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Questions and Answers
What distinguishes cardiac muscle tissue from skeletal muscle tissue?
What distinguishes cardiac muscle tissue from skeletal muscle tissue?
Which functional characteristic of muscle enables it to respond to stimuli?
Which functional characteristic of muscle enables it to respond to stimuli?
What component of a skeletal muscle fiber stores oxygen?
What component of a skeletal muscle fiber stores oxygen?
Which of the following describes smooth muscle tissue?
Which of the following describes smooth muscle tissue?
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What is the primary role of muscles in maintaining posture?
What is the primary role of muscles in maintaining posture?
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What structural component contributes to the striated appearance of skeletal muscle?
What structural component contributes to the striated appearance of skeletal muscle?
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Which of the following muscle types is controlled by involuntary neural mechanisms?
Which of the following muscle types is controlled by involuntary neural mechanisms?
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What is the primary function of muscle activity in terms of body temperature?
What is the primary function of muscle activity in terms of body temperature?
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What is the main function of the Z disc in a sarcomere?
What is the main function of the Z disc in a sarcomere?
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Which structure in a sarcomere is where thick filaments are primarily located?
Which structure in a sarcomere is where thick filaments are primarily located?
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Which protein is primarily responsible for the composition of thin filaments?
Which protein is primarily responsible for the composition of thin filaments?
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What is the role of tropomyosin in myofilaments?
What is the role of tropomyosin in myofilaments?
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Which region of the sarcomere does not contain overlapping thick and thin filaments?
Which region of the sarcomere does not contain overlapping thick and thin filaments?
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What is the primary function of elastic filaments within a sarcomere?
What is the primary function of elastic filaments within a sarcomere?
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What distinguishes thick filaments from thin filaments?
What distinguishes thick filaments from thin filaments?
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What role does the sarcoplasmic reticulum play in muscle contraction?
What role does the sarcoplasmic reticulum play in muscle contraction?
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Study Notes
Muscle Types
- Muscle terminology uses similar root words (myo, mys, sacro) that refer to muscles.
- Three types: skeletal, cardiac, and smooth, differing in structure, location, function, and activation.
Skeletal Muscle Tissue
- Has striations (banding patterns).
- Found in skeletal muscles attached to the skeleton.
- Controlled voluntarily.
- Highly adaptable, able to exert varying force.
Cardiac Muscle Tissue
- Also striated, similar to skeletal muscle.
- Located only in the heart.
- Involuntary neural control allows response to bodily needs.
Smooth Muscle Tissue
- Lacks striations.
- Found in the walls of hollow organs.
- Involuntary, controlled by neural and hormonal mechanisms.
Functional Characteristics of Muscle
- Excitability (irritability): Ability to receive and respond to stimuli.
- Contractility: Ability to shorten forcibly.
- Extensibility: Ability to be stretched or extended.
- Elasticity: Ability to recoil and resume resting length.
Muscle Functions
- Producing movement: Muscle moves body parts or materials within the body.
- Maintaining posture: Keeps body upright against gravity.
- Stabilizing joints: Muscle tone reinforces joints.
- Generating heat: Important in regulating body temperature.
Skeletal Muscle Microscopic Anatomy
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A muscle cell is called a muscle fiber.
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Sarcolemma: Muscle fiber's cell membrane.
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Sarcoplasm: Cytoplasm of a large muscle fiber; contains glycogen (stored glucose) and myoglobin (oxygen-binding protein).
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Myofibrils: Dense, rod-like contractile elements within muscle fibers.
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Sarcomeres: Smallest contractile unit within a myofibril; arranged in a repeating series of dark (A bands) and light (I bands) striations.
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Myofilaments: Contractile proteins within sarcomeres.
- Thick filaments (myosin): Extend throughout the A band; have heads for cross-bridge formation.
- Thin filaments (actin): Extend across the I band and part of the A band; have active sites for myosin binding.
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Other components: I band, H zone, M line, Z disc, and A band form a repeating pattern.
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Sarcoplasmic reticulum: Elaborate smooth endoplasmic reticulum surrounding myofibrils; regulates calcium levels for muscle contraction.
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T tubules: Elongated tubes that penetrate the cell interior, connecting with sarcoplasmic reticulum at triads and conducting impulses for Ca2+ release.
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Triads: A structure formed by a T tubule and two terminal cisternae, which regulate Ca2+ release for muscle contraction.
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