Motor Unit and Muscle Contraction Quiz

What is a motor unit?

• A group of neurons

• A single neuron

• A motor neuron and the muscle fibers it innervates

• A group of muscle fibers

Which principle explains the increasing activation of motor units?

• All or None law

• Recruitment

• Reflex arc

• Wallerian degeneration

What is the site of synapse between a motor neuron and muscle fiber?

• Synaptic cleft

• Motor end plate

• Myofibril

• Axon hillock

Miniature End Plate Potentials are due to?

• Action potentials

• Random leakage of Na+

• Spontaneous release of ACh vesicles

• Muscle fatigue

Which structure stores and releases calcium for contraction?

• T-tubule

• Myofibril

• Sarcoplasmic reticulum

• Nucleus

Which part of sarcotubular system carries action potential into the fiber?

• Sarcoplasmic reticulum

• T-tubule

• Nucleus

• M-line

Which is a congenital disorder affecting NMJ?

• Parkinsonism

• Myasthenia Gravis

• Alzheimer’s disease

• Multiple sclerosis

Botulinum toxin blocks which step?

• ACh release

• ACh receptor binding

• Calcium reuptake

• ATP binding

Which enzyme degrades acetylcholine in NMJ?

• ATPase

• Acetylcholinesterase

• Myosinase

• Phosphorylase

Which of the following occurs during rigor mortis?

• ATP increases

• Muscles relax completely

• No crossbridge formation

• ATP is depleted