**Lecture 15

Question 1

Describe the structure and signal transduction of the olfactory system

Answer 1

STRUCTURE = lamina propria (connective tissue), olfactory bulb/tract, mucosal layer, neurons with axons extending to olfactory bulb and cilia (dendrites) to the mucosal layer, support cells

Signal transduction = odorant molecules dissolve through mucus to the receptors (GPCR) and bind. Activates Golf protein, adenylyl cyclase/cAMP, then opens cNTP gated Na channels to produce action potential
Only nerve to not synapse at the thalamus

Question 2

Describe the structure and signal transduction of the taste system

Answer 2

Structure: taste bud has taste pore, has multiple (50-150) taste cells joined by tight junctions within
Signal transduction = tastant molecule binds to sweet/umami/bitter GPCR (specialized to cell), activates Gustducin, causes increase of Ca2+ and release of ATP
Salt may go through support cells
H+ (sour) may be transported via proton pump, causes increase in Ca2+ and release of serotonin
ATP/serotonin goes onto primary gustatory neurons

Question 3

Describe the structure of the auditory system

Answer 3

Structure: pinna (funnel) (outer ear), (middle ear) stapes/malleus/incus (stirrup/hammer/anvil) (ossicles), (inner ear) tympanic membrane, cochlea (vestibular duct/cochlear duct/tympanic duct/oval window/round window). Vestibular duct/tympanic duct have perilymph similar to plasma in it, while cochlear duct has endolymph (similar to ICF).

Question 4

Describe the signal transduction of the auditory system

Answer 4

signal transduction: pinna funnels sound into the ear canal, vibrates the tympanic membrane (ear drum). Ossicles amplify vibration and transfer it to the oval window. Signal must be amplified because inner ear is fluid-filled. vibrations of oval window causes fluid to push on the membranes of the cochelar duct. Oval window transfers sound into cochlear duct, then crosses over into vestibular duct and then into tympanic duct before exiting through the round window. As it crosses from vestibular to tympanic, it vibrates the organ of corti and the basilar membrane. Organ of corti is a ridge of epithelial cells that rubs against the cilia of the hair cells. These cilia are mechanically gated, so stretch causes depolarization, or hyperpolarization if bent the other way to open/close ion channels. Causes neurotransmitter release to create action potentials to send to brain. Basilar membrane is floppy and for low pitch at the helicotrema (apex) while it is stiff and codes for high pitch near the oval window.