Muscular System Overview
45 Questions
3 Views

Choose a study mode

Play Quiz
Study Flashcards
Spaced Repetition
Chat to Lesson

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What percentage of total body weight do skeletal muscles typically make up in males?

About 40%.

Define contractility in relation to muscle properties.

Contractility is the ability of a muscle to shorten with force.

What is the capacity of a muscle to respond to a stimulus called?

Excitability.

Explain the importance of extensibility in muscle function.

<p>Extensibility allows muscles to stretch to their normal resting length and beyond to a limited degree.</p> Signup and view all the answers

What does the elasticity property of muscles indicate?

<p>Elasticity refers to the ability of muscle to recoil to its original resting length after being stretched.</p> Signup and view all the answers

What type of muscle is characterized as voluntary and can be consciously controlled?

<p>Skeletal muscle.</p> Signup and view all the answers

List one example of involuntary muscle action.

<p>Contraction of the stomach.</p> Signup and view all the answers

What are the primary functions served by muscle tissues?

<p>Muscle tissues serve functions such as movement, posture maintenance, and heat generation.</p> Signup and view all the answers

What causes the shortening of myofibrils during muscle contraction?

<p>The shortening of myofibrils is caused by the shortening of the sarcomeres as the distance between Z lines is reduced.</p> Signup and view all the answers

How do myosin cross bridges contribute to muscle contraction?

<p>Myosin cross bridges produce asynchronous power strokes that pull the thin filaments (actin) over the thick filaments (myosin).</p> Signup and view all the answers

What changes occur to the A and I bands during muscle contraction?

<p>The A bands remain the same length, while the adjacent I bands shorten as they are pulled closer together.</p> Signup and view all the answers

What is the role of the neuromuscular junction in muscle contraction?

<p>The neuromuscular junction transmits signals from motor neurons to muscle fibers, initiating muscle contraction.</p> Signup and view all the answers

How does the action potential propagate along the sarcolemma and into the muscle fiber?

<p>Action potentials travel over the sarcolemma and descend into the muscle via T tubules.</p> Signup and view all the answers

What effect does the release of acetylcholine (ACh) have at the neuromuscular junction?

<p>The release of ACh leads to large depolarizing end-plate potentials and generates action potentials in the muscle.</p> Signup and view all the answers

What is the relationship between T tubules and the sarcoplasmic reticulum (SR) during excitation-contraction coupling?

<p>APs in T tubules are linked to Ca2+ release from the SR, as channels in both structures interact mechanically.</p> Signup and view all the answers

What phenomenon is described when APs in T tubules result in Ca2+ release from the sarcoplasmic reticulum?

<p>This phenomenon is known as electromechanical coupling.</p> Signup and view all the answers

Why do H bands shorten during muscle contraction?

<p>H bands shorten as the thin filaments on the sides of the sarcomeres are pulled toward the center.</p> Signup and view all the answers

What retains its length during muscle contraction, and why is this significant?

<p>The A bands retain their length during contraction, which is significant because it indicates that the thick filaments do not change in size even as muscle fibers contract.</p> Signup and view all the answers

What happens to calcium ions during muscle relaxation?

<p>Calcium ions are pumped back into the sarcoplasmic reticulum by Ca2+-ATPase pumps, leading to no more calcium available to bind to troponin C.</p> Signup and view all the answers

Define a motor unit and its components.

<p>A motor unit consists of a single motor neuron and all the muscle fibers it innervates.</p> Signup and view all the answers

How does the number of muscle fibers in a motor unit affect muscle control?

<p>Finer muscle control requires smaller motor units, which have fewer muscle fibers.</p> Signup and view all the answers

What is the role of motor unit recruitment in muscle contraction strength?

<p>Motor unit recruitment increases contraction strength by activating more motor units to coordinate muscle fibers.</p> Signup and view all the answers

What occurs when a motor neuron is activated?

<p>When a motor neuron is activated, all muscle fibers in its motor unit contract simultaneously.</p> Signup and view all the answers

Give an example of a muscle with a high density of motor units and its significance.

<p>The eye muscles, which may have about 20 muscle fibers per motor unit, allow for precise control of eye movement.</p> Signup and view all the answers

Contrast the structure of motor units in fine control muscles versus larger muscles.

<p>Fine control muscles have smaller motor units with fewer fibers, while larger muscles have motor units with thousands of fibers.</p> Signup and view all the answers

What is the significance of Ca2+ binding to troponin C during muscle contraction?

<p>Ca2+ binding to troponin C is essential for forming cross bridges that lead to muscle contraction.</p> Signup and view all the answers

What happens when action potentials cease in muscle fibers?

<p>When action potentials cease, calcium is pumped back into the sarcoplasmic reticulum, ending muscle contraction.</p> Signup and view all the answers

Explain the trade-off between muscle control and strength.

<p>The trade-off is that finer muscle control generally comes from smaller motor units, while larger motor units provide greater strength.</p> Signup and view all the answers

What is muscle tone and how is it established?

<p>Muscle tone is the tension at rest in muscles, established by weak, involuntary contractions of motor units, regulated by neurons in the brain and spinal cord.</p> Signup and view all the answers

Differentiate between hypotonia and hypertonia.

<p>Hypotonia is characterized by decreased muscle tone leading to flaccid muscles, while hypertonia involves increased muscle tone causing stiffness and spasticity.</p> Signup and view all the answers

What are the differences between isometric and isotonic contractions?

<p>Isometric contractions occur without changing muscle length while generating force, whereas isotonic contractions involve changes in muscle length during contraction.</p> Signup and view all the answers

Describe the characteristics of Type I muscle fibers.

<p>Type I fibers, known as slow twitch fibers, are adapted for aerobic metabolism, have a high resistance to fatigue, and appear red due to rich myoglobin content.</p> Signup and view all the answers

What is the role of satellite cells in skeletal muscle repair?

<p>Satellite cells are stem cells located near muscle fibers that play a crucial role in muscle repair and regeneration following injury.</p> Signup and view all the answers

How do Type II A fibers differ from Type IIX fibers?

<p>Type II A fibers use aerobic metabolism and are intermediate in characteristics, while Type IIX fibers rely on anaerobic metabolism for fast, powerful contractions.</p> Signup and view all the answers

What is the significance of the alternating activation of motor units?

<p>The alternating activation of motor units maintains muscle firmness and helps prevent fatigue by distributing the workload among different muscle fibers.</p> Signup and view all the answers

What type of muscle tissue is striated and can be both voluntary and involuntary?

<p>Skeletal muscle.</p> Signup and view all the answers

What role does the autonomic nervous system play in muscle function?

<p>It directs the actions of involuntary muscles.</p> Signup and view all the answers

What is the primary structural unit of a muscle fiber?

<p>Myofibril.</p> Signup and view all the answers

What is the connective tissue that surrounds individual muscle fibers called?

<p>Endomysium.</p> Signup and view all the answers

What features distinguish cardiac muscle from smooth muscle?

<p>Cardiac muscle has striations and intercalated disks, while smooth muscle is not striated and has a centrally located nucleus.</p> Signup and view all the answers

What is the function of the sarcoplasmic reticulum in muscle fibers?

<p>It stores calcium ions necessary for muscle contraction.</p> Signup and view all the answers

What distinguishes smooth muscle in terms of its cellular structure?

<p>Smooth muscle cells have a single, centrally located nucleus and lack striations.</p> Signup and view all the answers

What is the collective term for the connective tissue that encases a muscle and its fascicles?

<p>Epimysium.</p> Signup and view all the answers

What is the smallest functional unit of a muscle that can contract?

<p>Sarcomere.</p> Signup and view all the answers

How does skeletal muscle achieve its striated appearance?

<p>Through the arrangement of myofibrils and the alternating patterns of the thick and thin filaments.</p> Signup and view all the answers

Flashcards

Muscle Cells

One of the four basic tissue types in the human body.

Skeletal Muscles

Make up a significant portion of our body's weight (approx. 40% males, 32% females).

Contractility (Muscle)

The ability of a muscle to shorten with force.

Excitability (Muscle)

The ability of a muscle to respond to a stimulus.

Signup and view all the flashcards

Extensibility (Muscle)

The ability of a muscle to stretch, beyond its resting length.

Signup and view all the flashcards

Elasticity (Muscle)

The ability of a muscle to recoil back to its original resting length after stretching.

Signup and view all the flashcards

Voluntary Muscles

Muscles controlled by our thoughts and nervous system (e.g., skeletal muscles).

Signup and view all the flashcards

Properties of Muscle

The key characteristics of muscle tissue, including contractility, excitability, extensibility, and elasticity.

Signup and view all the flashcards

Muscle Tissue Types

Skeletal, smooth, and cardiac are the three types of muscle tissue in the body.

Signup and view all the flashcards

Smooth Muscle

Found in the walls of organs (like the stomach and intestines), blood vessels, and some glands. Its actions are involuntary.

Signup and view all the flashcards

Cardiac Muscle

Found only in the heart, it's responsible for pumping blood. Its actions are involuntary.

Signup and view all the flashcards

Involuntary Muscle Actions

Actions not consciously controlled; directed by the autonomic nervous system.

Signup and view all the flashcards

Muscle Fiber

A single muscle cell.

Signup and view all the flashcards

Sarcomere

The basic contractile unit of a muscle fiber.

Signup and view all the flashcards

Myofibrils

Thread-like structures within muscle fibers that contain contractile proteins.

Signup and view all the flashcards

Muscle Fascicle

Bundles of muscle fibers.

Signup and view all the flashcards

Connective Tissues in Muscles

Epimysium, perimysium, and endomysium surround and support different levels of muscle structure.

Signup and view all the flashcards

Myofiber shortening

A myofiber shortens when the insertion of a muscle moves toward its origin.

Signup and view all the flashcards

Sarcomere shortening

The distance between Z lines in a sarcomere decreases during muscle contraction.

Signup and view all the flashcards

Sliding filament theory

Muscle contraction occurs by myofilaments sliding past each other, not by changing their own length.

Signup and view all the flashcards

Myosin cross-bridges

Myosin heads that bind to actin filaments to produce the force for muscle contraction.

Signup and view all the flashcards

A-band length

The length of the A band remains constant during muscle contraction; it is pulled toward the muscle's origin.

Signup and view all the flashcards

I-band shortening

The I bands, located between A bands, shorten during muscle contraction.

Signup and view all the flashcards

H-band shortening

The H band shortens as thin filaments are pulled towards the center of the sarcomere.

Signup and view all the flashcards

Neuromuscular Junction (NMJ)

The point where a motor neuron connects to a muscle fiber (cell).

Signup and view all the flashcards

Motor end plate

The specialized region of the muscle cell membrane where the NMJ occurs.

Signup and view all the flashcards

Excitation-contraction coupling

The process by which nerve signals are translated into muscle contractions.

Signup and view all the flashcards

Motor unit

A single motor neuron and all the muscle fibers it innervates. When activated, all muscle fibers in the motor unit contract together.

Signup and view all the flashcards

Motor neuron

A nerve cell that transmits signals from the brain or spinal cord to muscle fibers, causing them to contract.

Signup and view all the flashcards

Motor unit recruitment

The process of activating more motor units to increase muscle force.

Signup and view all the flashcards

Fine muscle control

The ability to make precise movements, often involving small muscles.

Signup and view all the flashcards

Muscle fiber density

The number of muscle fibers per motor unit, which determines the level of control over a muscle.

Signup and view all the flashcards

Trade-off between control and strength

Muscles with finer control have smaller motor units, while muscles with more strength have larger motor units.

Signup and view all the flashcards

Action potential ceases

The electrical signal that triggers muscle contraction stops.

Signup and view all the flashcards

Ca2+-ATPase pumps

Proteins in the muscle cell membrane that actively transport calcium ions (Ca2+) back into the sarcoplasmic reticulum (SR).

Signup and view all the flashcards

Cross bridges

Connections between the thick (myosin) and thin (actin) filaments in a muscle fiber, which are responsible for muscle contraction.

Signup and view all the flashcards

What is muscle tone?

The state of slight, continuous tension in resting skeletal muscles due to weak, involuntary contractions. It's maintained by neurons in the brain and spinal cord that excite the muscle's motor neurons.

Signup and view all the flashcards

What happens when motor neurons to a muscle are damaged?

The muscle becomes flaccid (limp) due to lack of neural stimulation. This results in no muscle tone and a loss of the ability to contract.

Signup and view all the flashcards

What is hypotonia?

Decreased or lost muscle tone. Muscles appear loose and flattened, becoming less resistant to stretching.

Signup and view all the flashcards

What is hypertonia?

Increased muscle tone. Muscles feel stiff and resistant to stretching. This can lead to spasticity, rigidity or both.

Signup and view all the flashcards

What are the types of muscle contractions?

There are four main types: reflexive, tonic, isometric and isotonic. Reflexive contractions are involuntary responses to stimuli. Tonic contractions maintain posture and stability. Isometric contractions generate force without changing muscle length. Isotonic contractions involve muscle shortening (concentric) or lengthening (eccentric) while generating force.

Signup and view all the flashcards

What are Type I muscle fibers?

Slow-twitch fibers, also called red slow oxidative fibers, are adapted for endurance activities. They contract slowly using aerobic respiration, are rich in oxygen-carrying myoglobin, and resist fatigue.

Signup and view all the flashcards

What are Type II muscle fibers?

Fast-twitch fibers, including Type IIX (white fast glycolytic) and Type IIA (red fast oxidative), are adapted for power and speed. They contract quickly using anaerobic metabolism, have fewer mitochondria and capillaries than Type I fibers, and fatigue faster.

Signup and view all the flashcards

Study Notes

Muscular System Overview

  • Muscle tissue is one of four basic tissue types.
  • Skeletal muscles make up a significant portion of body weight (40% in males, 32% in females).
  • Muscle tissues perform various functions.

Muscle Tissue Properties

  • Contractility: Ability of a muscle to shorten with force.
  • Excitability: Capacity of muscle to respond to a stimulus.
  • Extensibility: Ability of muscle to be stretched to its normal resting length and beyond.
  • Elasticity: Ability of muscle to recoil to its original resting length after stretched.

Muscle Classification

  • Voluntary Muscles: Controlled by conscious thought (skeletal muscles).
  • Involuntary Muscles: Not under conscious control (cardiac and smooth muscles).

Types of Muscle Tissue

  • Skeletal Muscle:
    • Attached to bones.
    • Multiple, peripherally located nuclei.
    • Striated.
    • Voluntary and involuntary (reflexes).
  • Smooth Muscle:
    • Found in walls of hollow organs, blood vessels, eye, glands, and skin.
    • Single, centrally located nucleus.
    • Not striated.
    • Involuntary, with gap junctions in visceral smooth.
  • Cardiac Muscle:
    • Found in the heart.
    • Single, centrally located nucleus.
    • Striated.
    • Involuntary, with intercalated discs.

Skeletal Muscle Structure

  • Most distinctive features: Striations and multinucleate.
  • Muscle fibers: Muscle cells, ensheathed by endomysium.
  • Sarcolemma: Plasma membrane of muscle fibers.
  • Myofibrils: Inside muscle fibers, composed of myofilaments.
  • Myofilaments: Composed of thick and thin filaments (myosin and actin).
  • Sarcomere: Basic contractile unit.
    • Contains thick filaments (myosin), thin filaments (actin), Z lines, M lines, and H bands
    • These structural proteins contribute to elastic recoil, and anchor myosin during contraction.
  • Connective tissues:
    • Epimysium: Covers the entire muscle.
    • Perimysium: Surrounds fascicles (bundles of muscle fibers).
    • Endomysium: Surrounds individual muscle fibers.

Mechanisms of Contraction

  • Sliding filament theory: Thin filaments (actin) slide over thick filaments (myosin).
  • Cross-bridge cycle: Myosin heads bind to actin, pivot, detach, and re-cock for the next cycle.
    • Step 1. Active-site exposure
    • Step 2. Cross-bridge formation
    • Step 3. Myosin head pivoting (power stroke)
    • Step 4. Cross-bridge detachment
    • Step 5. Myosin reactivation

Control of Contraction

  • Troponin-tropomyosin system: Regulates cross-bridge attachment to actin.
  • Calcium ions (Ca2+): Necessary for muscle contraction.
  • Relaxation: When action potentials cease, Ca2+ is pumped back into the SR.

Excitation-Contraction Coupling

  • Neuromuscular junction (NMJ): Where motor neuron meets muscle fiber.
  • Acetylcholine (ACh): Neurotransmitter that triggers muscle action potentials.
  • Action potential propagation: APs travel down T tubules, triggering Ca2+ release from SR.

Relationship of Action Potential

  • Direct relationship between action potential, intracellular Ca2+ concentration, and muscle contraction.

Muscle Relaxation

  • Action potential ceases.
  • Ca2+-ATPase pumps move Ca2+ back into the SR.
  • Cross-bridge formation stops.

Motor Units

  • Motor neuron innervates a variable number of muscle fibers.
  • Motor units vary in size based on needed precision of muscle control.
  • Recruitment of motor units is important for increasing contraction strength.

Muscle Tone

  • Skeletal muscles exhibit muscle tone in a resting state.
  • Due to weak, involuntary contractions of motor units.
  • Maintained by continually shifting activity of motor units.
  • Essential for posture and supporting certain body positions.

Muscle Tone Abnormalities

  • Hypotonia: Decreased or lost muscle tone.
  • Hypertonia: Increased muscle tone.

Types of Muscle Contractions

  • Isometric: Muscle produces tension but does not change length.
  • Isotonic: Muscle changes length and moves a load.
    • Concentric: Muscle shortens while producing tension.
    • Eccentric: Muscle lengthens while producing tension.

Types of Skeletal Muscle Fibers

  • Type 1 (Slow Oxidative): Adapted for endurance.
  • Type IIa (Intermediate): Mid-range of speed and endurance.
  • Type IIx (Fast Glycolytic): Adapted for speed and power.

Homeostatic Imbalance Disorders

  • Spasm/Cramp: Sudden, involuntary contraction of a muscle group.
  • Muscle fatigue: Reduced ability to produce muscle tension.
  • Delayed-onset muscle soreness (DOMS): Soreness 12–48 hours after strenuous exercise.
  • Muscle tone abnormalities.

Muscle Repair

  • Skeletal muscles have stem cells (satellite cells) near muscle fibers for repair and regeneration.

Muscle Decline With Aging

  • Reduced muscle mass, reduced capillary blood supply, and fewer satellite cells.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Quiz Team

Related Documents

L5 Muscular System PDF

Description

Explore the fundamentals of the muscular system, including muscle tissue properties and classifications. This quiz covers voluntary and involuntary muscles, as well as the types of muscle tissue in the human body. Test your knowledge and understanding of how muscles function.

More Like This

Muscular System Overview
29 questions

Muscular System Overview

StrongerLarch avatar
StrongerLarch
Muscular System: Types and Function
20 questions

Muscular System: Types and Function

ColorfulSalamander avatar
ColorfulSalamander
Human Anatomy: Muscle Tissue Overview
24 questions

Human Anatomy: Muscle Tissue Overview

ColorfulSalamander avatar
ColorfulSalamander
Use Quizgecko on...
Browser
Open
Browser
Browser