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Questions and Answers
What is the primary function of smooth muscle tissue?
What is the primary function of smooth muscle tissue?
Which characteristic is unique to cardiac muscle compared to the other muscle types?
Which characteristic is unique to cardiac muscle compared to the other muscle types?
Which of the following correctly describes skeletal muscle fibers?
Which of the following correctly describes skeletal muscle fibers?
How does the sliding filament model explain muscle contraction?
How does the sliding filament model explain muscle contraction?
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What role do skeletal muscles play in maintaining body temperature?
What role do skeletal muscles play in maintaining body temperature?
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Which muscle type is characterized by involuntary control and non-striated fibers?
Which muscle type is characterized by involuntary control and non-striated fibers?
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What features distinguish cardiac muscle from skeletal muscle?
What features distinguish cardiac muscle from skeletal muscle?
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What is the continuous sliding action of the myosin and actin filaments known as?
What is the continuous sliding action of the myosin and actin filaments known as?
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Which of the following statements about ATP and calcium ions in muscle contraction is true?
Which of the following statements about ATP and calcium ions in muscle contraction is true?
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What happens to the use of energy sources as the duration of exercise increases?
What happens to the use of energy sources as the duration of exercise increases?
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Which of the following pathways does not require oxygen to produce ATP for muscle contraction?
Which of the following pathways does not require oxygen to produce ATP for muscle contraction?
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Which two energy sources are stored in muscles for immediate use during contraction?
Which two energy sources are stored in muscles for immediate use during contraction?
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What is the function of bursae in the muscular system?
What is the function of bursae in the muscular system?
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Which muscle is considered the agonist when flexing the forearm?
Which muscle is considered the agonist when flexing the forearm?
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During muscle contraction, what happens to ATP?
During muscle contraction, what happens to ATP?
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What is the role of the antagonist muscle?
What is the role of the antagonist muscle?
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What structure surrounds each muscle fiber within a fascicle?
What structure surrounds each muscle fiber within a fascicle?
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What is the primary function of fascia in the muscular system?
What is the primary function of fascia in the muscular system?
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Which statement accurately describes the concept of muscle origins and insertions?
Which statement accurately describes the concept of muscle origins and insertions?
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In which part of the body would you find the fascicle structure of skeletal muscles?
In which part of the body would you find the fascicle structure of skeletal muscles?
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What happens to the tendons when a muscle contracts?
What happens to the tendons when a muscle contracts?
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What is the term for the muscle that is contracting during movement?
What is the term for the muscle that is contracting during movement?
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Which component of a muscle fiber acts as the plasma membrane?
Which component of a muscle fiber acts as the plasma membrane?
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What is the role of myoglobin in muscle fibers?
What is the role of myoglobin in muscle fibers?
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What type of myofilament is primarily composed of myosin?
What type of myofilament is primarily composed of myosin?
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What happens when both the agonist and antagonist muscles contract simultaneously?
What happens when both the agonist and antagonist muscles contract simultaneously?
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Which structure penetrates muscle fibers and is closely associated with the sarcoplasmic reticulum?
Which structure penetrates muscle fibers and is closely associated with the sarcoplasmic reticulum?
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What is the function of glycogen in the sarcoplasm of muscle fibers?
What is the function of glycogen in the sarcoplasm of muscle fibers?
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What is the primary function of myoglobin in muscle fibers?
What is the primary function of myoglobin in muscle fibers?
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Which of the following is NOT a type of muscle in the human body?
Which of the following is NOT a type of muscle in the human body?
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What shape do skeletal muscle fibers typically resemble?
What shape do skeletal muscle fibers typically resemble?
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What is the role of T tubules in muscle fibers?
What is the role of T tubules in muscle fibers?
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What is the primary function of the sarcoplasmic reticulum in muscle fibers?
What is the primary function of the sarcoplasmic reticulum in muscle fibers?
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Which component is primarily responsible for muscle striations?
Which component is primarily responsible for muscle striations?
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What makes up the A band in a sarcomere?
What makes up the A band in a sarcomere?
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During muscle contraction according to the sliding filament model, what happens to the I band?
During muscle contraction according to the sliding filament model, what happens to the I band?
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What is contained primarily in the H band of the sarcomere?
What is contained primarily in the H band of the sarcomere?
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What type of protein is myosin classified as?
What type of protein is myosin classified as?
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What is the primary structural component of thin myofilaments?
What is the primary structural component of thin myofilaments?
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What happens to the Z lines during muscle contraction?
What happens to the Z lines during muscle contraction?
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What supplies energy for muscle contraction?
What supplies energy for muscle contraction?
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Study Notes
Muscular System - Part 1
- Three types of muscle tissue: smooth, cardiac, and skeletal.
- Skeletal muscle cells are called muscle fibers.
- Smooth muscle fibers are shaped like cylinders with pointed ends.
- Smooth muscle fibers are uninucleated and arranged in parallel lines, forming sheets.
- Smooth muscle is not striated and is located in the walls of hollow internal organs and blood vessels.
- Smooth muscle contraction is involuntary.
- Cardiac muscle forms the heart wall.
- Cardiac muscle fibers are uninucleated, striated, and tubular.
- Cardiac muscle fibers branch and interlock at intercalated disks.
- Cardiac muscle contraction is involuntary and rhythmic.
- Skeletal muscle fibers are tubular, multinucleated, and striated.
- Skeletal muscle makes up skeletal muscles which are attached to the skeleton.
- Skeletal muscle fibers are very long and run the length of the muscle.
- Skeletal muscle contraction is under voluntary control.
- Skeletal muscles functions: support, movement of bones and other body structures (arms, legs, eyes, facial expressions, and breathing), maintenance of a constant body temperature, protection of the internal organs.
Learning Outcomes
- Identify the three types of muscle tissue and provide a function for each.
- Describe the general structure of a skeletal muscle.
- Identify the structures of a muscle fiber.
- Summarize how neuromuscular junction activities control muscle fiber contraction..
- Explain how the sliding filament model is responsible for muscle contraction..
- Muscles use different energy sources depending on exercise duration and intensity.
Overview of Muscular System
- Functions in movement of the entire organism and movement of materials within the organism (e.g., blood, food).
Basic Structure of Skeletal Muscles
- Fascicle: bundles of skeletal muscle fibers.
- Each fiber in a fascicle is surrounded by connective tissue.
- Fascicle is also surrounded by connective tissue.
Connecting Muscle to Bone
- Fascia: connective tissue that covers muscles extends to become the tendon.
- Bursae: small, fluid-filled sacs found between tendons and bones.
- Bursae act as cushions and lubrication.
Skeletal Muscles Work in Pairs
- Origin: attachment site to the stationary bone.
- Insertion: attachment on the bone that moves.
- When a muscle contracts, it pulls on the tendons at its insertion the bone moves (e.g., biceps brachii contracts, raising the forearm).
- Agonist: prime mover, the muscle that does most of the work.
- Antagonist: the muscle that acts opposite to the prime mover (e.g., biceps and triceps are antagonistic muscle pair).
Muscle Fibers and How They Slide (Part 1)
- Sarcolemma: plasma membrane.
- Sarcoplasm: cytoplasm.
- Sarcoplasmic reticulum: endoplasmic reticulum, calcium storage site.
- T (transverse) tubules: penetrate cells, come close to portions of the sarcoplasmic reticulum.
Muscle Fibers and How They Slide (Part 2)
- Sarcolemma contains many myofibrils (contractile parts of muscle fibers).
- Sarcoplasm contains glycogen (provides energy for muscle contraction).
- Sarcoplasm contains myoglobin (red pigment that binds oxygen).
The Structure of a Skeletal Muscle Fiber
- Cylindrical shape.
- Myofibrils grouped inside a larger cylinder.
- Myofibrils run entire length of the muscle fiber.
- Myofibrils are made of smaller cylinders called myofilaments.
- Two types of myofilaments: thick (myosin) and thin (actin).
Anatomy of a Muscle Fiber (Table)
- Sarcolemma: plasma membrane of a muscle fiber.
- Sarcoplasm: cytoplasm, contains organelles including myofibrils.
- Myoglobin: red pigment that stores oxygen for muscle contraction.
- T tubule: extension of the sarcolemma conveys impulses that cause calcium to be released from the sarcoplasmic reticulum.
- Sarcoplasmic reticulum: smooth endoplasmic reticulum, stores calcium.
- Myofibril: bundle of myofilaments that contract.
- Myofilament: actin or myosin filament, structure accounts for striations and contractions.
Myofibrils and Sarcomeres
- Myofibrils are divided into sarcomeres.
- Sarcomeres extend between Z lines.
- I band: light colored, made of only thin myofilaments.
- A band: made of overlapping thin and thick myofilaments.
- H band: located within the A band, contains only thick myofilaments.
Thick and Thin Myofilaments
- Thick filaments: composed of the protein myosin.
- Each myosin molecule is shaped like a golf club, with a globular head or cross-bridge.
- Thin filaments: made of two intertwining strands of actin, tropomyosin, and troponin.
Sliding Filament Model
- Muscle fiber contracts as sarcomeres shorten
- ATP supplies energy for muscle contraction
- Thin filaments slide past thick filaments.
- I band shortens, Z lines move inward, and the H band almost disappears.
Muscle Fiber Contraction (Part 1)
- Motor neuron: nervous system cell that stimulates muscle fibers to contract
- Nerve: group of neurons
- Axon: part of a neuron that stimulates a muscle fiber, branches so that multiple muscle fibers are stimulated.
Motor Neurons and Skeletal Muscle Fibers Join (Neuromuscular Junctions)
- Axon terminal comes near the sarcolemma.
- Synaptic cleft: space that separates the axon terminal and sarcolemma
- Axon terminals contain synaptic vesicles filled with the neurotransmitter acetylcholine (ACh).
- Nerve signals release ACh into the synaptic cleft.
Muscle Fiber Contraction (Part 2)
- ACh diffuses across the cleft and binds to receptors in the sarcolemma.
- This creates electrical signals that spread across the sarcolemma and down the T tubules.
- This causes calcium to be released from the sarcoplasmic reticulum.
More Muscle Fiber Contraction
- When calcium is released from the sarcoplasmic reticulum, it binds to troponin, exposing myosin-binding sites.
- Tropomyosin threads move and expose myosin-binding sites.
Steps of the Sliding Filament Theory (Part 1)
- Myosin heads have ATP-binding sites.
- ATP is split into ADP and P.
- Myosin heads attach to actin forming cross-bridges.
- ADP and P are released, causing the myosin head to bend (power stroke), pulling the actin filament toward the center of the sarcomere.
Steps of the Sliding Filament Theory (Part 2)
- ATP binding to myosin heads breaks cross-bridges.
- Myosin detaches from actin.
- The cycle begins again as myosin reattaches farther along the actin filament.
- The continuous sliding action of myosin and actin is called the ratchet mechanism.
- ATP and calcium are crucial for muscle contraction.
Check Your Progress (Part 1)
- Explanations for the role of myofibrils in a muscle fiber and the role of ATP and calcium ions in muscle contraction.
Muscular System - Part 2
- Summarize how muscle cells produce ATP for muscle contraction.
Energy for Muscle Contraction
- Muscles use glycogen, triglycerides, glucose, and fatty acids (stored muscle or from blood) for energy (depends on exercise intensity and duration).
- As exercise time increases, use of muscle energy stores decreases, while use of energy sources from the blood increases.
Sources of Energy for Muscle Contraction (Graph)
- Shows the percentage of energy expenditure from muscle triglycerides, plasma fatty acids, blood glucose, and muscle glycogen over time.
Sources of ATP for Muscle Contraction
- Muscle cells store limited amounts of ATP.
- Three pathways produce more ATP:
- Creatine phosphate pathway.
- Fermentation.
- Cellular respiration.
- Mitochondria uses oxygen, thus cellular respiration is aerobic, while CP and fermentation are anaerobic.
The Three Pathways (Diagram)
- Shows the three pathways (Creatine phosphate, Fermentation, and Cellular Respiration) by which muscle cells produce ATP.
The Creatine Phosphate Pathway (Part 1)
- Simplest and fastest way for muscle to make ATP.
The Creatine Phosphate Pathway (Part 2)
- Creatine phosphate is formed only when muscles are resting, with limited storage capacity.
- Creatine phosphate-derived ATP powers the first few seconds of muscle contraction.
- The CP pathway is used at the beginning of exercise.
Fermentation (Part 1)
- Anaerobic processes produce two ATPs from glucose breakdown producing lactate.
- Hormones signal cells to break down glycogen to make glucose (energy source).
- Fast-acting but results in lactate buildup.
- Short-term muscle aches and fatigue can result from lactate.
Fermentation (Part 2)
- Oxygen debt: heavy breathing needed after strenuous exercise to address lactate metabolism and return cells to their original energy state.
Cellular Respiration
- Slowest, most efficient ATP production mechanism.
- Occurs in mitochondria.
- Myoglobin delivers oxygen directly to mitochondria in muscle cells.
- Can use glucose from stored glycogen, glucose in the blood, and fatty acids.
Check Your Progress (Part 2)
- Summary of how the CP pathway, fermentation, and cellular respiration produce ATP for muscle contraction.
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Description
This quiz covers the fundamentals of the muscular system, focusing on the three types of muscle tissue: smooth, cardiac, and skeletal. You'll learn about the unique characteristics of each muscle type, including their structure, function, and contraction types. Test your knowledge on how these muscles contribute to bodily functions.
