Hello and welcome to the Zero to Finals podcast.

My name is Tom and in this episode I'm going to be talking to you about pupil disorders.

And you can find written notes on this topic at zero tofinals.com slash pupil disorders

or in the ophthalmology section of the second edition of the zero to finals medicine book.

Then you can find flashcards and questions to train your knowledge and help you remember the

information for longer at members.0 to finals.com. So let's get straight into it.

The pupil is formed by a hole in the centre of the iris.

Many conditions can cause abnormally shaped and sized pupils.

Let's start by talking about the pupil size.

The circular muscles in the iris are responsible for pupil constriction,

making the pupil smaller. They are stimulated by the parasympathetic nervous system

using acetylcholine as a neurotransmitter. The parasympathetic fibers travel along the oculomotor nerve or cranial nerve 3.

The dilator muscles in the iris are responsible for pupil dilation, making the pupil bigger.

The dilator muscles are arranged like spokes on a bicycle wheel,

travelling straight from the inside to the outside of the iris.

They're stimulated by the sympathetic nervous system using adrenaline as a neurotransmitter.

Therefore, the parasympathetic nervous system causes pupil constriction, and the sympathetic

nervous system causes pupil dilation.

Atoms it for you, I picture a parrot sitting on the arch of the circular muscles to remember

that the parasympathetic nervous system controls pupil constriction.

I think to myself parrot sympathetic.

Next let's talk about the causes of an abnormal pupil shape.

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