The SensesOur SENSES tell us:

• What is out in the environment?

• How much is out there?

• Is there more or less of it than before?

• Where is it?

• Is it changing in time or place? Other

senses?

Each of the senses uses specialized receptors to detect relevant incoming stimuli.

Sense Receptors in Humans

TouchTasteHearingVision Smell

Meissner’sCorpuscle

Freenerve ending

Rod Cone

The Senses• Everyone is their own

laboratory with which to test the senses.

• Non-human animals are sensitive to different “energies” in the environment.

Energy as Information

Forms of energy that can affect cellular processes and thus stimulate sensory systems:• Mechanical (touch, pressure, stretch)• Electromagnetic (light, magnetic, electrical)• Chemical (smell, taste)

Vision – The Eye

Many Different Kinds of Eyes

• Different types of structures to detect light

• Distinctive views of the world needed for survival.

Differences in Visible Wavelengths

Ultraviolet

Insects that feed on flowers, such as bees, have eyes that also can detect ultraviolet

Electromagnetic Spectrum

UltravioletUltraviolet

Because bees help pollinate them, flowers display ultraviolet markings that attract and guide the bee to the pollen.

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InfraredInfraredHeat (infrared) has longer wavelengths

Electromagnetic Spectrum

Vision – The Eye

Vision – The Eye

2.5 cm;7 g

Vision – The Eye

?

Lens

Retina

?

Vision – The Eye

Vision – The Eye

Rods: most sensitive to light and dark changes, shape and movement and contain only one type of light-sensitive pigment.

- not good for color vision. - more numerous than cones in the periphery of the retina.- 120 million rods in the human retina.

Cones: are not as sensitive to light as the rods. - cones are most sensitive to one of three different colors (green, red or blue); perception of color; work in bright light. - fine details. - 6 million cones in the human retina.     

ColorCards

Vision – The Eye

Vision – The Eye

Location of Rods vs Cones?

++

Movement?Color?Detail?

3

Vision – The EyeIshihara Colorblindness Tests

Vision – The Eye

Optic Disk – no photoreceptors!

Vision – The Brain

Right Left

Left Right    

Vision – The Brain

Path that visual information takes in the brain

Primary visual cortex

Color area

Number appearance area

Ramachandran, V.S. and Hubbard Ed (2003), Hearing Colors, Tasting Shapes, Scientific American, Vol 288 Issue 5 (May 2003), 42-49.

Do your eyes fool your brain?

Color Aftereffects

Adaptation

Do your eyes fool your brain?

Do your eyes fool your brain?

Do your eyes fool your brain?

Do your eyes fool your brain?

Do you see a triangle?

Do your eyes fool your brain?

A

B

C

Which line does “A”

match up with?

It depends on how you look at it!

It depends on how you look at it!

Why Do We Have 2 Eyes?

Advantages/disadvantages of eye placement?

Blind spot?Depth Perception?Predator vs. Prey

Why Do We Have 2 Eyes?

Overlapping visual field

Depth PerceptionMonocular/binocular cues?

Relative size

Interposition

Linear perspective

Aerial perspective

Light and shade

Monocular movement parallax