muscle anatomy

The I band within a skeletal muscle fiber is indicated by ________.

• Label A

• Label B

• Label C

• Label D

What organelle wraps and surrounds the myofibril and stores calcium?

• sarcoplasmic reticulum

• cross bridge

• sarcomere

• sarcolemma

According to the sliding filament theory, how does muscle contraction occur?

• Both thick and thin filaments shorten as the muscle contracts.

• Myosin heads attach and detach from thin filaments, causing thin filaments to shorten.

• A bands bunch up and shorten as myosin heads attach to thin filaments.

• Myosin cross bridges pull thin filaments, causing them to slide.

The A band within a myofibril is indicated by ________.

• Label A

• Label B

• Label C

• Label D

The H zone is represented by ________.

• Label A

• Label B

• Label C

• Label D

The myofilament composed of actin is indicated by ________.

• Label A

• Label C

• Label D

• Label B

The epimysium is represented by ________.

• Label B

• Label D

• Label A

• Label C

The muscle fiber (cell) is indicated by ________.

• Label C

• Label B

• Label A

• Label D

What is released by axon terminals into the synaptic cleft to stimulate a muscle to contract?

• sodium ions

• acetylcholine

• actin

• myosin heads

Why are calcium ions necessary for skeletal muscle contraction?

• Calcium ions cause ATP binding to actin.

• Calcium ions release the inhibition on Z discs.

• Calcium ions trigger the binding of myosin heads to actin filaments.

• Calcium ions increase the speed of the action potential transmitted along the sarcolemma.