BMS1052 Lecture Notes - Lecture 12: Iris Sphincter Muscle, Vitreous Body, Aqueous Humour

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Lecture 12- Vision and the Eye
Learning objectives
describe the external anatomy and structure of the eye
describe how errors of refraction account for the most common problems of vision,
and how they can be corrected
describe the process of phototransduction in photoreceptors
identify the major neuron types in the retina and draw a simple retinal circuit
diagram
distinguish the mechanisms that produce ON- and OFF- bipolar cells
identify the key difference between the responses of bipolar cells and retinal
ganglion cells
defie a euro’s reeptie field
Lecture overview
Signal transmission
External anatomy and structure of the eye
Image formation and optical correction
Signal Transduction
Retinal photoreceptors
Retinal circuitry
structure and general circuit
Factors affecting acuity
Bipolar cells and retinal ganglion cells (the retinal outputs)
External anatomy and structure of the eye
Anatomy of the human eye
Fluid filled chambers aqueous humor in anterior chamber; small posterior chamber;
vitreous humor in the vitreous chamber.
Light enters the eye through pupil
Iris muscles control pupil diameter
(dilate or contract)
- dilator pupillae
- sphincter pupillae
The optic nerve is comprised of axons
from retinal ganglion cells.
tough white protective outer layer
sclera.
Cornea and lens are responsible for
focusing the image on the retina
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Image formation and optical correction
Light entering the eye is refracted to form a focussed image at the retina
Light rays from distant objects are ~parallel.
Convex lens strength
1 diopter => focuses parallel rays 1 m from lens
10 diopter => focus 0.1 m from lens
Cornea ~42 dioptres
Lens ~ up to 20 dioptres
Light can be refracted or bent when it passes from one transparent medium to another air
to the cornea and lens of the eye. This is due to the light changing speed because of the
different refractive indices
Light entering the eye must be focused on the retina for clear vision.
The major focusing part of the eye is actually the cornea lens provides additional
accommodation.
The point at which the light waves focus or converge is called the focal point.
Lens curvature is controlled by ciliary muscles.
To focus on a nearby object requires a rounded lens => contract ciliary muscles, which
loosens the zonule fibers, causing the lens to become more spherical.
Image formation in the Normal eye (Emmetropia)
Far source (>9 m) light rays are parallel do’t eed to refrat light rays as uh.
For a close source, light rays are diverging need stronger refraction.
Lens curvature is controlled by ciliary muscles.
To focus on a nearby object requires a rounded lens => contract ciliary muscles, which
loosens the zonule fibers, causing the lens to become more spherical.
Optic disk point of entry/exit for optic nerve and blood supply.
Since there are no photoreceptors lid spot. We do’t orally
notice this blind spot for two reasons:
1 we have two eyes, and the blind spot in one eye, corresponds to
a region with photoreceptors in the other eye
2 e pereptually fill-i or iterpolate the isual see aroud
the blind spot.
Fovea point of highest acuity, where photoreceptors are most
densely packed.
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Document Summary

Signal transmission: external anatomy and structure of the eye. Retinal circuitry structure and general circuit: factors affecting acuity, bipolar cells and retinal ganglion cells (the retinal outputs) Iris muscles control pupil diameter (dilate or contract) The optic nerve is comprised of axons from retinal ganglion cells. Tough white protective outer layer sclera. Cornea and lens are responsible for focusing the image on the retina. Fluid filled chambers aqueous humor in anterior chamber; small posterior chamber; vitreous humor in the vitreous chamber. Optic disk point of entry/exit for optic nerve and blood supply. Since there are no photoreceptors (cid:271)li(cid:374)d spot. We do(cid:374)"t (cid:374)or(cid:373)ally notice this blind spot for two reasons: 1 we have two eyes, and the blind spot in one eye, corresponds to a region with photoreceptors in the other eye. 2 (cid:449)e per(cid:272)eptually (cid:862)fill-i(cid:374)(cid:863) or i(cid:374)terpolate the (cid:448)isual s(cid:272)e(cid:374)e arou(cid:374)d the blind spot. Fovea point of highest acuity, where photoreceptors are most densely packed.

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