Joint Classification Overview
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Joint Classification Overview

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Questions and Answers

What type of joint is characterized by being immovable and primarily found in the skull?

  • Symphyses
  • Sutures (correct)
  • Gomphoses
  • Syndesmoses

    • Which of the following statements correctly describes synovial joints?

  • They consist only of cartilage.
  • They have a joint cavity filled with synovial fluid. (correct)
  • They are always immovable.
  • They are primarily found in the axial skeleton.

    • What distinguishes fibrous joints from cartilaginous joints?

  • Fibrous joints are formed by dense, fibrous connective tissue. (correct)
  • Fibrous joints contain a joint cavity.
  • Fibrous joints absorb shock better than cartilaginous joints.
  • Fibrous joints allow more movement than cartilaginous joints.

    • Which type of joint is considered freely movable and commonly found in the appendicular skeleton?

    <p>Diarthroses</p> Signup and view all the answers

    Which feature of synovial joints provides stability by preventing excessive movement?

    <p>Reinforcing Ligaments</p> Signup and view all the answers

    Which type of joint allows for limited movement and acts as a shock absorber due to its fibrocartilage composition?

    <p>Symphyses</p> Signup and view all the answers

    Which of the following would most likely be a symptom of tendinitis?

    <p>Pain around a tendon</p> Signup and view all the answers

    What is the primary role of synovial fluid in synovial joints?

    <p>To absorb shock and reduce friction</p> Signup and view all the answers

    Which factor contributes the most to joint stability?

    <p>Muscle tone as they cross joint</p> Signup and view all the answers

    What movement does plantar flexion refer to?

    <p>Moving the toes away from the shin</p> Signup and view all the answers

    Which type of synovial joint allows for the greatest range of motion?

    <p>Ball-and-socket joint</p> Signup and view all the answers

    What is the primary action involved in rotation at a joint?

    <p>Turning of bone around its own long axis</p> Signup and view all the answers

    What would be considered a sign of a possible joint injury?

    <p>Swelling or tenderness around the joint</p> Signup and view all the answers

    What is the effect of having more ligaments at a joint?

    <p>Stronger joint structure</p> Signup and view all the answers

    Which type of joint movement is described as 'moving back toward the midline'?

    <p>Adduction</p> Signup and view all the answers

    What type of joint movement is characterized as exceeding the anatomical position?

    <p>Hyperextension</p> Signup and view all the answers

    What type of joint is formed by the mandibular condyle and the temporal bone?

    <p>Modified hinge joint</p> Signup and view all the answers

    Which ligaments contribute to the stability of the glenohumeral joint?

    <p>Coracohumeral and Glenohumeral ligaments</p> Signup and view all the answers

    What surgical procedure is often required for a torn Ulnar Collateral Ligament (UCL) in athletes?

    <p>Tommy John Surgery</p> Signup and view all the answers

    What is a primary characteristic of the coxal joint compared to the glenohumeral joint?

    <p>Provides more joint stability</p> Signup and view all the answers

    Which structures help stabilize the humeroulnar joint?

    <p>Ulnar Collateral Ligament and Radial Collateral Ligament</p> Signup and view all the answers

    What movement does the glenohumeral joint primarily allow?

    <p>High degree of movement with low stability</p> Signup and view all the answers

    Which of the following is NOT a movement associated with the temporomandibular joint?

    <p>Extension of the arm</p> Signup and view all the answers

    In which activities is the tearing of the acetabular labrum commonly observed?

    <p>Dancing and gymnastics</p> Signup and view all the answers

    What type of joint is characterized by a peg-in-socket structure?

    <p>Gomphoses</p> Signup and view all the answers

    Which structural classification of joints allows for slight movement depending on ligament length?

    <p>Syndesmoses</p> Signup and view all the answers

    Which feature of synovial joints serves to lubricate and nourish the articular cartilage?

    <p>Synovial fluid</p> Signup and view all the answers

    What type of cartilage is primarily found in synchondroses joints?

    <p>Hyaline cartilage</p> Signup and view all the answers

    Which type of joint is primarily characterized by the presence of a joint cavity?

    <p>Synovial joints</p> Signup and view all the answers

    What structural feature of a synovial joint helps stabilize the articulating bones and mitigate wear and tear?

    <p>Articular discs</p> Signup and view all the answers

    In which type of joint are intervertebral discs found, allowing limited movement?

    <p>Cartilaginous joints</p> Signup and view all the answers

    What function do bursae serve in synovial joints?

    <p>Reduce friction</p> Signup and view all the answers

    What is the primary function of the temporomandibular joint (TMJ)?

    <p>To facilitate both vertical and horizontal movements of the jaw</p> Signup and view all the answers

    Which structures enhance the stability of the glenohumeral joint?

    <p>Fibrocartilaginous glenoid labrum and Muscle Tendons</p> Signup and view all the answers

    What type of joint movement is significantly restricted at the humeroulnar joint?

    <p>Lateral movement</p> Signup and view all the answers

    What is a distinguishing feature of the coxal joint compared to the shoulder joint?

    <p>Deeper socket design for increased stability</p> Signup and view all the answers

    In which scenario is a tear of the fibrocartilaginous glenoid labrum more likely to occur?

    <p>During activities involving high overhead movements</p> Signup and view all the answers

    What role does the anular ligament play in the humeroradius joint?

    <p>It holds the radial head in place</p> Signup and view all the answers

    The main function of muscle masses surrounding the hip joint is to provide?

    <p>Stability and support</p> Signup and view all the answers

    What surgical procedure is commonly associated with a torn Ulnar Collateral Ligament (UCL)?

    <p>Tommy John Surgery</p> Signup and view all the answers

    What is the primary consequence of having a shallower articular surface in a joint?

    <p>Reduced joint stability</p> Signup and view all the answers

    Which movement describes bringing a limb or body part back toward the midline?

    <p>Adduction</p> Signup and view all the answers

    What is the effect of increased muscle tone on joint stability?

    <p>Keeps tendons taut</p> Signup and view all the answers

    Which of the following accurately defines hyperextension?

    <p>Extension movement beyond anatomical position</p> Signup and view all the answers

    Which pairs of movements occur in the ankle when dorsiflexion is performed?

    <p>Toes move toward the shin</p> Signup and view all the answers

    What movement is characterized by a rotation away from the midline of the body?

    <p>External rotation</p> Signup and view all the answers

    How does the number and location of ligaments affect joint strength?

    <p>More ligaments create a stronger joint</p> Signup and view all the answers

    What is circumduction?

    <p>Circular movement of a limb</p> Signup and view all the answers

    What is the function of the medial and lateral collateral ligaments in the knee joint?

    <p>Prevent medial and lateral collapse of the knee</p> Signup and view all the answers

    What typically causes cartilage tears in the knee?

    <p>Compression or shear (rotational) stress</p> Signup and view all the answers

    What is the Unhappy Triad injury associated with?

    <p>Damage to the ACL, MCL, and medial meniscus</p> Signup and view all the answers

    How long does it typically take for a partial ligament tear to heal?

    <p>8 – 12 weeks</p> Signup and view all the answers

    What is a common cause of tendonitis?

    <p>Inflammation due to overuse</p> Signup and view all the answers

    Which statement accurately describes the role of bursae in the knee joint?

    <p>Assist in smooth, free movement</p> Signup and view all the answers

    What is the primary characteristic of tendonitis compared to bursitis?

    <p>Inflammation of the tendon sheath</p> Signup and view all the answers

    What is one common consequence of meniscal removal following a cartilage tear?

    <p>Loss of joint stability</p> Signup and view all the answers

    What is the primary cause behind osteoarthritis?

    <p>Irreversible wear and tear of cartilage</p> Signup and view all the answers

    Which chronic arthritis form is most common and characterized by advanced joint degeneration?

    <p>Osteoarthritis</p> Signup and view all the answers

    What characteristic of gouty arthritis can lead to serious complications if untreated?

    <p>Painful crystal deposits in joints</p> Signup and view all the answers

    Which age group is most likely to develop rheumatoid arthritis?

    <p>Adults aged 40-50 years</p> Signup and view all the answers

    What happens to bones in osteoarthritis as cartilage wears away?

    <p>Bone ends thicken, causing movement restriction</p> Signup and view all the answers

    Lyme disease can lead to which of the following symptoms aside from joint pain?

    <p>Neurological symptoms if untreated</p> Signup and view all the answers

    What is a common treatment approach for osteoarthritis?

    <p>Moderate physical activity and pain relievers</p> Signup and view all the answers

    Which statement is true regarding rheumatoid arthritis?

    <p>It is an autoimmune disease that often affects hands and feet.</p> Signup and view all the answers

    What is the primary energy system utilized by Type IIx muscle fibers?

    <p>Phosphagen system and anaerobic glycolysis</p> Signup and view all the answers

    Which component of the muscle contraction process is directly associated with excitation-contraction coupling?

    <p>Action potential generation at the neuromuscular junction</p> Signup and view all the answers

    How many ATP molecules are produced through oxidative phosphorylation during one complete cycle?

    <p>32 ATP</p> Signup and view all the answers

    What role does troponin play in the muscle contraction mechanism?

    <p>Binds calcium and facilitates myosin-actin interaction</p> Signup and view all the answers

    What structural feature distinguishes smooth muscle fibers from skeletal muscle fibers?

    <p>Slower contraction speed and lower energy cost</p> Signup and view all the answers

    What is the primary consequence of disuse atrophy in muscle tissue?

    <p>Increased connective tissue density</p> Signup and view all the answers

    Which muscle type is primarily responsible for maintaining posture?

    <p>Type I fibers</p> Signup and view all the answers

    What is the primary mechanism of action for calcium ions in muscle contraction?

    <p>They facilitate the opening of myosin binding sites by binding to troponin.</p> Signup and view all the answers

    How does the sliding filament model describe muscle contraction?

    <p>Actin filaments slide over myosin filaments without changing length.</p> Signup and view all the answers

    What effect does aging have on muscle tissue composition?

    <p>Decrease in muscle mass and increase in connective tissue</p> Signup and view all the answers

    What triggers the opening of calcium channels in the excitation-contraction coupling process?

    <p>Voltage-sensitive proteins being activated by T-tubules</p> Signup and view all the answers

    What is the primary role of ATP in muscle contraction?

    <p>To ensure myosin detaches from actin after a contraction</p> Signup and view all the answers

    In the sliding filament model, what causes muscle contraction?

    <p>Shortening of the sarcomere due to actin and myosin sliding over each other</p> Signup and view all the answers

    What is primarily responsible for the generation of action potentials in muscle fibers?

    <p>Sodium influx and potassium efflux following receptor activation</p> Signup and view all the answers

    What occurs to muscle fibers when the excitation-contraction coupling process halts?

    <p>Calcium is pumped back into the sarcoplasmic reticulum</p> Signup and view all the answers

    In which order are motor units typically recruited according to the size principle?

    <p>Small motor units before large motor units</p> Signup and view all the answers

    What type of muscle contraction occurs when the muscle length remains constant while external force is applied?

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

    What is the result of calcium binding to troponin during muscle contraction?

    <p>It exposes myosin-binding sites on actin</p> Signup and view all the answers

    What characterizes isokinetic contractions in muscle activity?

    <p>Constant speed with changing muscle length and tension</p> Signup and view all the answers

    What effect does fatigue have on muscle contraction?

    <p>It impairs the ability to maintain membrane depolarization</p> Signup and view all the answers

    What is the primary role of the sarcoplasmic reticulum in muscle fibers?

    <p>To release and reuptake calcium ions</p> Signup and view all the answers

    During muscle contraction, what happens to the H-zone in a sarcomere?

    <p>It shrinks and can disappear</p> Signup and view all the answers

    What initiates the power stroke in the sliding filament model?

    <p>Release of ADP and Pi from myosin</p> Signup and view all the answers

    What is the role of motor neurons in muscle contraction?

    <p>To initiate action potentials at the neuromuscular junction</p> Signup and view all the answers

    What component of a muscle cell helps maintain its resting potential?

    <p>Sarcoplasmic membrane</p> Signup and view all the answers

    What sequence occurs first in the excitation-contraction coupling process?

    <p>Action potential generation in the motor neuron</p> Signup and view all the answers

    What happens to myosin heads when ATP binds to them?

    <p>They release from the actin binding site</p> Signup and view all the answers

    Which structure in the muscle fiber helps in the delivery of action potentials to deep regions of the myofiber?

    <p>T-Tubules</p> Signup and view all the answers

    Which structure is primarily responsible for the contractile function of a muscle?

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

    What is the effect of calcium binding to troponin during muscle contraction?

    <p>It allows myosin-binding sites on actin to be exposed</p> Signup and view all the answers

    In the sliding filament model, how does the sarcomere change during muscle contraction?

    <p>It shortens as actin filaments move toward the M-line</p> Signup and view all the answers

    What do myonuclei in myofibers assist with?

    <p>Growth and repair of myofibrils</p> Signup and view all the answers

    Which structure is NOT part of a muscle's neuromuscular junction?

    <p>Muscle belly</p> Signup and view all the answers

    What determines the responsiveness of a muscle cell to stimuli?

    <p>Excitability</p> Signup and view all the answers

    What is the primary energy system used by Type IIx skeletal muscle fibers?

    <p>Phosphagen system</p> Signup and view all the answers

    Which energy system produces the most ATP per cycle?

    <p>Oxidative phosphorylation</p> Signup and view all the answers

    What happens to muscle fibers as individuals age after the age of 30?

    <p>Muscle fibers decrease and are replaced by connective tissue</p> Signup and view all the answers

    Which type of skeletal muscle fiber primarily uses oxidative phosphorylation?

    <p>Type I</p> Signup and view all the answers

    What is a characteristic of smooth muscle compared to skeletal muscle?

    <p>It has a lower energy cost for contraction</p> Signup and view all the answers

    How does disuse atrophy affect muscle tissue?

    <p>Muscle mass decreases and functionality is also lost</p> Signup and view all the answers

    What is the main feature of isometric contractions?

    <p>Muscle tension increases without changing length</p> Signup and view all the answers

    What is the consequence of paralysis on muscle mass?

    <p>Muscle shrinks to 25% of its initial size</p> Signup and view all the answers

    What characterizes Type IIa skeletal muscle fibers?

    <p>Use a combination of anaerobic and aerobic energy systems</p> Signup and view all the answers

    What is the primary function of calcium in muscle contraction?

    <p>It binds to troponin to allow myosin binding sites to open</p> Signup and view all the answers

    What initiates the opening of sodium (Na+) and potassium (K+) channels during the action potential generation in muscle fibers?

    <p>Change in membrane potential</p> Signup and view all the answers

    What role do T-tubules play in muscle contraction?

    <p>They help action potentials propagate into the muscle fiber</p> Signup and view all the answers

    What happens to calcium ions after a neuronal action potential ceases?

    <p>They are actively transported back into the sarcoplasmic reticulum</p> Signup and view all the answers

    What characterizes isometric muscle contractions?

    <p>Muscle produces force without changing length</p> Signup and view all the answers

    In the size principle, what type of motor units are recruited last during muscle contraction?

    <p>Larger motor units for higher forces</p> Signup and view all the answers

    What is the effect of low ATP levels on myosin during muscle contraction?

    <p>Myosin cannot attach to actin or detach</p> Signup and view all the answers

    Which muscle contraction type is characterized by a consistent external load while the muscle length changes?

    <p>Isotonic</p> Signup and view all the answers

    What is a primary cause of muscle fatigue?

    <p>Excessive ion imbalances and inadequate ATP replenishment</p> Signup and view all the answers

    During contraction, which action occurs alongside concentric muscle contraction?

    <p>Eccentric contraction of the opposing muscle</p> Signup and view all the answers

    How does exercise influence motor unit recruitment in muscles?

    <p>Allows earlier recruitment of larger motor units</p> Signup and view all the answers

    What is the main characteristic of cardiac muscle tissue?

    <p>Striated and involuntary</p> Signup and view all the answers

    Which of the following is NOT a characteristic of muscle tissue?

    <p>Heterogeneity</p> Signup and view all the answers

    What role do T-tubules play in muscle contraction?

    <p>Transmit action potentials deep into myofibers</p> Signup and view all the answers

    What is the primary function of sarcomeres in muscle fibers?

    <p>Act as contractile units</p> Signup and view all the answers

    How does myosin contribute to muscle contraction?

    <p>Pulls actin filaments closer together</p> Signup and view all the answers

    What structure serves as the membrane potential in muscle fibers?

    <p>Sarcolemma</p> Signup and view all the answers

    Which molecule is essential for the sliding filament model to occur?

    <p>ATP</p> Signup and view all the answers

    What occurs at the neuromuscular junction when a muscle is stimulated?

    <p>Acetylcholine binds to receptors on the sarcolemma</p> Signup and view all the answers

    What is the result of calcium binding to troponin during muscle contraction?

    <p>Movement of tropomyosin away from myosin-binding sites</p> Signup and view all the answers

    In the context of skeletal muscle contraction, which zone disappears during contraction?

    <p>H-zone</p> Signup and view all the answers

    What is the primary function of satellite cells in muscle tissue?

    <p>Differentiate into specialized muscle tissues</p> Signup and view all the answers

    Which structure is responsible for the stiffness and restoration of sarcomeres during relaxation?

    <p>Titin</p> Signup and view all the answers

    What contributes to the initial depolarization of the sarcolemma during muscle contraction?

    <p>Sodium ion influx</p> Signup and view all the answers

    Which component is found within the sarcomere and is essential for the contraction process?

    <p>Myofibrils</p> Signup and view all the answers

    Study Notes

    Joint Classification

    • Joints are classified based on structure and function.
    • Structural Classifications refer to the material that binds the joint and whether or not a joint cavity exists.
      • Fibrous joints are joined by dense, fibrous connective tissue.
      • Cartilaginous joints are joined by cartilage.
      • Synovial joints are the only joints with a fluid filled joint cavity.
    • Functional Classifications describe the range of motion at the joint.
      • Synarthroses are immovable joints.
      • Amphiarthroses are slightly movable joints.
      • Diarthroses are freely movable joints.
      • Most joints in the axial skeleton are synarthroses or amphiarthroses while most joints in the appendicular skeleton are diarthroses.

    Fibrous & Cartilaginous Joints

    • Fibrous joints connect bones via dense fibrous connective tissue.
      • Sutures are found only in the skull, creating "seams." These are synarthrotic and protect the brain.
      • Syndesmoses connect via ligaments and fibrous tissue, such as between the tibia and fibula or radius and ulna. They can be amphiarthrotic.
      • Gomphoses are peg-in-socket joints found only with teeth.
    • Cartilaginous joints are connected via cartilage.
      • Synchondroses use hyaline cartilage plates to connect bones, like the epiphyseal plate connecting bone shaft to ends.
      • Symphyses use fibrocartilage connecting bones, acting as a strong shock absorber and permitting limited motion (amphiarthrotic).

    Synovial Joints

    • Synovial joints have a fluid-filled joint cavity.
    • General Features:
      • Articular cartilage: hyaline cartilage covering the ends of bones.
      • Joint (Synovial) Cavity: a fluid-filled space separating bones.
      • Articular (Joint) Capsule: has 2 layers, a fibrous layer and a synovial membrane.
      • Synovial Fluid: viscous, plasma filtrate containing hyaluronic acid, lubricates and nourishes articular cartilage.
      • Reinforcing Ligaments: provides stability.
      • Nerves and Blood Vessels: detect pain, monitor stretch, and supply synovial fluid.
    • Other Features:
      • Articular Discs: fibrocartilage separating and improving bone fit, stabilizing and mitigating wear, and absorbing shock.
      • Bursae: sacs of synovial fluid surrounding the joint, reducing friction between structures like ligaments, muscles, skin, tendons, and bones.

    Synovial Joint Stability

    • Factors Influencing Stability:
      • Shape of Articular Surfaces: Deeper surfaces are more stable.
      • Number and Location of Ligaments: More ligaments means a stronger joint.
      • Muscle Tone: Taut tendons are crucial for stability, especially in the shoulder, knee, and foot arches.

    Synovial Joint Movements

    • Flexion: Decreases joint angle by bringing articulating segments closer.
    • Extension: Reverses flexion by increasing joint angle.
    • Hyperextension: Extension beyond the anatomical position.
    • Abduction: Movement away from the midline. For fingers and toes, it means spreading them apart.
    • Adduction: Movement toward the midline, returning to anatomical position.
    • Circumduction: Circular movement involving flexion, abduction, extension, and adduction.
    • Rotation: Turning a bone around its long axis.
      • Internal (medial) Rotation: Rotation toward the midline.
      • External (lateral) Rotation: Rotation away from the midline.
    • Radial & Ulnar Rotation named based on palm positioning.
      • Supination: Palms face anteriorly, radius rotates over ulna.
      • Pronation: Palms face posteriorly, radius and ulna are parallel.

    Types of Synovial Joints

    • Plane (Gliding) Joints: Flat surfaces that slip or glide past each other.
    • Hinge Joints: Allow movement in one plane, like a door hinge.
    • Pivot Joints: Bone rotates around the axis of another bone.
    • Condyloid Joints: One bone has an oval-shaped articulating surface that fits into a cavity on another bone.
    • Saddle Joints: Two bones each have a saddle-shaped articular surface.
    • Ball-and-Socket Joints: A spherical head fits into a cup-like socket, allowing for free movement in all planes.

    Select Synovial Joints

    • Temporomandibular Joint (TMJ): Modified hinge joint allowing for movement of the mandible.
    • Glenohumeral Joint (Shoulder): Ball-and-socket joint allowing for high mobility, but low stability.
    • Humeroulnar Joint (Elbow): Hinge joint allowing for flexion and extension.
    • Coxal Joint (Hip): Ball-and-socket joint allowing for high stability.
    • Tibiofemoral Joint (Knee): Hinge joint with some rotation.

    Temporomandibular Joint (TMJ)

    • Mandibular condyle articulates with temporal bone.
    • Elevation and depression of mandible.
    • Lateral movement for chewing.
    • Protraction/Retraction to move chin forward/backward.

    Glenohumeral (Shoulder) Joint

    • Large humeral head fits in the shallow glenoid cavity of the scapula.
    • Glenoid labrum deepens the cavity.
    • Stability reinforced by ligaments and muscle tendons.
      • Coracohumeral & Glenohumeral ligaments (anteriorly).
      • Biceps & Deltoid tendons (anteriorly).
      • Rotator Cuff tendons encircle shoulder.

    Humeroulnar (Elbow) Joint

    • Humerus, radius, and ulna form a hinge joint.
    • Stability provided by the Ulnar Collateral Ligament (UCL) and Radial Collateral Ligament (RCL).
    • Radial head held in place by anular ligament allows for pronation and supination.

    Coxal (Hip) Joint

    • Large femoral head fits into the deep acetabulum of the pelvis.
    • Stability provided by ligaments and surrounding muscles.
    • Iliofemoral, Pubofemoral, Ischiofemoral ligaments.
    • Ligament of head of femur.
    • Acetabular labrum deepens the socket.

    Tibiofemoral Joint (Knee)

    • Largest and most complex joint in body.
    • Hinge joint allowing flexion, extension, and some rotation.
    • Medial and Lateral Menisci are fibrocartilage pads that deepen the articular surface, help with stability and shock absorption.
    • Secured by ligaments, including ACL, PCL, MCL, and LCL.

    Joint Classification

    • Joints are classified based on their structural and functional properties.

    Structural Classification

    • Fibrous joints: joined by dense, fibrous connective tissue; 3 types:

      • Sutures: found in the skull; synarthrotic (immovable)
      • Syndesmoses: connected by ligaments and fibrous tissues; can be amphiarthrotic (slightly movable) depending on ligament length; examples: tibia and fibula, radius and ulna
      • Gomphoses: "peg-in-socket"; only seen in teeth

    • Cartilaginous joints: bones united by cartilage; 2 types:

      • Synchondroses: plate of hyaline cartilage connects bones; synarthrotic; example: epiphyseal plate
      • Symphyses: fibrocartilage in joint; strong; often act as shock absorbers and permit limited movement (amphiarthrotic); examples: intervertebral joints, pubic symphysis

    • Synovial joints: bones separated by a fluid-filled joint cavity; only type with a joint cavity; freely movable; contains 6 general features:

      • Articular cartilage: hyaline cartilage covering ends of bones
      • Joint (Synovial) Cavity: fluid-filled space separating articulating bones
      • Articular (Joint) Capsule: two-layered thick; fibrous layer and synovial membrane
      • Synovial Fluid: viscous plasma filtrate with hyaluronic acid; lubricates and nourishes articular cartilage
      • Reinforcing Ligaments: provide stability
      • Nerves & Blood Vessels: detect pain, monitor stretch; supply filtrate for synovial fluid

    • Additional components of synovial joints:

      • Articular Discs (menisci & labra): fibrocartilage separating and improving the "fit" of articulating bone surfaces; stabilize joint, mitigate wear and tear, shock absorption
      • Bursae: bags of synovial fluid surrounding joint; reduce friction between ligaments, muscles, skin, tendons, or bone

    Synovial Joint Stability

    • 3 factors determine synovial joint stability:
      • Shape of Articular Surface: deeper surface = more stable
      • Number and Location of Ligaments: more ligaments = stronger joint
      • Muscle Tone: keeps tendons taut; extremely important for stability of shoulder, knee, and foot arches

    Movements Allowed by Synovial Joints

    • Flexion: bending movement, decreasing joint angle; moves articulating segments closer together.
    • Extension: reverse of flexion, increasing joint angle; straightens flexed limb/joint.
    • Hyperextension: extension movement beyond return to anatomical position.
    • Abduction: movement away from midline; for fingers and toes = spreading them apart; ankle performs foot eversion turning sole of foot laterally.
    • Adduction: reverse of abduction, moving back towards midline; for fingers and toes = return to anatomical position; ankle performs foot inversion turning sole of foot medially.
    • Circumduction: circular movement involving flexion, abduction, extension, and adduction of limb.
    • Rotation: turning of bone around its own long axis; internal (medial) rotation = rotation towards midline; external (lateral) rotation = rotation away from midline.
    • Radial & Ulnar Rotation:
      • Supination: palms face anteriorly; radius rotates over ulna.
      • Pronation: palms face posteriorly; radius and ulna are parallel.

    Types of Synovial Joints

    • Plane Joints: short gliding or sliding movements; examples: intercarpal joints, intertarsal joints
    • Hinge Joints: uniaxial allowing only flexion and extension; examples: elbow joint, knee joint, interphalangeal joints of fingers and toes.
    • Pivot Joints: uniaxial allowing only rotation; examples: proximal radioulnar joint, atlantoaxial joint.
    • Condylar Joints: biaxial permitting flexion/extension and abduction/adduction; examples: metacarpophalangeal joints (knuckles), temporomandibular joint.
    • Saddle Joint: allows for wide range of motion; biaxial; example:
      • Carpometacarpal joint of thumb
    • Ball-and-Socket Joint: most freely moving; multiaxial; examples: shoulder joint (glenohumeral) and hip joint (coxal)

    Select Synovial Joints

    • Temporomandibular Joint (TMJ): mandibular condyle articulates with temporal bone; modified hinge joint; allows elevation, depression, lateral movement, protraction, and retraction.
    • Glenohumeral Joint (Shoulder): humeral head (ball) fits in shallow glenoid cavity of scapula (socket); allows for high degree of movement, but relatively low stability; reinforced by ligaments and muscle tendons.
    • Humeroulnar Joint (Elbow): humerus articulates distally with radius and ulna; hinge joint allowing only flexion and extension movements; radial articulation with ulna allows pronation and supination movements
    • Coxal Joint (Hip): large, spherical head of femur (ball) articulates with deep acetabulum on pubis (socket); provides most of joint’s stability, but limits range of motion; reinforced by ligaments and muscle masses surrounding the joint.
    • Tibiofemoral Joint (Knee): largest and most complex joint of the body; a combination of two joints: femoropatellar joint and tibiofemoral joint; stabilized by numerous ligaments.

    Clinical Connection – Knee Injuries

    • The knee absorbs a lot of vertical forces but susceptible to horizontal and torsional forces.
    • Most common injuries involve: collateral ligaments, cruciate ligaments, and cartilages (menisci).
    • Lateral blows to extended knee can result in Unhappy Triad injury: damage to MCL, ACL, and medial meniscus.
    • ACL can be damaged in running with sudden directional changes or landings where the knee shifts forwards and collapses inwards.

    Common Joint Injuries

    • Cartilage Tears: usually caused by compression or shear stress; fragments may cause joint to lock or bind; repaired with surgery as cartilage does not repair itself.
    • Sprains: reinforcing ligaments get overly stretched or torn; partial tears will repair but slowly; complete tears require surgical repair.
    • Dislocations (Luxations): bones forced out of alignment; usually caused by a serious fall or collision; must be reduced to treat.
    • Tendonitis: inflammation of the tendon sheath due to overuse.
    • Bursitis: inflammation of a bursa caused by a direct blow or friction.

    Arthritis

    • Umbrella term for over 100 inflammatory or degenerative conditions which damage joints, characterized by pain, stiffness, and swelling; most acute forms caused by bacteria.
    • 4 Chronic Forms:
      • Osteoarthritis (OA): most common, irreversible "wear and tear"; cartilage broken down faster than it can be replaced; can only moderate activity and take pain relievers; may require surgery to replace joints.
      • Rheumatoid Arthritis (RA): chronic, inflammatory, autoimmune disease; causes joint pain, swelling, weakness, and cardiovascular problems; especially affects hands and feet; affects women 3x more frequently.
      • Gouty Arthritis: excess uric acid crystals deposited in joint and soft tissue; more common in men; can fuse and immobilize the joint if left untreated.
      • Lyme Disease: autoimmune condition acquired from spirochete bacteria in deer tick bites; can cause joint pain, rash, and flu-like symptoms.

    Joints Summary

    • Joints are characterized both by their structure and function.
    • Key considerations include: what holds the joint together? Is there a joint cavity present? How much can the joint move?

    Muscle Tissue

    • Makes up approximately 42% of total body mass in Males (AMAB) and 36% in Females (AFAB)
    • "Myo-", "mys-", and "sarco-" prefixes often used to refer to muscle-related tissues
    • Can be categorized by 3 types: skeletal, cardiac, and smooth
    • Skeletal muscle is striated and voluntary
    • Cardiac muscle is striated and involuntary
    • Smooth muscle is non-striated and involuntary

    Characteristics of Muscle Tissue

    • Excitability (responsiveness)
    • Contractility (ability to forcibly shorten)
    • Extensibility (ability to stretch)
    • Elasticity (ability to return to original length without being disfigured)

    Muscle Tissue Functions

    • Produce Movement: Locomotion and joint manipulation
    • Maintain Posture & Position: Keep body upright and everything in place
    • Joint Stabilization: Prevent joints from dislocating or overextending
    • Heat: Help maintain thermoregulation and metabolism

    Skeletal Muscle Makeup

    • Multilayered, with multiple levels of organization:
      • Muscle Belly: all fascicles surrounded by epimysium
      • Fascicle: Bundle of myofibers surrounded by perimysium
      • Myofiber: Bundle of myofibrils surrounded by sarcolemma and endomysium; contains sarcoplasm
      • Myofibril: Bundle of sarcomeres connected in series and parallel; takes up 80% of myofiber volume
      • Sarcomere: Series of myofilaments; the functional contractile unit of muscle

    Myofiber Structures

    • Mitochondria for energy production (ATP)
    • Sarcoplasmic Reticulum for Calcium (Ca2+) release and reuptake
    • T-Tubues for carrying action potentials from sarcolemma deep into myofiber
    • Myonuclei to create new myofibrils
    • Satellite Cells "Muscle stem cells" that differentiate into whatever tissue is needed

    Sarcomere Structure

    • Made of 3 main myofilaments: Actin (thin), Myosin (thick), and Titin (elastic)
    • Actin filaments contain Troponin and Tropomyosin
    • Myosin filaments are the contractile filaments
    • Titin filaments provide elasticity to the sarcomere
    • Key structural features:
      • Z-Disc: Ends of Actin filaments; demarcate the ends of the sarcomere
      • M-Line: Midline of sarcomere
      • H-zone: Area on either side of the M-line with no Actin-Myosin overlap

    Skeletal Muscle Contraction

    • Relaxed Sarcomeres (and myofibers) are at full length; some Actin-Myosin overlap is present
    • Contracted Sarcomeres (and myofibers) shorten through the sliding filament model:
      • Calcium binding to troponin and ATP hydrolysis cause Myosin to bind to Actin forming a cross-bridge
      • Thin filaments slide past thick filaments, causing Actin-Myosin overlap
      • This overlap results in the shrinking and disappearance of the H-zone

    Sliding Filament Model

    • Rest: Myosin head is in a "low energy" state with bound ATP, not yet attached to Actin
    • Cross-Bridge: ATP Hydrolysis; Myosin head energizes and attaches to an Actin binding site
    • Power Stroke: ADP and Pi are released; Myosin tail contracts and pulls on the Actin-Myosin bridge
    • Cleavage: New ATP binds to the Myosin head; Myosin detaches from the binding site returning to a low-energy state
    • Cross-Bridge Cycling: Cycles repeat as long as Calcium (Ca2+) and ATP are available

    Excitation-Contraction Coupling

    • Requires an action potential (stimulus) from the brain or spinal cord
    • Motor Unit: A motor neuron and all the myofibers it innervates
    • Neuromuscular Junction: Where the motor neuron "meets" its myofiber group
      • Synaptic Vesicles: Hold the neuron's neurotransmitter
      • Synaptic Cleft: Space between neuron's axon terminal and the sarcolemma
      • End-Plate Receptors: For binding the neurotransmitter

    Membrane Potential

    • The sarcolemma is polarized and maintains a resting negative charge
    • Motor neuron stimuli depolarize the sarcolemma, flipping the charge and generating an action potential
    • This is accomplished by causing ion shuttling across the sarcolemma membrane

    Goal of Excitation-Contraction Coupling

    • Convert an electrical signal (brain stimulus) into a chemical signal (neurotransmitter release)
    • Then, the chemical signal triggers an electrical signal (sarcolemma depolarization)
    • Finally, the electrical signal is converted back into a chemical signal (calcium release) that stimulates the sliding filament model

    Excitation-Contraction Coupling Steps

    • Neuron releases ACh: ACh binds to end-plate receptors, opening ligand-gated channels that allow ion flow
    • Sarcolemma Depolarization: Ion influx and efflux cause a change in membrane potential leading to an action potential via voltage-gated channels
    • Action Potential Propagates: Continuous ion shuttling "pushes" the potential down the entire sarcolemma
    • T-Tubules: Action potential reaches the T-tubules triggering voltage-sensitive proteins that open calcium channels, releasing calcium into the sarcoplasm
    • Sliding Filament Model: Calcium binds to troponin causing tropomyosin to uncover myosin binding sites
    • Calcium Reuptake: Once the neuronal action potential ceases, calcium is transported back into the SR and contraction ceases

    Size Principle

    • Motor units are recruited in order of size
    • Smaller motor units are recruited first which are used for finer motor tasks
    • Larger motor units are recruited last for higher forces

    Muscle Contractions

    • Isometric: External load (or muscle tension) changes, but muscle length remains constant
    • Isotonic: External load (or muscle tension) is constant, but muscle length changes
      • Concentric: Muscle shortening
      • Eccentric: Muscle lengthening
    • Isokinetic: External load changes as muscle length changes, but movement speed is constant

    Energy for Muscle Contractions

    • Muscle needs ATP to contract
    • Raw ATP stores only last for ~4-6 seconds
    • Fatigue sets in when energy use rates exceed our energy replenishment rate
    • Several energy systems are used:

    Energy Systems

    • Phosphagen (PCr) System
      • Most immediate source of ATP
      • Lasts about 15 seconds
      • Anaerobic
    • Glycolysis
      • Conversion of glucose into ATP
      • Anaerobic (lasts ~ 60 seconds) or Aerobic (lasts until glucose depleted)
    • Oxidative Phosphorylation
      • Occurs in the mitochondria and uses pyruvate from glucose to produce ATP
      • Lasts until all fuel sources are depleted

    Skeletal Muscle Fiber Typing

    • Classified based upon primary energy system used
      • Type IIx (Fast-glycolytic): Rely on PCr and anaerobic glycolysis; high force & power; highly fatigable
      • Type IIa (Fast-oxidative): Use a combination of anaerobic glycolysis and oxidative phosphorylation; moderate force & power; moderately fatigable
      • Type I (Slow-oxidative): Rely on oxidative phosphorylation; low force & power; fatigue-resistant

    Muscle Development & Decay

    • Muscle growth and development reflect changes in neuromuscular control
    • Muscle mass declines after age 30 (sarcopenia)
    • Muscle degeneration (disuse atrophy) occurs with paralysis, immobilization, or bedridden state
    • While there are gender differences in muscle masses, muscle strength is similar relative to body mass

    Smooth Muscle

    • Fewer Myosin filaments than skeletal muscle
    • Uses Calmodulin to bind Calcium (instead of troponin)
    • Less forceful but more efficient with prolonged contractions
    • Regenerate throughout the lifespan

    Muscle Tissue Summary

    • Functionally complex structures, requiring coordinated innervation and contraction across all units
    • Contractions are carried out through Excitation-Contraction Coupling
    • Strength of action potential and force of contraction are regulated by the frequency and intensity of the stimulus as well as the size principle
    • Different muscle fiber types vary in their energy systems and fatigability
    • Types of muscle contractions include isometric, isotonic, and isokinetic

    Muscle Tissue

    • Muscle tissue comprises about 42% of total body mass in males and about 36% of total body mass in females.
    • Muscle-related tissues often have prefixes like myo- , mys- , and sarco- . For example, sarcoplasm refers to the cytoplasm of a muscle cell.
    • There are three main types of muscle tissue: skeletal, cardiac, and smooth.
    • Skeletal muscle is attached to bones and skin, is striated, and is under voluntary control.
    • Cardiac muscle is found only in the heart (myocardium), is striated, and is under involuntary control.
    • Smooth muscle is found in the walls of hollow organs (like the digestive tract, urinary bladder, blood vessels, and airways) and is non-striated and under involuntary control.

    Muscle Tissue Characteristics and Function

    • There are four main characteristics of muscle tissue: excitability, contractility, extensibility, and elasticity.

    • Excitability means responsiveness to stimuli.

    • Contractility refers to the ability to shorten forcefully.

    • Extensibility is the ability to be stretched.

    • Elasticity is the ability to recoil to its resting length.

    • Muscle tissue has four main functions: produce movement, maintain posture and position, joint stabilization, and heat generation.

    • Movement includes locomotion and joint manipulation.

    • Posture involves keeping the body upright and everything in place.

    • Stabilization keeps joints from dislocating or overextending.

    • Muscles generate heat as a byproduct of contraction, which helps maintain thermoregulation and metabolism.

    Skeletal Muscle Makeup

    • Skeletal muscle is multilayered: a muscle belly that is composed of fascicles which in turn are composed of myofibers which are composed of myofibrils which are composed of sarcomeres.
    • The muscle belly is surrounded by the epimysium.
    • The fascicles are surrounded by the perimysium.
    • The myofibers are surrounded by the endomysium.
    • The sarcolemma is a membrane under the endomysium that surrounds each myofiber.
    • Sarcoplasm fills the space between myofibers.
    • Myofibrils make up 80% of the volume of a myofiber and are composed of sarcomeres connected in series and parallel.
    • The sarcomere is the functional contractile unit of a muscle and is a series of myofilaments.

    Myofiber Structures

    • Each myofiber contains various structures that aid in its function.
    • Mitochondria are responsible for energy (ATP) production.
    • The sarcoplasmic reticulum (SR) releases and reuptakes calcium (Ca2+) ions, which are critical for the Sliding Filament Model.
    • T-tubules carry action potentials from the sarcolemma deep into the myofiber and open calcium channels from the SR into the sarcoplasm.
    • Myonuclei contain DNA for the creation of new myofibrils, which are necessary for growth and repair.
    • Satellite cells are "muscle stem cells" that can differentiate into any tissue needed for growth and repair.

    Sarcomere Structure

    • Sarcomeres are made up of three myofilaments: actin (thin), myosin (thick), and titin (elastic).
    • Actin filaments are made up of subunits of troponin, tropomyosin, and actin.
    • Troponin is a calcium-binding protein.
    • Tropomyosin is a strand-like structure that covers myosin-binding sites; it moves to reveal these sites when calcium binds to troponin.
    • Myosin filaments are “contractile” filaments that bind and pull on actin filaments.
    • Titin filaments give the sarcomere its elasticity.
    • Key demarcations within the sarcomere include the Z-disc, the M-line, and the H-zone.
    • The Z-disc marks the end of the actin filaments and the ends of the sarcomere.
    • The M-line is the midline of the sarcomere.
    • The H-zone is the area on either side of the M-line where there is no actin-myosin overlap (only myosin).

    Skeletal Muscle Contraction and the Sliding Filament Model

    • When muscle is relaxed, sarcomeres (and myofibers) are at their full length and there is some actin-myosin overlap; distinct M-line and H-zone are visible.
    • When muscle contracts, sarcomeres (and myofibers) shorten, and the Sliding Filament Model occurs.
    • Calcium binding to troponin along with ATP hydrolysis causes myosin to bind to actin, forming a cross-bridge.
    • The thin filaments slide past the thick filaments, increasing the overlap of actin and myosin; the H-zone shrinks and disappears.

    Steps of the Sliding Filament Model

    • Rest: The myosin head is in a low energy state, with ATP bonded and not yet attached to actin.
    • Cross-Bridge: ATP hydrolysis occurs. The myosin head is energized and attaches to a binding site on actin.
    • Power Stroke: ADP and Pi are released, causing the myosin tail to contract, cocking and pulling the actin-myosin bridge. The actin filament moves closer to the M-line, and the sarcomere shortens.
    • Cleavage: New ATP binds to the myosin head and myosin is released from the binding site on actin, returning to its low energy state.
    • Cross-Bridge Cycling: This cycle repeats as long as calcium is available (bound to troponin, keeping myosin-binding sites open) and ATP is available (maintaining the energized myosin head).

    Excitation-Contraction Coupling

    • Muscle contraction requires a stimulus (action potential) from the brain or spinal cord.
    • Motor units consist of a motor neuron and all the myofibers it innervates.
    • The neuromuscular junction is where a motor neuron "meets" its fiber group.
    • It contains three primary components: synaptic vesicles, the synaptic cleft, and end-plate receptors.
    • Synaptic vesicles hold the neurotransmitter acetylcholine (ACh) in the neuron's axon.
    • The synaptic cleft is the space between the neuron's axon terminal and the sarcolemma.
    • End-plate receptors are binding proteins for ACh.

    Membrane Potential

    • The sarcolemma is polarized and holds a resting, negative charge.
    • This charge is carefully maintained by balancing ions on either side of the membrane.
    • Motor neuron stimuli seek to depolarize the sarcolemma by generating an action potential, which flips the charge and causes ion shuttling across the membrane.

    The Goal of Excitation-Contraction Coupling

    • To convert an electrical signal (from the brain) to a chemical signal (neurotransmitter release), then back to an electrical signal (sarcolemma depolarization, action potential), and finally to a chemical signal (calcium release) that stimulates the Sliding Filament Model.

    Steps of Excitation-Contraction Coupling

    • 1: Neuron Releases ACh: ACh binds to end-plate receptors, opening ligand-gated channels (which open only when a specific chemical messenger binds) to facilitate ion movement.
    • 2: Sarcolemma Depolarizes: The open ion channels allow an influx of sodium (Na+) and efflux of potassium (K+). This "increases" the membrane charge toward threshold. When threshold is reached, an action potential is generated. Voltage-gated channels (which open only in response to a change in membrane potential) are opened.
    • 3: Action Potential Propagates along Sarcolemma: The continued shuttling of Na+ and K+ ions pushes the potential down the entire sarcolemma.
    • 4: T-Tubules: The action potential reaches the T-tubules and triggers voltage-sensitive proteins to open calcium (Ca2+) channels from the SR, flooding the sarcoplasm with calcium ions. Calcium then binds to troponin.
    • 5: Sliding Filament Model: The process described above occurs.
    • 6: Calcium Reuptake: Once the neuronal action potential ceases, sodium and potassium channels close, membrane potential normalizes back to resting, calcium is reuptaken into the SR, tropomyosin covers myosin-binding sites, and contraction ceases.

    The Size Principle

    • Motor units are recruited in order of their size, starting with smaller motor units for finer motor tasks and lower forces, and ending with larger motor units for higher forces.
    • This provides an orderly recruitment of muscle fibers.
    • Training and exercise can allow larger motor units to be recruited earlier.

    Muscle Contractions

    • There are three main types of muscle contractions: isometric, isotonic, and isokinetic.
    • Isometric contractions involve a change in external load (or muscle tension) but a constant muscle length. This is commonly used in rehabilitation and characterizes many stabilization contractions, much like pressing against a brick wall.
    • Isotonic contractions involve a constant external load (or muscle tension) but a change in muscle length. These contractions are the most common type of movement, and are divided into concentric contractions (muscle shortening while doing work, such as lifting something) and eccentric contractions (muscle lengthening while producing force, such as resisting something). To help keep joints stable, when muscles are contracting concentrically, their opposing muscles typically contract eccentrically.
    • Isokinetic contractions involve a variable external load (or muscle tension) that changes with muscle length so that movement speed is constant. They are not commonly seen in daily activities, but are more prevalent in rehabilitation and research settings to study the force-velocity relationship and joint torque.

    Energy for Contractions

    • Muscle requires ATP to contract.
    • When ATP is not available, myosin cannot detach from actin and myosin cannot become energized and attach to actin.
    • ATP is derived from various sources, including raw ATP stores (which last about 4-6 seconds), the phosphagen (PCr) system, glycolysis, and oxidative phosphorylation.
    • Fatigue sets in when the rate at which energy is used exceeds the rate at which it is replenished. Fatigue can also be caused by ion imbalances that disrupt membrane depolarization.

    Energy Systems

    • There are three main energy systems: phosphagen (PCr) system, glycolysis, and the oxidative phosphorylation system.
    • The phosphagen (PCr) system is the most immediate source of ATP and uses phosphocreatine to phosphorylate (add a phosphate to) ADP.
    • The phosphagen system is anaerobic, lasts for about 15 seconds, and produces +1 ATP per cycle.
    • Glycolysis is the conversion of glucose into ATP. It can be fueled by sugar stores within the muscle or from the blood.
    • Anaerobic glycolysis produces lactate, while aerobic glycolysis produces pyruvate. Anaerobic glycolysis lasts for about 60 seconds or until glucose stores are depleted, while aerobic glycolysis can continue until glucose stores are depleted. Glycolysis provides a net +2 ATP per cycle (initial energy investment of -1 ATP).
    • Oxidative phosphorylation uses pyruvate to fuel the Krebs cycle, which generates electron carriers that then proceed through the electron transport chain, shuttling H+ ions to make ATP. This process is aerobic and can last until all fuel sources are depleted. It provides a net +32 ATP per cycle.

    Skeletal Muscle Fiber Typing

    • There are three types of muscle fibers, classified largely based on their primary energy system: type IIx (fast-glycolytic), type IIa (fast-oxidative), and type I (slow-oxidative).
    • Type IIx fibers rely heavily on the PCr system and anaerobic glycolysis. They produce high force and power but are highly fatigable. These fibers power activities like sprinting, jumping, and throwing.
    • Type IIa fibers use a combination of anaerobic glycolysis and oxidative phosphorylation. They generate moderate force and power and are moderately fatigable. They are used in sustained sprints and most weight-based exercise.
    • Type I fibers rely primarily on oxidative phosphorylation. They generate low force and power but are fatigue-resistant. These fibers power activities like maintaining posture, endurance running, and most everyday activities.

    Muscle Development and Decay

    • As we age, muscle growth and development changes.
    • In infancy, this reflects changes in neuromuscular control and occurs from head to toe, proximal to distal (which explains why babies lift their heads first, reach before grasping, crawl before walking). Neuromuscular control peaks in mid-adolescence, but exercise and training can extend this.
    • After age 30, muscle mass begins to decline (sarcopenia) as muscle fibers decrease and are replaced with connective tissue fibers. Training and exercise can slow or reverse this process.
    • If paralyzed, immobilized, or bedridden, muscle tissue will irreversibly degenerate (disuse atrophy), leading to a loss of both muscle mass and functionality (about 5% decrease in strength per day). Muscle can atrophy to 25% of its initial size when paralyzed.
    • Although men tend to have larger muscles, muscle strength relative to body mass is similar between genders.

    Smooth Muscle

    • Smooth muscle differs from skeletal muscle in several ways.
    • It has fewer myosin filaments than skeletal muscle.
    • It uses calmodulin to bind calcium instead of troponin (although tropomyosin is still present).
    • It is less forceful and powerful than skeletal muscle, but more efficient, with slower contractions and relaxations.
    • Smooth muscle can maintain contractions for prolonged periods of time (smooth muscle tone) without fatiguing, at minimal energy cost.
    • Additionally, smooth muscle can regenerate throughout the lifespan, while skeletal muscle has limited regenerative capacity.

    Muscle Tissue Summary

    • Muscles are intricate multilayered structures requiring coordinated contraction of all innervated units.
    • Contractions are carried out via excitation-concentration coupling, a process involving the following steps: a motor neuron innervates its motor unit, generating an action potential on the sarcolemma that stimulates Ca2+ release, which then binds to troponin, causing tropomyosin to open myosin-binding sites and triggering the Sliding Filament Model.
    • Action potential strength and contraction force are regulated by the frequency and intensity of the stimulus and the size principle.
    • Muscle fiber types are classified based on their primary means of ATP replenishment, which determines their fatigability.
    • Skeletal muscles can perform isometric, isotonic, or isokinetic contractions depending on the changes in load, muscle length, and/or movement speed.

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    This quiz covers the classification of joints based on their structure and function. You'll learn about fibrous, cartilaginous, and synovial joints, as well as their range of motion. Test your knowledge on the types of joints in the axial and appendicular skeleton.

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