Some on the eye

• Myopia: Near sightedness– The image focuses

in front of the retina

Pathology of myopia varies

• Japan -44% of adult pop.

• U.S. – 20-25% of adults

• Reading and education level

Are risk factors

• During one of the Chinese revolutions, they killed people with glasses because it meant they had read

Hyperopia

• Farsightedness

• At times confused with loss of vision at onset of age

• Note ostrich eyes are bigger than its brain

Ostriches are ridiculous

Presbyopia

• Greek Presby: “old person”

• Theory is that with age the crystallin lens loses elasticity.– Become far sited

• So they get bifocals– Ben Franklin

Astigmatism

• defect of the eye, where vision is blurred by an irregularly shaped cornea.

• A refractive problem

• Might be able to focus in horizontal plane, but not vertical

Evolution of the Eye

• Homologous organ

• First eyes 540 mya

• “arms race” idea

• Adaptation: Birds have better vision

• Night birds can pick up U.V. Light

• Euglena bacteria has a light sensitive patch (2)

• Planarians have eyespots

• Is it too complex to evolve piece by piece? – “what good is half an eye?”– Argument from personal belief

• But there are a lot of sub optimal eyes in nature.

• Even in people a myopic person has an advantage over the blind.

• Humans don’t have the best eyes by a long shot

• The mantis shrimp has eyes divided into three parts; trinocular vision.– We have 4 visual pigments, they have 16.

Can pick up U.V. and polarized light

Sea Sickness

• In Part results from your brain focusing on stable side of boat, waves moving closs, and waves moving far away on the horizon.

Decibels

• Logarithmic unit, measures sound levels

• Originally a bell was the amount of sound lost over 1 mile of telephone line

Source of sound Sound pressure

sound pressure level

  Pa dB re 20 µPa

immediate soft tissue damage 50000 approx. 185

rocket launch equipment acoustic tests approx. 165

threshold of pain 100 134

hearing damage during short-term effect 20 approx. 120

jet engine, 100 m distant 6–200 110–140

jack hammer, 1 m distant / discotheque 2 approx. 100

hearing damage from long-term exposure 0.6 approx. 85

traffic noise on major road, 10 m distant 0.2–0.6 80–90

moving passenger car, 10 m distant 0.02–0.2 60–80

TV set -- typical home level, 1 m distant 0.02 ca. 60

normal talking, 1 m distant 0.002–0.02 40–60

very calm room 0.0002–0.0006 20–30

quiet rustling leaves, calm human breathing

0.00006 10

auditory threshold at 2 kHz -- undamaged human ears

0.00002 0

Ear Wax

• Cerumen• Cleans, lubricates (prevents

itching), and protects• From sebaceous and

apocrine glands• Two genetic types: Wet

Dominant, Dry: recessive– Asians, Am Indians: Dry– Africans, Europeans: Wet

• Builds up in whales like rings in a tree

Wet type ear wax flouresces under U.V. light

Taste & Smell: Chemical senses

• McDonald’s Fries– Win best taste competitions– Not the method, potatoes, or machinery– Taste of fried foods determined by

cooking oil– McD’s uses 7% cottonseed oil, 93%

beef tallow: a fry has more beef fat/ oz than a burger

– McD’s worldlocations

Obviously there was criticism

• McD’s changed to pure veg. oil 1990

• Problem: how to make them taste like beef without using beef?

• “natural flavor”– Explains why most of our food taste the way it

does.

Natural Flavor vs. Artificial Flavor

• Both are man made• 90% of our food $ is for processed food• Canning, freezing, & dehydrating destroy flavor• Big money in making flavor• Name food brands• Name the companies that makes flavor

International Flavors & Fragrances (IFF)

• World’s largest flavor company– Also makes smell of best selling perfume’s,

deodorant, and soaps– 2005: 1.9 Bil.

• Givaudan: 2nd

• Haarman & Reimer: Largest German

• Takasago: Largest Japanese

Smell owns taste

• Aroma can be 90% of a food’s flavor

• What evolutionary benefit would organisms with a better sense of smell have?– Find food– Distinguish good food

from bad

Evolution puts pressure on us.

Flavors vs. smells

• Taste buds can detect ~ 5 basic flavors– Sweet, sour, bitter,

salty, astringent, umami

– About 4-10K taste buds on tongue, cheek, pharynx, epiglottis

– Bumps called papillae

• Olfactory system can percieve thousands of different chemicals

Mastication releases gases

• Thin layer of nerve cells called olfactory epithelium receives gases and transduces them into smell signals

• Brain combines smells signals with simple taste signals and decides if its something you want to eat.

Food preferences & personality form early in life

• Babies will adjust to hot & spicy, bland health food, or fast food depending on what the people around them eat.

Baby eating sushi

We don’t know it all yet

• Psychosomatic effects happen

• Color of food can determine perception of its taste

• People can grow accustomed to bad smells. – Come back from a long vacation

and immediately take a good whiff of what your house smells like. Other people smell that whenever they visit you

Aroma & memory• Nerve signals for smell go right past parts

of our brain associated with memory.– Smelling salts (ammonium carbonate can

wake you up by causing an inhalation reflex– Smells can bring back memories– Comfort foods– McD’s makes billions on this (Happy Meals)

Flavor in history

• Empires built, seas crossed, religions and philosophies changed over taste.

• Columbus went looking for flavor

• Salzburg Germany: Founded to protect salt trade

• Saffron is 12$ a gram

• So artificial flavors cropped up from perfume companies after canning started

• German scientist playing with chemicals: suddenly lab smells like grapes methyl anthranilate grape Kool-Aid purplesaurus rex

1.4 Bil a year

• ~10K new food products a year

• ~9/10 fail

Tech

• Spectrometers

• Gas chromatographs

• Vapor detectors

• Can discern chemicals at 1 ppb

• Human nose can tell 0.000000000003 %

• Dogs better still

Complex flavors

• Coffee, roast beast, strawberries; thousands of chemicals at once

• Chemical responsible for flavor of Bell pepper only need 0.02 ppb: a drop could flavor a swimming pool

• And its cheap: flavor in 12oz of Coke = ½ cent

• Often though, 1 chemical provides the over-riding sense of the food.

• Ethyl-2-methyl butyrate = apple

• Methyl-2-peridylketone = popcorn

• Ethyl-3-hydroxybutanoate = marshmallow

• Hexanal = fresh cut grass

• 3-methyl butanoic acid = B.O.

So what?So natural flavor means its made using old technology

• Natural

Getting amyl acetate from distilling bananas with a solvent

• Artificial

Getting amyl acetate from mixing vinegar with amyl alcohol, adding H2SO4 as a catalyst

Both taste exactly the same, both happen in the same factory, but people want to see natural on their label.

Art or Science?

• Mouthfeel: Its not just flavor,

• TA.XT2i Texture analyzer uses 250 probes to create an artificial mouth that senses bounce, creep, crunch, density, chewiness, gumminess, lumpiness, rubberiness, slipperiness, softness, wetness, spread, spring-back, tackiness

• How do you juggle all of this with subtleties of flavor?

Genetics

• Dominant gene • Phenylthiocarbamide,

also known as PTC, or phenylthiourea tastes very bitter or not at all depending on genetics

• Discovered when a guy at duPont accidently spilled a bunch of crystalline PTC, some complained, some did not

• May explain why some people are more offended by cig. smoke

Super Taster

~25% of people of European dissent

• Maybe more fungiform papillae

• Linked to food preference, body type

• Coffee, alcohol, may be too intense

• Olives too salty

Things go horribly awry• Ageusia (pronounced ay-GOO-see-uh)

Loss of sense of taste – From neural damage

• anosmia - a loss of the sense of smell. – Cold– Parkinson’s– Alzheimer's