Textbook Notes (363,103)
Canada (158,195)

CNS 5 the ear and hearing.doc

3 Pages
Unlock Document

McMaster University
Health Sciences
Alexander Ball

CNS 5 the ear and hearing Cranial Nerves involved in hearing (3) V-5th CN(trigeminal):muscles of mastication & tensor tympani-control vibrations by controlling muscles durring chewing VII-7th CN(facial): stapedius muscle of middle ear -facial expressions and reduce sound when it's really loud VIII-8th CN(vestibulocochlear)(from pons): vestibular cochlear-> hearing and balance: actually 2 nerves only cochlear division has to do with hearing Note: X-10th CN(Vagus): sensory to auditory canal 3 Parts of the ear -External Ear Auricle: or pinna is a flap of skin and elastic cartilage shaped like a funnel which allows for sounds infront of you to get in where sounds behind you are less funneled. External Auditory Canal: curved tube(2/3 cartilage, 1/3 bone) lies along temporal bone and leads to ear drum Ceruminous Glands: specialized sweat glands secrete earwax(cerumen). Which with help of hairs prevent dust and other foreign objects like bugs from entering the ear as well as damage to the delicate skin. Tympanic Membrane (Ear Drum): thin membrane that divides external and middle ear. Is attached to the periosteum of bone therefore has a lot of pressure and pimple can cause a lot of pain. -connective tissue with skin on externally covering, and mucus membrane(mucosa) internally covering -Tearing= perforated eardrum, will heal itself -connected to middle ear bones, gives it cone like shape and acts like a speaker -Middle Ear -Ossicles (Malleus, Incus, Stapes): -bones with sinonial joints between them(elderly: arthritis impairs these joints therefore difficulty with hearing) -Mechanical relay of Vibrations of Tympanic Membrane are relayed as bony movements to oval window membrane of inner ear and set up a series of vibrations within the fluid -muscles modulate their movement and lessen the vibrations. -Tensor Tympani m. (CN V): runs parallel to auditory canal and puts tension on the tympanic membrane -Stapedius m. (CN VII): attached to the stapes to prevent damage from loud noises by preventing the stapes from putting to much vibration into the inner ear -muscle fatigues, therefore high exposure to loud sounds could lead to loss of this function -Auditory Tube: air sinus in head that allows for communication with outside air pressure, from nasal pharynx up to middle ear- usually shut but when yawn or chew gun it uses pharingeal muscles it momentarily opens -allows for pressure equilibrium -Mastoid process(bone) attachment site for the sternoclavomastoid muscle that moves the neck(1 of 4), to then keep the head light theres lots of air cells that must communicate to the outside so there is a hole in the middle ear that gives opening to mastoid air cells -Mucous Membrane -protects middle ear by keeping it sterile, same membrane as mouth and nose Complications of Middle Ear infections (mastoiditis, meningitis) -upper respiratory tract infection spreads from the nasopharyx spreads into the ear when coughing sneezing opens auditory tube and allows virus or bacteria into the middle ear-middle ear infection -infection of mucous membrane with no where for fluid to drain, builds up pressure which can... 1) Rupture tympanic membrane and drainage of fluid into external ear 2) Infection spread into mastoid air cells leading to mastoiditis 3) Roof of middle ear is very thin and the infection can cause erosion of temoral bone above middle ear leading to meningitis which is infection of the meninges -especially in children as there auditory tube is even smaller Inner Ear -is a system of Channels in the petrous portion of the Temporal Bone -Vestibule- deals with balance and muscle coordination -Semi Circular Canals – bony canals that project from the vestibule and contain semicircular ducts. -Cochlea- hearing -Oval & Round Window: middle ear is air filled and inner is fluid(CSF) filled these membranes seperate the two and prevent the CSF from leaking out. Oval -ossicles put pressure to relay vibrations into the inner ear. Round -relief valve -Bony Labyrinth: are channels and cannals filled with CSF-
More Less

Related notes for HTHSCI 1H06

Log In


Don't have an account?

Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.