Fibrillation of skeletal muscle is associated with all except: March 2011
**Core Concept**
Fibrillation potentials are a type of abnormal electrical activity observed in skeletal muscle, reflecting the spontaneous discharge of muscle fibers. This phenomenon is often seen in conditions affecting the muscle membrane or the motor neurons that innervate them.
**Why the Correct Answer is Right**
Fibrillation potentials are characteristic of muscle denervation, where the motor neuron's signal is disrupted or absent. This can occur due to various reasons such as peripheral neuropathy, muscle trauma, or neurodegenerative diseases like amyotrophic lateral sclerosis (ALS). The denervation leads to the uncontrolled release of acetylcholine from the motor neuron's terminal end, causing the muscle fiber to depolarize and generate fibrillation potentials.
**Why Each Wrong Option is Incorrect**
**Option A:** Fibrillation of skeletal muscle is indeed a feature of denervation, making this option incorrect.
**Option B:** Muscle fatigue, characterized by low-frequency fatigue, can also lead to fibrillation potentials, so this option is incorrect.
**Option C:** Fibrillation potentials can be seen in conditions affecting the muscle membrane, such as myotonia congenita, where the muscle membrane becomes hyperexcitable, leading to abnormal electrical activity. Thus, this option is incorrect.
**Clinical Pearl / High-Yield Fact**
A key feature of fibrillation potentials is that they are often associated with a reduction in the amplitude of the muscle action potential, reflecting the denervation of the muscle fiber.
**Correct Answer: C. Muscle cramps are not associated with fibrillation of skeletal muscle.**