Muscle Physiology Quiz
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Questions and Answers

What is the resting membrane potential (RMP) of muscle cells?

  • -70
  • -100
  • -80
  • -90 (correct)

How does the resting membrane potential of muscle cells compare to that of nerve cells?

  • They are the same; both have an RMP of -90 mV. (correct)
  • They are different; muscle cells have a lower RMP.
  • They are different; nerve cells have a higher RMP.
  • Muscle cells have no defined RMP.

Which of the following best describes the Muscle Action Potential (AP)?

  • It is unrelated to resting membrane potential.
  • It initiates contraction when the membrane depolarizes. (correct)
  • It occurs only in smooth muscle cells.
  • It is a constant potential that does not change.

What value represents the resting membrane potential in muscle cells?

<p>Negative 90 mV (B)</p> Signup and view all the answers

Which statement about muscle RMP is true?

<p>It is the same as the RMP in nerves. (A)</p> Signup and view all the answers

What extends all the way across myofibrils in a sarcomere?

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

Which band contains only actin filaments within a sarcomere?

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

What structure is not part of a sarcomere?

<p>Sarcoplasmic reticulum (D)</p> Signup and view all the answers

Which of the following best describes the I band in the context of muscle structure?

<p>It consists of actin filaments only. (B)</p> Signup and view all the answers

What defines the boundaries of each sarcomere?

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

What is the main function of the myosin head in muscle contraction?

<p>Releasing energy from ATP (A), Binding to actin filaments (B)</p> Signup and view all the answers

Which protein is NOT part of the thin filament structure in muscle fibers?

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

What are the cross bridges formed during muscle contraction made of?

<p>Actin and myosin interactions (C)</p> Signup and view all the answers

What role does tropomyosin play in muscle contraction?

<p>It helps prevent actin from interacting with myosin when muscle is not contracted (C)</p> Signup and view all the answers

Which statement about thick myosin filaments is correct?

<p>They are composed of cross bridges and have an ATP site on the head. (A)</p> Signup and view all the answers

What does EM refer to in the context of sliding filament evidence?

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

Which of the following best describes the sliding filament theory?

<p>Muscle contraction involves the sliding of filaments past each other. (D)</p> Signup and view all the answers

What role do the filaments play in muscle contraction according to the general theory?

<p>They slide to facilitate movement. (D)</p> Signup and view all the answers

Which structure primarily contains the sliding filaments in muscle tissue?

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

What is the significance of the evidence provided by EM regarding sliding filaments?

<p>It confirms the physical structure of filaments during contraction. (A)</p> Signup and view all the answers

What does the term 'Class No. according to Calendar' refer to in an academic setting?

<p>An identifier for specific classes scheduled within the academic calendar (B)</p> Signup and view all the answers

In the context of a college setting, what does 'اسم الكلية' translate to?

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

When is the phrase 'حاضرة حسب التقويم' relevant?

<p>When referring to the attendance of classes according to the calendar (D)</p> Signup and view all the answers

How might the information presented affect a student's academic planning?

<p>It specifies class times and dates affecting scheduling (A)</p> Signup and view all the answers

Why is knowing the 'Class No.' important for students?

<p>It assists in locating specific courses and tracking academic progress (A)</p> Signup and view all the answers

What event occurs first when a new ATP molecule binds to the myosin head?

<p>Detachment of myosin from actin (B)</p> Signup and view all the answers

What happens to the myosin head after it detaches from actin?

<p>The myosin head swings back to its original position (B)</p> Signup and view all the answers

What role does ATP play in the myosin-actin interaction?

<p>It allows the cycle of muscle contraction to repeat (D)</p> Signup and view all the answers

What triggers the repeating cycle of muscle contraction?

<p>The binding of a new ATP to the myosin head (C)</p> Signup and view all the answers

What is the immediate consequence after ATP occupies the myosin head site?

<p>Myosin detaches from actin immediately (A)</p> Signup and view all the answers

Flashcards

Muscle Action Potential

The electrical signal that travels along muscle fibers, triggering muscle contraction.

Muscle Resting Membrane Potential (RMP)

The electrical charge difference across the muscle cell membrane when it is at rest, typically -90 millivolts (mV).

Muscle Action Potential vs. Nerve Action Potential

Both muscle and nerve action potentials are electrical signals, but they occur in different types of cells and have slightly different characteristics.

Why is muscle RMP important?

The muscle RMP is crucial for maintaining the readiness of the muscle to respond to stimuli and initiate contraction.

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How does the muscle RMP compare to nerve RMP?

Both muscle and nerve cells have a negative RMP, but the magnitude may differ slightly. In general, muscle RMP is slightly more negative than nerve RMP.

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EM Evidence

Electron microscopy (EM) provides visual evidence for the sliding filament theory of muscle contraction.

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Sliding Filaments

The sliding filament theory describes how muscle contraction occurs. Thin (actin) filaments slide past thick (myosin) filaments, shortening the sarcomere and causing muscle contraction.

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Sarcomere

The basic unit of muscle contraction. It is composed of overlapping actin and myosin filaments.

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Actin Filaments

Thin filaments in muscle fibers. They are composed of the protein actin, which provides binding sites for myosin.

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Myosin Filaments

Thick filaments in muscle fibers. They are composed of the protein myosin, which has heads that bind to actin and pull the filaments past each other.

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What are Z discs?

Z discs are lines that extend across myofibrils, marking the boundaries of each sarcomere.

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What are sarcomeres?

Sarcomeres are the functional units of a muscle fiber, the smallest unit that can contract.

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What is the I band?

The I band is a region within a sarcomere that contains only actin filaments, appearing lighter under a microscope.

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What is the A band?

The A band is a region within the sarcomere that contains both actin and myosin filaments, appearing darker under a microscope.

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What is the H zone?

The H zone is a region within the A band that contains only myosin filaments, appearing slightly lighter.

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Myosin Detachment

The release of myosin from actin, triggered by a new ATP molecule binding to the myosin head.

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Myosin Swing Back

Once detached from actin, the myosin head swings back to its original position, ready to bind to a new actin filament.

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Muscle Contraction Cycle

The continuous process of myosin binding to actin, pulling, detaching, and swinging back, resulting in muscle shortening.

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ATP's Role in Detachment

ATP binds to myosin, causing a conformational change that weakens the myosin-actin bond, leading to detachment.

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Actin Movement

During muscle contraction, actin filaments slide past myosin filaments, causing the sarcomere to shorten, but the filaments themselves do not change length.

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Sarcomere Structure: What's the I band?

The I band is a light area within a sarcomere containing only Actin filaments. It shrinks during muscle contraction.

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Sarcomere Structure: What's the A band?

The A band is a dark area within a sarcomere containing both Actin and Myosin filaments.

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Sarcomere Structure: What's the H zone?

The H zone is a lighter area within the A band that contains only Myosin filaments.

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What's the Sliding Filament Theory?

This theory explains muscle contraction: Actin filaments slide past Myosin filaments, shortening the sarcomere.

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Actin

A protein that forms thin filaments in muscle fibers. These filaments slide past thick filaments during muscle contraction.

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Troponin

A protein that binds to both actin and tropomyosin in muscle fibers. It plays a crucial role in regulating muscle contraction by allowing or blocking the interaction of actin and myosin.

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Tropomyosin

A protein that sits on top of actin filaments in muscle fibers. It helps regulate muscle contraction by blocking or exposing sites where myosin can bind to actin.

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Myosin Head

The globular head of the myosin protein in muscle fibers. It binds to actin filaments during muscle contraction and uses ATP energy to pull the filaments towards each other.

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Cross Bridges

Links formed between myosin heads and actin filaments during muscle contraction. These cross bridges act like tiny motors that generate the force needed for contraction.

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Study Notes

Skeletal Muscle Contraction

  • Learning Objectives: Students should understand the physiological anatomy of skeletal muscle, the mechanisms of skeletal muscle contraction and relaxation, and the sliding filament mechanism.

Muscle Action Potential (AP)

  • Resting Membrane Potential (RMP): -90 mV (same as in nerves).
  • Duration of AP: 1-5 ms (longer than nerve AP, which is usually about 1 ms).
  • Conduction Velocity: 3-5 m/s (slower than large nerves).

Muscle Structure

  • Muscle Fiber (Cell): Covered by a cell membrane called Sarcolemma.
  • Myofibrils: Each muscle cell contains hundreds to thousands of myofibrils.
  • Sarcomere: The contractile unit of muscle; the zone between two Z lines (discs) - 2 micrometers in length in resting state. Z discs extend across myofibrils. Inside each sarcomere are 3 bands:
    • I band (actin only)
    • H band (myosin only)
    • A band (actin & myosin)

Myofibril Structure

  • Actin Filaments (Thin): Part of the myofibril.
  • Myosin Filaments (Thick): Part of the myofibril.
    • Myosin filament has a head and a tail, cross bridges, and an ATP site at the head.

Sliding Filament Mechanism

  • During muscle contraction, actin and myosin filaments slide past each other, shortening the sarcomere length.
  • This is the process of muscle contraction.

EM Evidence for Sliding Filaments

  • Electron micrographs (EM images) show the sliding of actin and myosin filaments during muscle contraction.

Sarcoplasm, Sarcoplasmic Reticulum, and T-tubules

  • Sarcoplasm: Matrix inside muscle fiber where myofilaments are suspended.
  • Sarcoplasmic Reticulum: Endoplasmic reticulum inside the sarcoplasm, full of calcium (Ca).
  • T-tubules: Extend from one side of the muscle to the other.

Muscle Proteins

  • Thick Filament: Myosin
  • Thin Filament: Actin, Troponin, Tropomyosin

Molecular Mechanism of Muscle Contraction

  • Excitation-Contraction Coupling: The process linking muscle excitation (AP) to contraction (sliding filaments).

Events of Muscle Contraction

  • Acetylcholine release: From motor nerve.
  • Muscle AP spread: Into T tubules, releasing Ca from sarcoplasmic reticulum into cytoplasm.
  • Ca binds to troponin: Causes tropomyosin to move, exposing binding sites on actin.
  • Myosin heads bind: To actin, pulling actin filaments.
  • ATP used for Power stroke: Myosin heads bend, pulling actin, releasing ADP and inorganic phosphate (Pi), requiring ATP.
  • ATP binds to detaches: Myosin detaches from actin, requires a new ATP molecule. The cycle repeats.

Events of Relaxation

  • Ca pumped back: Into sarcoplasmic reticulum.
  • Tropomyosin covers actin: Ca detachment causes tropomyosin to cover actin-binding sites
  • Muscle relaxation: Myosin and actin detach, the muscle relaxes

ATP Need

  • ATP needed for: Power stroke, detachment of myosin from actin, and pumping calcium back into the sarcoplasmic reticulum.
  • Muscle relaxation is an active process: Because it requires ATP.

Calcium Need

  • Ca++ needed for: Exocytosis in nerves and muscle contraction.

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Physiology of Muscle Contraction PDF

Description

Test your knowledge on muscle physiology, focusing on resting membrane potential, action potentials, and the structure of sarcomeres. This quiz covers key concepts related to muscle cell membrane properties and structural components. Perfect for students in biology or health sciences.

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