Smooth and Cardiac Muscle
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Questions and Answers

What type of smooth muscle contracts independently, with each muscle fiber contracting on its own?

  • Syncytial smooth muscle
  • Single-unit smooth muscle
  • Visceral smooth muscle
  • Multi-unit smooth muscle (correct)

    • Which type of smooth muscle responds to neural, hormonal, and stretch stimuli?

  • Single-unit smooth muscle (correct)
  • Visceral smooth muscle
  • Unitary smooth muscle
  • Syncytial smooth muscle

    • Where is single-unit smooth muscle commonly found in the body?

  • Heart
  • Brain
  • Skeletal muscles
  • Gastrointestinal tract (correct)

    • Which of the following is a characteristic of multi-unit smooth muscle?

    <p>Each muscle fiber contracts independently (A)</p> Signup and view all the answers

    What is one of the functions of smooth muscle in the body?

    <p>Regulation of blood flow (D)</p> Signup and view all the answers

    Which type of smooth muscle has fibers that are connected by many gap junctions?

    <p>Single-unit smooth muscle (B)</p> Signup and view all the answers

    What is a distinguishing feature of fusiform smooth muscle?

    <p>Does not contain sarcomeres (D)</p> Signup and view all the answers

    What neurotransmitter is associated with the function of single-unit smooth muscles?

    <p>Acetylcholine (C)</p> Signup and view all the answers

    What distinguishes the smooth muscle of each organ?

    <p>Organization into bundles or sheets (A)</p> Signup and view all the answers

    Which types of stimuli can the smooth muscle respond to?

    <p>Local factors such as O2 levels (C)</p> Signup and view all the answers

    How does the physical structure of smooth muscle vary in different organs?

    <p>Adjusts to the specific organs it is in (C)</p> Signup and view all the answers

    What type of nervous system provides signals to the smooth muscle?

    <p>Sympathetic and Parasympathetic nervous system (C)</p> Signup and view all the answers

    What enables coordinated contractions in smooth muscle?

    <p>Organization into bundles or sheets (D)</p> Signup and view all the answers

    Which factors can stimulate smooth muscle contraction?

    <p>Local factors like O2, CO2, and H2 (D)</p> Signup and view all the answers

    What role do intercalated disks play in cardiac muscle function?

    <p>Facilitate coordinated contractions (B)</p> Signup and view all the answers

    How does smooth muscle's response differ from cardiac muscle's response?

    <p>'Smooth muscle responds to local factors, while cardiac muscle does not' (A)</p> Signup and view all the answers

    What type of muscle contracts involuntarily without conscious control?

    <p>Smooth muscle (A)</p> Signup and view all the answers

    Where is smooth muscle commonly found in the body?

    <p>In the walls of blood vessels (A)</p> Signup and view all the answers

    Which type of muscle exhibits slower contraction and relaxation times compared to skeletal muscle?

    <p>Smooth muscle (D)</p> Signup and view all the answers

    What type of cells make up the myocardium in the heart?

    <p>Cardiomyocytes (B)</p> Signup and view all the answers

    What is the primary function of smooth muscle in the body?

    <p>Regulating blood pressure (C)</p> Signup and view all the answers

    What is the purpose of the heart in the cardiovascular system?

    <p>Pumping blood to facilitate exchange of substances between cells and environment (B)</p> Signup and view all the answers

    Which type of muscle tissue is specifically found only in the heart?

    <p>Cardiac muscle tissue (C)</p> Signup and view all the answers

    What is the function of the myocardium?

    <p>To contract and pump blood throughout the body (D)</p> Signup and view all the answers

    What specialized cell structure is responsible for cell-to-cell adhesion in cardiac muscle?

    <p>Desmosomes (A)</p> Signup and view all the answers

    What type of muscle is cardiac muscle?

    <p>Involuntary muscle (C)</p> Signup and view all the answers

    What allows cell-to-cell conduction of electrical currents in cardiac muscle?

    <p>Gap junctions (C)</p> Signup and view all the answers

    Which type of ions enter the cardiac myocytes through long-lasting Calcium channels during the action potential?

    <p>$Ca^{2+}$ ions (A)</p> Signup and view all the answers

    What provides mechanical strength and stability in tissues subjected to mechanical forces?

    <p>Desmosomes (A)</p> Signup and view all the answers

    What is the function of intercalated discs in cardiac muscle cells?

    <p>To connect adjacent cells electrically (D)</p> Signup and view all the answers

    Which structure in cardiac muscle serves as low-resistance pathways between cells?

    <p>$Gap$ junctions (B)</p> Signup and view all the answers

    What type of conduction occurs in cardiac muscle?

    <p>$Ionic$ conduction (B)</p> Signup and view all the answers

    What is the main difference between the arrangement of actin and myosin filaments in smooth muscle compared to striated muscle?

    <p>Smooth muscle has myosin filaments inserted among the actin filaments, while striated muscle has actin and myosin filaments arranged in a regular pattern (D)</p> Signup and view all the answers

    What is unique about the arrangement of the myosin cross-bridges in smooth muscle?

    <p>The myosin cross-bridges are arranged in a bipolar fashion, with some bending in one direction and others bending in the opposite direction (B)</p> Signup and view all the answers

    What is the maximum contraction capability of smooth muscle compared to skeletal muscle?

    <p>Smooth muscle can contract up to 80% of their length, while skeletal muscle can contract up to 30% (A)</p> Signup and view all the answers

    What is the main source of calcium ions for contraction in smooth muscle?

    <p>Calcium ions from the extracellular fluid are the main source for smooth muscle contraction (B)</p> Signup and view all the answers

    What is the energy requirement for maintaining a tonic contraction in smooth muscle compared to skeletal muscle?

    <p>Smooth muscle requires 1/10 to 1/300 of the energy necessary to maintain a tonic contraction compared to skeletal muscle (B)</p> Signup and view all the answers

    What is the main advantage of the side-polar arrangement of myosin cross-bridges in smooth muscle?

    <p>It allows smooth muscle to contract over a wider range of lengths (D)</p> Signup and view all the answers

    What is the primary function of the dense bodies in smooth muscle?

    <p>The dense bodies serve as attachment sites for the actin filaments, similar to the Z-discs in striated muscle (B)</p> Signup and view all the answers

    What is the primary advantage of the low frequency of cross-bridge cycles in smooth muscle?

    <p>It allows smooth muscle to maintain a tonic contraction with less energy expenditure (C)</p> Signup and view all the answers

    What is the primary role of caveolae in smooth muscle cells?

    <p>They make contact with the surface of the sarcoplasmic reticulum (SR) and are believed to excite calcium release from the SR. (A)</p> Signup and view all the answers

    What is the primary advantage of the low frequency of cross-bridge cycles in smooth muscle?

    <p>It allows for more efficient energy utilization during sustained contractions. (B)</p> Signup and view all the answers

    What is the main difference between the arrangement of actin and myosin filaments in smooth muscle compared to striated muscle?

    <p>Smooth muscle has a side-polar arrangement of myosin cross-bridges, unlike the bipolar arrangement in striated muscle. (B)</p> Signup and view all the answers

    What is the main source of calcium ions for contraction in smooth muscle?

    <p>Release of calcium from the sarcoplasmic reticulum (SR). (D)</p> Signup and view all the answers

    Which type of smooth muscle has fibers that are connected by many gap junctions?

    <p>Single-unit smooth muscle. (C)</p> Signup and view all the answers

    What is the primary function of the dense bodies in smooth muscle cells?

    <p>They serve as anchoring points for actin filaments. (D)</p> Signup and view all the answers

    What is the main advantage of the side-polar arrangement of myosin cross-bridges in smooth muscle?

    <p>It allows for more efficient energy utilization during sustained contractions. (C)</p> Signup and view all the answers

    What is the primary role of calmodulin in the smooth muscle contraction process?

    <p>Calmodulin activates the enzyme myosin light chain kinase (MLCK), which then phosphorylates myosin. (B)</p> Signup and view all the answers

    What is the primary difference in the mode of contraction between cardiac muscle and skeletal muscle?

    <p>Cardiac muscle contraction is involuntary (D)</p> Signup and view all the answers

    Which specialized cells are responsible for generating the cardiac action potential?

    <p>Pacemaker cells (D)</p> Signup and view all the answers

    What feature of cardiac muscle allows it to function as a single unit?

    <p>Intercalated disks connecting fibers (C)</p> Signup and view all the answers

    How does the development of cardiac muscle fibers differ from skeletal muscle fibers?

    <p>Cardiac myocytes fuse into multinucleated fibers (B)</p> Signup and view all the answers

    What differentiates the initiation of the cardiac action potential from nervous activity?

    <p>Pacemaker cells generate the action potential (D)</p> Signup and view all the answers

    Which structural feature contributes to the synchronized contractions in cardiac muscle?

    <p>Intercalated disks connecting myocytes (C)</p> Signup and view all the answers

    Why does cardiac muscle contract involuntarily?

    <p>Controlled via the autonomic nervous system (D)</p> Signup and view all the answers

    What characteristic feature distinguishes cardiac muscle fibers from skeletal muscle fibers?

    <p>Bifurcation and branching during cardiac fiber development (A)</p> Signup and view all the answers

    Which type of smooth muscle is characterized by muscle fibers that are connected via gap junctions, allowing them to contract together as a single unit?

    <p>Single-unit smooth muscle (C)</p> Signup and view all the answers

    In which organs of the body is single-unit smooth muscle commonly found?

    <p>Gastrointestinal tract, bile ducts, ureters, and uterus (B)</p> Signup and view all the answers

    What is the primary function of multi-unit smooth muscle?

    <p>Finer control and independent contractions (B)</p> Signup and view all the answers

    Which of the following is a distinguishing feature of fusiform smooth muscle cells?

    <p>They have a central, single nucleus (D)</p> Signup and view all the answers

    What is the primary advantage of the side-polar arrangement of myosin cross-bridges in smooth muscle?

    <p>It reduces the energy required for maintaining tonic contractions (B)</p> Signup and view all the answers

    Which of the following neurotransmitters is associated with the function of single-unit smooth muscle?

    <p>Acetylcholine (C)</p> Signup and view all the answers

    What is the primary source of calcium ions for contraction in smooth muscle?

    <p>Both extracellular fluid and intracellular stores (D)</p> Signup and view all the answers

    Which type of nervous system provides signals to the smooth muscle?

    <p>Autonomic nervous system (C)</p> Signup and view all the answers

    What is the primary advantage of the low frequency of cross-bridge cycles in smooth muscle?

    <p>It enables smooth muscle to maintain tonic contractions for extended periods with low energy expenditure. (D)</p> Signup and view all the answers

    Which of the following statements about the arrangement of myosin filaments in smooth muscle is correct?

    <p>Myosin filaments have side-polar cross-bridges that allow them to pull actin filaments in opposite directions simultaneously. (D)</p> Signup and view all the answers

    What is the primary source of calcium ions for contraction in smooth muscle?

    <p>The extracellular fluid (C)</p> Signup and view all the answers

    What is the maximum contraction capability of smooth muscle compared to skeletal muscle?

    <p>Smooth muscle can contract up to 80% of its length, while skeletal muscle can contract up to 30%. (B)</p> Signup and view all the answers

    What is the function of the dense bodies in smooth muscle?

    <p>They serve as attachment points for actin filaments, similar to Z-discs in skeletal muscle. (D)</p> Signup and view all the answers

    How does the energy requirement for maintaining a tonic contraction in smooth muscle compare to that of skeletal muscle?

    <p>Smooth muscle requires 1/10 to 1/300 of the energy necessary for skeletal muscle. (D)</p> Signup and view all the answers

    Which of the following statements about the sarcoplasmic reticulum in smooth muscle is correct?

    <p>The sarcoplasmic reticulum is slightly developed and is not the major source of calcium ions for contraction. (A)</p> Signup and view all the answers

    What is the primary function of smooth muscle in the body?

    <p>To control the movement of substances within the body and regulate the diameter of various passages. (D)</p> Signup and view all the answers

    What is the primary function of intercalated discs in cardiac muscle?

    <p>To allow cell-to-cell conduction of electrical signals (B)</p> Signup and view all the answers

    What is the role of desmosomes in cardiac muscle?

    <p>They provide cell-to-cell adhesion and mechanical strength (D)</p> Signup and view all the answers

    How does calcium ion entry during contraction differ in cardiac muscle compared to skeletal muscle?

    <p>Calcium ions enter through both the sarcoplasmic reticulum and long-lasting calcium channels (D)</p> Signup and view all the answers

    What is a key structural difference between cardiac muscle cells and skeletal muscle cells?

    <p>Cardiac muscle cells are connected by intercalated discs, while skeletal muscle cells lack such connections (C)</p> Signup and view all the answers

    What is the primary function of gap junctions in cardiac muscle?

    <p>To allow cell-to-cell conduction of electrical signals (C)</p> Signup and view all the answers

    Which of the following statements about cardiac muscle is correct?

    <p>Cardiac muscle contraction is controlled by the autonomic nervous system (C)</p> Signup and view all the answers

    What is a key difference between smooth muscle and cardiac muscle in terms of contraction regulation?

    <p>Smooth muscle contraction is regulated by both neural and hormonal factors, while cardiac muscle contraction is primarily regulated by neural factors (C)</p> Signup and view all the answers

    Which type of muscle tissue exhibits a slower contraction and relaxation time compared to skeletal muscle?

    <p>Smooth muscle (C)</p> Signup and view all the answers

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