Neuromuscular disorders Practice Questions
20 free Neuromuscular disorders practice questions for the Physiology. Tap an option to answer — you get instant feedback, the correct answer, and a detailed explanation for every question.
Myasthenia gravis is primarily caused by antibodies against which structure at the neuromuscular junction?
- A Voltage-gated sodium channels
- B Acetylcholine receptors
- C Acetylcholinesterase enzyme
- D Calcium channels
Correct answer: Acetylcholine receptors
Myasthenia gravis is an autoimmune disorder targeting postsynaptic acetylcholine receptors. This reduces neuromuscular transmission and causes muscle weakness.
The hallmark feature of myasthenia gravis is:
- A Muscle rigidity
- B Muscle fatigue that improves with activity
- C Muscle weakness that worsens with activity
- D Muscle spasm at rest
Correct answer: Muscle weakness that worsens with activity
In myasthenia gravis, repeated use of muscles leads to increasing weakness. This occurs due to depletion of functional acetylcholine receptors.
Which drug is commonly used to improve neuromuscular transmission in myasthenia gravis?
- A Atropine
- B Neostigmine
- C Dantrolene
- D Botulinum toxin
Correct answer: Neostigmine
Neostigmine inhibits acetylcholinesterase, increasing acetylcholine availability at the neuromuscular junction. This improves muscle strength.
Lambert-Eaton myasthenic syndrome is caused by antibodies against:
- A Postsynaptic acetylcholine receptors
- B Presynaptic calcium channels
- C Acetylcholinesterase
- D Sodium channels
Correct answer: Presynaptic calcium channels
Lambert-Eaton syndrome involves antibodies against presynaptic voltage-gated calcium channels. This reduces acetylcholine release.
Which feature distinguishes Lambert-Eaton syndrome from myasthenia gravis?
- A Presence of prominent muscle weakness at rest
- B Frequent association with autoimmune thyroid disease
- C Improvement of strength with repeated activity
- D Predominant involvement of ocular muscles
Correct answer: Improvement of strength with repeated activity
In Lambert-Eaton syndrome, muscle strength improves with brief repeated use as calcium accumulates and boosts acetylcholine release. This contrasts with myasthenia gravis, where activity worsens weakness.
Botulinum toxin causes neuromuscular paralysis by:
- A Blocking acetylcholine receptors
- B Inhibiting acetylcholine release
- C Increasing acetylcholine breakdown
- D Blocking sodium channels
Correct answer: Inhibiting acetylcholine release
Botulinum toxin prevents the release of acetylcholine from presynaptic terminals. This leads to flaccid paralysis.
Which neuromuscular disorder is associated with thymoma?
- A Guillain-Barré syndrome
- B Myasthenia gravis
- C Muscular dystrophy
- D Multiple sclerosis
Correct answer: Myasthenia gravis
Thymoma is frequently associated with myasthenia gravis. The thymus plays a role in the autoimmune process.
Curare causes muscle paralysis by:
- A Blocking acetylcholine release
- B Blocking acetylcholine receptors
- C Enhancing acetylcholinesterase activity
- D Blocking calcium channels
Correct answer: Blocking acetylcholine receptors
Curare competitively blocks nicotinic acetylcholine receptors at the neuromuscular junction. This prevents muscle contraction.
Which condition results from progressive degeneration of motor neurons?
- A Myasthenia gravis, an antibody-mediated disorder
- B Guillain-Barré syndrome, a demyelinating polyneuropathy
- C Amyotrophic lateral sclerosis
- D Lambert-Eaton myasthenic syndrome
Correct answer: Amyotrophic lateral sclerosis
Amyotrophic lateral sclerosis involves degeneration of both upper and lower motor neurons, producing progressive muscle weakness and atrophy.
The primary pathology in Duchenne muscular dystrophy involves deficiency of:
- A Myosin heavy chain
- B Actin filament protein
- C Dystrophin
- D Troponin complex
Correct answer: Dystrophin
Duchenne muscular dystrophy is caused by absence of dystrophin, which links the muscle cytoskeleton to the extracellular matrix. Its loss leads to muscle fibre damage and progressive weakness.
Which neuromuscular disorder presents with ascending paralysis?
- A Myasthenia gravis with fatigable weakness
- B Guillain-Barré syndrome
- C Lambert-Eaton myasthenic syndrome
- D Poliomyelitis of the anterior horn
Correct answer: Guillain-Barré syndrome
Guillain-Barré syndrome typically presents with ascending paralysis caused by immune-mediated demyelination of peripheral nerves.
In myasthenia gravis, which muscles are commonly affected first?
- A Respiratory muscles
- B Proximal limb muscles
- C Ocular muscles
- D Paraspinal muscles
Correct answer: Ocular muscles
Ocular muscles are often the first affected in myasthenia gravis. This leads to ptosis and diplopia.
Which test is commonly used to confirm myasthenia gravis?
- A Electroencephalogram
- B Tensilon test
- C Nerve biopsy
- D Muscle creatine kinase levels
Correct answer: Tensilon test
The Tensilon test uses a short-acting acetylcholinesterase inhibitor. Temporary improvement in strength supports the diagnosis.
Poliomyelitis primarily affects which neurons?
- A Upper motor neurons
- B Lower motor neurons
- C Sensory neurons
- D Interneurons
Correct answer: Lower motor neurons
Poliomyelitis selectively destroys lower motor neurons in the spinal cord. This results in flaccid paralysis.
Which neuromuscular disorder is characterized by muscle fiber necrosis and regeneration?
- A Myasthenia gravis
- B Muscular dystrophy
- C Guillain-Barré syndrome
- D Lambert-Eaton syndrome
Correct answer: Muscular dystrophy
Muscular dystrophies involve repeated muscle fiber damage and regeneration. Over time, this leads to muscle weakness.
A decrease in acetylcholine release at the neuromuscular junction is most characteristic of:
- A Myasthenia gravis
- B Lambert-Eaton syndrome
- C Curare poisoning
- D Organophosphate poisoning
Correct answer: Lambert-Eaton syndrome
Lambert-Eaton syndrome reduces acetylcholine release due to presynaptic calcium channel dysfunction. This impairs neuromuscular transmission.
Which feature is common to lower motor neuron lesions?
- A Spastic paralysis
- B Hyperreflexia
- C Muscle atrophy
- D Clonus
Correct answer: Muscle atrophy
Lower motor neuron lesions cause muscle atrophy due to denervation. Reflexes are typically reduced or absent.
Organophosphate poisoning affects neuromuscular transmission by:
- A Blocking acetylcholine receptors
- B Inhibiting acetylcholinesterase
- C Reducing acetylcholine synthesis
- D Blocking sodium channels
Correct answer: Inhibiting acetylcholinesterase
Organophosphates inhibit acetylcholinesterase, leading to excessive acetylcholine accumulation. This causes continuous stimulation and paralysis.
Which neuromuscular disorder is inherited as an X-linked recessive condition?
- A Myasthenia gravis, an autoimmune disorder
- B Duchenne muscular dystrophy
- C Guillain-Barré syndrome, an immune neuropathy
- D Lambert-Eaton myasthenic syndrome
Correct answer: Duchenne muscular dystrophy
Duchenne muscular dystrophy is inherited in an X-linked recessive pattern and therefore almost exclusively affects boys.
Failure of neuromuscular transmission in myasthenia gravis mainly affects which phase of muscle contraction?
- A Action potential propagation
- B Acetylcholine release
- C End-plate potential generation
- D Calcium release from sarcoplasmic reticulum
Correct answer: End-plate potential generation
In myasthenia gravis, reduced acetylcholine receptor availability decreases end-plate potential amplitude. This prevents effective muscle fiber depolarization.