NROC64H3 Chapter Notes - Chapter 9: Retina Horizontal Cell, Transducin, Lightdark

40 views8 pages
17 Mar 2012

For unlimited access to Textbook Notes, a Class+ subscription is required.

Chapter 9 The Eye
- Vision: Detect things , sensitivity to light allows us to see things
- Light: Electromagnetic energy emitted in waves
- Retina: Contains photoreceptors to convert light energy neural activity, rest of eye forms crisp images
Made to detect differences n intensity of light falling on different parts of it
- 1st relay in pathway that serves visual perception occurs in cell group of
dorsal thalamus called the lateral geniculate nucleus LGN
- LGN visual info ascends to cerebral cortex for interpretation and
Properties of Light
- Light is electromagnetic radiation that is visible to our eyes
- Electromagnetic radiation has wavelength (distance b/w successive
peaks/troughs), frequency (number of waves per second), amplitude
- Radiation w/ high frequency (short wavelengths as hihest energy content
- Reflection: Bouncing of light rays off surface
- Absorption: Transfer of light energy to particle or surface
- Refraction: Imagies formed on eye this way, bending of light rays that
can occur when they travel form 1 transparent medium to another (i.e.
ray of light passing through air or water)
The Structure of the Eye
Gross Anatomy of the Eye
- Pupil: Opening that allows light to enter eye and reach the retina
- Iris: Pigmentation for eye colour, contains 2 muscles that makes it
smaller when it contracts, the other makes it larger
- Cornea: Glassy tansparent external surgace of eye
- Sclera: “white of eye”, continuous w/ cornea, forms tough wall of
- Extraocular Muscles: Move eyeball in orbit (eyeball socket)
- Conjuntiva: Membrane that folds back form inside of eyelids and
ataches to sclera
- Optic Nerve: Carries axons from retina, exits the back of eye, through
orbit and reaches base of brain near pituitary gland
Opthalmoscopic Appearance of the Eye
- Opthalmoscope: Device to see into eye through pupil to retina
- Optic Disk: Where optic nerve fibers exit the retina
Unlock document

This preview shows pages 1-3 of the document.
Unlock all 8 pages and 3 million more documents.

Already have an account? Log in
- Macula: Middle of each retina is darker coloured region w/
yellowish hue (Latin “spot”), distinguished by relative absence of
large blood vessels
- Fovea: Dark spot ~2mm in diameter (Latin “pit”), center of retina
anatomical regferencepoint,
Part of retina closer to nose than fovea = nasal
Part of retina lies near the temple = temporal
Part of retina above fovea = superior
Part of retina below fovea = inferior
Of Special Interest: Demonstrating the Blind Spots of your Eye
Pg 314
Cross-Sectional Anatomy of the Eye
- Aqeuous Humor: Fluid that nourishes cornea
- Lens: Transparent, located behing iris
- Ciliary Muscles: Suspend lens by ligaments/zonule fibers,
attached to sclera and form ring insde eye
- Vitreous Humou: B/w lens and retina, pressure serves to
keep eyeball spherical
Image Formation by the Eye
Refraction by the Cornea
- As light passes into edium where speed is slowed, it will bend
toward a line that is perpendicular
- Light rays strike curved cornea so they converge on back of eye
- Distance from refractive surface to potin where parallel light
rays converge is called focal distance, depends on ciurvature of
corna tigher the curce short the focal distance
- Reciprocal of focal distance in meter is dioptre
Accomodation by the Lens
- Accomodation: As objects approach, light rays can no longer
be parallel, they diverge and greater refractive power is
required to bring them into focus FOCUSING POWER BY
During accommodation, ciliary muscle contracts and swells
making area inside muscle smaller decrease tension lens
becomes rounder and thicker increases curvature of lens surface
increase refractive power
Unlock document

This preview shows pages 1-3 of the document.
Unlock all 8 pages and 3 million more documents.

Already have an account? Log in
Of Speical Interest: Eye Disorders pg 317, Vision Correction 318, 319
The Pupillary Light Reflex
- Pupillary Light Reflex: COnnectionbw retina and neuron on brain stem
that control muscles that constrict pupils, consensual so lack of consensual
papillary light reflex si sign of neurological disorder
The Visual Field
- Visual Field
Visual Acuity
- Visual acuity: Ability to distinguish 3 nearby points
- Visual angle: Distance across retina , in degrees
Microscopic Anatomy of the Retina
- Most direct pathway for visual info to exit eye is from photoreceptors bipolar cells ganglion cell
- Ganglion cells fire APs in response to light go down optic nerve rest of brain
1. Horizonal cells: Receive
input from photoreceptors
and project neurites
laterally to influence
surrounding bipolar cells
and photoreceptors
2. Amacrine Cells: Receive
input form bipolar cells and
project laterally to
influence surrounding
ganglion cells, bipolar cells
and other Amacrine cells
1. Only light-sensitive cells
in retina are
2. Ganglion cells are the
only source of out put
The Lamina Organization of
the Retina
- Laminar organization: cells are organized in layers
- Light passes from vitreous humour ganglion and bipolar cells photoreceptors
- Advantage of inside-out arrangement is pigemented epithelium that lies below the photoreceptors plays critical
role in maintenance of photoreceptors and photopigments, absorbs any light that passes through retina = minimize
reflection of light
- Innermost layer = ganglion cell layer, contains all cells bodies of ganglion cells
- 2ND innermost layer = inner nuclear layer, contains all cell bodies for bipolar cells
- B/w ganglion cell layer and inner nuclear layer = inner plexiform layer, contains synaptic contacts b/w bipolar
cells, Amacrine cells and ganglions cells
- 3rd later = outer nuclear layer, contains all cell bodies for photoreceptors
- B/w inner and outer nuclear layer is oter plexiform layer, photoreceptors make synaptic contact w/ bipolar
and horizontal cells
- 4th layer = layer of photocreceptor outer segments, contains light-sensitive elements of retina, embedded
in pigmented epithelium
Unlock document

This preview shows pages 1-3 of the document.
Unlock all 8 pages and 3 million more documents.

Already have an account? Log in

Get access

$10 USD/m
Billed $120 USD annually
Homework Help
Class Notes
Textbook Notes
40 Verified Answers
Study Guides
1 Booster Class
$8 USD/m
Billed $96 USD annually
Homework Help
Class Notes
Textbook Notes
30 Verified Answers
Study Guides
1 Booster Class