lecture 23 extra senses n.
Download
Skip this Video
Loading SlideShow in 5 Seconds..
Lecture 23 : Extra senses PowerPoint Presentation
Download Presentation
Lecture 23 : Extra senses

Loading in 2 Seconds...

play fullscreen
1 / 68

Lecture 23 : Extra senses - PowerPoint PPT Presentation


  • 127 Views
  • Uploaded on

Lecture 23 : Extra senses. Fain chapter 10 11/23/09. Presentations. Talk length 3 minutes 3-4 slides Organization - Same as written material Intro - Why important - interesting (Methods - If you did analyses) Results - what was learned Discussion

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'Lecture 23 : Extra senses' - howell


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
lecture 23 extra senses

Lecture 23 : Extra senses

Fain chapter 10

11/23/09

presentations
Presentations
  • Talk length
    • 3 minutes
    • 3-4 slides
  • Organization - Same as written material
    • Intro - Why important - interesting
    • (Methods - If you did analyses)
    • Results - what was learned
    • Discussion
  • Practice helps make a smooth presentation
    • Especially important to keep us on time
topics
Topics
  • Thermoreception
  • Electroreception
  • Magnetoreception
diversity of skin receptors
Diversity of skin receptors
  • Neural termini come from different sources
    • Trunk - Dorsal root ganglia
    • Head - trigeminal ganglia
  • Free dermal endings involved in temperature sensation
    • Difficult to dissect out for single cell recordings
thermoreceptors
Thermoreceptors
  • More cold than warm receptors
    • Nose: 8-10 cold receptors / cm2
    • 1 warm receptor / cm2
  • Structure
    • Cold - myelinated axons terminate in epithelium
    • Warm - unmyelinated axons deeper in skin
warm temperature response
Warm temperature response
  • Extracellular recording in nerves from dorsal root ganglia
  • Warmth increases firing rate of “warm” receptors

Fig 10.1a

cold temperature response
Cold temperature response
  • Cold sensitive receptors respond to temperature drop
  • Increase firing rate for larger temp drops
  • Bursts
    • More action potentials per burst with colder temp
nociception
Nociception
  • Response to pain
    • Can be response to chemicals or temperature
  • Chemical response can be to capsaicin
    • Causes influx of cations
  • Not sure if it is modification of cell membrane or actual binding to receptor
adaptation
Adaptation
  • Over time, pain response decreases in response to capsaicin
    • Can use it as an analgesic!!
    • Results from desensitization
    • Also find destruction of nociceptors
method
Method

Make cDNA library from dorsal root ganglion

Pool 16,000 clones and express in HEK cells

Screen pools for capsaicin sensitivity by Ca+2 imaging

Continue until single clone - sequence

Subdivide pools

response to capsaicin cell culture
Response to capsaicin - cell culture
  • Screen pools
  • Break down to identify individual clone
  • Identify response by calcium fluorescing dye
cells expressing vr 1 respond
Cells expressing VR-1 respond
  • Capsaicin turns on response
  • Even more sensitive to resinferatoxin
  • Capsazepine and RR block response

Patch clamp response

also responds to heat
Also responds to heat
  • Increase in Temp
    • Inward current
    • Opening of nonselective channel (K+ Na+ Ca+2)
    • Ionotropic
  • Response to heat requires VR1 expression
  • Heat response is blocked by capsaicin antagonist
vanilloid receptor trpv1
Vanilloid receptor - TrpV1

Expressed in small diameter neurons in sensory ganglia

method1
Method

Make cDNA library from trigeminal cell culture

Pool 10,000 clones and express in HEK cells

Screen pools for menthol sensitivity by Ca+2 imaging

Continue until single clone - sequence

Subdivide pools

identify neurons responsive to menthol and cold ca 2 imaging
Identify neurons responsive to menthol and cold - Ca2+ imaging

If warm, menthol sensitivity can be overridden

cold channels
Cold channels
  • Decrease in Temp
    • Inward current
    • Opening of nonselective channel (K+ Na+ Ca+2)
    • Ionotropic
  • Express in Xenopus oocytes
identify receptor test response
Identify receptor - test response
  • Express in Xenopus oocytes
  • Determine sensitivity to different compounds
also responds to cold
Also responds to cold
  • Decrease in Temp
    • Inward current
    • Opening of nonselective channel (K+ Na+ Ca+2)
  • Menthol and temp add together to increase response
diversity of trp channels mechanosensation and temperature
Diversity of TRP channels - mechanosensation and temperature

Cold <23C

T < 17 C

T > 43 C

T > 52C

T > 33

T > 25

ir pit organ
IR pit organ
  • Bare nerve endings from trigeminal nerve (6000-7000 neurons)
  • Respond to heat by increased action potentials Sensitive to 0.003ºC changes

Fig 10.5

Fig 10.5

pit organ
Pit organ
  • Acts like pin hole camera
  • Constrained input angle provides directional information
detecting objects of interest
Detecting objects of interest

2 mice

Along pit axis

In front of snake

ir detection
IR detection
  • What is the receptor?
  • TRP channel??
electro communication
Electro-communication
  • Some species can detect electrical signals
    • Navigation
    • Prey detection
  • Some species can generate electrical signals
    • Probe environment
    • Communication
    • Stun prey
electroreception
Electroreception
  • Electric field detection
    • Sharks and rays; teleosts;
    • Some salamanders
    • Platypus
  • Huge sensitivity to electrical gradient
    • Skate can detect 0.01 V/cm
    • Same as 9V battery over 1000 km
salt water skates
Salt water skates
  • Skates detect electric field gradient from ampullary organ -canal with openings
  • Use hair cells modified from lateral line
  • Receptor??
electrolocation
Electrolocation
  • Sharks use to sense nerve activity from gill or muscles
    • Detect flatfish buried in sand
electrocommunication
Electrocommunication
  • Some organisms detect E field
  • Others can also generate E
    • Strongly electric - eels
    • Weakly electric - electric fish
generating discharge
Generating discharge
  • Discharge frequency set by pacemaker nucleus
  • Shape of discharge set by action potentials of electrocytes
field perturbed by insulators but not conductors
Field perturbed by insulators but not conductors

Fig 10.13 Use field to detect surroundings and navigate in dark

electrocyte discharge
Electrocyte discharge
  • Electrocyte is innervated by neuron
  • When receives signal, cell depolarizes = change in voltage

K+

Na+

-80 mV

Na+

K+

+50 mV

stacks of electrocytes add in series to increase total voltage in discharge
Stacks of electrocytes add in series to increase total voltage in discharge

130 mV

520 mV

Up to 700 V

electric discharge organs
Electric discharge organs
  • Different organs create different pulses
electric discharge organs1
Electric discharge organs
  • Gymnotids and mormyrids
  • Skates and eels
  • Wide variety of signals can be generated
slide51

Species specific discharges

Use during courtship

electric discharge for different species
Electric discharge for different species

A knifefish

B brown ghost

C electric eel

D pintailed knifefish

E Mormyrid

na v 1 4 expression in muscle vs electric organ eo1
Nav1.4 expression in muscle vs electric organ (EO)

Electric fish have Nav 1.4a only in EO

tree of na v 1 4a
Tree of Nav1.4a

Nonsynonymous

: Synonymous

tree of na v 1 4a1
Tree of Nav1.4a

Nonsynonymous

: Synonymous

Ka / Ks < 1 no selection

> 1 positive selection

dN/dS

electric discharge for different species1
Electric discharge for different species

A knifefish

B brown ghost

C electric eel

D pintailed knifefish

E Mormyrid

slide63
Key changes in inactivation siteSm - blackknife fish with slow responseAl- gene in muscleGp, Ed and Bp- very fast response
convergent evolution
Convergent evolution
  • Two different lineages of electric fish
  • Both have modified their Na1.4a gene
    • Express only in Electric Organ
    • Alter inactivation sites so can more rapidly change electric discharge
magnetoreception
Magnetoreception

Particles of magnetite detect the earth’s magnetic field

magnetic field direction
Magnetic field direction

Field is directed down north of the equator

Bacteria use field to detect down so swim into sediment

Bacteria in southern hemisphere orient magnetite particles opposite way from north - still use to swim down

many unknowns
Many unknowns
  • What is receptor?
  • How does it function?
  • How is magnetite generated / sequestered?