**Core Concept**
Cholinomimetic drugs are a class of medications that stimulate the parasympathetic nervous system (PNS) by mimicking the action of the neurotransmitter acetylcholine. This leads to a range of effects, including increased salivation, increased gut motility, and bronchodilation.

**Why the Correct Answer is Right**
Cholinomimetic drugs, such as pilocarpine and physostigmine, are used to treat conditions like closed-angle glaucoma (A), as they increase the outflow of aqueous humor from the eye, reducing intraocular pressure. They are also used in cobra bite (C), as they can counteract the effects of cobra venom, which can cause respiratory failure and other systemic complications. In myasthenia gravis (D), cholinomimetic drugs can help improve muscle strength by increasing acetylcholine levels at the neuromuscular junction. However, in bradycardia (B), the condition of having a slow heart rate, cholinomimetic drugs would actually worsen the condition, as they can further decrease heart rate and slow conduction through the heart.

**Why Each Wrong Option is Incorrect**
**Option A:** Closed-angle glaucoma is a condition where the pressure in the eye is too high, and cholinomimetic drugs can help reduce this pressure by increasing the outflow of aqueous humor.
**Option C:** Cobra bite is a medical emergency where the venom can cause respiratory failure and other systemic complications, and cholinomimetic drugs can help counteract these effects.
**Option D:** Myasthenia gravis is a condition where the immune system attacks the acetylcholine receptors, leading to muscle weakness, and cholinomimetic drugs can help improve muscle strength by increasing acetylcholine levels.

**Clinical Pearl / High-Yield Fact**
When using cholinomimetic drugs, it is essential to be aware of their potential side effects, such as bradycardia, bronchospasm, and increased salivation, which can be particularly problematic in patients with certain medical conditions.

**✓ Correct Answer: B. Bradycardia**