Amplification (i.e., abnormal DNA replication) of a DNA segment including a proto-oncogene, leading to overproduction of the encoded protein.

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#Unit 7. System Physiology – Animal

Each rod and cone photoreceptor is divided into:

an outer segment

an inner segment 

a synaptic terminal zone

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#Unit 7. System Physiology – Animal

The retina organized into layers: Outer nuclear layer contains the photoreceptors , rods & cones 

Inner nuclear layer contains the cell bodies of excitatory and

inhibitory interneurons including bipolar cells, horizontal cells, & amacrine cells

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#Unit 7. System Physiology – Animal

Rods 

Have low acuity or resolution

are sensitive to low-intensity light

receptors for night vision (scotopic vision)

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#Unit 7. System Physiology – Animal

Cones 

Higher visual acuity

responsible for vision in bright light (photopic vision) Participate in color vision

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#Unit 7. System Physiology – Animal

Inputs from eye to CNS: 

Input from the rods 

Input from the cones

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#Unit 7. System Physiology – Animal

Duplicity Theory 

The existence of these two kinds of input, each working maximally under different conditions of illumination