Motor unit

The tutorial explores how muscles and nerves collaborate to enable movement, focusing on the motor unit, which includes a motor neuron and the skeletal muscle fibers it innervates. It covers the anatomy and function of motor neurons, the structure of skeletal muscles, and the role of sarcomeres in muscle contraction. The video also discusses actin accumulation myopathy, a disorder affecting muscle contraction. The tutorial concludes with a summary of the key points covered.

What is a motor unit composed of?

• A sensory neuron and all the cardiac muscle fibers it innervates

• A motor neuron and all the skeletal muscle fibers it innervates

• A sensory neuron and all the skeletal muscle fibers it innervates

• A motor neuron and all the cardiac muscle fibers it innervates

Where is the cell body of a motor neuron located?

• In the brainstem

• In the posterior root ganglion

• In the anterior horn of the spinal cord

• In the dorsal horn of the spinal cord

What is the function of the myelin sheath surrounding the axon?

• To connect the axon to the muscle fibers

• To provide nutrients to the axon

• To insulate the axon and speed up impulse transmission

• To slow down electrical impulses

What is the role of tendons in skeletal muscles?

• To connect muscles to other muscles

• To connect bones to bones

• To connect nerves to muscles

• To connect muscles to bones

Which connective tissue layer surrounds the entire muscle belly?

• Endomysium

• Fascia

• Epimysium

• Perimysium

What are the contractile units within a myofibril called?

• Myocytes

• Sarcomeres

• Myoblasts

• Fascicles

What is the main protein component of thick filaments in muscle fibers?

• Tropomyosin

• Myosin

• Troponin

• Actin

What happens to the I-band during muscle contraction?

• It remains the same

• It disappears

• It shortens

• It lengthens

What is actin accumulation myopathy?

• A disorder caused by a mutation in the gene that makes myosin

• A rare autosomal dominant disorder affecting actin production

• A common disorder affecting muscle contraction

• A genetic disorder that strengthens muscle fibers

What is the primary muscle affected in actin accumulation myopathy?

• Biceps brachii

• Quadriceps

• Triceps

• Diaphragm