with
Endolymph
How does the cochlea transmits sound
Fluid is displaced and sound wave travels down basilar membrane
This affects the stretch mediated ion channels at tip of sensory hairs, opens K+ channels, depolarisation, Ca+ channels open = release of neurotransmitter
How does the ear tell the difference between high frequency and low frequency noise
- high frequency waves have maximum amplitudes near round windows
- low freq = near tip of cochlea
