Podcast
Questions and Answers
What triggers the muscle contraction process?
What triggers the muscle contraction process?
- Acetylcholine diffusing across the gap (correct)
- The release of ATP
- Calcium ions leaving the sarcolemma
- Increase in muscle fiber temperature
The I band in a sarcomere contains only thick filaments.
The I band in a sarcomere contains only thick filaments.
False (B)
What is the role of calcium ions (Ca2+) in muscle contraction?
What is the role of calcium ions (Ca2+) in muscle contraction?
Calcium ions expose binding sites on actin for myosin to attach.
At the neuromuscular junction, the neurotransmitter that signals muscle contraction is called __________.
At the neuromuscular junction, the neurotransmitter that signals muscle contraction is called __________.
Match the following structures with their functions:
Match the following structures with their functions:
Which type of muscle is responsible for heat generation?
Which type of muscle is responsible for heat generation?
Smooth muscle is primarily under voluntary control.
Smooth muscle is primarily under voluntary control.
What is the primary function of cardiac muscle?
What is the primary function of cardiac muscle?
During muscle contraction, muscle fibers are activated by __________.
During muscle contraction, muscle fibers are activated by __________.
Match the following muscle components with their descriptions:
Match the following muscle components with their descriptions:
Which characteristic of muscle cells allows them to stretch without damage?
Which characteristic of muscle cells allows them to stretch without damage?
The neuromuscular junction is involved in the contraction of smooth muscle.
The neuromuscular junction is involved in the contraction of smooth muscle.
Name the muscle responsible for chewing.
Name the muscle responsible for chewing.
Which of the following best describes cardiac muscle?
Which of the following best describes cardiac muscle?
Smooth muscle cells have more than one nucleus per cell.
Smooth muscle cells have more than one nucleus per cell.
What is the function of desmosomes in cardiac muscle cells?
What is the function of desmosomes in cardiac muscle cells?
Smooth muscle is responsible for involuntary actions such as ______ in the stomach.
Smooth muscle is responsible for involuntary actions such as ______ in the stomach.
Match the muscle type with its characteristic:
Match the muscle type with its characteristic:
Flashcards
Excitability
Excitability
The ability of a muscle cell to respond to a stimulus, such as a nerve impulse.
Contractibility
Contractibility
The ability of a muscle cell to shorten forcefully.
Extensibility
Extensibility
The ability of a muscle cell to be stretched or elongated.
Elasticity
Elasticity
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Skeletal muscle
Skeletal muscle
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Cardiac muscle
Cardiac muscle
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Smooth muscle
Smooth muscle
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Epimysium
Epimysium
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What is a sarcomere?
What is a sarcomere?
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What is Actin?
What is Actin?
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What is Myosin?
What is Myosin?
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What is an I band?
What is an I band?
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What is the Neuromuscular Junction?
What is the Neuromuscular Junction?
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Intercalated discs
Intercalated discs
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Dense bodies in smooth muscle
Dense bodies in smooth muscle
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Study Notes
Muscular System Overview
- The muscular system is responsible for movement, posture, and heat generation.
- Muscle cells are excitable, contractible, extensible, and elastic.
- Muscle cells do not change length unless signaled.
Types of Muscle Tissue
- Skeletal Muscle: Voluntary, striated, multinucleated, long cylindrical cells.
- Cardiac Muscle: Involuntary, striated, branched, uni- or binucleate cells connected by intercalated discs. Found only in the heart.
- Smooth Muscle: Involuntary, non-striated, fusiform, uninucleated cells. Found in the walls of internal organs and blood vessels.
Skeletal Muscle Structure
- Epimysium: Outermost layer of connective tissue surrounding the entire muscle.
- Perimysium: Connective tissue surrounding fascicles (bundles of muscle fibers).
- Endomysium: Connective tissue surrounding individual muscle fibers (cells).
- Muscle fiber (cell): Contains myofibrils.
- Fascicles: Bundles of muscle fibers.
Skeletal Muscle Fiber Detail
- Sarcolemma: Muscle cell membrane.
- Sarcoplasmic Reticulum (SR): Stores calcium ions.
- T-tubules: Extensions of sarcolemma, rapidly transmitting signals into the cell.
- Myofibrils: Long protein filaments, containing sarcomeres.
- Sarcomeres: Functional units of muscle contraction, composed of thick and thin filaments.
- Actin (thin) filaments: Attached to Z lines.
- Myosin (thick) filaments: Between actin filaments.
- Z lines: Boundaries of sarcomeres.
Myofibril Structure Detail
- I band: Light band, contains only actin filaments.
- A band: Dark band, contains both actin and myosin filaments.
- H zone: Middle of A band, contains only myosin filaments.
- M line: Middle of H zone, connecting myosin filaments.
- Sarcomere Shortening: Shortening of the sarcomere during muscle contraction—actin and myosin filaments slide past each other.
Muscle Contraction Mechanism
- Neuromuscular Junction: Where nerve impulses stimulate muscle cells.
- Acetylcholine (ACh): Released neurotransmitter.
- Calcium Ions (Ca2+): Released from SR, initiates contraction.
- ATP: Necessary for the sliding of actin and myosin filaments.
Chemistry of Muscle Contraction
- ATP production: ADP + P = ATP.
- Energy sources: Creatine phosphate, glycogen, myoglobin, aerobic metabolism, anaerobic metabolism (lactic acid).
Contraction Regulation
- All-or-nothing principle: Muscle fibers either contract fully or not at all.
- Twitch contraction: A single contraction-relaxation cycle.
- Motor units: Motor neuron and all the muscle fibers it supplies (fine vs. gross control).
Other Important Information
- Important muscles of the head and neck, abdomen, thoracic limbs, pelvic limbs, and respiration.
- Muscles of respiration: The main muscles responsible for breathing.
- Muscle types in the iris, lens, and airways
- Cardiac muscle cells and their unique properties.
- Intercalated discs: Intercellular junctions connecting heart muscle cells
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