The process by which the sensitivity to a certain stimulus is modified by previous exposure is called sensory __________. A) transduction B) adaptation C) modulation D) amplification E) range fractionation

Each taste bud is composed of taste cells, supporting cells, and basal cells. A) True B) False

T F In order for taste and/or olfaction to occur, the chemical being sensed must be first be in solution.

Outline I.How do our eyes sense light II.How our eyes adapt to the light & dark

Back of Eye Front of Eye Bipolar Cells Rods & Cones Ganglion Cells Choroid

Front of Eye Back of Eye

Visual Pathway of the Retina Rods & Cones –Photoreceptors of eye –some convergence occurs –100 million rods/eye –3 million cones/eye

Visual Pathway of the Retina Rods & Cones –Photoreceptors of the eye –some convergence occurs –100 million rods in each eye –3 million cones in each eye Bipolar cells –synapse with ganglion cells –large amount of convergence

Visual Pathway of the Retina Rods & Cones –Photoreceptors of the eye –some convergence –100 million rods in each eye –3 million cones in each eye Bipolar cells –synapse with ganglion cells –lots of convergence Ganglion cells –axons of these form optic nerve –more convergence

Rod Rods: High sensitivity Low acuity Allow “night vision” Outside fovea

RodCone Rods: High sensitivity Low acuity Allow “night vision” Outside fovea Cones: Low sensitivity High acuity Allow color vision Mainly in fovea

Rod and Cone Distribution in Eyes

Structure of a Rod Outer Segment (contains photopigment) Inner Segment

Photopigments: Light-sensitive Proteins Photopigment of rods is ____________

Photopigments: Light-sensitive Proteins Photopigment of rods is ____________ Photopigments have two parts: 1)protein called opsin 2)derivative of vitamin A called retinal

Photopigments: Light-sensitive Proteins Photopigment of rods is ____________ Photopigments have two parts: 1)protein called opsin 2)derivative of vitamin A called retinal Cones contain photopsin –Opsins have different amino acids that determine which wavelengths are absorbed –Red, green, and blue cones absorb red, green, and blue light, respectively

Selectivity of Rods & Cones Rods are generalists Cones are specialists - Blue cones - Green cones - Red cones

Cone Absence leads to Colorblindness Red-Green Colorblindness: results from absence of red or green cones in retina

Transduction in Rods and Cones In complete darkness, rods and cones are ___________ by influx of Na +

Transduction in Rods and Cones In complete darkness, rods and cones are ___________ by influx of Na + Send IPSP’s to bipolar neuron

Transduction in Rods and Cones In complete darkness, rods and cones are ___________ by influx of Na + Send IPSP’s to bipolar neuron Light stimulates breakdown of photopigments

Transduction in Rods and Cones Photopigment breakdown results in the closing of Na + channels

Transduction in Rods and Cones Photopigment breakdown results in the closing of Na + channels IPSP’s stop

Total Dark Na+ Influx (depolarization) No AP to Ganglion Cell IPSP’s to Bipolar Neuron No AP to Visual Cortex

Total Dark Na+ Influx (depolarization) No AP to Ganglion Cell IPSP’s to Bipolar Neuron No AP to Visual Cortex Light Photopigment Breakdown Na + channels Close Stop IPSP’s to BPN AP sent to Ganglion Cell AP sent to Visual Cortex

Outline I.How do our eyes sense light II.How our eyes adapt to the light & dark

Light/Dark Adaptation of Eyes

Visual sensitivity depends on concentration of photopigments Dark Adaptation of Eyes

Visual sensitivity depends on concentration of photopigments When first entering the dark theatre, you see: Dark Adaptation of Eyes

Photopigments broken down by light Dark Adaptation of Eyes

Photopigments broken down by light Photopigments regenerated in the dark (created faster than broken down) Dark Adaptation of Eyes

Photopigments broken down by light Photopigments regenerated in the dark (created faster than broken down) Highly-sensitive rods “turned on” Dark Adaptation of Eyes

Light Adaptation of Eyes When leaving the theater …. Eyes highly sensitive to bright light

Light Adaptation of Eyes Photopigments break down

Light Adaptation of Eyes Photopigments break down Light sensitivity decreases

Light Adaptation of Eyes Photopigments break down Light sensitivity decreases Rods “burned out” as rhodopsin is broken down

Light Adaptation of Eyes Photopigments break down Light sensitivity decreases Rods “burned out” as rhodopsin is broken down Brain switches vision from _____ to _____

Changes in Pupil Size Circular and Radial Muscles Pupil size controlled by sympathetic and parasympathetic nervous stimulation

Dude, What Just Happened?

Summary Rods allow high sensitivity/low acuity night vision; Cones allow low sensitivity/high acuity daylight vision Vision is somewhat counterintuitive Photopigment breakdown and regeneration, change in pupil diameter, and switching of photoreceptor type allows for light/dark adaptation of the eyes