Muscle Types and Characteristics
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Questions and Answers

What is a key structural characteristic of cardiomyocytes?

  • Multinucleate cells
  • Voluntary control
  • Centralized single nucleus (correct)
  • Striated myofibrils

Which of the following statements about skeletal muscles is true?

  • They can tire quickly. (correct)
  • Their fibers are not bundled by connective tissue.
  • They have a single nucleus per cell.
  • They are involuntary muscles.

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

  • Facilitate direct chemical communication (correct)
  • Prevent cell division
  • Increase mitochondrial density
  • Provide structural strength only

Which characteristic is NOT associated with smooth muscle cells?

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

What is the significance of gap junctions in cardiac muscle tissue?

<p>They allow direct diffusion of ions and small molecules. (D)</p> Signup and view all the answers

Which muscle type requires conscious control for its movement?

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

What allows skeletal muscles to develop great force?

<p>Dense packing of fibers by connective tissue (D)</p> Signup and view all the answers

Which protein is abundant in cardiomyocytes to store oxygen?

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

What is the primary function of muscle tissue?

<p>Production of force and motion (C)</p> Signup and view all the answers

Which muscle type is characterized by involuntary contractions?

<p>Both B and C (A)</p> Signup and view all the answers

What describes the structure of skeletal muscle tissue?

<p>Striated fibers that are multinucleated (D)</p> Signup and view all the answers

What is a key characteristic of cardiac muscle tissue?

<p>It contains intercalated discs (C)</p> Signup and view all the answers

Which process is NOT a function attributed to muscle tissue?

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

What is the primary function of desmosomes in cell structure?

<p>To stabilize the position of adjacent cells. (C)</p> Signup and view all the answers

What characterizes the I band in a sarcomere?

<p>It is a region with no thick filaments. (A)</p> Signup and view all the answers

Which protein is responsible for elastic properties in the sarcomere?

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

What is the primary fuel source for fast twitch (white) muscle fibers?

<p>Carbohydrates. (D)</p> Signup and view all the answers

Which statement best describes the dynamics of contractility in slow twitch muscle fibers?

<p>They are characterized by slow contractions with little fatigue. (D)</p> Signup and view all the answers

What structure in a sarcomere connects thick filaments and is located at the center?

<p>M line. (C)</p> Signup and view all the answers

How does the density of capillaries differ between slow twitch and fast twitch muscle fibers?

<p>Slow twitch fibers have high capillary density. (D)</p> Signup and view all the answers

What is the average resting length of a sarcomere?

<p>$2.0 - 2.2 , ext{µm}$ (A)</p> Signup and view all the answers

What does the H zone contain in a sarcomere?

<p>Thick filaments with no thin filaments. (B)</p> Signup and view all the answers

Which muscle type is primarily associated with aerobic energy release?

<p>Slow twitch muscle. (B)</p> Signup and view all the answers

Flashcards

Muscle

Specialized tissue composed of cells rich in protein filaments (actin and myosin) that slide past each other, enabling contraction.

Syncytium

A multinucleated cell formed by the fusion of multiple cells. It allows for coordinated contraction.

Skeletal Muscle

Muscle tissue responsible for voluntary movements, attached to bones.

Cardiac Muscle

Muscle tissue found in the heart, responsible for involuntary pumping action.

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Smooth Muscle

Muscle tissue found in the walls of internal organs, responsible for involuntary movements.

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Desmosomes

Structures that connect the plasma membrane of adjacent cells, aiding in cell-to-cell adhesion. They consist of a dense plaque formed by intermediate filaments composed of keratin or desmin.

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Sarcomere

The repeating functional unit of a myofibril or cardiomyocyte, responsible for muscle contraction. Each sarcomere is about 2-2.2 µm long and comprises several distinct regions.

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A band

The darker band in a sarcomere, spanning the entire length of the thick (myosin) filaments, where both thick and thin filaments overlap.

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Structural Syncytium

A type of syncytium where cells are physically connected, allowing for direct electrical transmission.

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Functional Syncytium

A type of syncytium where cells are not physically connected but still coordinate activity.

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Intercalated Discs

The cells in a structural syncytium are physically connected through specialized structures called intercalated discs

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Gap Junctions

Specialized junctions within intercalated discs that allow for direct electrical communication between cardiac muscle cells.

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Cardiomyocyte

A type of muscle cell found in the heart, responsible for heart contractions.

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Myoglobin

A specialized protein found in cardiomyocytes that stores oxygen for energy production during muscle contraction.

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Smooth Muscle Cell

A specific type of muscle cell found in various organs, responsible for controlling involuntary actions.

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Study Notes

Muscle Types and Characteristics

  • Muscles are soft tissues with cells rich in actin and myosin filaments, causing contraction
  • Muscles produce force and motion
  • Main functions include maintaining/changing posture, locomotion, and movement of internal organs (e.g., heart, digestion, breathing, blood vessel constriction/dilation)

Structural and Functional Differences of Muscle Types

  • Skeletal muscle:

    • Attached to bones by tendons
    • Multinucleated (myofibres)
    • Striated myofibrils arranged in myofibers
    • Voluntary (conscious control)
    • Develops great force, but fatigues quickly

  • Cardiac muscle:

    • Single, centrally located nucleus
    • Branching structure
    • Rich in mitochondria and myoglobin
    • Cells connected by intercalated discs via gap junctions for electrical coupling
    • Involuntary (automatic contractions)

  • Smooth muscle:

    • Interconnected cells with specialized membranes and gap junctions for coordinated electrical activity
    • Involuntary
    • Found in internal organs (digestive system, etc.)

Syncytium

  • A syncytium is a multinucleated cell formed from multiple cells fusing.
  • Specialized membrane with gap junctions connect cells, allowing for electrical synchronization.
  • Skeletal Muscle is a structural syncytium
  • Cardiac Muscle is a functional syncytium
  • Smooth muscles are also functional syncytium

Sarcomere

  • Sarcomere: Repeating functional unit in myofibrils/cardiomyocytes
  • About 2-2.2 µm
  • Includes:
    • A band (dark band): Entire length of thick filament
    • I band (light band): Z disks to ends of thick filaments (no thick filaments)
    • Z disk: protein filamentous network, attaches to actin myofilaments
    • M line: protein to which thick filaments attach
    • H zone: thick filaments only (no thin)

Muscle Contraction

  • Thick filaments (myosin) and thin filaments (actin) slide past each other using energy
  • Actomyosin complexes drive this sliding mechanism

Types of Skeletal Muscle Fibers

  • Red muscle: High mitochondrial content, capillaries, and myoglobin
    • Aerobic, (oxidative phosphorylation)
    • Slow twitch, lasts long with little fatigue
    • Little force
  • Mixed muscle: Medium mitochondrial content
    • Intermediate properties
  • White muscle: Low mitochondrial content
    • Anaerobic (glycolysis)
    • Fast twitch, develops force quickly but fatigues quickly
    • High force

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Description

Explore the fundamental characteristics of skeletal, cardiac, and smooth muscles. Understand their structure, function, and the differences that define each muscle type. Test your knowledge on how muscles contribute to various bodily movements and functionalities.

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