Questions and Answers
What are the three types of muscles?
What type of muscle is multinucleate?
Skeletal muscle
How many nuclei does cardiac muscle have?
Generally one nucleus
How many nuclei do smooth muscles have?
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What is muscle contraction?
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What do tendons connect?
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What encloses a single muscle fiber?
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What wraps around a fascicle of muscle fibers?
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What covers the entire skeletal muscle?
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What do motor neurons stimulate to contract?
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What neurotransmitter is associated with skeletal muscle?
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What is the function of myofibrils?
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Muscle contraction occurs when myosin heads attach to actin filaments.
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What is the bare zone that lacks actin filaments?
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What is responsible for releasing and storing calcium in muscle cells?
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What is the ability of a muscle to shorten when stimulated?
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What occurs in isotonic contractions?
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What is muscle tone?
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What enhances muscle flexibility and resistance to fatigue?
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What increases muscle size and strength?
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What are the five golden rules of skeletal muscle activity?
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What is the term for decreasing the angle of a joint?
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What is the term for increasing the angle of a joint?
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What combines flexion, extension, abduction, and adduction in a circular movement?
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Study Notes
Muscle Types
- Three types of muscles: skeletal, cardiac, smooth.
- Skeletal muscle is multinucleate; cardiac muscle generally has one nucleus; smooth muscle has one nucleus.
Muscle Structure
- Skeletal and smooth muscle cells are elongated.
- Striations present in skeletal and cardiac muscles.
- Endomysium surrounds individual muscle fibers; perimysium wraps around fascicles; epimysium covers the entire skeletal muscle.
- Fascia is located outside the epimysium.
- Tendons connect muscles to bones and cross joints due to toughness.
Muscle Cells and Contraction Mechanism
- Muscle contraction results from the movement of microfilaments.
- Sarcolemma is a specialized plasma membrane in muscle cells.
- Myofibrils, long organelles in muscle cells, contain distinct light (I band) and dark (A band) bands.
- Sarcomeres are the contractile units with thick (myosin) and thin (actin) filaments.
Muscle Filaments
- Myosin filaments contain ATPase enzymes and overlap slightly with actin filaments, which are anchored to the Z disc.
- H Zone is a bare zone of the sarcomere that lacks actin filaments at rest.
- Sarcoplasmic reticulum stores and releases calcium.
Muscle Properties
- Excitability: ability to respond to stimuli.
- Contractility: ability to shorten in response to stimuli.
- Extensibility: capability to stretch.
- Elasticity: ability to return to resting length after stretching.
Neural Stimulation
- Motor neurons are necessary for skeletal muscle contraction.
- The neuromuscular junction is the site where nerve impulses stimulate muscle contraction through neurotransmitters like acetylcholine.
- Transmission of nerve impulses involves the release of neurotransmitters, generating action potential, and thereby facilitating muscle contraction.
Muscle Contraction Mechanisms
- Sliding filament theory explains muscle contraction through the binding of myosin heads to actin, resulting in myofilament sliding and muscle shortening.
- Muscle contractions can be graded by varying frequency and the number of muscle fibers stimulated.
- Tetanus results from the summation of contractions, leading to sustained contraction.
Energy for Contraction
- Initially, muscles use stored ATP for energy.
- Creatine phosphate transfers energy to ADP, regenerating ATP quickly before depletion.
- Aerobic respiration uses glucose to produce ATP requiring continuous oxygen; anaerobic glycolysis produces ATP rapidly but leads to lactic acid buildup.
Muscle Fatigue
- Muscle fatigue occurs when muscles cannot contract even with stimulation, primarily due to oxygen debt and accumulating lactic acid.
- Increasing acidity and lack of ATP diminish muscle contraction efficacy.
Types of Muscle Contractions
- Isotonic contractions result in muscle shortening with movement.
- Isometric contractions involve increased tension without muscle shortening.
Muscle Tone and Exercise
- Muscle tone is maintained through the involuntary contraction of different fibers.
- Aerobic exercise enhances muscle strength, flexibility, and overall metabolism.
- Resistance exercise (Isometric) increases muscle strength and size.
Muscle Movement and Terms
- Flexion decreases the joint angle, while extension increases it.
- Abduction moves limbs away from the midline; adduction brings them closer.
- Rotation occurs around a bone's axis; circumduction is a circular movement.
- Various movements include dorsiflexion (lifting foot) and plantar flexion (pointing toes).
Muscle Anatomy
- Key muscles include:
- Frontalis (raises eyebrows)
- Orbicularis oculi (closes eyes)
- Masseter (closes jaw)
- Pectoralis major (adducts humerus)
Muscle Classification
- Muscles are named based on direction, size, location, number of origins, attachments, shape, and action.
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Description
This quiz explores the different types of muscles, their structures, and the mechanisms of contraction. Learn about skeletal, cardiac, and smooth muscles, along with the cellular components involved in muscle contraction. Test your knowledge on muscle anatomy and physiology.
