Topic 8-9 Part 2 Muscular System

Myosin heads contain ___ and ___

• ADP and actin-binding sites
• ATP and myosin-binding sites
• ADP and myosin-binding sites
• ATP and actin-binding sites

At rest, tropomyosin:

• activates the myosin-binding sites on actin
• prevents the binding of ATP to myosin
• blocks the myosin-binding sites on actin
• binds to the myosin-binding sites on actin

During skeletal muscle excitation, ___ binds to troponin which allows for ___

• Ca2+,

  myosin to move out of the way

• K+,

  tropomyosin to move out of the way

• Ca2+,

  tropomyosin to move out of the way

• Na+,

  tropomyosin to move out of the way

Which neurotransmitter is essential for skeletal muscle contraction?

• norepinephrine
• serotonin
• dopamine
• acetylcholine

At the neuromuscular junction, ACh is released from the terminal bouton due to the opening of ___

• voltage-gated sodium channels

• ligand-gated potassium channels

• ligand-gated chloride channels

• voltage-gated calcium channels

During skeletal muscle action potentials, ___ receptors activate allowing for the activation of ___ receptors on the sarcoplasmic reticulum

• Dihydropyridine receptors, sodium channels

• Dihydropyridine receptors, ryanodine receptors

• GABA receptors, potassium channels
• muscarinic acetylcholine receptors, ryanodine receptors

Upon binding to calcium ions, the troponin-tropomyosin complex changes shape and:

• exposes active sites on actin

• binds to actin filaments
• releases calcium ions
• inhibits muscle contraction

What is required for myosin heads to detach from actin?

• ATP binding
• phosphorylation
• ADP binding
• calcium binding

What helps to remove ACh from the synaptic cleft?

• Acetylcholine
• Acetylcholinesterase inhibitor
• Acetylcholinesterase activator
• Acetylcholinesterase

What pumps Ca2+ back into the sarcoplasmic reticulum?

• ATPase
• Na+/K+ pump
• SERCA
• Golgi apparatus