Muscle Tissue Quiz
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Questions and Answers

Which type of muscle tissue is primarily attached to bones and is under voluntary control?

  • Smooth muscle tissue
  • Epithelial muscle tissue
  • Skeletal muscle tissue (correct)
  • Cardiac muscle tissue

What is a key characteristic of cardiac muscle tissue?

  • Striated and voluntary
  • Non-striated and involuntary
  • Striated and involuntary (correct)
  • Cylindrical and voluntary

Which function is NOT associated with the muscular system?

  • Producing body movements
  • Providing nutrient reserves
  • Producing enzymes for digestion (correct)
  • Guarding body entrance and exit

What term is used to describe the long cylindrical cells found in skeletal muscle tissue?

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

What type of muscle tissue is found primarily in internal organs?

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

Which structure is NOT a component of skeletal muscle tissue?

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

How many nuclei are typically found in skeletal muscle fibers?

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

What is the role of the neuromuscular junction?

<p>To transmit signals from nerves to muscles (D)</p> Signup and view all the answers

What phase occurs first during a muscle twitch?

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

Which statement correctly describes incomplete tetanus?

<p>The muscle remains in a state of partial relaxation between stimuli (D)</p> Signup and view all the answers

What primarily influences the total strength of a muscle contraction?

<p>The size of the motor units activated (C)</p> Signup and view all the answers

Which type of skeletal muscle fiber is characterized by a high resistance to fatigue?

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

What is the consequence of muscle fibers using ATP faster than it can be produced?

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

Which of the following describes isometric muscle contraction?

<p>Tension rises while muscle length remains constant (D)</p> Signup and view all the answers

What is the primary feature of white muscle fibers?

<p>Fast contraction speed (A)</p> Signup and view all the answers

Which muscle unit configuration is likely to provide precise control of movement?

<p>Small motor units with few fibers (B)</p> Signup and view all the answers

What is a characteristic of concentric contraction?

<p>Muscle length decreases while tension rises (B)</p> Signup and view all the answers

What happens to muscle fibers during rigor mortis?

<p>Cross bridges remain intact due to lack of ATP (C)</p> Signup and view all the answers

What initiates the contraction of skeletal muscle?

<p>Action potential at the neuromuscular junction (D)</p> Signup and view all the answers

During muscle contraction, calcium ions bind to which protein to initiate the sliding filament process?

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

What is the correct sequence of events during muscle contraction?

<p>Calcium release, cross-bridge formation, power stroke (A)</p> Signup and view all the answers

What occurs during the recovery stroke of muscle contraction?

<p>ATP binds to the myosin head (D)</p> Signup and view all the answers

What role does acetylcholinesterase play in muscle contraction?

<p>Breaks down acetylcholine to limit contraction duration (D)</p> Signup and view all the answers

What is necessary for the continuation of the contraction cycle?

<p>High levels of calcium and availability of ATP (D)</p> Signup and view all the answers

Which process describes the interaction between thick and thin filaments during contraction?

<p>Thick and thin filaments slide past each other (A)</p> Signup and view all the answers

Which event occurs at the axon terminal of a motor neuron to initiate muscle contraction?

<p>Release of acetylcholine (C)</p> Signup and view all the answers

The power stroke in muscle contraction is characterized by which action?

<p>Myosin cross-bridges rotate toward the H zone (B)</p> Signup and view all the answers

What is the primary result of myosin hydrolyzing ATP during muscle contraction?

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

What triggers the muscle action potential (AP)?

<p>Binding of ACh to receptors in the motor end plate (C)</p> Signup and view all the answers

Which mechanism prevents further action potentials until more ACh is released?

<p>Destruction of ACh by acetylcholinesterase (B)</p> Signup and view all the answers

What is the effect of Ca2+ binding to troponin on the thin filament?

<p>It activates the dissolution of the troponin-tropomyosin complex (A)</p> Signup and view all the answers

During muscle contraction, what role does ATP play?

<p>It is required for myosin heads to bind, swivel, and release (B)</p> Signup and view all the answers

What occurs when Ca2+ release channels in the sarcoplasmic reticulum close?

<p>Ca2+ levels in the sarcoplasm drop as transport pumps activate (C)</p> Signup and view all the answers

How does the troponin-tropomyosin complex influence muscle contraction?

<p>It blocks the binding sites on actin until Ca2+ is present (C)</p> Signup and view all the answers

What initiates the release of calcium ions from the sarcoplasmic reticulum?

<p>Muscle AP traveling along the transverse tubule (C)</p> Signup and view all the answers

What happens to the muscle after the calcium levels in the sarcoplasm decrease?

<p>The muscle relaxes as troponin-tropomyosin complex returns to its original position (B)</p> Signup and view all the answers

What is the primary role of pacemaker cells in the heart?

<p>To send electrical signals for rhythmic contraction (D)</p> Signup and view all the answers

Which type of muscle tissue is characterized by being striated and under voluntary control?

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

What role does smooth muscle play in the body?

<p>Movement of food through the digestive tract (D)</p> Signup and view all the answers

Which component of skeletal muscle fibers stores calcium ions necessary for contraction?

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

What term describes the contractile units within skeletal muscle fibers?

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

What initiates muscle contraction at the neuromuscular junction?

<p>Binding of acetylcholine to receptors (C)</p> Signup and view all the answers

Which of the following best describes the function of tropomyosin in muscle fibers?

<p>To cover active sites on actin filaments (A)</p> Signup and view all the answers

What is the primary function of skeletal muscle tissue?

<p>To enable voluntary movements and maintain posture (B)</p> Signup and view all the answers

Which structure is responsible for transmitting action potentials along the muscle fiber?

<p>T-tubules (C)</p> Signup and view all the answers

Which of the following processes occurs during the contraction of skeletal muscle?

<p>Interaction between actin and myosin filaments (B)</p> Signup and view all the answers

What is the role of epimysium in skeletal muscles?

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

What type of muscle tissue is not striated?

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

Which component is crucial for generating cross-bridges during muscle contraction?

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

Flashcards

Skeletal muscle

The most abundant in the human body, attached to bones, striated, and voluntary.

Cardiac muscle

Forms the wall of the heart, striated, and involuntary.

Smooth muscle

Located in internal organs like the digestive system, non-striated (smooth), and involuntary.

Skeletal muscle fiber

The basic unit of skeletal muscle tissue, long and cylindrical, containing many nuclei and striations.

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Action potential

The process by which a muscle cell receives a signal from a nerve, leading to contraction.

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Neuromuscular junction

The specialized junction between a motor neuron and a muscle fiber.

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Muscle contraction

The process by which a muscle fiber contracts, involving the sliding of filaments within the muscle cell.

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Muscle relaxation

The process by which a muscle fiber relaxes, returning to its resting length.

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Motor Neuron Impulse

The electrical signal that travels down a motor neuron, triggering the release of acetylcholine (ACh) at the neuromuscular junction.

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Acetylcholine (ACh)

A chemical messenger released from motor neurons that binds to receptors on muscle fibers, initiating muscle contraction.

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Motor End Plate

A specialized region of the muscle fiber membrane where ACh receptors are located.

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Muscle Action Potential

The electrical signal that travels along the muscle fiber, triggering the release of calcium ions (Ca2+).

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Transverse Tubule (T-Tubule)

The network of tubules that carry the muscle action potential deep into the muscle fiber, allowing for rapid and efficient contraction.

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Sarcoplasmic Reticulum (SR)

The intracellular storage site for calcium ions (Ca2+).

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Troponin

The protein that binds to calcium ions (Ca2+), initiating a conformational change that exposes the myosin-binding sites on actin.

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Tension Production in Muscle Fibers

The force of a muscle contraction depends on the number of cross bridges formed between actin and myosin filaments.

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Muscle Twitch

A single contraction and relaxation of a muscle in response to a stimulus.

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Muscle Summation

The summation of multiple twitches before the muscle has a chance to fully relax.

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Tetanus (Muscle Contraction)

A state of sustained muscle contraction where relaxation phases are minimized, resulting in a smoother, powerful contraction.

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Motor Unit

A motor neuron and all the muscle fibers it innervates, working together as a functional unit.

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Motor Unit Recruitment

The phenomenon where increasing the number of motor units involved in a contraction increases the force generated.

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Muscle Fatigue

A state where muscle fibers cannot contract due to insufficient ATP, resulting in weakened contraction.

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Isometric Contraction

A type of muscle contraction where the muscle length remains constant while tension increases.

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Isotonic Contraction

A type of muscle contraction where the muscle tension remains constant, while the muscle length changes.

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Fast Muscle Fibers (Type II)

Muscle fibers that contract quickly but fatigue rapidly, often found in muscles involved in explosive movements.

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Pacemaker Cells

Specialized muscle cells in the upper part of the heart responsible for generating electrical signals that cause the heart to contract rhythmically, enabling blood circulation.

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Smooth Muscle Tissue

Muscle tissue found in internal organs like the stomach, intestines, and blood vessels. It's involuntary, meaning you can't consciously control it.

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Cardiac Muscle Tissue

Muscle tissue found in the heart. It's involuntary and responsible for pumping blood throughout the body.

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Skeletal Muscle Tissue

Muscle tissue attached to bones, responsible for movement, posture, and other functions. It's voluntary, allowing conscious control.

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What is the primary function of skeletal muscle tissue?

The primary function of skeletal muscle tissue is to create movement by contracting and relaxing.

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How do skeletal muscles contribute to posture?

Skeletal muscles help maintain posture by holding the body in a stable position.

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How do skeletal muscles support soft tissues?

Skeletal muscles provide support for soft tissues, helping to protect internal organs and maintain body structure.

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What is the role of skeletal muscles in guarding body openings?

Skeletal muscles guard openings in the body, like the mouth and anus, to control entry and exit of substances.

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How do skeletal muscles help regulate body temperature?

Skeletal muscles can generate heat through contractions, contributing to overall body temperature regulation.

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Epimysium

A tough connective tissue layer that surrounds an entire skeletal muscle.

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Perimysium

A connective tissue layer that sheaths bundles of muscle fibres within a skeletal muscle.

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Endomysium

A thin connective tissue layer that covers individual muscle fibers.

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Tendons

Fibrous cords that attach muscles to bones or other muscles.

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Sarcolemma

The cell membrane of a muscle fibre.

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Sarcoplasm

The cytoplasm of a muscle fibre, containing many structures involved in muscle contraction.

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Initiation of Muscle Contraction

The process of muscle contraction is initiated when a nerve impulse arrives at the axon terminal of a motor neuron, triggering the release of acetylcholine (ACh).

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Sliding Filament Theory

The sliding filament theory describes how muscle fibers contract. Thick and thin filaments within the sarcomere slide past each other, shortening the sarcomere and causing muscle contraction.

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Role of Calcium in Muscle Contraction

Calcium ions (Ca2+) are essential for muscle contraction. They bind to troponin, which then moves tropomyosin, exposing the active sites on actin. This allows the myosin heads to bind to actin and initiate the contraction cycle.

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Cross-Bridge Formation

The myosin head binds to the exposed active site on actin, forming a cross-bridge. This binding causes the myosin head to pivot, pulling the actin filament towards the center of the sarcomere.

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Role of ATP in Muscle Contraction

The energy for the power stroke comes from the hydrolysis of ATP. After the power stroke, a new ATP molecule binds to the myosin head, causing it to detach from the actin.

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Role of Motor Neurons

Motor neurons transmit signals from the central nervous system to muscle fibers, triggering muscle contraction.

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Sarcomere

Sarcomeres are the basic functional units of muscle fibers. They are composed of thin (actin) and thick (myosin) filaments, organized in repeating units.

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Sarcoplasmic Reticulum

The sarcoplasmic reticulum is a network of membranes within muscle fibers. It stores and releases calcium ions, which are essential for muscle contraction.

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Study Notes

Musculoskeletal System (Part 2)

  • Learning Outcomes: At the end of the lessons, students will be able to list the types of muscles present in the human body; list basic characteristics of each muscle type; understand the mechanism of action potential; identify components of the neuromuscular junction and associated events; and understand the mechanism of muscle tissue contraction and relaxation.

Functions of Muscular System

  • Producing body movements
  • Stabilizing body positions
  • Moving substances within the body
  • Producing heat
  • Supporting soft tissues
  • Guarding body entrances and exits
  • Providing nutrient reserves

Types of Muscle Tissues

  • Skeletal muscle tissue
  • Cardiac muscle tissue
  • Smooth muscle tissue

3 Types of Muscle Tissue

  • Skeletal Muscle Tissue: Primarily attached to bones, it is striated and voluntary.
  • Cardiac Muscle Tissue: Forms the wall of the heart, it is striated and involuntary.
  • Smooth Muscle Tissue: Located primarily in internal organs, it is non-striated (smooth) and involuntary.

Skeletal Muscle Tissue

  • The most abundant tissue in the human body.
  • Under voluntary control.
  • Contains skeletal muscle cells, connective tissues, blood vessels, and nerves.
  • Each skeletal muscle cell is called a skeletal muscle fiber.
  • Each skeletal muscle fiber is a long cylindrical cell, containing many nuclei and striated (alternating light and dark bands).
  • Skeletal muscle fibers bind together with connective tissue, nerves, and blood vessels to form bundles.
  • These bundles bind together to form muscles.

Cardiac Muscle Tissue

  • Only found in the heart.
  • Cardiac muscle tissue is made of cardiac muscle cells known as cardiocytes.
  • It is striated.
  • Usually contain centrally located single nuclei.
  • Not under voluntary control.
  • A bundle of specialized muscle cells called pacemaker cells in the upper part of the heart sends electrical signals through the cardiac muscle tissue, causing the heart to rhythmically contract and pump blood throughout the body.

Smooth Muscle Tissue

  • Found in many internal organs (abdomen and intestines) and in blood vessel walls.
  • Spindle-shaped with a single nucleus.
  • Not striated.
  • Not under voluntary control.
  • The contractions in the smooth muscles move food through the digestive tract, control blood flow through the circulatory system, and increase the pupil size in bright light.

Skeletal Muscle Organization of Connective Tissues

  • Epimysium surrounds the muscle.
  • Perimysium sheathes bundles of muscle fibers.
  • Epimysium and perimysium contain blood vessels and nerves.
  • Endomysium covers individual muscle fibers.
  • Tendons attach muscle to bone or muscle.

Skeletal Muscle Fibers

  • Sarcolemma (cell membrane)
  • Sarcoplasm (muscle cell cytoplasm)
  • Sarcoplasmic Reticulum (modified ER) → high concentration of Ca2+
  • T-tubules and myofibrils aid in contraction
  • Sarcomeres – regular arrangement of myofibrils

Muscle Fiber

  • Thin filaments:
    • Actin
    • Tropomyosin - Covers active sites on actin
    • Troponin - Binds to G-actin and holds tropomyosin in place (site for Ca2+ attachment).
  • Thick filaments:
    • Bundles of myosin fibers around titan core
    • Myosin molecules have an elongate tail and a globular head
    • Heads form cross-bridges during contraction
    • Interactions between actin and myosin prevented by tropomyosin during rest.

The Contraction of Skeletal Muscle

  • Begins with excitation at the neuromuscular junction.
  • Action potential at the post-synaptic membrane
  • Calcium release from the sarcoplasmic reticulum
  • Thick/thin filament interaction
  • Muscle fiber contraction

Sliding Filament Theory

  • Thick and thin filaments slide past each other during contraction.
  • Cyclic process beginning with calcium release from the sarcoplasmic reticulum.
  • Calcium binds to troponin.
  • Troponin moves.
  • Myosin head forms a cross-bridge and bends towards the H zone.
  • ATP allows release of cross-bridge.

Muscle Contraction

  • Action potential along T-tubules causes release of calcium from cisternae of Sarcoplasmic Reticulum.
  • Exposure of attachment sites.
  • Cross-bridge formation.
  • Power stroke.
  • ATP binds to myosin head.
  • Cross-bridge release.
  • Recovery stroke.

Relaxation

  • Acetylcholinesterase breaks down ACh.
  • Limits the duration of contraction

Tension Production

  • Amount of tension depends on the number of cross-bridges formed.
  • Skeletal muscle contracts most forcefully over a narrow range of resting lengths
  • Twitch: contraction and relaxation of a muscle in response to a stimulus.
    • 3 phases: lag, contraction, and relaxation.
    • Repeated stimulation occurs after a relaxation phase.

Summation

  • Repeated stimulation before the relaxation phase has been completed .
  • Wave summation = one twitch added to another.
  • Incomplete tetanus = muscle never relaxes completely.
  • Complete tetanus = relaxation phase is totally eliminated.

Motor Units and Recruitment

  • Consist of a motor neuron and the muscle fibers it stimulates.
  • Axon of motor neuron branches out forming neuromuscular junctions.
  • A motor neuron makes contact with about 150 muscle fibers.
  • Control of precise movements consists of many small motor units.

Fatigue

  • Muscle fibers use ATP faster than they produce it.
  • Resulting in weaker contraction.
  • Binding of new ATP with the head of myosin is necessary to break down the cross bridge.
    • Examples: Muscle cramps and rigor mortis (muscle stiffness after death).

Types of Muscle Contractions

  • Isometric (equal distance): Tension rises, length of muscle remains constant.
  • Isotonic (equal tensions): Tension rises, length of muscle changes.
    • Resistance and speed of contraction are inversely related.
    • Return to resting length due to elastic components, opposing muscle groups, and gravity.
    • Concentric and eccentric contractions

Muscle Performance

  • Fast fibers (type II myosin): large diameter, densely packed myofibrils large glycogen reserves, relatively few mitochondria, produce rapid, powerful contractions of short duration, fatigue quickly, white muscle.
  • Slow fibers (type I myosin): half the diameter of fast fibers, take three times as long to contract, abundant mitochondria, extensive capillary supply, high concentrations of myoglobin, contract for long periods of time, greater resistance to fatigue, red and dark muscle.

Muscle Performance and Fiber Distribution

  • Pale muscles (dominated by fast fibers) are called white muscles.
  • Dark muscles (dominated by slow fibers and myoglobin) are called red muscles.
  • Training can lead to hypertrophy (enlargement of muscle fiber) of stimulated muscles.

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Musculoskeletal System Part 2 PDF

Description

Test your knowledge on different types of muscle tissues, their characteristics, and functions. This quiz covers skeletal, cardiac, and smooth muscle tissues along with key anatomical features and physiological roles. Perfect for students studying anatomy and physiology.

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