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Questions and Answers
What is a characteristic of skeletal muscle tissue?
What is a characteristic of skeletal muscle tissue?
What is NOT a function of the muscular system?
What is NOT a function of the muscular system?
Which type of muscle tissue is primarily found in the heart?
Which type of muscle tissue is primarily found in the heart?
Which feature distinguishes cardiac muscle tissue from skeletal muscle tissue?
Which feature distinguishes cardiac muscle tissue from skeletal muscle tissue?
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Which of the following is true about smooth muscle tissue?
Which of the following is true about smooth muscle tissue?
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What makes skeletal muscle fibers unique compared to other muscle types?
What makes skeletal muscle fibers unique compared to other muscle types?
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What occurs during the contraction of muscle tissue?
What occurs during the contraction of muscle tissue?
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Which component is part of the neuromuscular junction?
Which component is part of the neuromuscular junction?
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What role does acetylcholinesterase play in muscle action?
What role does acetylcholinesterase play in muscle action?
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What causes the muscle action potential to travel along the transverse tubule?
What causes the muscle action potential to travel along the transverse tubule?
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What initiates the exposure of binding sites for myosin on the actin filament?
What initiates the exposure of binding sites for myosin on the actin filament?
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What happens to calcium ions after the muscle contraction phase?
What happens to calcium ions after the muscle contraction phase?
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What triggers the opening of calcium release channels in the sarcoplasmic reticulum?
What triggers the opening of calcium release channels in the sarcoplasmic reticulum?
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How does ATP contribute to muscle contraction?
How does ATP contribute to muscle contraction?
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What effect does elevated calcium levels in the sarcoplasm have on muscle contraction?
What effect does elevated calcium levels in the sarcoplasm have on muscle contraction?
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What occurs when calcium ions bind to troponin?
What occurs when calcium ions bind to troponin?
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What primarily determines the amount of tension produced by muscle fibers?
What primarily determines the amount of tension produced by muscle fibers?
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Which phase is NOT part of a muscle twitch?
Which phase is NOT part of a muscle twitch?
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What is the result of incomplete tetanus in muscle contractions?
What is the result of incomplete tetanus in muscle contractions?
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What characterizes a motor unit involved in precise movements?
What characterizes a motor unit involved in precise movements?
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What occurs when ATP is used faster than it is produced in muscle fibers?
What occurs when ATP is used faster than it is produced in muscle fibers?
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Which type of contraction occurs when muscle tension rises but the muscle length remains constant?
Which type of contraction occurs when muscle tension rises but the muscle length remains constant?
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Which type of muscle fiber is characterized by having a large diameter and fatigue quickly?
Which type of muscle fiber is characterized by having a large diameter and fatigue quickly?
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What are pale muscles that are predominantly fast fibers commonly referred to as?
What are pale muscles that are predominantly fast fibers commonly referred to as?
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What is the effect of training on muscle fibers?
What is the effect of training on muscle fibers?
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What is the primary function of myoglobin in slow muscle fibers?
What is the primary function of myoglobin in slow muscle fibers?
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What initiates the contraction of skeletal muscle?
What initiates the contraction of skeletal muscle?
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Which component directly binds to calcium during muscle contraction?
Which component directly binds to calcium during muscle contraction?
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Which of the following describes the sliding filament theory?
Which of the following describes the sliding filament theory?
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What is the role of ATP in the contraction cycle of muscle fibers?
What is the role of ATP in the contraction cycle of muscle fibers?
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What happens to acetylcholine after it triggers muscle contraction?
What happens to acetylcholine after it triggers muscle contraction?
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What occurs during the recovery stroke of muscle contraction?
What occurs during the recovery stroke of muscle contraction?
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Which step is NOT part of the muscle contraction process?
Which step is NOT part of the muscle contraction process?
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What is the final outcome of cross-bridge cycling in muscle fibers?
What is the final outcome of cross-bridge cycling in muscle fibers?
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What triggers the release of calcium from the sarcoplasmic reticulum?
What triggers the release of calcium from the sarcoplasmic reticulum?
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What is the main role of troponin in muscle contraction?
What is the main role of troponin in muscle contraction?
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What is the role of pacemaker cells in the heart?
What is the role of pacemaker cells in the heart?
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Which of the following statements about smooth muscle is true?
Which of the following statements about smooth muscle is true?
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Which muscle type is responsible for voluntary movements?
Which muscle type is responsible for voluntary movements?
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What is the function of the epimysium in skeletal muscle?
What is the function of the epimysium in skeletal muscle?
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What structure stores calcium ions necessary for muscle contraction?
What structure stores calcium ions necessary for muscle contraction?
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What initiates the process of muscle contraction at the neuromuscular junction?
What initiates the process of muscle contraction at the neuromuscular junction?
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Which protein in muscle fibers covers the active sites on actin?
Which protein in muscle fibers covers the active sites on actin?
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What is primarily responsible for the striated appearance of skeletal muscle?
What is primarily responsible for the striated appearance of skeletal muscle?
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What is a primary function of skeletal muscle tissue?
What is a primary function of skeletal muscle tissue?
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Which component of the muscle fiber is responsible for producing the action potential?
Which component of the muscle fiber is responsible for producing the action potential?
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How does actin interact with myosin during muscle contraction?
How does actin interact with myosin during muscle contraction?
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What happens to acetylcholine after it binds to its receptor at the neuromuscular junction?
What happens to acetylcholine after it binds to its receptor at the neuromuscular junction?
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What is the role of myofibrils in muscle fibers?
What is the role of myofibrils in muscle fibers?
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Study Notes
Musculoskeletal System (Part 2)
- Learning Outcomes: Students will be able to list muscle types, describe basic muscle characteristics, understand action potentials, identify neuromuscular junction components and events, and understand muscle contraction/relaxation mechanisms.
Functions of Muscular System
- Producing body movements
- Stabilizing body positions
- Moving substances within the body
- Producing heat
- Supporting soft tissue
- 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 heart wall, it is striated and involuntary.
- Smooth muscle tissue: Located mainly 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.
- Skeletal muscle fibers are long, cylindrical cells, containing many nuclei and striated (alternating light and dark bands).
- These fibers bind together with connective tissues, nerves, and blood vessels to form bundles.
- These bundles then form muscles.
Cardiac Muscle Tissue
- Found only in the heart.
- Made of cardiac muscle cells (cardiocytes).
- Striated.
- Typically contains a centrally located single nucleus.
- Not under voluntary control.
- A bundle of specialized cells in the upper part of the heart (pacemaker cells) sends electrical signals through the cardiac muscle tissue to rhythmically contract and pump blood.
Smooth Muscle Tissue
- Found in many internal organs (e.g., abdomen, intestines, blood vessels).
- Spindle-shaped, with a single nucleus.
- Not striated.
- Not under voluntary control.
- Contractions move food through the digestive tract, regulate blood flow, and adjust pupil size.
Organization of Connective Tissues
- Epimysium surrounds muscles.
- Perimysium sheathes bundles of muscle fibers.
- Perimysium and epimysium 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 Ca+
- 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 (calcium binding site)
-
Thick filaments:
- Bundles of myosin fibers around a titan core
- Myosin molecules have an elongate tail and globular head
- Heads form cross-bridges during contraction
- Interactions between actin and myosin are prevented by tropomyosin during rest.
Sliding Filament Theory
- Thick and thin filaments slide past each other during contraction.
- A cyclic process begins with calcium release from the sarcoplasmic reticulum.
- Calcium binds to troponin.
- Troponin moves, exposing actin active site, allowing the myosin head to form a cross-bridge and bend towards the H zone.
- ATP allows release of the cross-bridge.
Muscle Contraction
- Action potential along the T-tubule 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 acetylcholine (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 is the contraction and relaxation of the muscle in response to a stimulus.
- 3 phases: lag, contraction, and relaxation
- Repeated stimulation after relaxation phase has been completed.
Summation
- Repeated stimulation before relaxation phase has been completed.
- Wave summation - one twitch is added to another.
- Incomplete tetanus - muscle never relaxes completely.
- Complete tetanus - relaxation phase is eliminated.
- Myograms illustrate these responses graphically.
Motor Units and Recruitment
- Consists of a motor neuron and the muscle fibers it stimulates.
- Axon branches form neuromuscular junctions with muscle fibers.
- A motor neuron contacts about 150 muscle fibers.
- Control of precise movements consists of many small motor units.
- Strength of a contraction depends on the size of motor units and the number activated.
Fatigue
- Muscle fibers use ATP faster than they produce it, resulting in weaker contraction.
- Binding of new ATP with the myosin head is necessary to break down the cross-bridge
Types of Muscle Contractions
- Isometric: Tension rises, length remains the same.
- Isotonic: Tension rises, length changes. Resistance and speed are inversely related. Return to resting lengths due to elastic components, opposing muscle groups, gravity. Concentric and eccentric contractions.
Muscle Performance
-
Fast fibers (type II myosin):
- Large diameter, dense myofibrils, large glycogen reserves, few mitochondria, rapid powerful contractions, short durations, fatigue quickly, white muscle.
-
Slow fibers (type I myosin):
- Half the diameter of fast fibers, take longer to contract, abundant mitochondria, extensive capillary supply, high myoglobin concentration, prolonged contractions, greater resistance to fatigue, red/dark muscles.
Muscle Performance and 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 fibers(of stimulated muscle).
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Description
This quiz covers the anatomy and functions of the muscular system, including the types of muscle tissues and their characteristics. Students will explore action potentials, neuromuscular junctions, and the mechanisms of muscle contraction and relaxation. Perfect for those studying human anatomy and physiology.
