The Senses

Vision

Anatomy of the Eye Sclera – white of eye; covers all but cornea Sclera – white of eye; covers all but cornea Cornea – transparent; covers iris Cornea – transparent; covers iris Sclera

Anatomy of the Eye Iris – Donut- shaped with hole in center Iris – Donut- shaped with hole in center Pupil – hole in iris to control light entering eye Pupil – hole in iris to control light entering eye Sclera

Anatomy of the Eye Lens – transparent; focuses light onto retina Lens – transparent; focuses light onto retina Retina – posterior ¾; cells react to light Retina – posterior ¾; cells react to light Sclera

Anatomy of the Eye Optic nerve – sends message to brain Optic nerve – sends message to brain Conjunctiva – mucous membrane that covers eye & lines eyelids Conjunctiva – mucous membrane that covers eye & lines eyelids Sclera

IMAGE FORMATION – HOW DO WE SEE?

Step 1 – Refraction of Light Refraction = bending Refraction = bending Done by lens and cornea Done by lens and cornea Images on retina are upside down and reversed Images on retina are upside down and reversed Brain learns early in life to coordinate visual images with orientations Brain learns early in life to coordinate visual images with orientations

Step 1 – Refraction of Light Photopigments – Rods & cones Photopigments – Rods & cones Rods – dim light; very sensitive Rods – dim light; very sensitive Cones – bright light (colors) Cones – bright light (colors)

Step 2 - Accommodation Accommodation – increase in curvature of lens for close objects Accommodation – increase in curvature of lens for close objects Normal eye – can refract light from 6 feet away so clear image is focused on retina Normal eye – can refract light from 6 feet away so clear image is focused on retina

Step 2 - Abnormalities Myopia – “nearsighted”; eyeball too long Myopia – “nearsighted”; eyeball too long

Step 2 - Abnormalities Hyperopia – “farsighted”; eyeball too short Hyperopia – “farsighted”; eyeball too short

Step 2 - Abnormalities Astigmatism – irregular curvature of eye Astigmatism – irregular curvature of eye

Step 2 - Abnormalities Presbyopia – Eye loses elasticity with age Presbyopia – Eye loses elasticity with age

CONTACTS & GLASSES

Step 3 – Pupil Constriction/Dilation Occurs simultaneously with accomodation Occurs simultaneously with accomodation

Step 4 - Convergence Movement of eyeball toward nose to maintain binocular vision Movement of eyeball toward nose to maintain binocular vision

Touch Receptors

HEARING

Physiology of Hearing Auricle/pinna directs sounds waves into auditory canal Auricle/pinna directs sounds waves into auditory canal Sound waves vibrate ear drum Sound waves vibrate ear drum Intensity & frequency Intensity & frequency Eardrum connects to hammer/malleus & vibrates it Eardrum connects to hammer/malleus & vibrates it Then incus/anvil, then stapes/stirrup Then incus/anvil, then stapes/stirrup

Physiology of Hearing Stapes moves back & forth and pushes oval window in & out Stapes moves back & forth and pushes oval window in & out Starts fluid waves in cochlea Starts fluid waves in cochlea

Physiology of Hearing Fluid moves hairs in cochlea – bending hairs send messages to brain via nerves Fluid moves hairs in cochlea – bending hairs send messages to brain via nerves

Physiology of Hearing Sounds interpreted by brain Sounds interpreted by brain Direction – timing to each ear Direction – timing to each ear Distance – often volume-related Distance – often volume-related

Cochlear Implants =zeg4qTnYOpw =zeg4qTnYOpw =zeg4qTnYOpw =zeg4qTnYOpw

Auditory Brainstem Implant Maggie Gleason Maggie Gleason =CCarj_p3OIA =CCarj_p3OIA =CCarj_p3OIA =CCarj_p3OIA =2VUPh2JLDUA =2VUPh2JLDUA =2VUPh2JLDUA =2VUPh2JLDUA

Smell & Taste

SMELL & TASTE Involves chemoreceptors Involves chemoreceptors Respond to chemicals in aqueous solutions Respond to chemicals in aqueous solutions Chemicals dissolve in mucus of nose & saliva in mouth Chemicals dissolve in mucus of nose & saliva in mouth

SMELL RECEPTORS Located in roof of nasal cavity Located in roof of nasal cavity Non-motile cilia covered by mucus Non-motile cilia covered by mucus Axons go to the brain Axons go to the brain Lifespan Lifespan days days

Physiology of Smell Brain can analyze ~400 odor molecules Brain can analyze ~400 odor molecules Must be gas & then dissolve Must be gas & then dissolve We can recognize > 1 trillion odors We can recognize > 1 trillion odors QUICK adaptation QUICK adaptation 50% in first second & slowly thereafter 50% in first second & slowly thereafter

Taste Taste buds – receptors with hairs covered by saliva Taste buds – receptors with hairs covered by saliva Most found in papillae Most found in papillae Lifespan = 7-10 days Lifespan = 7-10 days 5 options – sour, sweet, bitter, salty, umami 5 options – sour, sweet, bitter, salty, umami Each triggered by different chemicals Each triggered by different chemicals

Taste Preferences 80% of taste is actually smell 80% of taste is actually smell Mouth also has thermoreceptors, mechanoreceptors, & nocioreceptors Mouth also has thermoreceptors, mechanoreceptors, & nocioreceptors Chili peppers = pain Chili peppers = pain Interpretation of the stimuli is KEY Interpretation of the stimuli is KEY So can we LEARN to like brussel sprouts? So can we LEARN to like brussel sprouts?