Physiology 3120 Lecture Notes - Lecture 7: Tonotopy, Brainstem, Visual Cortex

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Hore Lecture 7
-prof likes Purves textbook
-reason auditory system is much faster than visual system is because auditory system uses hair
cells whereas in visual system it is done using second messenger cascades, etc.
-image shows that there are many cilia stacked up together to form one hair cell
-it is easy for a loud sound to whip these hair cells around and to shear them off their base 
cannot grow back hair cells so once you lose them, they are gone forever
-this frequency range is for young people which narrows down with age
-people older than 60 cannot hear beyond 10,000Hz
-damage to hair cells when listen to more than 100 decibels for more than 5 minutes  very
delicate system
-spatial resolution so can pinpoint from where exactly sound is coming
-hair cells transduce energy in the envt into AP
-cochlea deconstructs sound into different frequency components
-pinna is also known as outer ear
Middle ear has three bony ossicles
-inner ear is where the hair cells are located in fluid-filled membranous tubules
-top shows what the cochlea looks like when uncurled
-so have external ear, auditory canal and the three bony ossicles are called the maleus, incus
and stapes
-have small skeletal muscles on these ossicles that contract to stabilize the ossicles when
know that there will be a loud sound
-unexpected loud sounds cause a lot of damage because these ossicles are not stabilized
-having such a delicate system with ossicles may not sound like the best design but it is an
ancient system that was passed down from ancestors because it works so well
-then come into inner ear where have hair cells on the basement membrane
-hair cells + basement membrane = Organ of Corti
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