Lecture 16 : Hearing Fain ch 6 10/28/09

Midterm project Dr. Payne is in search of - # trp channels in inverts Is there conservation of pore - Ca+2 selectivity Evolutionary constraint across inverts All inverts have the same Ca+2 selectivity All have D621 There is more than one type of invert Trp Might differ in pore region, D621

Align w/ Drosophila Trp

Tree TrpN TrpV TrpM TrpC TrpA

Trp M D Trp C

How should we name sequences for big tree? Dme = First letter of Genus , 1st two of species Add last four or five numbers of gene # Gi|123943828|

What do you want for an outgroup? Possibilities: Make fasta file with all of your sequences + Dr Paynes limulus + outgroup + Drosophila trp + trpl + trpgamma + Human trpC1 and 3

What data should each of you give him? Table of genes - acc# - Trp box1 seq - pore site (5 AA) - site 621 Notes - ex. Missing pore region - ignored Tree w/ TrpM, N, V , A

How should we present data to Dr. Payne next week? Tree - For TrpCs label pore site and Trp box1

To do list Today - Fasta file with renamed seqs Next week - one ppt slide with tree (TrpCs labeled with pore) Stuff emailed to Dr Payne Wait till after class on Wed

Monday I will be visiting Duke to give a seminar Dr. Chris Hofmann will give a lecture on vertebrate vision and my favorite cichlid fish He can answer questions on phylogenetics

Questions What is the structure of the ear? Why are hair cells important? How do hair cells transmit signals? What molecules are important?

Hearing is a key sense Detect sound Intensity Frequency Direction

Ear http://weboflife.ksc.nasa.gov/images/earRevAFlat.jpg

Vestibular organs Semicircular canals Otolith organs Anterior Posterior Lateral Otolith organs Utriculus Sacculus Lagena (sometimes) Anterior Posterior Lateral http://weboflife.ksc.nasa.gov/images/semiCircRevAFlat.jpg Hair cells in ampullae

Hair cells in ampulae All hair cells point same way in a given canal Detect fluid or otolith motion Fig 6.15

Vestibular Endolymph High in Ca+2 K+ Depolarize when K+ enters through hair cell channels

Sensing head motion Fig 6.16

Hair cells in semicircular canals Detect position and movement of head Hair cells detect motion in different directions http://www.sti.nasa.gov/tto/Spinoff2004/rd_2.html Fig 6.1

Neuromast with cupula Cupula - gelatinous covering http://www.bio.nagoya-u.ac.jp:8000/Yama10fig4.jpeg Cupula - gelatinous covering

Ear http://weboflife.ksc.nasa.gov/images/earRevAFlat.jpg

Middle ear http://cache.eb.com/eb/image?id=14303&rendTypeId=4

Inner ear Semicircular canals Cochlea http://weboflife.ksc.nasa.gov/images/semiCircRevAFlat.jpg

Cochlea has hair cells supported by basilar membrane http://www.pc.rhul.ac.uk/staff/J.Zanker/PS1061/L5/inner_ear.gif Basilar membrane responds to high, med and low freq as move down the cochlea

Organ of Corti 15,000 hair cells in mammals Fig 6.18

Hair cells in cochlea Inner hair cells Organ of Corti on basilar membrane Outer hair cells http://instruct1.cit.cornell.edu/courses/biog105/pages/demos/105/unit10/5.hearing.html Cochlear hair cells have lost kinocilium

Organ of Corti Stereocilia bathed by endolymph: K+ rich Tectorial membrane Stereocilia bathed by endolymph: K+ rich Rest of cochlea bathed in perilymph Na+ rich Fig 6.18

Frequency response Frequency response differs down membrane http://www.blackwellpublishing.com/matthews/ear.html Frequency response differs down membrane Actual freq response is narrower than expect

Cochlear amplifier Inner hair cells make 90-95% of neural connections Outer hair cells Tune frequency response Change shape in response to sound Depolarize - shorten Hyperpolarize - lengthen Motion conferred by protein called prestin Moves Organ of Corti up and accentuates basilar membrane motion http://instruct1.cit.cornell.edu/courses/biog105/pages/demos/105/unit10/5.hearing.html

Hair cells

Electrical resonance Cells have frequencies at which respond maximally to oscillating potential Response to sounds at resonant frequency will be amplified Cells differ in electrical response down cochlea Difference in Ca+2 gated K+ channels

Cell response Mechanosensation - depolarize Opens voltage gated Ca+2 channels - depolarize and let in Ca+2 Ca+2 triggers Ca+2 gated K+ channels - hyperpolarize Density of channels and properties of Kca channels will “tune” resonant frequency Depolarization changes membrane potential. This potential change opens the voltage gated Ca channels. These depolarize and let calcium in. Calcium gates the calcium gated potassium channels which hyperpolarize - let K out.

Electrical resonance Cells have frequencies at which respond maximally to oscillating potential Response to sounds at resonant frequency will be amplified Cells differ in electrical response down cochlea Difference in Ca+2 gated K+ channels