Questions and Answers
What is the function of calcium in muscle contraction?
It triggers the binding of myosin to nearby actin filaments
What is the name of the streak that bounds each sarcomere?
Z line
What is the name of the protein that makes up thin filaments?
Actin
What is the name of the theory that explains muscle contraction?
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What is the name of the structure formed when myosin binds to actin filaments?
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What is the function of ATP in muscle contraction?
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What is the name of the structure that passes through the sarcoplasm?
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What is the name of the type of muscle fiber that is stimulated by a nerve fiber?
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What is the main function of the epimysium in skeletal muscle organization?
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Which muscle originates from the inferior angle of the scapula and inserts into the humerus?
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What is the term for the thin layer of connective tissue that envelops individual muscle cells?
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What is the function of the quadratus lumborum muscle?
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Which of the following is NOT a function of the perimysium?
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Which muscle group originates from the sacrum and inserts into the occipital bone?
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What is the term for the tendinous attachment of a muscle that is broad and flat?
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What is the deepest muscle of the abdominal wall?
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What is the main function of the connective tissue within the entire muscle?
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What is the function of the rectus abdominis muscle?
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Which of the following is a characteristic of skeletal muscle cells?
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What is the term for the cytoplasm of muscle cells?
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What is the function of the contraction of the muscles of the abdominal wall on one side only?
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What is the function of calcium in muscle contraction?
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What is the function of the coracobrachialis muscle?
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What is the function of the deltoid muscle?
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Study Notes
Muscle Tissue
- There are three types of muscle tissue: skeletal muscle, smooth muscle, and cardiac muscle
- Muscle tissue consists of specialized contractile cells (fibers)
Skeletal Muscle
- Skeletal muscles produce body movements
- Each muscle consists of a fleshy part (made up of striped fibers) and tendinous parts (made up of fibrous tissue)
- Tendinous attachments can be broad and flat (aponeurosis)
- Muscles are arranged in groups, some of which are antagonistic to each other
- To produce movement at a joint, a group of muscles contracts while the antagonists relax
Skeletal Muscle Organization
- Multiple layers of connective tissue within the muscle transmit the force of contraction from each individual muscle cell to its point of attachment to the skeleton
- Epimysium: connective tissue sheath that covers the entire muscle
- Perimysium: connective tissue sheath attached to each bundle
- Endomysium: thin layer of connective tissue enveloping individual muscle cells
Structure of a Skeletal Cell
- Each cell has several nuclei found just below the cell membrane (sarcolemma)
- Cytoplasm of muscle cells (sarcoplasm) is filled with:
- Contractile filaments (actin and myosin)
- Many mitochondria
- Myoglobin (oxygen reserve)
- Large intracellular stores of calcium, released into the sarcoplasm by nerve stimulation
Contraction of Skeletal Muscle
- Skeletal muscle contracts in response to stimulation of a nerve fiber
- Synapse between a motor nerve and a skeletal muscle is called a neuromuscular junction
- Calcium triggers the binding of myosin to actin, forming cross-bridges
- ATP provides energy for the filaments to slide past each other, shortening the sarcomere
- This is known as the sliding filament theory
Muscles of Different Parts of the Body
- Face: muscles involved in changing facial expression and movement of the lower jaw during chewing and speaking
- Back: muscles involved in extension of the vertebral column (bending backwards)
- Abdominal wall: 5 pairs of muscles that form the abdominal wall, including:
- Rectus abdominis
- External oblique
- Internal oblique
- Transversus abdominis
- Quadratus lumborum
Functions of Abdominal Muscles
- Compress abdominal organs
- Flex the vertebral column in the lumbar region
- Contraction of muscles on one side only bends the trunk towards that side
- Contraction of oblique muscles on one side rotates the trunk
