NUR1 239 Chapter Notes - Chapter 16: Tubercle, Carcinoma, Keloid
10 May 2016
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Middle, ear seperate from the external by the eardrum (typanic membrane) + ossicles bone. Cranial nerve viii (13), brain stem : locate the direction of the sound in space and indentifying the sound. Air conduction, is the normal and most efficient way to hear. Bone conduction, alternative for hearing (skull bone) directly to the inner ear and cranial nerve (faster, less efficient) Conductive hearing loss : mechanical dysfonction of external or middle ear, partial loss. Cause by : impacted cerumen, foreign bodies, perforated eardrum, pus or serum (middle ear) or otosclerosis (capacity of ossicle) *able to hear if sound amplitude is increased. Sensorineural hearing loss : disease of inner ear, cranial nerve or in the cerebral cortex. Cause by : presbycusis (gradual nerve degeneration with aging) or ototoxic drugs (affecting the hair cells in cochlea. *not always possible to hear even with increased sound amplitude. *otosclerosis is a common cause of deafness in youg adults (20-40)
