Class Notes (922,925)
CA (543,002)
UTSG (45,883)
BIO (2,273)
BIO271H1 (40)
Ohana (6)
Lecture

Lecture 5

8 Pages
71 Views

Department
Biology
Course Code
BIO271H1
Professor
Ohana

This preview shows pages 1-3. Sign up to view the full 8 pages of the document.
Lecture 5
Sensory Physiology: Photoreception
Cross Section In the Cochlea:
oOuter hairs amplify quiet sound
Change shape in response to sound
Do not release neurotransmitter
The change in the shape of the hair cell increases the
movement of the basilar membrane increased stimulus
to inner hair cells
Inhibited by efferent neurons in response to loud sounds
Cristae Detect Angular Acceleration
Photoreception
oAbility to detect small proportion of the electromagnetic wave:
from near infared to near UV
A small proportion of the electromagnetic spectrum from
ultraviolet to near infared
Ability to detect this range of wavelengths supports idea
that animals evolved in water
Wavelengths around the visible light travels well in
water; other wavelengths do not
Electromagnetic Spectrum
oMost creatures dont detect
oVisible light for humans
oVisible light is must less attenuated in water
Photoreceptors
oRange from single light-sensitive cells to complex, image-
forming eyes
oTwo major types of photoreceptor cells:
Ciliary photoreceptors
Have a single, highly folded cilium
Folds form disks that contain photopigments
Rhabdomeric photoreceptors
Apical surface covered with multiple outfoldings
called microvillar projections
Microvillar projections contain photopigments
oPhotopigments
Molecules that absorb energy from photons
Phylogeny of Photoreceptors
oVertebrates have ciliary receptors, but other chordata have both
www.notesolution.com
oDont have to know details of evolutionary tree
Vertebrate Photoreceptors
oHave ciliary photoreceptors
Rods
Cones
oBoth have inner and outer segments
oOuter segment (an extension of the colium) photopigments
oInner segment - forms synapses with other cells
Rods and Cones
oDifference the rods are sensitive to dim light, cones are
sensitive to bright light
oMore than one type of cones in mammals (color) whereas one
type of rod (black and white only)
Diversity in Rod and Cone Shape
oDiverse among vertebrates
oShape does not determine properties of photoreceptor
Properties depend on its photopigment
Photopigments
oHave two covalently bonded parts
Chromophore
Derivative of vitamin A
Ex.. retinal
Contains carbon-carbon double bonds
Absorption of light converts bond from cis to trans
oOpsin
G-protein could receptor protein
Opsin structure determines photopigment characteristics
Ex. Wavelength of light absorbed
Retinal
oLight changes the C bond at position 12, from cis to all trans
Phototransduction
oLight arrives photopigment is released now G protein can be
activated
Vertebrate ligand gated channel that is gated by ligand;
when there is light, the channel closes less Na flowing
in (hyperpolarization)
Rhabdomeric depolarization
Phototransduction
oSteps in photoreception:
oChromophore absorbs energy from photon
oChromophore changes shape
www.notesolution.com
Double bond isomerizes from cis to trans
oActivated chromophore dissociates from opsin
Bleaching
oOpsin activates G-protein
oFormation of second messenger
oIon channels open or close
oChange in membrane potential
The Eye
oEyespots
Cells or regions of a cell that contain photosensitive
pigment ex. Protist Euglena
oEyes are complex organs
Detect direction of light
Light-dark contrast
Some can form an image
Types of Eyes
oFlat sheet eyes
Some sense of light direction and intensity
Often in larval forms or as accessory eyes in adults
Layer of photoreceptor cells no shape for it pigments
layer (epithelial cell)
Layer to absorb light
oCup-shaped eyes
Retinal sheet is folded to form a narrow aperture
Discrimination of light direction and intensity
Lightdark contrast
Image formation
Poor resolution
Depends on how narrow the opening is
When opening starts to close similar to camera
image formation
oVesicular eyes (present in most vertebrates)
Lens in the aperture improves clarity and intensity
Lens refracts light and focuses it onto a single point on
the retina
Image formation
oGood resolution
oConvex eyes (annelids, mollusks, anthropods)
Bees etc.
Photoreceptors radiate outward
oConvex retina
www.notesolution.com

Loved by over 2.2 million students

Over 90% improved by at least one letter grade.

Leah — University of Toronto

OneClass has been such a huge help in my studies at UofT especially since I am a transfer student. OneClass is the study buddy I never had before and definitely gives me the extra push to get from a B to an A!

Leah — University of Toronto
Saarim — University of Michigan

Balancing social life With academics can be difficult, that is why I'm so glad that OneClass is out there where I can find the top notes for all of my classes. Now I can be the all-star student I want to be.

Saarim — University of Michigan
Jenna — University of Wisconsin

As a college student living on a college budget, I love how easy it is to earn gift cards just by submitting my notes.

Jenna — University of Wisconsin
Anne — University of California

OneClass has allowed me to catch up with my most difficult course! #lifesaver

Anne — University of California
Description
Lecture 5 Sensory Physiology: Photoreception Cross Section In the Cochlea: o Outer hairs amplify quiet sound Change shape in response to sound Do not release neurotransmitter The change in the shape of the hair cell increases the movement of the basilar membrane increased stimulus to inner hair cells Inhibited by efferent neurons in response to loud sounds Cristae Detect Angular Acceleration Photoreception o Ability to detect small proportion of the electromagnetic wave: from near infared to near UV A small proportion of the electromagnetic spectrum from ultraviolet to near infared Ability to detect this range of wavelengths supports idea that animals evolved in water Wavelengths around the visible light travels well in water; other wavelengths do not Electromagnetic Spectrum o Most creatures dont detect o Visible light for humans o Visible light is must less attenuated in water Photoreceptors o Range from single light-sensitive cells to complex, image- forming eyes o Two major types of photoreceptor cells: Ciliary photoreceptors Have a single, highly folded cilium Folds form disks that contain photopigments Rhabdomeric photoreceptors Apical surface covered with multiple outfoldings called microvillar projections Microvillar projections contain photopigments o Photopigments Molecules that absorb energy from photons Phylogeny of Photoreceptors o Vertebrates have ciliary receptors, but other chordata have both www.notesolution.com
More Less
Unlock Document


Only pages 1-3 are available for preview. Some parts have been intentionally blurred.

Unlock Document
You're Reading a Preview

Unlock to view full version

Unlock Document

Log In


OR

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


OR

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.


Submit