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Questions and Answers
What is the primary energy source that allows myosin heads to attach and detach during muscle contraction?
What is the primary energy source that allows myosin heads to attach and detach during muscle contraction?
During isotonic contractions, the muscle length remains unchanged while producing force.
During isotonic contractions, the muscle length remains unchanged while producing force.
False
What is the central region of a relaxed sarcomere that lacks actin filaments called?
What is the central region of a relaxed sarcomere that lacks actin filaments called?
bare zone
During _____ contractions, the muscle attempts to shorten but does not, resulting in increased tension.
During _____ contractions, the muscle attempts to shorten but does not, resulting in increased tension.
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Match the type of body movement with its correct description:
Match the type of body movement with its correct description:
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Which of the following statements is NOT one of the 5 golden rules of skeletal muscle activity?
Which of the following statements is NOT one of the 5 golden rules of skeletal muscle activity?
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The sliding filament theory describes how actin and myosin filaments slide past one another to cause muscle contraction.
The sliding filament theory describes how actin and myosin filaments slide past one another to cause muscle contraction.
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What happens to the myofilaments during isotonic contraction?
What happens to the myofilaments during isotonic contraction?
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Which type of muscle is under voluntary control?
Which type of muscle is under voluntary control?
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Cardiac muscle fibers are multinucleate cells.
Cardiac muscle fibers are multinucleate cells.
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What are the two types of myofilaments found in muscle fibers?
What are the two types of myofilaments found in muscle fibers?
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The H zone is located in the middle of the __________ band.
The H zone is located in the middle of the __________ band.
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Match the type of muscle with its primary characteristic:
Match the type of muscle with its primary characteristic:
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Which statement about smooth muscle is true?
Which statement about smooth muscle is true?
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Muscle contraction generates heat as a byproduct.
Muscle contraction generates heat as a byproduct.
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What structural feature connects cardiac muscle fibers?
What structural feature connects cardiac muscle fibers?
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Study Notes
Sarcomere Structure
- Thick filaments protrude from ends of sarcomere
- Thin filaments overlap thick filaments, but don't extend into central relaxed sarcomere region
- Central region without actin filaments is called the bare zone
Sliding Filament Theory
- Nervous system activates muscle fibers
- Myosin heads attach to binding sites on thin filaments
- Sliding begins, myosin heads attach and detach repeatedly, powered by ATP
- Thin filaments are pulled towards the center of the sarcomere
- Muscle cell shortens
Types of Muscle Contraction
- Isotonic contractions: muscle shortens, myofilaments successfully slide, movement occurs
- Isometric contractions: muscle doesn't shorten, myosin myofilaments 'skid their wheels', tension increases, muscle is pitted against an immovable object
Five Golden Rules of Skeletal Muscle Activity
- Muscles cross at least one joint
- Muscle bulk lies proximal to the joint crossed
- Muscles have two attachments: origin and insertion
- Muscles can only pull, not push
- During contraction, muscle insertion moves towards the origin
Types of Body Movements
- Flexion: decreasing joint angle, brings bones closer together
- Extension: increasing joint angle, moves bones further apart
- Rotation: movement around longitudinal axis
- Abduction: movement away from midline
- Adduction: movement towards midline
Types of Muscle
- Skeletal, cardiac, smooth
Similarities in Muscle Types
- Skeletal and smooth muscle cells are elongated, called muscle fibers
- Ability to contract depends on two types of myofilaments
Skeletal Muscle
- Attached to skeleton
- Cigar-shaped, multinucleate cells, largest muscle fiber type
- Striated muscle, voluntary, subject to conscious control
- Can be activated by reflexes
Smooth Muscle
- Found in hollow visceral organs (stomach, bladder, respiratory passages)
- No striations, involuntary
- Spindle-shaped cells, single nucleus
- Arranged in sheaths or layers, often two layers (circular and longitudinal)
Cardiac Muscle
- Found only in the heart
- Striated, involuntary
- Branching cells joined by intercalated discs
Functions of Muscles
- Producing movement
- Maintaining posture
- Stabilizing joints
- Generating heat (ATP usage releases heat, important for body temperature regulation)
Microscopic Structure of Skeletal Muscle
- Myofibrils nearly fill the cytoplasm
- Light (I) and dark (A) bands
- Light I band has a dark midline interruption called the Z disc
- Dark A band has a lighter central area called the H zone
- M line in the center of the H zone contains protein rods that hold adjacent thick filaments together
Myofilaments
- Actin filaments: thin filaments, anchored to the Z disc, found only in light I band
- Myosin filaments: thick filaments, extend the entire length of the dark A band
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Description
This quiz covers key concepts of muscle anatomy, including sarcomere structure, the sliding filament theory, different types of muscle contraction, and the essential rules of skeletal muscle activity. Test your knowledge on how muscles function and their physiology!
