Musculoskeletal System and Muscle Tissue - MCAT Biological and Biochemical Foundations of Living Systems
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A sarcoplasmic reticulum is found within a muscle cell. The sarcoplasmic reticulum is a modified version of the endoplasmic reticulum.
What is the modified characteristic of a sarcoplasmic reticulum?
A sarcoplasmic reticulum is found within a muscle cell. The sarcoplasmic reticulum is a modified version of the endoplasmic reticulum.
What is the modified characteristic of a sarcoplasmic reticulum?
The sarcoplasmic reticulum contains a large amount of Ca2+ ions. This calcium is released from the sarcoplasmic reticulum when an electrical signal is sent to the cell. This release of calcium allows for contraction.
The sarcoplasmic reticulum contains a large amount of Ca2+ ions. This calcium is released from the sarcoplasmic reticulum when an electrical signal is sent to the cell. This release of calcium allows for contraction.
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What is the purpose of calcium in the muscles?
What is the purpose of calcium in the muscles?
The proteins troponin and tropomyosin are attached to the actin filaments in sarcomeres. These proteins function to block the myosin-binding site on the actin protein, preventing unnecessary contraction. When calcium is released from the sarcoplasmic reticulum, it will attach to troponin. The troponin will then pull tropomyosin away from the actin filament, which allows myosin heads to attach and cause a contraction.
ATP binds myosin to release it from the actin binding site and is converted to ADP in order to adjust the myosin head to a high-energy position.
The proteins troponin and tropomyosin are attached to the actin filaments in sarcomeres. These proteins function to block the myosin-binding site on the actin protein, preventing unnecessary contraction. When calcium is released from the sarcoplasmic reticulum, it will attach to troponin. The troponin will then pull tropomyosin away from the actin filament, which allows myosin heads to attach and cause a contraction.
ATP binds myosin to release it from the actin binding site and is converted to ADP in order to adjust the myosin head to a high-energy position.
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Which of the following muscles is an antagonist for the biceps brachii?
Which of the following muscles is an antagonist for the biceps brachii?
An antagonist is defined as the muscle that strecthes when another muscle (the agonist) is contracting. When the antagonist contracts, it will stretch the agonist and move the bone in the opposite direction.
The biceps brachii is responsible for flexion of the forearm, while the triceps brachii is responsible for the extension of the forearm. As a result, we say that the triceps brachii is the antagonist of the biceps brachii.
An antagonist is defined as the muscle that strecthes when another muscle (the agonist) is contracting. When the antagonist contracts, it will stretch the agonist and move the bone in the opposite direction.
The biceps brachii is responsible for flexion of the forearm, while the triceps brachii is responsible for the extension of the forearm. As a result, we say that the triceps brachii is the antagonist of the biceps brachii.
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Skeletal muscle and cardiac muscle are similar in that they both .
Skeletal muscle and cardiac muscle are similar in that they both .
Cardiac muscle and skeletal muscle are both composed of sarcomeres. This layout gives both muscle types a striated appearance, alternating dark bands of myosin with lighter bands of actin. Only cardiac muscle has intercalated discs and skeletal muscle is the only type that is multinucleated. No muscle type is attached directly to bone, but skeletal muscle is linked to bone via tendons.
Cardiac muscle and skeletal muscle are both composed of sarcomeres. This layout gives both muscle types a striated appearance, alternating dark bands of myosin with lighter bands of actin. Only cardiac muscle has intercalated discs and skeletal muscle is the only type that is multinucleated. No muscle type is attached directly to bone, but skeletal muscle is linked to bone via tendons.
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Which of the following types of muscle is under voluntary motor control?
Which of the following types of muscle is under voluntary motor control?
Skeletal muscle is under voluntary control, and are innervated by the somatic nervous system. Skeletal muscle is responsible for skeletal movement, such as swinging the arms or lifting the legs.
Cardiac and smooth muscle are under the control of the autonomic nervous system. Cardiac muscle contracts the heart autonomously, without additional neuronal input.
Skeletal muscle is under voluntary control, and are innervated by the somatic nervous system. Skeletal muscle is responsible for skeletal movement, such as swinging the arms or lifting the legs.
Cardiac and smooth muscle are under the control of the autonomic nervous system. Cardiac muscle contracts the heart autonomously, without additional neuronal input.
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What structure serves to connect different Haversian canals and provides a means for communication and nutrient transport?
What structure serves to connect different Haversian canals and provides a means for communication and nutrient transport?
Volkmann canals connect different Haversian systems, allowing the osteocytes within their lacuna to communicate via chemical and cellular signalling.
Canaliculi form a "spiderweb" of tiny channels to facilitate communication between osteocytes within a single Haversian system, but do not permit communication between different osteons.
Volkmann canals connect different Haversian systems, allowing the osteocytes within their lacuna to communicate via chemical and cellular signalling.
Canaliculi form a "spiderweb" of tiny channels to facilitate communication between osteocytes within a single Haversian system, but do not permit communication between different osteons.
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A sarcoplasmic reticulum is found within a muscle cell. The sarcoplasmic reticulum is a modified version of the endoplasmic reticulum.
What is the modified characteristic of a sarcoplasmic reticulum?
A sarcoplasmic reticulum is found within a muscle cell. The sarcoplasmic reticulum is a modified version of the endoplasmic reticulum.
What is the modified characteristic of a sarcoplasmic reticulum?
The sarcoplasmic reticulum contains a large amount of Ca2+ ions. This calcium is released from the sarcoplasmic reticulum when an electrical signal is sent to the cell. This release of calcium allows for contraction.
The sarcoplasmic reticulum contains a large amount of Ca2+ ions. This calcium is released from the sarcoplasmic reticulum when an electrical signal is sent to the cell. This release of calcium allows for contraction.
Compare your answer with the correct one above
What is the purpose of calcium in the muscles?
What is the purpose of calcium in the muscles?
The proteins troponin and tropomyosin are attached to the actin filaments in sarcomeres. These proteins function to block the myosin-binding site on the actin protein, preventing unnecessary contraction. When calcium is released from the sarcoplasmic reticulum, it will attach to troponin. The troponin will then pull tropomyosin away from the actin filament, which allows myosin heads to attach and cause a contraction.
ATP binds myosin to release it from the actin binding site and is converted to ADP in order to adjust the myosin head to a high-energy position.
The proteins troponin and tropomyosin are attached to the actin filaments in sarcomeres. These proteins function to block the myosin-binding site on the actin protein, preventing unnecessary contraction. When calcium is released from the sarcoplasmic reticulum, it will attach to troponin. The troponin will then pull tropomyosin away from the actin filament, which allows myosin heads to attach and cause a contraction.
ATP binds myosin to release it from the actin binding site and is converted to ADP in order to adjust the myosin head to a high-energy position.
Compare your answer with the correct one above
Which of the following muscles is an antagonist for the biceps brachii?
Which of the following muscles is an antagonist for the biceps brachii?
An antagonist is defined as the muscle that strecthes when another muscle (the agonist) is contracting. When the antagonist contracts, it will stretch the agonist and move the bone in the opposite direction.
The biceps brachii is responsible for flexion of the forearm, while the triceps brachii is responsible for the extension of the forearm. As a result, we say that the triceps brachii is the antagonist of the biceps brachii.
An antagonist is defined as the muscle that strecthes when another muscle (the agonist) is contracting. When the antagonist contracts, it will stretch the agonist and move the bone in the opposite direction.
The biceps brachii is responsible for flexion of the forearm, while the triceps brachii is responsible for the extension of the forearm. As a result, we say that the triceps brachii is the antagonist of the biceps brachii.
Compare your answer with the correct one above
Skeletal muscle and cardiac muscle are similar in that they both .
Skeletal muscle and cardiac muscle are similar in that they both .
Cardiac muscle and skeletal muscle are both composed of sarcomeres. This layout gives both muscle types a striated appearance, alternating dark bands of myosin with lighter bands of actin. Only cardiac muscle has intercalated discs and skeletal muscle is the only type that is multinucleated. No muscle type is attached directly to bone, but skeletal muscle is linked to bone via tendons.
Cardiac muscle and skeletal muscle are both composed of sarcomeres. This layout gives both muscle types a striated appearance, alternating dark bands of myosin with lighter bands of actin. Only cardiac muscle has intercalated discs and skeletal muscle is the only type that is multinucleated. No muscle type is attached directly to bone, but skeletal muscle is linked to bone via tendons.
Compare your answer with the correct one above
Which of the following types of muscle is under voluntary motor control?
Which of the following types of muscle is under voluntary motor control?
Skeletal muscle is under voluntary control, and are innervated by the somatic nervous system. Skeletal muscle is responsible for skeletal movement, such as swinging the arms or lifting the legs.
Cardiac and smooth muscle are under the control of the autonomic nervous system. Cardiac muscle contracts the heart autonomously, without additional neuronal input.
Skeletal muscle is under voluntary control, and are innervated by the somatic nervous system. Skeletal muscle is responsible for skeletal movement, such as swinging the arms or lifting the legs.
Cardiac and smooth muscle are under the control of the autonomic nervous system. Cardiac muscle contracts the heart autonomously, without additional neuronal input.
Compare your answer with the correct one above
What structure serves to connect different Haversian canals and provides a means for communication and nutrient transport?
What structure serves to connect different Haversian canals and provides a means for communication and nutrient transport?
Volkmann canals connect different Haversian systems, allowing the osteocytes within their lacuna to communicate via chemical and cellular signalling.
Canaliculi form a "spiderweb" of tiny channels to facilitate communication between osteocytes within a single Haversian system, but do not permit communication between different osteons.
Volkmann canals connect different Haversian systems, allowing the osteocytes within their lacuna to communicate via chemical and cellular signalling.
Canaliculi form a "spiderweb" of tiny channels to facilitate communication between osteocytes within a single Haversian system, but do not permit communication between different osteons.
Compare your answer with the correct one above
Duchenne Muscular Dystrophy is an X-linked recessive genetic disorder, resulting in the loss of the dystrophin protein. In healthy muscle, dystrophin localizes to the sarcolemma and helps anchor the muscle fiber to the basal lamina. The loss of this protein results in progressive muscle weakness, and eventually death.
In the muscle fibers, the effects of the disease can be exacerbated by auto-immune interference. Weakness of the sarcolemma leads to damage and tears in the membrane. The body’s immune system recognizes the damage and attempts to repair it. However, since the damage exists as a chronic condition, leukocytes begin to present the damaged protein fragments as antigens, stimulating a targeted attack on the damaged parts of the muscle fiber. The attack causes inflammation, fibrosis, and necrosis, further weakening the muscle.
Studies have shown that despite the severe pathology of the muscle fibers, the innervation of the muscle is unaffected.
When a healthy muscle fiber is activated, Ca2+ ions will .
Duchenne Muscular Dystrophy is an X-linked recessive genetic disorder, resulting in the loss of the dystrophin protein. In healthy muscle, dystrophin localizes to the sarcolemma and helps anchor the muscle fiber to the basal lamina. The loss of this protein results in progressive muscle weakness, and eventually death.
In the muscle fibers, the effects of the disease can be exacerbated by auto-immune interference. Weakness of the sarcolemma leads to damage and tears in the membrane. The body’s immune system recognizes the damage and attempts to repair it. However, since the damage exists as a chronic condition, leukocytes begin to present the damaged protein fragments as antigens, stimulating a targeted attack on the damaged parts of the muscle fiber. The attack causes inflammation, fibrosis, and necrosis, further weakening the muscle.
Studies have shown that despite the severe pathology of the muscle fibers, the innervation of the muscle is unaffected.
When a healthy muscle fiber is activated, Ca2+ ions will .
The troponin-tropomyosin complex wraps around actin when the muscle fiber is inactive, blocking all myosin-binding sites. When Ca2+ is released it binds to troponin, inducing a change in tropomyosin, which shifts its position to expose the myosin-binding sites on the actin filament.
Calcium does not bind any of the other listed answer choices.
The troponin-tropomyosin complex wraps around actin when the muscle fiber is inactive, blocking all myosin-binding sites. When Ca2+ is released it binds to troponin, inducing a change in tropomyosin, which shifts its position to expose the myosin-binding sites on the actin filament.
Calcium does not bind any of the other listed answer choices.
Compare your answer with the correct one above
Duchenne Muscular Dystrophy is an X-linked recessive genetic disorder, resulting in the loss of the dystrophin protein. In healthy muscle, dystrophin localizes to the sarcolemma and helps anchor the muscle fiber to the basal lamina. The loss of this protein results in progressive muscle weakness, and eventually death.
In the muscle fibers, the effects of the disease can be exacerbated by auto-immune interference. Weakness of the sarcolemma leads to damage and tears in the membrane. The body’s immune system recognizes the damage and attempts to repair it. However, since the damage exists as a chronic condition, leukocytes begin to present the damaged protein fragments as antigens, stimulating a targeted attack on the damaged parts of the muscle fiber. The attack causes inflammation, fibrosis, and necrosis, further weakening the muscle.
Studies have shown that despite the severe pathology of the muscle fibers, the innervation of the muscle is unaffected.
ATP is required for muscle contraction. Identify which of the following are true
I. ATP binding causes myosin to release actin
II. Actin carries an inactive ADP when myosin binds
III. The myosin head movement to contract the muscle converts ATP to ADP
Duchenne Muscular Dystrophy is an X-linked recessive genetic disorder, resulting in the loss of the dystrophin protein. In healthy muscle, dystrophin localizes to the sarcolemma and helps anchor the muscle fiber to the basal lamina. The loss of this protein results in progressive muscle weakness, and eventually death.
In the muscle fibers, the effects of the disease can be exacerbated by auto-immune interference. Weakness of the sarcolemma leads to damage and tears in the membrane. The body’s immune system recognizes the damage and attempts to repair it. However, since the damage exists as a chronic condition, leukocytes begin to present the damaged protein fragments as antigens, stimulating a targeted attack on the damaged parts of the muscle fiber. The attack causes inflammation, fibrosis, and necrosis, further weakening the muscle.
Studies have shown that despite the severe pathology of the muscle fibers, the innervation of the muscle is unaffected.
ATP is required for muscle contraction. Identify which of the following are true
I. ATP binding causes myosin to release actin
II. Actin carries an inactive ADP when myosin binds
III. The myosin head movement to contract the muscle converts ATP to ADP
This question requires us to know the ATP binding cycle associated with muscle contraction. I is true; binding of ATP causes myosin to release actin. When there is no ATP present, the myosin remains bound and the muscle becomes stiff (rigor mortis). II is false; actin does not bind ATP. III is also false; ATP is converted to ADP when the myosin head goes from the contracted position to the relaxed position, not the other way around.
This question requires us to know the ATP binding cycle associated with muscle contraction. I is true; binding of ATP causes myosin to release actin. When there is no ATP present, the myosin remains bound and the muscle becomes stiff (rigor mortis). II is false; actin does not bind ATP. III is also false; ATP is converted to ADP when the myosin head goes from the contracted position to the relaxed position, not the other way around.
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The area where the motor neuron intersects the muscle is known as the .
The area where the motor neuron intersects the muscle is known as the .
The neuromuscular junction is where the nerve fibers directly connect to the muscle to deliver signals from the brain to the muscle tissue. "Cross bridge" refers to the linkage of actin and myosin filaments. The other answers sound similar, but are incorrect.
The neuromuscular junction is where the nerve fibers directly connect to the muscle to deliver signals from the brain to the muscle tissue. "Cross bridge" refers to the linkage of actin and myosin filaments. The other answers sound similar, but are incorrect.
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Muscle contraction is mainly powered by which chemical?
Muscle contraction is mainly powered by which chemical?
ATP (adenosine triphosphate) is the primary chemical that provides the power for muscle contraction. ADP (adenosine diphosphate) is the resulting chemical when ATP is expended. ATP is required for the cross-bridge cycle. Acetylcholine is a neurotransmitter used in muscle contraction, but does not provide a power source. Lactic acid results from anaerobic production of ATP.
ATP (adenosine triphosphate) is the primary chemical that provides the power for muscle contraction. ADP (adenosine diphosphate) is the resulting chemical when ATP is expended. ATP is required for the cross-bridge cycle. Acetylcholine is a neurotransmitter used in muscle contraction, but does not provide a power source. Lactic acid results from anaerobic production of ATP.
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A muscle will not have all of its fibers contract at once. Instead, the muscle is divided into multiple bundles of muscle fibers, with a neuron innervating all of the fibers in a given bundle. Each collection of fibers controlled by a single neuron is referred to as a motor unit.
Which of the following statements is false when discussing motor units?
A muscle will not have all of its fibers contract at once. Instead, the muscle is divided into multiple bundles of muscle fibers, with a neuron innervating all of the fibers in a given bundle. Each collection of fibers controlled by a single neuron is referred to as a motor unit.
Which of the following statements is false when discussing motor units?
Smaller motor units are activated first during muscular contraction. If more force is needed, larger motor units will be recruited in order to provide the necessary force.
Smaller motor units are activated first during muscular contraction. If more force is needed, larger motor units will be recruited in order to provide the necessary force.
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A toxin prevents calcium from being actively pumped back into the sarcoplasmic reticulum. What would you expect to be a consequence of this toxin's presence in the body?
A toxin prevents calcium from being actively pumped back into the sarcoplasmic reticulum. What would you expect to be a consequence of this toxin's presence in the body?
Before a contraction, calcium is released from the sarcoplasmic reticulum and attaches to troponin. Troponin will then remove tropomyosin from the active site on actin where myosin is able to attach.
If calcium is never pumped back into the sarcoplasmic reticulum, the active site on actin will stay exposed, which allows myosin to attach at all times.
Note that calcium is also responsible for initiating acetylcholine release from the neuron at the neuromuscular junction; however, this process involves extracellular calcium ions and is not linked to the sarcoplasmic reticulum.
Before a contraction, calcium is released from the sarcoplasmic reticulum and attaches to troponin. Troponin will then remove tropomyosin from the active site on actin where myosin is able to attach.
If calcium is never pumped back into the sarcoplasmic reticulum, the active site on actin will stay exposed, which allows myosin to attach at all times.
Note that calcium is also responsible for initiating acetylcholine release from the neuron at the neuromuscular junction; however, this process involves extracellular calcium ions and is not linked to the sarcoplasmic reticulum.
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What role does calcium play during muscle contraction?
What role does calcium play during muscle contraction?
Calcium is released from the sarcoplasmic reticulum and binds to troponin. At rest, troponin interacts with tropomyosin to block the active sites on actin, preventing myosin from binding. When calcium binds troponin, it causes a conformational change in tropomyosin. This allows the myosin heads to bind to the actin active sites, initiating the contraction process. ATP is used to cause the dissociation of the myosin head from the actin filament, and is not involved in initiating actin-myosin interaction.
Calcium is released from the sarcoplasmic reticulum and binds to troponin. At rest, troponin interacts with tropomyosin to block the active sites on actin, preventing myosin from binding. When calcium binds troponin, it causes a conformational change in tropomyosin. This allows the myosin heads to bind to the actin active sites, initiating the contraction process. ATP is used to cause the dissociation of the myosin head from the actin filament, and is not involved in initiating actin-myosin interaction.
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Rigor mortis, a recognizable sign of death, is the stiffness observed in the muscle of an individual who has just passed away. On a molecular level, what causes rigor mortis?
Rigor mortis, a recognizable sign of death, is the stiffness observed in the muscle of an individual who has just passed away. On a molecular level, what causes rigor mortis?
After the myosin head has attached to the actin filament, a power stroke occurs, which causes the "sliding filament theory" (contraction).This process occurs in a cycle as long as two conditions are present: calcium must be available to bind to troponin, revealing the binding sites on actin, and ATP must be available for the movement of the myosin head. When an individual is no longer alive, calcium is no longer sequestered and remains available to bind to troponin, revealing the binding sites. This would allow continued normal contraction, but is not the cause of sustained contraction seen in rigor mortis. After death, cellular metabolism no longer produces ATP, and stores of ATP are quickly depleted. This results in a break in the contraction cycle. ATP is necessary to detach the myosin head from the actin filament. Without ATP present, the myosin head remains bound and the contraction is sustained. The depletion of ATP is thus the cause of rigor mortis, causing stiffness due to myosin's inability to detach from actin.
After the myosin head has attached to the actin filament, a power stroke occurs, which causes the "sliding filament theory" (contraction).This process occurs in a cycle as long as two conditions are present: calcium must be available to bind to troponin, revealing the binding sites on actin, and ATP must be available for the movement of the myosin head. When an individual is no longer alive, calcium is no longer sequestered and remains available to bind to troponin, revealing the binding sites. This would allow continued normal contraction, but is not the cause of sustained contraction seen in rigor mortis. After death, cellular metabolism no longer produces ATP, and stores of ATP are quickly depleted. This results in a break in the contraction cycle. ATP is necessary to detach the myosin head from the actin filament. Without ATP present, the myosin head remains bound and the contraction is sustained. The depletion of ATP is thus the cause of rigor mortis, causing stiffness due to myosin's inability to detach from actin.
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