Biology Chapter 9: Smooth Muscle Structure and Contraction
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Questions and Answers

What is the primary mechanism by which smooth muscle cells contract?

  • By a sliding-filament mechanism (correct)
  • Through the use of tropomyosin
  • Through the release of calcium ions from the mitochondria
  • Via the binding of actin to troponin

    • What is the effect of phosphorylation of smooth muscle myosin?

  • It increases the rate of ATP splitting
  • It allows myosin to bind to actin and undergo cross-bridge cycling (correct)
  • It inhibits the binding of Ca2+ by calmodulin
  • It reduces the tension produced per unit cross-sectional area

    • What is the role of the sarcoplasmic reticulum in smooth muscle contraction?

  • It is involved in the regulation of smooth muscle relaxation
  • It is the primary source of ATP for smooth muscle contraction
  • It is responsible for the release of calcium ions into the cytosol (correct)
  • It is the site of smooth muscle myosin phosphorylation

    • What happens to the tension produced by smooth muscle when cytosolic calcium ions are increased?

    <p>It increases due to the increased binding of myosin to actin</p> Signup and view all the answers

    What is the characteristic of smooth muscle myosin that differs from striated muscle myosin?

    <p>It has a lower rate of ATP splitting</p> Signup and view all the answers

    What is the role of calmodulin in smooth muscle contraction?

    <p>It binds to Ca2+ and activates myosin light-chain-kinase</p> Signup and view all the answers

    What type of channels are responsible for the influx of calcium ions during the rising phase of the smooth muscle action potential?

    <p>voltage-gated Ca2+ channels</p> Signup and view all the answers

    What is the term for the spontaneous, periodic depolarizations of the membrane potential seen in some smooth muscle pacemaker cells?

    <p>Slow waves</p> Signup and view all the answers

    What is the characteristic of smooth muscle cells in terms of their response to neurotransmitters?

    <p>They may be influenced by neurotransmitters from more than one neuron</p> Signup and view all the answers

    What is the main difference between smooth muscle cells and cardiac muscle cells in terms of their structure?

    <p>Smooth muscle cells have a specialized end-plate region</p> Signup and view all the answers

    What is the term for the type of smooth muscle that can generate action potentials in the absence of any external input?

    <p>Pacemaker smooth muscle</p> Signup and view all the answers

    How do smooth muscle cells differ from skeletal muscle cells in terms of their response to neurotransmitters?

    <p>Smooth muscle cells respond to neurotransmitters, whereas skeletal muscle cells do not</p> Signup and view all the answers

    What is a key difference between cardiac muscle excitation-contraction coupling and skeletal muscle excitation-contraction coupling?

    <p>L-type Ca2+ channels are involved in cardiac muscle but not skeletal muscle</p> Signup and view all the answers

    What is a characteristic shared by cardiac muscle and smooth muscle?

    <p>Arrangement in layers around hollow cavities</p> Signup and view all the answers

    What is a key similarity between cardiac muscle and skeletal muscle?

    <p>Striation pattern</p> Signup and view all the answers

    What is a feature of cardiac muscle contractions that is not seen in skeletal muscle?

    <p>The strength and frequency of contraction are modulated by autonomic neurotransmitters and hormones</p> Signup and view all the answers

    What can be said about the comparison of skeletal, smooth, and cardiac muscles?

    <p>Cardiac muscle shares characteristics with both skeletal and smooth muscles</p> Signup and view all the answers

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