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Questions and Answers
What is one of the key contributors to muscle fatigue?
What is one of the key contributors to muscle fatigue?
Which type of contraction involves the muscle lengthening while generating force?
Which type of contraction involves the muscle lengthening while generating force?
What type of exercise primarily promotes stronger and more flexible muscles?
What type of exercise primarily promotes stronger and more flexible muscles?
Which of the following is NOT a result of resistance or isometric exercise?
Which of the following is NOT a result of resistance or isometric exercise?
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Which situation could lead to a failure of action potentials needed for muscle contraction?
Which situation could lead to a failure of action potentials needed for muscle contraction?
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What does the term 'myology' refer to?
What does the term 'myology' refer to?
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Which of the following properties of muscle tissue allows it to return to its original size and shape after use?
Which of the following properties of muscle tissue allows it to return to its original size and shape after use?
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Which type of muscle tissue is responsible for involuntary contractions of the heart?
Which type of muscle tissue is responsible for involuntary contractions of the heart?
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What surrounds each muscle fiber within a fascicle?
What surrounds each muscle fiber within a fascicle?
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What is the function of the sarcoplasmic reticulum in muscle cells?
What is the function of the sarcoplasmic reticulum in muscle cells?
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Which component of skeletal muscle is primarily involved in contraction?
Which component of skeletal muscle is primarily involved in contraction?
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What is the primary role of myosin in muscle tissue?
What is the primary role of myosin in muscle tissue?
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What distinguishes skeletal muscle from cardiac and smooth muscle?
What distinguishes skeletal muscle from cardiac and smooth muscle?
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What is the main role of actin in muscle contraction?
What is the main role of actin in muscle contraction?
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Which proteins are part of the thin filament alongside actin?
Which proteins are part of the thin filament alongside actin?
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What initiates muscle fiber contraction at the neuromuscular junction (NMJ)?
What initiates muscle fiber contraction at the neuromuscular junction (NMJ)?
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Which structure contains a high concentration of acetylcholine receptors?
Which structure contains a high concentration of acetylcholine receptors?
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What is the primary function of somatic motor neurons?
What is the primary function of somatic motor neurons?
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How does calcium influx facilitate the release of acetylcholine?
How does calcium influx facilitate the release of acetylcholine?
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What happens to acetylcholine after it binds to its receptors?
What happens to acetylcholine after it binds to its receptors?
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What are T-tubules primarily responsible for in muscle fibers?
What are T-tubules primarily responsible for in muscle fibers?
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What triggers the production of a muscle action potential?
What triggers the production of a muscle action potential?
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How does acetylcholine (ACh) terminate its activity at the neuromuscular junction?
How does acetylcholine (ACh) terminate its activity at the neuromuscular junction?
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What is the role of calcium ions (Ca²⁺) in muscle contraction?
What is the role of calcium ions (Ca²⁺) in muscle contraction?
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What occurs during the relaxation of a muscle?
What occurs during the relaxation of a muscle?
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What is the first pathway for ATP production used during muscle contraction?
What is the first pathway for ATP production used during muscle contraction?
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In the sliding filament theory, which proteins interact to cause muscle contraction?
In the sliding filament theory, which proteins interact to cause muscle contraction?
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What happens to the troponin-tropomyosin complex when calcium ion concentration decreases?
What happens to the troponin-tropomyosin complex when calcium ion concentration decreases?
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What is produced through anaerobic glycolysis during muscle activity?
What is produced through anaerobic glycolysis during muscle activity?
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Study Notes
Muscular System Overview
- Myology is the study of muscles.
- Myo = muscle, logy = study of, sarco = flesh.
- Three types of muscle tissue: skeletal, cardiac, and smooth.
Types of Muscle Tissue
-
Skeletal Muscle:
- Located attached to bones.
- Long, cylindrical cells.
- Multiple nuclei.
- Striated (striped appearance).
- Voluntary control.
- Function: body movement.
-
Smooth Muscle:
- Found in walls of hollow organs and blood vessels.
- Spindle-shaped cells.
- Single nucleus.
- Non-striated.
- Involuntary control.
- Function: moving substances through the body.
-
Cardiac Muscle:
- Found in the heart.
- Branching, cylindrical cells.
- Single nucleus.
- Striated.
- Involuntary control.
- Function: pumping blood.
Properties of Muscle Tissue
- Excitability: Responds to stimuli with electrical signals.
- Contractility: Generates force and movement.
- Extensibility: Stretches without damage.
- Elasticity: Returns to original shape after stretching.
Functions of Muscular Tissue
- Producing body movements.
- Stabilizing body positions.
- Storing and moving substances within the body.
- Thermogenesis (producing heat).
Organization of Muscle Tissue
- Muscles are comprised of muscle fibers, nerves, blood vessels, and connective tissue (Epimysium, Perimysium, and Endomysium).
- Epimysium: Outer layer surrounding the entire muscle.
- Perimysium: Surrounds fascicles (bundles of muscle fibers).
- Endomysium: Penetrates each fascicle, wrapping around individual muscle fibers, primarily made of fine reticular fibers.
Organization of Muscle Tissue (Muscle Fibers)
- Muscle Fiber (muscle cell): Includes nuclei, capillary, sarcolemma (plasma membrane), sarcoplasm (cytoplasm), transverse tubules, mitochondria, sarcoplasmic reticulum (stores/releases Ca2+ for contraction), and myofibrils (contractile organelles).
- Myofibrils: Contain actin and myosin filaments (myofilaments).
Myofilaments (Actin & Myosin)
- Myosin: Main component of thick filaments, tail points toward M line, head has actin and ATP binding sites.
- Actin: Main component of thin filaments, binding sites for myosin heads.
- Tropomyosin and troponin: regulatory proteins that control muscle contraction.
Myofilaments (Actin & Myosin) - Sarcomere
- Sarcomere: Functional unit of muscle contraction.
- Z-discs: Separate one sarcomere from the next.
- A band: Entire length of myosin filaments.
- I band: Contains actin filaments only.
- H zone: Region in center of A band containing only myosin filaments.
- M line: Middle of sarcomere, responsible for holding thick filaments together.
Actin and Myosin Structure
- Myosin has a head and a tail. Myosin heads form cross-bridges.
- Actin filaments have active sites for myosin heads to bind.
- Regulatory proteins (troponin and tropomyosin) control the interaction between actin and myosin.
Skeletal Muscle Contraction Physiology
- Somatic motor neurons: Stimulate skeletal muscle fibers.
- Muscle fiber contraction: Action potentials travel along the sarcolemma and T-tubules. Initiation occurs at Neuromuscular Junction (NMJ).
Neuromuscular Junction (NMJ)
- Axon Terminal/Synaptic End Bulbs: End of motor neuron, containing synaptic vesicles (ACh).
- Synaptic cleft: Gap between neuron and muscle cell, signals transmitted chemically.
- Motor end plate: Portion of muscle fiber sarcolemma facing synaptic knob; contains ACh receptors (ligand-gated ion channels).
Neuromuscular Junction (NMJ) Physiology
- Nerve impulse and Ca2+ influx: Nerve impulse triggers calcium influx into the neuron, causing ACh release.
- Release of Acetylcholine (ACh): Ca2+ influx prompts release of ACh into the synaptic cleft.
- Diffusion and binding of ACh: ACh diffuses across the cleft and binds to ACh receptors.
- Opening of ion channels: ACh binding opens ion channels, allowing Na+ to enter the muscle fiber.
- Production of muscle action potential: Na+ influx causes a change in membrane charge, triggering a muscle action potential.
- Termination of ACh activity: Acetylcholinesterase (AChE) breaks down ACh, ending the contraction signal.
Sliding Filament Theory
- Muscle contraction results from the sliding of actin and myosin filaments past each other.
- Myosin heads bind to actin, pull actin filaments toward the center of the sarcomere (power stroke).
Summary of Skeletal Muscle Contraction
- Action potential travels along axon.
- Ca2+ enters axon terminal.
- ACh released, diffuses to motor end plate.
- ACh binds to receptors, causes Na+ channels to open.
- Action potential travels along muscle fiber membrane, triggering Ca2+ release from sarcoplasmic reticulum.
- Ca2+ exposes myosin-binding sites on actin.
- Myosin heads bind to actin, cycle repeats until contraction is complete or Ca2+ decreases.
Muscle Relaxation
- ACh breakdown stops signal.
- Ca2+ pumped back into sarcoplasmic reticulum.
- Tropomyosin and troponin block myosin-binding sites.
- Myosin heads detach from actin.
- Muscle relaxes.
Production of ATP for Muscle Contraction
- Creatine Phosphate: Quickly replenishes ATP during short, intense exertion.
- Anaerobic Glycolysis: Produces ATP without oxygen but yields less ATP and produces lactic acid.
- Aerobic Respiration: Most efficient way to produce ATP but requires oxygen, slow process.
Muscle Fatigue
- Inability to maintain force of contraction after prolonged activity.
- Reduced Ca2+ release, depletion of creatine phosphate, insufficient oxygen, and other factors contribute.
Types of Muscle Contraction
-
Isotonic: Muscle changes length during contraction (movement).
- Concentric: Muscle shortens.
- Eccentric: Muscle lengthens.
- Isometric: Muscle does not change length during contraction (no movement but tension is maintained).
Effects of Exercise on Muscles
- Aerobic: Increases muscle endurance, strength, flexibility, and neuromuscular coordination.
- Resistance/Isometric: Strengthens muscles and improves ability to contract against resistance.
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Description
Explore the fascinating world of the muscular system, focusing on the three types of muscle tissue: skeletal, smooth, and cardiac. Learn about their structures, functions, and the key properties that define muscle tissue. Perfect for anyone looking to deepen their understanding of myology.
