Final answer:
Muscarinic stimulation leads to the contraction of the sphincter muscle and the ciliary muscle in the eye, resulting in a decrease in pupil size, a process known as pupillary constriction or miosis. This is part of the parasympathetic nervous system's response.
Step-by-step explanation:
The question relates to the effects of muscarinic stimulation on the eye, specifically on the sphincter muscle and the ciliary muscle. When the muscarinic receptors, which are a type of acetylcholine receptor, are stimulated, the following effects occur:
- The sphincter muscle of the iris contracts, which leads to pupillary constriction (also known as miosis).
- Next, the ciliary muscle contracts, which results in the lens becoming more rounded. This condition is known as accommodation and helps in focusing on near objects.
This process is part of the parasympathetic response and is in contrast to sympathetic stimulation, which leads to pupillary dilation and ciliary muscle relaxation. Knowledge of these responses is essential in the field of ophthalmology and for understanding how certain medications can affect eye function.
Muscarinic stimulation causes the sphincter muscle to contract and the ciliary muscle to contract, leading to pupillary constriction.