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Questions and Answers
Smooth muscle can be stimulated to contract by which of the following?
Smooth muscle can be stimulated to contract by which of the following?
- Nervous signals
- Stretch of the muscle
- Hormonal stimulation
- All of the above (correct)
Where is smooth muscle found?
Where is smooth muscle found?
- In the walls of hollow organs (correct)
- In the heart muscles
- In the tendons
- In the skeletal muscles
Which type of smooth muscle contracts coordinately because the cells are linked by gap junctions?
Which type of smooth muscle contracts coordinately because the cells are linked by gap junctions?
- Unitary smooth muscle (correct)
- Multiunit smooth muscle
- Visceral smooth muscle
- Single unit smooth muscle
Which protein controls the interaction of actin and myosin in smooth muscle?
Which protein controls the interaction of actin and myosin in smooth muscle?
What regulates myosin-light-chain kinase in smooth muscle?
What regulates myosin-light-chain kinase in smooth muscle?
Which type of smooth muscle has little or no coupling between cells?
Which type of smooth muscle has little or no coupling between cells?
What is required to cause smooth muscle relaxation?
What is required to cause smooth muscle relaxation?
Which type of muscle fiber is densely innervated by postganglionic fibers of the parasympathetic and sympathetic nervous systems?
Which type of muscle fiber is densely innervated by postganglionic fibers of the parasympathetic and sympathetic nervous systems?
Smooth muscle contraction depends on the concentration of which ion in the extracellular fluid?
Smooth muscle contraction depends on the concentration of which ion in the extracellular fluid?
How long does a single smooth muscle contraction typically last?
How long does a single smooth muscle contraction typically last?
Which type of muscle is made up of cells called muscle fiber or myocyte?
Which type of muscle is made up of cells called muscle fiber or myocyte?
What percentage of the body is composed of skeletal muscle?
What percentage of the body is composed of skeletal muscle?
What is the diameter range of muscle fibers in skeletal muscles?
What is the diameter range of muscle fibers in skeletal muscles?
What is the function of transverse tubules (T tubules) in skeletal muscle fibers?
What is the function of transverse tubules (T tubules) in skeletal muscle fibers?
What is the role of titin in skeletal muscle?
What is the role of titin in skeletal muscle?
What is the thinnest filament in a sarcomere?
What is the thinnest filament in a sarcomere?
What is the function of the sarcoplasmic reticulum (SR) in skeletal muscle?
What is the function of the sarcoplasmic reticulum (SR) in skeletal muscle?
What is the role of myofibrils in skeletal muscle fibers?
What is the role of myofibrils in skeletal muscle fibers?
What is the function of the sarcolemma in skeletal muscle fibers?
What is the function of the sarcolemma in skeletal muscle fibers?
What is the smallest unit of a myofibril that has the ability to contract?
What is the smallest unit of a myofibril that has the ability to contract?
Which proteins make up the thin filaments in skeletal muscle?
Which proteins make up the thin filaments in skeletal muscle?
What protein anchors the entire myofibrillar array to the cell membrane?
What protein anchors the entire myofibrillar array to the cell membrane?
What is the term for all the muscle fibers innervated by a single nerve fiber?
What is the term for all the muscle fibers innervated by a single nerve fiber?
What triggers the release of calcium ions from the sarcoplasmic reticulum in skeletal muscle?
What triggers the release of calcium ions from the sarcoplasmic reticulum in skeletal muscle?
What is the main source of energy for muscle contraction in the first few seconds?
What is the main source of energy for muscle contraction in the first few seconds?
What happens to the tension in a contracting muscle as the actin and myosin filaments overlap?
What happens to the tension in a contracting muscle as the actin and myosin filaments overlap?
In smooth muscle, what serves the same role as the Z disks in skeletal muscle?
In smooth muscle, what serves the same role as the Z disks in skeletal muscle?
What allows smooth muscle cells to contract as much as 80% of their length?
What allows smooth muscle cells to contract as much as 80% of their length?
What is the name of the protein that binds up to 40 calcium ions in the sarcoplasmic reticulum?
What is the name of the protein that binds up to 40 calcium ions in the sarcoplasmic reticulum?
What happens to the tension in a contracting muscle as the sarcomere shortens?
What happens to the tension in a contracting muscle as the sarcomere shortens?
Which type of muscle makes up about 40% of the body?
Which type of muscle makes up about 40% of the body?
What is the diameter range of muscle fibers in skeletal muscles?
What is the diameter range of muscle fibers in skeletal muscles?
What is the function of the sarcolemma in skeletal muscle fibers?
What is the function of the sarcolemma in skeletal muscle fibers?
What is the name of the thin membrane enclosing a skeletal muscle fiber?
What is the name of the thin membrane enclosing a skeletal muscle fiber?
What is the function of transverse tubules (T tubules) in skeletal muscle fibers?
What is the function of transverse tubules (T tubules) in skeletal muscle fibers?
What surrounds the myofibrils in skeletal muscle fibers?
What surrounds the myofibrils in skeletal muscle fibers?
What is the most small unit of the myofibril that has the ability to contract?
What is the most small unit of the myofibril that has the ability to contract?
What protein keeps the myosin and actin filaments in place in skeletal muscle?
What protein keeps the myosin and actin filaments in place in skeletal muscle?
What is the function of the sarcoplasmic reticulum (SR) in skeletal muscle?
What is the function of the sarcoplasmic reticulum (SR) in skeletal muscle?
What are skeletal muscles composed of?
What are skeletal muscles composed of?
Which type of muscle contracts coordinately because the cells are linked by gap junctions?
Which type of muscle contracts coordinately because the cells are linked by gap junctions?
What is the main source of energy for muscle contraction in smooth muscle?
What is the main source of energy for muscle contraction in smooth muscle?
Where is smooth muscle found?
Where is smooth muscle found?
What regulates myosin-light-chain kinase in smooth muscle?
What regulates myosin-light-chain kinase in smooth muscle?
What is the function of the sarcoplasmic reticulum (SR) in skeletal muscle?
What is the function of the sarcoplasmic reticulum (SR) in skeletal muscle?
What is the diameter range of muscle fibers in skeletal muscles?
What is the diameter range of muscle fibers in skeletal muscles?
What happens to the tension in a contracting muscle as the actin and myosin filaments overlap?
What happens to the tension in a contracting muscle as the actin and myosin filaments overlap?
What is the function of transverse tubules (T tubules) in skeletal muscle fibers?
What is the function of transverse tubules (T tubules) in skeletal muscle fibers?
What is the role of myofibrils in skeletal muscle fibers?
What is the role of myofibrils in skeletal muscle fibers?
What happens to the tension in a contracting muscle as the sarcomere shortens?
What happens to the tension in a contracting muscle as the sarcomere shortens?
What is the role of dystrophin in skeletal muscle?
What is the role of dystrophin in skeletal muscle?
What triggers the release of acetylcholine (ACh) at the neuromuscular junction?
What triggers the release of acetylcholine (ACh) at the neuromuscular junction?
What protein is responsible for carrying depolarization from the muscle cell surface to the interior of the fiber?
What protein is responsible for carrying depolarization from the muscle cell surface to the interior of the fiber?
What triggers the release of calcium ions from the sarcoplasmic reticulum in skeletal muscle?
What triggers the release of calcium ions from the sarcoplasmic reticulum in skeletal muscle?
What is the main source of energy for muscle contraction in the first few seconds?
What is the main source of energy for muscle contraction in the first few seconds?
What is the function of calsequestrin in the sarcoplasmic reticulum?
What is the function of calsequestrin in the sarcoplasmic reticulum?
What allows smooth muscle cells to contract as much as 80% of their length?
What allows smooth muscle cells to contract as much as 80% of their length?
What protein controls the interaction of actin and myosin in smooth muscle?
What protein controls the interaction of actin and myosin in smooth muscle?
What is the role of the sarcolemma in skeletal muscle fibers?
What is the role of the sarcolemma in skeletal muscle fibers?
What is the function of the sarcoplasmic reticulum (SR) in skeletal muscle?
What is the function of the sarcoplasmic reticulum (SR) in skeletal muscle?
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Study Notes
Smooth Muscle
- Can be stimulated to contract by various factors
- Found in walls of hollow organs and tubes, such as blood vessels, digestive tract, and airways
- Unitary smooth muscle contracts coordinately due to gap junctions between cells
- Calmodulin controls the interaction of actin and myosin
- Myosin-light-chain kinase is regulated by calcium and calmodulin
- Multiunit smooth muscle has little or no coupling between cells
- Relaxation requires a decrease in calcium ion concentration
- Dense innervation by postganglionic fibers of the parasympathetic and sympathetic nervous systems
- Contraction depends on extracellular calcium ion concentration
- A single contraction typically lasts around 1-5 seconds
Skeletal Muscle
- Composed of cells called muscle fibers or myocytes
- Makes up around 40% of the body
- Muscle fibers have a diameter range of 10-100 μm
- Transverse tubules (T-tubules) rapidly transmit the action potential to the interior of the fiber
- Titin plays a role in muscle contraction and relaxation
- The thinnest filament in a sarcomere is actin
- Sarcoplasmic reticulum (SR) is the site of calcium ion storage and release
- Myofibrils are the contractile units of skeletal muscle fibers
- Sarcolemma is the plasma membrane of a muscle fiber
- A sarcomere is the smallest unit of a myofibril that can contract
- Thin filaments are composed of actin, tropomyosin, and troponin
- Dystrophin anchors the entire myofibrillar array to the cell membrane
- A motor unit is all the muscle fibers innervated by a single nerve fiber
- Action potential triggers the release of calcium ions from the SR
- Main source of energy for muscle contraction in the first few seconds is ATP and PCr
- Tension decreases as the actin and myosin filaments overlap
- Smooth muscle cells can contract up to 80% of their length due to the absence of Z-disks
- Calsequestrin binds up to 40 calcium ions in the SR
- Tension increases as the sarcomere shortens
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