Muscle and Contractile Proteins

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Questions and Answers

What factor affects a muscle's ability to generate force and contract by influencing the number of motor units stimulated?

  • Frequency of muscle stimulation (correct)
  • Type of myosin isoforms present in the muscle
  • Degree of stretch (Frank-Starling relationship)
  • Whether the muscle is allowed to shorten (Force-velocity relationship)

What clinical feature is associated with MyHC IIa mutations?

  • Atrophy near shoulders, back, hand, and thigh muscles (correct)
  • Improved muscle contractility
  • Joint stiffness
  • Excessive muscle growth

Which protein makes up approximately 10-15% of the total protein in the body?

  • Troponin
  • Titin
  • Actin
  • Myosin (correct)

In the context of muscle physiology, what does the 'Force-Velocity relationship' primarily refer to?

<p>Whether a muscle is allowed to shorten (D)</p> Signup and view all the answers

What disease is associated with mutations in embryonic MyHC (MYH3)?

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

What is the primary function of myosin V?

<p>Involved in melanosome transport and certain neurological functions (C)</p> Signup and view all the answers

What is the structure of muscle myosin II?

<p>A dimer with each heavy chain having a motor domain and a tail (D)</p> Signup and view all the answers

What is the role of the active site in the motor domain of myosin?

<p>Hydrolyzing ATP to provide energy for muscle contraction (C)</p> Signup and view all the answers

Which myosin type is involved in maintaining the organization of actin-filled stereocilia in the inner ear?

<p>Myosin VI and Myosin VII (B)</p> Signup and view all the answers

Which component of the myosin molecule is responsible for binding to actin filaments?

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

What is the primary function of myosin VI in muscle physiology?

<p>Maintains the organization of actin-filled stereocilia in the inner ear (D)</p> Signup and view all the answers

Which molecule blocks myosin binding sites on actin filaments?

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

In muscle physiology, what is the main role of myosin VII?

<p>Plays a role in smooth muscle regulation (C)</p> Signup and view all the answers

Which myosin type is responsible for binding to actin filaments in muscle contraction?

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

What is the effect of calcium binding to Troponin C in muscle physiology?

<p>Moves tropomyosin away from myosin binding sites (B)</p> Signup and view all the answers

What is the primary function of CapZ and tropomodulin in muscle sarcomeres?

<p>Cap the ends of actin filaments to maintain constant length (A)</p> Signup and view all the answers

Which protein complex is responsible for regulating the interaction between myosin and actin in skeletal muscle?

<p>Troponin-tropomyosin (A)</p> Signup and view all the answers

What is the primary role of troponin C in muscle contraction?

<p>Bind to calcium ions, causing a conformational change in tropomyosin (C)</p> Signup and view all the answers

Which protein is responsible for maintaining the position of thick filaments within muscle sarcomeres?

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

What is the primary function of tropomyosin in muscle contraction?

<p>Block or expose myosin-binding sites on actin filaments (B)</p> Signup and view all the answers

What is the primary difference between myosin V and myosin II?

<p>Myosin V has a high duty ratio, while myosin II has a low duty ratio. (C)</p> Signup and view all the answers

How do muscle sarcomeres contract in the context of myosin and actin filaments?

<p>Myosin thick filaments and actin thin filaments slide past each other. (A)</p> Signup and view all the answers

What is the role of accessory proteins like CapZ and tropomodulin in muscle?

<p>CapZ and tropomodulin cap ends of actin to maintain filament length. (D)</p> Signup and view all the answers

What is the primary function of titin in muscle sarcomeres?

<p>Titin maintains the position of thick filaments within the sarcomere. (C)</p> Signup and view all the answers

How are myosin II molecules assembled in muscle?

<p>By association of hydrophobic regions in the tail. (A)</p> Signup and view all the answers

What term describes the phenomenon where a single stimulus is not strong enough to cause a muscle fiber to contract, but multiple stimuli in rapid succession result in a sustained contraction?

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

During the refractory period following a muscle twitch, what physiological phenomenon ensures that a second contraction cannot be elicited regardless of the stimulus strength?

<p>Recovery of calcium ions into the sarcoplasmic reticulum (B)</p> Signup and view all the answers

What is the term for the phenomenon where multiple stimuli are applied to a muscle in rapid succession before it has completely relaxed, leading to a stronger muscle contraction?

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

Which statement best describes the relationship between motor units and muscle twitch?

<p>Multiple motor units are recruited to generate stronger muscle contractions. (D)</p> Signup and view all the answers

How does the time interval between two stimuli affect the force generated by a muscle in a second contraction?

<p>A shorter interval leads to temporal summation and increased force in the second contraction. (A)</p> Signup and view all the answers

What factor influences a muscle's ability to generate force and contract by considering the number of motor units stimulated?

<p>Frequency of stimulation (A)</p> Signup and view all the answers

In the context of muscle physiology, what aspect is primarily affected by the 'Frank-Starling relationship'?

<p>Length-tension relationship (B)</p> Signup and view all the answers

Which factor can alter actin-myosin ATPase activity and lead to muscle disorders if mutations occur?

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

What phenomenon involves maintaining a nearly constant tension in the total muscle through asynchronous motor-unit activity?

<p>Motor unit summation (C)</p> Signup and view all the answers

How does the 'Force-Velocity curve' concept illustrate the relationship between shortening velocity and load in muscle physiology?

<p>By showing the trade-off between speed and force production (A)</p> Signup and view all the answers

Which of the following describes the relationship between muscle length and the force it can generate?

<p>The shorter the muscle, the greater the force it can generate. (A)</p> Signup and view all the answers

The Frank-Starling mechanism refers to the relationship between:

<p>End-diastolic volume and stroke volume (C)</p> Signup and view all the answers

Which type of muscle contraction occurs when the muscle generates force but does not change length?

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

How does the isotonic twitch response of a muscle fiber change when a greater load is applied?

<p>The twitch amplitude decreases and the contraction time increases. (D)</p> Signup and view all the answers

The Force-Velocity relationship in muscle physiology primarily describes the connection between:

<p>Muscle shortening velocity and the load it is moving against (C)</p> Signup and view all the answers

Which muscle disease is associated with mutations in the myosin heavy chain (MYH) gene?

<p>Distal arthrogryposis (D)</p> Signup and view all the answers

What is the primary function of myosin V in muscle physiology?

<p>Transporting melanosomes for pigmentation (D)</p> Signup and view all the answers

Which type of muscle myopathy is associated with mutations in the embryonic myosin heavy chain (MYH3) gene?

<p>Freeman-Sheldon Syndrome (D)</p> Signup and view all the answers

What is the primary effect of mutations in the MYH3 gene associated with Sheldon-Hall Syndrome?

<p>Contractures of the distal limbs (A)</p> Signup and view all the answers

Which muscle disease is associated with a point mutation in the myosin Va gene?

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

What is the primary function of muscle myosin II in cell division?

<p>Involved in cell division (A)</p> Signup and view all the answers

What is the function of myosin V?

<p>Involved in melanosome transport (A)</p> Signup and view all the answers

Which disease is associated with mutations in myosin Va and leads to hypopigmentation and neurological defects?

<p>Griscelli's Syndrome (B)</p> Signup and view all the answers

What is the primary role of non-muscle myosin VI and myosin VII?

<p>Maintaining organization of actin-filled stereocilia (D)</p> Signup and view all the answers

In muscle physiology, what does the dimeric structure of muscle myosin II consist of?

<p>Motor domain and tail (C)</p> Signup and view all the answers

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