Final answer:
The root 'mydriat' in the term mydriatic refers to the dilation of the pupils, which is called mydriasis. It can be caused naturally by the sympathetic nervous system or be induced by medications like phenylephrine. Drugs such as pilocarpine can reverse this effect for medical purposes.
Step-by-step explanation:
In the term mydriatic, the root mydriat refers to the dilation or widening of the pupils, a process known as mydriasis. This phenomenon can occur naturally as a part of the sympathetic nervous system response or be induced by certain medications. For instance, when norepinephrine, a neurotransmitter, binds to an adrenergic receptor in the radial fibers of the iris, it causes the pupils to dilate. Medications like phenylephrine mimic this action and are applied in drop form during eye exams.
Conversely, pilocarpine is a medication that acts as a nonspecific muscarinic agonist and is used to reverse mydriasis induced by drugs such as phenylephrine. It works by constricting the pupil through action on the smooth muscle of the iris and also reduces intraocular pressure, useful in treating glaucoma.