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Discuss the pupil reflex by describing the opposing actions of the circular and radial muscles in the iris.

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Cambridge IGCSE BiologyCoordination and responseSupplement content

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Discuss the pupil reflex by describing the opposing actions of the circular and radial muscles in the iris

  • This point belongs to Sense organs, especially Sense organs outcomes.
  • You need to be able to discuss the pupil reflex by describing the opposing actions of the circular and radial muscles in the iris.
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Paper 4Theory (Extended)4 marks

Diagram Description

Diagram of the iris muscles

The diagram shows the circular muscles arranged in a ring around the pupil and the radial muscles arranged like spokes radiating outward from the pupil.

  1. a

    Explain how the circular and radial muscles in the iris work together to control the size of the pupil in different light conditions.

    Aim for approximately 4 distinct marking points.

    [4]
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