Skeletal muscle physiology

What is the primary structural unit of skeletal muscle that contains overlapping actin and myosin filaments?

• Sarcomere

• Epimysium

• Perimysium

• Fascicle

In excitation-contraction coupling:

• The muscle action potential propagates along the sarcolemma and down the transverse tubules.

• Ca2+ released from the sarcoplasmic reticulum binds to tropomyosin.

• Troponin blocks binding of myosin heads to actin filaments.

• Relaxation occurs when Ca2+ is excreted from the muscle fibre.

Epimysium surrounds

• skeletal muscle fibers

• skeletal muscle fascicles

• skeletal muscles

• smooth muscle cells

Fascicles are

• groupings of collagen surrounding skeletal muscle fibers

• groupings of arteries supplying skeletal muscle fibers

• groupings of skeletal muscle fibers

• groupings of nerve fibers innervating skeletal muscle fibers

The sarcolemma is

• the plasma membrane of muscle cells

• the endoplasmic reticulum of muscle cells

• the contractile unit of muscle cells

• cytoplasm of muscle cells

The A-band

• is the band where myosin filaments are anchored

• contains both actin and myosin

• contains myosin, but not actin

• contains actin, but not myosin

The two principal contractile proteins in skeletal muscles are

• actin and troponin

• actin and tropomyosin

• actin and myosin

• myosin and tropomyosin

The trigger to initiate the contractile process in skeletal muscle is

• calcium binding to tropomyosin

• ATP binding to the myosin cross bridges

• calcium binding to troponin

• potassium binding to myosin

Which of the following statements best explains the sliding filament theory of muscle contraction?

• Actin filaments slide away from the Z-line during contraction.

• Myosin filaments slide towards the H-zone during relaxation.

• Actin and myosin filaments lengthen during muscle shortening.

• Myosin heads attach to actin filaments and pull them toward the M-line.

At the neuromuscular junction

• the muscle membrane possesses muscarinic receptors

• there is a one-to-one transmission of excitatory impulses from the motor neurone to the muscle fibres it innervates

• the motor nerve endings secrete noradrenaline

• the typical summed end plate potential (EPP) is usually 10 times the potential necessary to trigger an action potential