This lesson describes how the action of the radial and circular muscles of the iris causes the pupil to dilate or contract. The PowerPoint has been designed to cover point 8.6 (ii) of the Edexcel International A-level Biology specification and includes key details such as the innervation of the smooth muscles by divisions of the autonomic nervous system.
Students will learn how:
-
the contraction of the radial muscles pulls the iris radially and enlarges the pupil, allowing more light to enter when an individual is in a room with dim light and that this contraction is the result of the conduction of an electrical impulse along a sympathetic motor neurone.
-
the contraction of the circular muscles constricts the pupil to reduce the light that enters the eye, in order to prevent damage to the photosensitive cells in the retina. This is the result of innervation by an impulse conducted along a parasympathetic neurone
Something went wrong, please try again later.
This resource hasn't been reviewed yet
To ensure quality for our reviews, only customers who have downloaded this resource can review it
Report this resourceto let us know if it violates our terms and conditions.
Our customer service team will review your report and will be in touch.