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Questions and Answers
What is the characteristic shape of fusiform muscles?
What is the characteristic shape of fusiform muscles?
Which type of muscle arrangement has fascicles inserting into only one side of a central tendon?
Which type of muscle arrangement has fascicles inserting into only one side of a central tendon?
Which muscle is primarily responsible for closing the mouth and protruding the lips?
Which muscle is primarily responsible for closing the mouth and protruding the lips?
What action is facilitated by the temporalis muscle?
What action is facilitated by the temporalis muscle?
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Which muscle is referred to as the 'smiling' muscle?
Which muscle is referred to as the 'smiling' muscle?
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What is a common feature of pennate muscles?
What is a common feature of pennate muscles?
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Which of the following facial muscles allows the movement of the eyebrows?
Which of the following facial muscles allows the movement of the eyebrows?
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Which facial muscle is often linked with the ability to squint and blink?
Which facial muscle is often linked with the ability to squint and blink?
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What is the primary purpose of the heat generated by muscle activity?
What is the primary purpose of the heat generated by muscle activity?
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What are myofibrils primarily composed of?
What are myofibrils primarily composed of?
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Which protein forms the thick filaments in muscle cells?
Which protein forms the thick filaments in muscle cells?
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What is the function of the sarcoplasmic reticulum in muscle fibers?
What is the function of the sarcoplasmic reticulum in muscle fibers?
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What are the thin filaments primarily composed of?
What are the thin filaments primarily composed of?
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What structure in muscle cells is analogous to a sleeve surrounding an arm?
What structure in muscle cells is analogous to a sleeve surrounding an arm?
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What do cross bridges link together during muscle contraction?
What do cross bridges link together during muscle contraction?
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Which of the following describes the appearance of muscle cells due to the organization of myofibrils?
Which of the following describes the appearance of muscle cells due to the organization of myofibrils?
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What function do the fibularis muscles primarily perform?
What function do the fibularis muscles primarily perform?
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Which muscle is known as a prime mover for plantar flexion of the foot?
Which muscle is known as a prime mover for plantar flexion of the foot?
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What occurs when acetylcholine is released at the neuromuscular junction?
What occurs when acetylcholine is released at the neuromuscular junction?
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How is the action potential described in the context of muscle contraction?
How is the action potential described in the context of muscle contraction?
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What is the role of enzymes in muscle contraction?
What is the role of enzymes in muscle contraction?
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What initiates the contraction of skeletal muscle cells?
What initiates the contraction of skeletal muscle cells?
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What is a key structural feature of the soleus muscle?
What is a key structural feature of the soleus muscle?
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What occurs to the muscle cell after a contraction is initiated?
What occurs to the muscle cell after a contraction is initiated?
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What is the primary role of the prime mover in muscle action?
What is the primary role of the prime mover in muscle action?
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Which muscle type serves to oppose or reverse a movement?
Which muscle type serves to oppose or reverse a movement?
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The term 'rectus' in a muscle's name indicates what about its fiber arrangement?
The term 'rectus' in a muscle's name indicates what about its fiber arrangement?
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What do fixators do in the context of muscle action?
What do fixators do in the context of muscle action?
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What underlying principle defines the arrangement of circular muscles?
What underlying principle defines the arrangement of circular muscles?
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When a muscle's name contains 'biceps,' what can be inferred about its structure?
When a muscle's name contains 'biceps,' what can be inferred about its structure?
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Which of the following describes the features of convergent muscles?
Which of the following describes the features of convergent muscles?
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Which term is used to describe muscles that help prime movers by reducing undesirable movements?
Which term is used to describe muscles that help prime movers by reducing undesirable movements?
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What is the primary function of the gluteus maximus muscle?
What is the primary function of the gluteus maximus muscle?
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Which muscle is involved in stabilizing the pelvis during walking?
Which muscle is involved in stabilizing the pelvis during walking?
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Which group of muscles is known for adducting the thighs?
Which group of muscles is known for adducting the thighs?
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What is the main action of the iliopsoas muscle?
What is the main action of the iliopsoas muscle?
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Which muscles are part of the hamstring group?
Which muscles are part of the hamstring group?
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Which muscle is primarily responsible for extending the knee?
Which muscle is primarily responsible for extending the knee?
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What is the action of the tibialis anterior muscle?
What is the action of the tibialis anterior muscle?
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Which muscle is a prime mover for toe extension?
Which muscle is a prime mover for toe extension?
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Study Notes
Muscle Functions and Heat Generation
- Muscle activity generates body heat as a by-product of ATP usage, with nearly three-quarters of energy escaping as heat, crucial for maintaining normal body temperature.
Microscopic Anatomy of Skeletal Muscle
- Skeletal muscle cells are multinucleate, with oval nuclei located just beneath the sarcolemma (plasma membrane).
- Myofibrils are long, ribbon-like organelles nearly filling the cytoplasm, giving muscle cells a striated appearance due to alternating light and dark bands.
- Myofibrils are composed of sarcomeres, the tiny contractile units aligned end to end.
- Two types of myofilaments exist: thick (myosin) and thin (actin), enabling muscle contraction through the interaction of their components.
- Thick filaments contain ATPase enzymes for ATP splitting, facilitating muscle contraction via cross bridges that link thick and thin filaments.
- Thin filaments consist of actin and regulatory proteins, anchored to the Z disc, allowing for muscle contraction regulation.
- The sarcoplasmic reticulum is a specialized organelle storing and releasing calcium, essential for muscle contraction.
Muscle Movements and Types
- Muscles exhibit a variety of movements categorized by roles:
- Prime movers initiate a movement.
- Antagonists oppose the movement, remaining relaxed when prime movers contract.
- Synergists assist prime movers, enhancing or stabilizing movements.
- Fixators stabilize bones or origins for efficient movement execution.
Naming Skeletal Muscles
- Muscle names detail aspects such as:
- Direction of fibers (rectus = straight, oblique = slanted).
- Relative size (maximus = largest, minimus = smallest, longus = long).
- Location (temporal and frontal muscles named after nearby bones).
- Number of origins (biceps, triceps, quadriceps indicating two, three, four origins, respectively).
- Shape and action of the muscle contribute to naming conventions.
Fascicle Arrangement in Skeletal Muscles
- Fascicle arrangements influence muscle structure and function:
- Circular: arranged in concentric rings; common in muscles surrounding openings.
- Convergent: fascicles converge toward a single tendon; typically triangular or fan-shaped.
- Parallel: fascicles run parallel to muscle's long axis; fusiform muscles are a subtype.
- Pennate: short fascicles attach obliquely to a central tendon; categorized as unipennate, bipennate, or multipennate based on attachment.
Head and Neck Muscles
- Facial muscles are grouped as either facial or chewing muscles:
- Five primary facial muscles include frontalis, orbicularis oculi, orbicularis oris, buccinator, and zygomaticus, each with distinct functions ranging from raising eyebrows to facilitating smiling.
Chewing Muscles
- The masseter and temporalis are significant chewing muscles responsible for jaw movement; the masseter closes the jaw, while the temporalis aids in jaw elevation.
Muscles at the Hip Joint
- Gluteus maximus serves as a powerful hip extensor; gluteus medius stabilizes the pelvis; iliopsoas is the primary hip flexor; adductor muscles facilitate thigh adduction.
Movement at the Knee Joint
- The hamstring group (biceps femoris, semimembranosus, semitendinosus) flexes the knee, while the quadriceps group (rectus femoris, vastus muscles) is crucial for knee extension.
Movement at the Ankle and Foot
- Key muscles for ankle and foot movement include:
- Tibialis anterior: dorsiflexion and extension of toes.
- Extensor digitorum longus: toe extension and foot dorsiflexion.
- Fibularis muscles: plantar flexion and foot eversion.
- Gastrocnemius: prime mover for plantar flexion; soleus lies beneath, aiding in foot movement without affecting the knee.
Nerve Stimulus and Action Potential
- Skeletal muscle contraction is initiated by nerve impulses, releasing acetylcholine (ACh) at axon terminals.
- Increased permeability of the sarcolemma to sodium ions generates an action potential, leading to muscle contraction.
- Acetylcholine is broken down post-contraction, preventing continuous stimulation of the muscle fiber.
Mechanism of Muscle Contraction
- Myosin heads attach to thin filament binding sites upon nervous system activation, initiating the sliding mechanism for muscle contraction.
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Description
This quiz explores Chapter 2 of the Anatomy of the Muscular System, focusing on the functions of muscles, including their role in heat generation and body temperature regulation. It also delves into the microscopic anatomy of skeletal muscle from Chapter 3, examining cellular structures like sarcolemma and nuclei.
