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Questions and Answers
Which characteristic of skeletal muscle refers to its ability to respond to stimuli?
Which characteristic of skeletal muscle refers to its ability to respond to stimuli?
What is the primary function of the epimysium in skeletal muscles?
What is the primary function of the epimysium in skeletal muscles?
In the sliding filament theory, which structure enhances muscle contraction by interacting with myosin?
In the sliding filament theory, which structure enhances muscle contraction by interacting with myosin?
Which type of muscle attachment is typically less moveable in appendicular muscles?
Which type of muscle attachment is typically less moveable in appendicular muscles?
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What characterizes a small motor unit?
What characterizes a small motor unit?
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Which organizational pattern of skeletal muscle fibers forms a muscle that is wider in the middle and tapers at both ends?
Which organizational pattern of skeletal muscle fibers forms a muscle that is wider in the middle and tapers at both ends?
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Which component of the sarcomere anchors the thin filaments?
Which component of the sarcomere anchors the thin filaments?
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What is the function of calcium ions (Ca++) stored in the sarcoplasmic reticulum?
What is the function of calcium ions (Ca++) stored in the sarcoplasmic reticulum?
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What characteristic of skeletal muscle allows it to return to its original shape after being stretched?
What characteristic of skeletal muscle allows it to return to its original shape after being stretched?
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What term describes the muscle that is typically more movable during an axial muscle contraction?
What term describes the muscle that is typically more movable during an axial muscle contraction?
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Which connective tissue surrounds individual muscle fibers within a fascicle?
Which connective tissue surrounds individual muscle fibers within a fascicle?
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In the sliding filament theory, which process best describes the role of the myosin crossbridges?
In the sliding filament theory, which process best describes the role of the myosin crossbridges?
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What is indicated by the term 'motor unit' in relation to skeletal muscle?
What is indicated by the term 'motor unit' in relation to skeletal muscle?
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Which organizational pattern of muscle fibers allows for a greater range of motion?
Which organizational pattern of muscle fibers allows for a greater range of motion?
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Which part of the sarcomere is where actin filaments are anchored?
Which part of the sarcomere is where actin filaments are anchored?
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What is the primary function of the terminal cisternae within the sarcoplasmic reticulum?
What is the primary function of the terminal cisternae within the sarcoplasmic reticulum?
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Which feature describes the muscle fiber organization in an unipennate muscle?
Which feature describes the muscle fiber organization in an unipennate muscle?
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The term 'aponeurosis' refers to which of the following?
The term 'aponeurosis' refers to which of the following?
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Study Notes
Functions of the Muscular System
- Movement of body parts and substances
- Stabilization of posture
- Protection and support of internal organs
- Elimination of materials
- Heat generation
Defining Characteristics of Muscle
- Excitability: ability to respond to stimuli
- Conductivity: ability to transmit electrical signals
- Contractility: ability to shorten
- Extensibility: ability to lengthen
- Elasticity: ability to return to original length after stretching
Naming Muscles
- Location: where the muscle is located
- Size: relative size (e.g., major, minor, longus, brevis)
- Shape: general form (e.g., deltoid, trapezius)
- Action: what the muscle does (e.g., flexor, extensor)
- Number: number of heads or bellies (e.g., biceps, triceps)
Skeletal Muscle Attachments
- Tendon: connects muscle to bone, skin, or another muscle
- Aponeurosis: thin, flattened sheetlike tendon
- Axial Muscles:
- Superior attachment (usually more moveable)
- Inferior attachment (usually less moveable)
- Appendicular muscles:
- Proximal attachment (usually less moveable)
- Distal attachment (usually more moveable)
Organizational Patterns of Skeletal Muscle Fibers
- Circular: muscle fibers arranged in concentric circles
- Parallel: muscle fibers run parallel to the long axis of the muscle
- Convergent: muscle fibers converge towards a single tendon
-
Pennate: muscle fibers attach to a tendon at an angle, increasing force
- Unipennate: fibers attach to one side of tendon
- Bipennate: fibers attach to both sides of tendon
- Multipennate: fibers attach to multiple tendons
Stabilizing Connective Tissues of Skeletal Muscle
- Epimysium: outermost layer, surrounds the entire muscle, binds fascicles together
- Perimysium: surrounds fascicles (bundles of muscle fibers)
- Endomysium: innermost layer, surrounds individual muscle fibers
- Fascicle: bundle of muscle fibers
Microanatomy of a Muscle Fiber
-
Sarcomere: contractile unit of a myofibril
- Thick filaments: myosin
- Thin filaments: actin
- Z line/disc: anchors actin, defines the ends of the sarcomere
- M-line: anchors myosin
- I band: light band, contains only actin
- A band: dark band, contains both actin and myosin
Sarcoplasmic Reticulum (SR)
- Function: stores and releases calcium ions (Ca++)
- Terminal Cisternae: enlarged areas of the SR that act as Ca++ reservoirs
Motor Unit
- Definition: a motor neuron and all the muscle fibers it innervates
-
Number of fibers innervated: varies
- Small motor unit: < 5 muscle fibers
- Large motor unit: > 1000 muscle fibers
Neuromuscular Junction (NMJ)
- Where a motor neuron meets a muscle fiber
- Synaptic knob: terminal end of the motor neuron
- Synaptic cleft: narrow gap between the neuron and muscle fiber
- Motor end plate: specialized region of the muscle fiber where the neuron makes contact
Sliding Filament Theory
- Explains how muscle contraction occurs
-
Process:
- Myosin crossbridges attach to binding sites on actin
- Myosin pulls on actin towards the center of the sarcomere
- Myosin releases actin and attaches to the next binding site
- This cycle repeats, causing actin to slide past myosin and shorten the sarcomere
Is skeletal muscle voluntary or involuntary? What does it need to contract?
- Skeletal muscle is voluntary.
-
To contract, skeletal muscle needs:
- Stimulation from a motor neuron
- Calcium ions (Ca++) for the sliding filament mechanism to occur
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Description
Test your knowledge on the characteristics and functions of skeletal muscles with this quiz. From the sliding filament theory to muscle attachment types, this assessment covers key concepts in muscle anatomy and physiology. Perfect for students studying biology or kinesiology.
