How does the eye focus on a near object?
Reveal answer
Ciliary muscles contract → ligaments slacken → lens fatter → more refraction.
Key words: ciliary · fatter
3(j) CO-ORDINATION AND RESPONSE · RECALL
3.42 Focusing and responding to light
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How does the eye focus on a distant object?
Reveal answer
Ciliary muscles relax → ligaments tight → lens thinner → less refraction.
Key words: thinner
Pupil response in bright light?
Reveal answer
Circular muscles contract, radial relax → pupil smaller.
Key words: circular
Pupil response in dim light?
Reveal answer
Radial muscles contract, circular relax → pupil wider.
Key words: radial
What changes the shape of the lens?
Reveal answer
The ciliary muscles (via suspensory ligaments).
Key words: ciliary
What is meant by the term suspensory ligaments?
Reveal answer
Fibres transmitting tension between ciliary body and lens.
Key words: suspensory ligaments
What is meant by the term pupil reflex?
Reveal answer
Automatic iris response to light intensity.
Key words: pupil reflex
What is meant by the term antagonistic?
Reveal answer
Acting in opposing ways.
Key words: antagonistic
Two eye responses: for Near object, give the muscle action and the outcome.
Reveal answer
Muscle action: Ciliary contracts; ligaments slacken. Outcome: Lens thicker; more refraction.
Key words: Near object
Two eye responses: for Distant object, give the muscle action and the outcome.
Reveal answer
Muscle action: Ciliary relaxes; ligaments tighten. Outcome: Lens thinner; less refraction.
Key words: Distant object
Two eye responses: for Bright light, give the muscle action and the outcome.
Reveal answer
Muscle action: Circular iris contracts; radial relaxes. Outcome: Pupil constricts.
Key words: Bright light
Two eye responses: for Dim light, give the muscle action and the outcome.
Reveal answer
Muscle action: Radial iris contracts; circular relaxes. Outcome: Pupil dilates.
Key words: Dim light
True or false, and why? “Ciliary muscles pull the lens flat when they contract.”
Reveal answer
False. Contraction reduces ligament tension, allowing the lens to thicken.
True or false, and why? “The pupil focuses the image.”
Reveal answer
False. The cornea and lens focus; the pupil controls light amount.
True or false, and why? “Both iris muscle sets contract together.”
Reveal answer
False. Circular and radial muscles act antagonistically.