Chapter 14: Coordination and Response: II Animal Receptor Organs

What is the role of cornea?

Role of cornea is to "refract light" inside the eye.

What is the role of iris?

Role of iris is to "control the amount of light entering" by contracting and dilating pupil.

What is the role of pupil?

Role of cornea is to "allow entrance of light".

What is the role of lens?

Role of lens is to "focus image on retina".

What is the role of fovea?

Role of fovea is to "provide clear images".

What is the role role of ciliary muscles?

Role of ciliary muscles is to "alter the thickness of muscles".

What is the role of choroid coat?

Role of choroid coat is to"prevent internal reflection of light.

What are photoreceptors; rods and cons?

They are found in "retina". Rods are used in "monochromatic night vision", while cons are used in "bright light vision".

How is entrance of light controlled?

Light enters through:

• achieved by "altering diameter of pupil"

• size of pupil "controlled by iris muscles" - circular and radial muscles

• when "circular muscle contract, radial muscles relax", and pupil becomes smaller

• when "radial contract, circular muscle relax", and pupil enlarges (diltes)

• "pupil enlarges when surrounding light intensity is low", and "smaller when the light intensity is high"

What is meant by term accommodation?

It is the "adjustment of lens" of the eye so that "clear images of objects at different distances" are formed on retina.

How does your eye focus on distant object?

Our eye focuses on distant object when "circular ciliary muscles relax" and "suspensory ligaments" are "pulled tighter" and lens becomes "flatter and less convex".

How does your eye focus on nearer object?

Our eye focuses on nearer objects when; "circular ciliary muscles contract" and "suspensory ligaments" are "released loosely" and lens becomes "thicker and more convex".