Name them!! There are 5! Hearing Sight Touch Taste Smell

Information Flow in Senses

Eye Exploratorium

Lacrimal Glands/ Tear Glands

Normal Lacrimal Gland Blocked lacrimal gland Blockage site

Conjunctiva Prevents entry of pathogens into eye socket (and  brain) If infection or damage occurs  conjunctivitis (pink eye)

Label the diagram of the eye! Sclera Choroid Retina Fovea centralis Optic nerve Blood vessels Blind spot Blood vessels Vitreous humor Ciliary body Iris Conjunctiva Pupil Lens Aqueous humor Cornea Anterior chamber Suspensory ligament Eye muscleRectus muscle

Thirteen-year-old Amanda Guthrie shows off her prosthetic eye yesterday at Misericordia Hospital's craniofacial osseointegration and maxillofacial prosthetic rehabilitation unit (COMPRU). The North Battleford, Sask., teen lost her right eye to cancer in 1999.

Let’s go on a tour!!

Cataracts Clouding of the lens Vision becomes progressively more blurry Caused by denaturation (“cooking”) of lens protein (UV light, old age). Treatment: cut out the lens, replace it with an artificial one

A B C A B C Accommodation: FarAccommodation: Near Ciliary muscle Suspensory Ligaments Lens

Accommodation Controlled by Ciliary muscle Far Objects Ciliary muscle relaxed Suspensory ligament tight Lens flat Near Objects Ciliary muscle contracted Suspensory ligament slack Lens bulged

Myopia Eye is too long and light comes into focus in front of the retina. Objects can be seen distinctly only when near the eye, not at a distance.

Hyperopia Eye is too short and light rays focus behind the retina. Vision is best at a distance

Presbyopia Lens becomes less flexible, less able to accommodate.

Astigmatism An irregularly shaped cornea causes light rays to focus at different points. The result is blurry vision near or distant

Glaucoma Buildup of aqueous humor in anterior chamber due to over production by ciliary body. Pressure builds up on lens, vitreous and retina Anterior Chamber Ciliary Body

Glaucoma –Can cause damage to the optic nerve, leading to partial and eventually total blindness.

Remember what’s in the front and back!! Notice the position of the fovea/macula

Pathway of Light into Eye Conjunctiva Cornea Aqueous humor Pupil (surrounded by iris) Lens Vitreous humor Retina Choroid (light does not penetrate this) Sclera (light does not penetrate this)

Retina made of rods and cones Rods and Cones Rods are very sensitive to light and function well in low light intensities Cones function well in high light intensity and detect color.

Surprisingly….. Light rays must pass through 2 layers of neurons in the retina before reaching the rods and cones These layers are the bipolar cells and ganglion cells whose long axons form the.. Optic nerve!!!!

Pathway of Light

The Visual Pathway

Rhodopsin in Rods Absorbs light and causes: –a conformational change in retinal that results in the separation of retinal from opsin –ultimately, this stimulates action potentials in sensory neurons (ganglion cells) Rods only work well in low light because: in bright light, rhodopsin breaks down faster than it can be produced; as a result, rods are not functional in bright light

Optic Nerve Thalamus Primary Visual Cortex in the Occipital Lobe of the Cerebrum

Can we trust our visual sense 100%???

Image Upside down

Inverted Image Thalamus Occipital Lobe of the Cerebrum

Visual Processing Edge enhancement –in the retina, rods are grouped together in “receptive fields” –those rods in the centre of the receptive field will EXCITE ganglion cells while those in the periphery will INHIBIT ganglion cells –So, how light shines on the receptive fields and how other cells in the retina (eg. horizontal and amacrine) modify the information, will affect the pattern of ganglion cell stimulation –this helps us with contrast and with the enhancement of edges –this can be illustrated with the Hermann Grid

Hermann Grid Illusion

Contralateral Processing -images from right enter left side of retina then head to left visual cortex