Eyes 1 - Eye Structure & Iris Reflex

This lesson covers:

  1. The different structures in the eye 
  2. How the eye responds to light in the iris reflex
  3. The roles of the circular and radial muscles in the iris

What is the cornea? 

A transparent layer at the front of the eye which refracts light

The gap through which light passes to reach the lens

The coloured part of the eye

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Diagram showing the structure of the eye with a labelled part marked as X.

The diagram above shows the labelled as 'X'.

optic
nerve

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Diagram of the eye structure with a label X indicating a specific part.

What is the structure labelled X in the image above?

Cornea 

Retina

Ciliary muscle 

Iris

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What is the pupil? 

The coloured part of the eye

The gap through which light passes to reach the lens

A transparent layer at the front of the eye which refracts light

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Diagram of the eye with the structure labelled X highlighted.

What is the structure labelled X in the image above?

Optic nerve

Lens

Suspensory ligament 

Ciliary muscle 

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What are the names of the two types of receptor cells in the retina? 

Prism cells 

Rod cells

Cone cells 

Cube cells 

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Which light-sensitive cells in the retina enable you to see in colour?

Rod cells

Cone cells

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Illustration of the structure of the eye showing the iris and pupil.

The eye is a sense organ. Which two stimuli are the receptor cells of the eye sensitive to?

Vibration

Light intensity 

Colour 

Temperature 

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Which light sensitive cells in the retina enable you to see in the dark?

Cone cells

Rod cells

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Diagram showing the structure of the eye with a focus on the retina.

The point where light focuses on the retina is called the . This region contains the highest concentration of cone cells and gives the sharpest image. 

fovea

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What is the purpose of the iris reflex?

To ensure the optimum amount of light enters the eye

To prevent dust from entering the eye

To focus on light from different distances 

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Illustration showing a comparison between a constricted pupil and a dilated pupil.

When the pupil is very large, do we describe it as 'constricted' or 'dilated'? 

Constricted 

Dilated 

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Which two muscles make up the iris? 

Radial muscles 

Round muscles 

Circular muscles 

Linear muscles 

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When the eye is exposed to bright light, will the pupil constrict or dilate?

Constrict 

Dilate

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What happens to the circular and radial muscles when the pupil constricts?

(Select all that apply)

The circular muscle relaxes 

The radial muscle relaxes 

The circular muscle contracts 

The radial muscle contracts 

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