Sensation

· What is?

· This is the way we interact with outside world.

· How do we know what’s outside?

· We have to use our brain to figure out.

· But, brain needs information.

So, what’s outside?

· Physical energies

§ Light wave

§ Sound wave

§ Chemical

§ Hard surface that resist force

How to translate?

· Use sense organs.

§ Accessory structure – modify energies

§ Receptors – transduce energies.

§ Send information by way of sensory nerve.

How many?

· Auditory sense

· Visual sense

· Olfactory sense

· Gustatory sense

· Tactile sense

· Kinesthetic sense (scratching back, gymnist)

· Proprioceptive sense

· Vestibular sense (which is up and down)

· Internal sense (organs)

Visual Sense

· Physical energy – light wave

· Sense organs

· Eyes transduce three characteristics

§ Wavelength - hue

§ Amplitude – brightness

Photo-receptor cells

· Cone

§ Located in and around the fovea

§ Work best under bright light.

§ Produce sharp images.

§ Produce colors.

· Rods

§ Located away from the fovea

§ Work best under dim lighting condition.

§ Do not produce sharp images.

§ Do not produce colors.

Dark adaptation

· Two photoreceptors produce two-stage dark adaptation.

After the receptors

· Bipolar cell

· Ganglion Cell

§ Generate action potential capable of traveling to the brain.

· Optic nerve

Controversy

· How do we detect colors?

§ Trichromatic theory – three types of cones.

o Red, Green, and Blue

§ Opponent process theory – Three systems.

o Green – Red

o Blue – yellow

o Black – white

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