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Questions and Answers
What is the primary cause of muscle fatigue?
What is the primary cause of muscle fatigue?
Which statement accurately describes muscle tone?
Which statement accurately describes muscle tone?
What occurs during the recruitment of motor units?
What occurs during the recruitment of motor units?
How does the body primarily produce heat?
How does the body primarily produce heat?
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Which of the following describes how lactic acid is utilized in the body?
Which of the following describes how lactic acid is utilized in the body?
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What role does acetylcholine (ACh) play in muscle contraction?
What role does acetylcholine (ACh) play in muscle contraction?
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During excitation-contraction coupling, what happens to calcium ions?
During excitation-contraction coupling, what happens to calcium ions?
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How does the Sliding Filament Model describe muscle contraction?
How does the Sliding Filament Model describe muscle contraction?
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Which process is responsible for returning calcium to the sarcoplasmic reticulum during relaxation?
Which process is responsible for returning calcium to the sarcoplasmic reticulum during relaxation?
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What is the primary energy source for muscle contractions during short, intense activities?
What is the primary energy source for muscle contractions during short, intense activities?
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In the aerobic phase of cellular respiration, what is produced primarily?
In the aerobic phase of cellular respiration, what is produced primarily?
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What is the function of myoglobin in muscle cells?
What is the function of myoglobin in muscle cells?
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Which event occurs first in the process of muscle fiber contraction?
Which event occurs first in the process of muscle fiber contraction?
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Which type of muscle tissue is primarily under conscious control?
Which type of muscle tissue is primarily under conscious control?
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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 structure is known as the site where an axon and muscle fiber meet?
Which structure is known as the site where an axon and muscle fiber meet?
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What are the two main types of myofilaments in skeletal muscle fibers?
What are the two main types of myofilaments in skeletal muscle fibers?
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Which connective tissue covering surrounds the entire skeletal muscle?
Which connective tissue covering surrounds the entire skeletal muscle?
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Which part of the sarcomere is known to be the region where actin and myosin overlap?
Which part of the sarcomere is known to be the region where actin and myosin overlap?
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What type of muscle is striated and not under conscious control?
What type of muscle is striated and not under conscious control?
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Which of the following structures is NOT found in skeletal muscle fibers?
Which of the following structures is NOT found in skeletal muscle fibers?
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Study Notes
Human Anatomy and Physiology - Chapter 9 - Muscular System
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Skeletal Muscle:
- Usually attached to bones
- Under conscious control
- Striated
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Cardiac Muscle:
- Found in the heart wall
- Not under conscious control
- Striated
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Smooth Muscle:
- Forms walls of many internal organs, blood vessels, and skin
- Not under conscious control
- Not striated
Structure of Skeletal Muscle
- Organ of the muscular system
- Skeletal muscle tissue
- Nervous tissue
- Blood
- Connective tissues (fascia, tendons, aponeuroses)
Connective Tissue Coverings
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Epimysium (outermost layer)
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Perimysium (surrounds fascicles)
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Fascicles (bundles of muscle fibers)
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Endomysium (surrounds individual muscle fibers)
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Muscle
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Fascicles
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Muscle fibers
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Myofibrils
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Thick and thin filaments
Skeletal Muscle Fibers
- Sarcolemma (muscle cell membrane)
- Sarcoplasm (cytoplasm of muscle cell)
- Sarcoplasmic reticulum (smooth ER)
- Transverse tubules (invaginations of sarcolemma)
- Triad (one T-tubule and two terminal cisternae of sarcoplasmic reticulum)
- Cisternae
- Transverse tubules
- Myofibril
- Actin filaments
- Myosin filaments
- Sarcomere
Sarcomere
- I bands
- A bands
- H zone
- Z lines
- M line
Myofilaments
- Thick filaments: composed of myosin, have cross-bridges.
- Thin filaments: composed of actin, associated with tropomyosin and troponin.
Neuromuscular Junction
- Also known as myoneural junction
- Site where motor neuron axon and muscle fiber meet
- Motor neuron
- Motor end plate
- Synapse
- Synaptic cleft
- Synaptic vesicles
- Neurotransmitters (acetylcholine)
Motor Unit
- Single motor neuron and all muscle fibers it controls.
- Whole muscle composed of many motor units.
- Controlled recruitment of motor units.
- Increase in the number of motor units that are activated.
Stimulus for Contraction
- Acetylcholine (ACh) release
- Nerve impulse causes synaptic vesicles to release ACh
- ACh binds to ACh receptors on motor end plate
- Generates a muscle impulse
- Muscle impulse travels to the SR
- Release of calcium ions into the sarcoplasm
- Muscle impulse reaches sarcolemma and sarcoplasmic reticulum
Excitation-Contraction Coupling
- Muscle impulses cause sarcoplasmic reticulum to release calcium ions into cytosol
- Calcium binds to troponin, changing its shape
- Position of tropomyosin altered, exposing binding sites on actin
- Actin and myosin molecules bind
- Muscle contraction
Sliding Filament Model of Muscle Contraction
- Shortening of sarcomeres
- Thick and thin filaments slide past one another
- H zones and I bands narrow
- Z lines move closer together
Cross-Bridge Cycling
- Myosin cross-bridge attaches to actin binding site
- Myosin cross-bridge pulls thin filament
- ADP and phosphate released from myosin
- New ATP binds to myosin
- Linkage between actin and myosin cross-bridge breaks
- ATP splits, myosin cross-bridge returns to original position
Relaxation
- Acetylcholinesterase quickly decomposes acetylcholine remaining in the synapse
- Muscle impulse stops
- Stimulus to sarcolemma and muscle fiber membrane ceases
- Calcium moves back into sarcoplasmic reticulum
- Myosin and actin binding prevented
- Muscle fiber relaxes
Major Events of Muscle Contraction and Relaxation
- Detailed summary of events leading to muscle contraction and subsequent relaxation.
Energy Sources for Contraction
- Creatine phosphate: stores energy to quickly convert ADP to ATP.
- Cellular respiration
Oxygen Supply and Cellular Respiration
- Anaerobic phase (glycolysis): occurs in cytoplasm, produces little ATP.
- Aerobic phase (citric acid cycle, electron transport chain): occurs in the mitochondria, produces most ATP.
- Myoglobin stores extra oxygen.
Oxygen Debt
- Amount of oxygen needed to convert accumulated lactic acid back to glucose by the liver
Muscle Fatigue
- Inability of muscle to contract
- Often due to decreased blood flow, ion imbalances, and lactic acid accumulation
- Sustained, involuntary muscle contraction called a cramp.
Heat Production
- By-product of cellular respiration
- Muscle cells are the major source of body heat
- Blood transports heat throughout the body.
Length-Tension Relationship
- Relationship between the length of a muscle fiber and the force it can generate.
Recruitment of Motor Units
- Increased number of motor units activated in response to increased force demands.
- Whole muscle composed of many motor units
- Precise movements use fewer muscle fibers.
- as intensity of stimulation increases, recruitment of motor units continues until all motor units are activated.
Sustained Contractions
- Smaller motor units are recruited first, then larger motor units when stronger contractions are needed
- Smaller motor units produce smoother movements.
- Muscle tone: continuous state of partial contraction.
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Description
Explore the intricacies of the muscular system in this quiz focusing on human anatomy and physiology. Delve into the types of muscle tissues, their structure, and function, including skeletal, cardiac, and smooth muscles. Test your knowledge on the connective tissue coverings and muscle fibers.
