Help with Other Muscle Physiology - Anatomy
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Which of the following statements does not describe type 2 muscle fibers?
Which of the following statements does not describe type 2 muscle fibers?
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Type 2 muscle fibers are fast twitch, and grossly appear white due to decreased mitochondria and myoglobin concentration. Because of the decreased number of mitochondria, sustained activity of type 2 muscle fibers results in lactic acid accumulation due to anaerobic glycolysis.
Type 1 muscle fibers are slow twitch, and grossly appear red due to increased mitochondria and myoglobin concentration, which allows for oxidative phosphorylation. Type 1 muscle fibers allow for low, sustained muscle contraction.
Type 2 muscle fibers are fast twitch, and grossly appear white due to decreased mitochondria and myoglobin concentration. Because of the decreased number of mitochondria, sustained activity of type 2 muscle fibers results in lactic acid accumulation due to anaerobic glycolysis.
Type 1 muscle fibers are slow twitch, and grossly appear red due to increased mitochondria and myoglobin concentration, which allows for oxidative phosphorylation. Type 1 muscle fibers allow for low, sustained muscle contraction.
Which ion is quintessential for muscle contraction in skeletal muscle, but not in smooth muscle?
Which ion is quintessential for muscle contraction in skeletal muscle, but not in smooth muscle?
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The sarcoplasmic reticulum of the muscle fiber is used to store calcium. When an action potential causes depolarization of the T-tubules, adjacent proteins cause the calcium channels of the sarcoplasmic reticulum to open. The released calcium binds to troponin, influencing a change in tropomyosin and allowing myosin to bind the active sites of actin. Without the presence of calcium, tropomyosin remains in place to block myosin binding and contraction cannot occur.
This process, however, does not occur in smooth muscle. Smooth muscle lacks both troponin and tropomyosin, and is thus not reliant on calcium for contraction.
The sarcoplasmic reticulum of the muscle fiber is used to store calcium. When an action potential causes depolarization of the T-tubules, adjacent proteins cause the calcium channels of the sarcoplasmic reticulum to open. The released calcium binds to troponin, influencing a change in tropomyosin and allowing myosin to bind the active sites of actin. Without the presence of calcium, tropomyosin remains in place to block myosin binding and contraction cannot occur.
This process, however, does not occur in smooth muscle. Smooth muscle lacks both troponin and tropomyosin, and is thus not reliant on calcium for contraction.
What process releases the myosin head from actin?
What process releases the myosin head from actin?
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In order for the myosin head to perform a power stroke, an ATP must be cleaved to form ADP and a phosphate. This places the head in a cocked, high energy position. When the phosphate and ADP are expelled from the head, the myosin moves to a low energy position and drags the actin, causing the sarcomere to shorten. Once a new ATP is attached to the myosin, it detaches from the actin filament to begin the process again.
Lack of ATP causes myosin to remain attached to actin. This is the cause of rigor mortis.
In order for the myosin head to perform a power stroke, an ATP must be cleaved to form ADP and a phosphate. This places the head in a cocked, high energy position. When the phosphate and ADP are expelled from the head, the myosin moves to a low energy position and drags the actin, causing the sarcomere to shorten. Once a new ATP is attached to the myosin, it detaches from the actin filament to begin the process again.
Lack of ATP causes myosin to remain attached to actin. This is the cause of rigor mortis.
A scientist is examining a sample of tissue taken from a skeletal muscle biopsy. Which of the following is most likely true of sample?
A scientist is examining a sample of tissue taken from a skeletal muscle biopsy. Which of the following is most likely true of sample?
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The sarcoplasmic reticulum is a specialized cell structure, characteristic of skeletal muscle cells, that is used to store calcium ions.
Upon neural stimulation, depolarization of the T-tubules causes a cellular reaction to open ion channels in the membrane of the sarcoplasmic reticulum. Calcium is released into the cell, where it can bind to troponin and allow for muscle contraction.
The endoplasmic reticulum is found in most eukaryotic cells, and is used for lipid synthesis, detoxification, and several other functions. Sodium and potassium play significant role in regulating membrane potential, but are not stored in the muscle cell in large amounts as calcium is.
The sarcoplasmic reticulum is a specialized cell structure, characteristic of skeletal muscle cells, that is used to store calcium ions.
Upon neural stimulation, depolarization of the T-tubules causes a cellular reaction to open ion channels in the membrane of the sarcoplasmic reticulum. Calcium is released into the cell, where it can bind to troponin and allow for muscle contraction.
The endoplasmic reticulum is found in most eukaryotic cells, and is used for lipid synthesis, detoxification, and several other functions. Sodium and potassium play significant role in regulating membrane potential, but are not stored in the muscle cell in large amounts as calcium is.
Three muscle cells are placed side by side.
In muscle cell 1, striations are clearly visible.
In muscle cell 2, striations are also present, with sharp discs periodically found along muscle fibers. Further examination shows gap junctions between adjacent cells.
In muscle cell 3, no striations are present.
Which of the three cells could have been sampled from the upper third of the esophagus?
Three muscle cells are placed side by side.
In muscle cell 1, striations are clearly visible.
In muscle cell 2, striations are also present, with sharp discs periodically found along muscle fibers. Further examination shows gap junctions between adjacent cells.
In muscle cell 3, no striations are present.
Which of the three cells could have been sampled from the upper third of the esophagus?
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Of the three primary muscle types, only skeletal muscle is under voluntary control. The upper third of the esophagus is under voluntary control by the cerebral cortex, and thus relies on skeletal muscle to contract. This can be appreciated when one initiates a swallow. The swallow is started deliberately, and then continues down deeper into the esophagus without conscious or voluntary effort.
Striations are characteristic of skeletal muscle, eliminating the option of muscle cell 3. Muscle cell 2 is said to contain gap junctions, which are characteristic of cardiac muscle, but not skeletal muscle. We can conclude that muscle cell 1 corresponds to skeletal muscle, and must be the only answer.
Of the three primary muscle types, only skeletal muscle is under voluntary control. The upper third of the esophagus is under voluntary control by the cerebral cortex, and thus relies on skeletal muscle to contract. This can be appreciated when one initiates a swallow. The swallow is started deliberately, and then continues down deeper into the esophagus without conscious or voluntary effort.
Striations are characteristic of skeletal muscle, eliminating the option of muscle cell 3. Muscle cell 2 is said to contain gap junctions, which are characteristic of cardiac muscle, but not skeletal muscle. We can conclude that muscle cell 1 corresponds to skeletal muscle, and must be the only answer.
During fasting, blood sugar begins to drop as time from the last meal increases. As blood sugar drops and activity level increases, which of the following is most likely to happen in skeletal muscle tissue?
During fasting, blood sugar begins to drop as time from the last meal increases. As blood sugar drops and activity level increases, which of the following is most likely to happen in skeletal muscle tissue?
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During fasting, glycogen production is reduced and glycogen catabolism (glycogenolysis) is increased. Glycogen stored within muscle is broken down into glucose by circulating catecholamines (epinephrine, not glucagon) during prolonged fasting.
Prolonged fasting also causes glycogen breakdown in the liver. This process is mediated by glucagon.
During fasting, glycogen production is reduced and glycogen catabolism (glycogenolysis) is increased. Glycogen stored within muscle is broken down into glucose by circulating catecholamines (epinephrine, not glucagon) during prolonged fasting.
Prolonged fasting also causes glycogen breakdown in the liver. This process is mediated by glucagon.
After a heavy meal, which type of glucose transporters are most likely to be found in muscle cells?
After a heavy meal, which type of glucose transporters are most likely to be found in muscle cells?
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GLUT4 glucose transporters are insulin-mediated, and found on the apical membrane of certain cells. Insulin release follows a heavy meal, and thus we would expect to find increased levels of GLUT4 transporters on muscle cells following the meal, with the absorbed glucose being used to produce intra-muscular glycogen.
The remaining glucose transporters are located as follows:
GLUT1: Erythrocytes, constitutively expressed
GLUT2: Pancreatic islet cells monitoring serum glucose levels, constitutively expressed
GLUT3: Brain tissue, highest glucose affinity & constitutively expressed
GLUT5: Present on the basolateral side of enterocytes to allow movement of absorbed carbohydrate from the enterocyte into the circulation, constitutively expressed
Note that GLUT4, in contrast to other subtypes, is inducible by insulin release.
GLUT4 glucose transporters are insulin-mediated, and found on the apical membrane of certain cells. Insulin release follows a heavy meal, and thus we would expect to find increased levels of GLUT4 transporters on muscle cells following the meal, with the absorbed glucose being used to produce intra-muscular glycogen.
The remaining glucose transporters are located as follows:
GLUT1: Erythrocytes, constitutively expressed
GLUT2: Pancreatic islet cells monitoring serum glucose levels, constitutively expressed
GLUT3: Brain tissue, highest glucose affinity & constitutively expressed
GLUT5: Present on the basolateral side of enterocytes to allow movement of absorbed carbohydrate from the enterocyte into the circulation, constitutively expressed
Note that GLUT4, in contrast to other subtypes, is inducible by insulin release.
What is the function of the levator scapulae?
What is the function of the levator scapulae?
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The levator scapulae is a long skeletal muscle of the shoulder girdle. It originates in the transverse processes of the atlas and axis as well the posterior tubercles of the 3rd and 4th cervical vertebrae (or in simple terms: it originates at the first four cervical vertebrae, and runs along the back and side of the neck). Its function is to elevate the scapula.
The levator scapulae is a long skeletal muscle of the shoulder girdle. It originates in the transverse processes of the atlas and axis as well the posterior tubercles of the 3rd and 4th cervical vertebrae (or in simple terms: it originates at the first four cervical vertebrae, and runs along the back and side of the neck). Its function is to elevate the scapula.
What is the action of the masseter muscle?
What is the action of the masseter muscle?
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The masseter muscle is a facial muscle that plays a major role in the chewing of solid foods (it is one of the muscles of mastication: masseter, temporalis, medial pterygoid, lateral pterygoid). The action of the muscle is to elevate the mandible (raise the lower jaw) which results in closing of the jaws. It connects to the mandible (lower jawbone) and the maxilla/zygomatic arch.
The masseter muscle is a facial muscle that plays a major role in the chewing of solid foods (it is one of the muscles of mastication: masseter, temporalis, medial pterygoid, lateral pterygoid). The action of the muscle is to elevate the mandible (raise the lower jaw) which results in closing of the jaws. It connects to the mandible (lower jawbone) and the maxilla/zygomatic arch.
Which function is performed by muscle cells?
Which function is performed by muscle cells?
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The correct answer is contraction. Muscle cells shorten or contract to move body parts. These contractions can be under voluntary or involuntary control. The primary function of muscle cell contraction is movement, but contraction is responsible for many other important functions like posture, joint stability and heat production. Muscles contract to allow maintenance of postures like sitting and help stabilize joints. Heat is also generated by contraction.
The other answer choices are functions performed by epithelial cells. Epithelial cells contain neuron endings (nerves) that perceive external stimuli and function as sensory receptors. Epithelial cells form coverings over body parts, including the skin, which prevents infection from microbes. They can form taste buds, line the nose and are located in the ear and eye. Epithelial cells serve an absorptive function through active-transport systems to absorb filtered material and transport to the rest of the body. Epithelial cells also secrete fluids necessary for other functions. For example, some epithelial cells secrete mucus, which lubricates body cavities and the passageways they line.
The correct answer is contraction. Muscle cells shorten or contract to move body parts. These contractions can be under voluntary or involuntary control. The primary function of muscle cell contraction is movement, but contraction is responsible for many other important functions like posture, joint stability and heat production. Muscles contract to allow maintenance of postures like sitting and help stabilize joints. Heat is also generated by contraction.
The other answer choices are functions performed by epithelial cells. Epithelial cells contain neuron endings (nerves) that perceive external stimuli and function as sensory receptors. Epithelial cells form coverings over body parts, including the skin, which prevents infection from microbes. They can form taste buds, line the nose and are located in the ear and eye. Epithelial cells serve an absorptive function through active-transport systems to absorb filtered material and transport to the rest of the body. Epithelial cells also secrete fluids necessary for other functions. For example, some epithelial cells secrete mucus, which lubricates body cavities and the passageways they line.
Force velocity relationship measures which of the following?
Force velocity relationship measures which of the following?
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The force velocity relationship measures the velocity of shortening of isotonic contractions when the muscle is challenged with different afterloads (the load against which the muscle must contract.) The velocity of shortening decreases as the afterload increases.
The force velocity relationship measures the velocity of shortening of isotonic contractions when the muscle is challenged with different afterloads (the load against which the muscle must contract.) The velocity of shortening decreases as the afterload increases.
In which type of muscular contraction is length held constant?
In which type of muscular contraction is length held constant?
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An isometric contraction, as the name implies, is a contraction in which the muscle length (-metric) is kept constant (iso-). In order for this to happen, the joint angle is kept constant, but there is an increase in muscle tension during contraction. Note that during isometric contraction there is no muscle shortening.
Isotonic contractions involve constant tension in the muscle, and a change in length. The two types of isotonic contractions are concentric and eccentric. Concentric contractions involve the shortening of a muscle throughout a contraction, eccentric contractions involve the lengthening of a muscle during contraction.
An isometric contraction, as the name implies, is a contraction in which the muscle length (-metric) is kept constant (iso-). In order for this to happen, the joint angle is kept constant, but there is an increase in muscle tension during contraction. Note that during isometric contraction there is no muscle shortening.
Isotonic contractions involve constant tension in the muscle, and a change in length. The two types of isotonic contractions are concentric and eccentric. Concentric contractions involve the shortening of a muscle throughout a contraction, eccentric contractions involve the lengthening of a muscle during contraction.
The length-tension relationship of active muscle is described as .
The length-tension relationship of active muscle is described as .
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The muscle length-tension relationship measures muscle tension developed during isometric contractions (the muscle is set to fixed lengths and length is held constant). Active tension is the difference between total tension and passive tension. Active tension is the active force created when the muscle contracts. Passive tension is created by stretching the muscle to different lengths. Total tension is the tension developed when the muscle is stimulated to contract at different lengths.
The muscle length-tension relationship measures muscle tension developed during isometric contractions (the muscle is set to fixed lengths and length is held constant). Active tension is the difference between total tension and passive tension. Active tension is the active force created when the muscle contracts. Passive tension is created by stretching the muscle to different lengths. Total tension is the tension developed when the muscle is stimulated to contract at different lengths.
Glucose uptake into skeletal muscle is an example of which of the following?
Glucose uptake into skeletal muscle is an example of which of the following?
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Glucose is transported into skeletal muscles via insulin dependent facilitated diffusion. This type of diffusion requires a specific trans-membrane protein to allow for the passage of glucose. In the presence of insulin, these membrane channels allow glucose to move from outside the cell to inside the cell in an effort to lower blood glucose levels.
Glucose is transported into skeletal muscles via insulin dependent facilitated diffusion. This type of diffusion requires a specific trans-membrane protein to allow for the passage of glucose. In the presence of insulin, these membrane channels allow glucose to move from outside the cell to inside the cell in an effort to lower blood glucose levels.
Which of these muscles is responsible for flexing the forearm?
Which of these muscles is responsible for flexing the forearm?
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All of the choices indicate muscles of the arm and hand, but they have different functions. The brachialis is involved in forearm flexion, along with muscles such as the biceps brachii and pronator teres. The triceps are involved with forearm extension, which is the opposite of flexion. The extensor carpi radialis longus is involved in extension and abduction of the hand. Lastly, the extensor carpi ulnaris is involved with extension and adduction of the hand. We can tell that the extensor carpi ulnaris and extensor carpi radialis longus are not involved in flexion because they are named "extensors," and, as stated, extension is the opposite of flexion.
All of the choices indicate muscles of the arm and hand, but they have different functions. The brachialis is involved in forearm flexion, along with muscles such as the biceps brachii and pronator teres. The triceps are involved with forearm extension, which is the opposite of flexion. The extensor carpi radialis longus is involved in extension and abduction of the hand. Lastly, the extensor carpi ulnaris is involved with extension and adduction of the hand. We can tell that the extensor carpi ulnaris and extensor carpi radialis longus are not involved in flexion because they are named "extensors," and, as stated, extension is the opposite of flexion.
Which of these is not a muscle of the foot?
Which of these is not a muscle of the foot?
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The extensor digitorum longus is not a muscle of the foot, but of the leg. It functions in extending the toes and dorsiflexing and everting the foot. The other three choices are all muscles of the foot. The extensor hallucis brevis functions in extending the big toe. The abductor digiti minimi functions in abducting the little toe. Lastly, the adductor hallucis functions in adducting the big toe.
The extensor digitorum longus is not a muscle of the foot, but of the leg. It functions in extending the toes and dorsiflexing and everting the foot. The other three choices are all muscles of the foot. The extensor hallucis brevis functions in extending the big toe. The abductor digiti minimi functions in abducting the little toe. Lastly, the adductor hallucis functions in adducting the big toe.
When measuring the heat generated by muscle contraction, there is an additional amount of heat, labelled as 'unexplained heat.'
What is the source of the 'unexplained heat' in the initial phase of muscle contraction?
When measuring the heat generated by muscle contraction, there is an additional amount of heat, labelled as 'unexplained heat.'
What is the source of the 'unexplained heat' in the initial phase of muscle contraction?
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The signal for muscle contraction causes the release of calcium from the sarcoplasmic reticulum. This calcium floods the cell and is necessary for causing muscle contraction. Parvalbumin, a protein in the cytoplasm, binds to calcium and acts as a slow-releaser of calcium. This binding reaction of calcium with parvalbumin causes the release of heat, which is termed as 'unexplained heat.' The 'unexplained heat' is also known as 'labile heat.'
The signal for muscle contraction causes the release of calcium from the sarcoplasmic reticulum. This calcium floods the cell and is necessary for causing muscle contraction. Parvalbumin, a protein in the cytoplasm, binds to calcium and acts as a slow-releaser of calcium. This binding reaction of calcium with parvalbumin causes the release of heat, which is termed as 'unexplained heat.' The 'unexplained heat' is also known as 'labile heat.'
Which of the following statements does not describe type 2 muscle fibers?
Which of the following statements does not describe type 2 muscle fibers?
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Type 2 muscle fibers are fast twitch, and grossly appear white due to decreased mitochondria and myoglobin concentration. Because of the decreased number of mitochondria, sustained activity of type 2 muscle fibers results in lactic acid accumulation due to anaerobic glycolysis.
Type 1 muscle fibers are slow twitch, and grossly appear red due to increased mitochondria and myoglobin concentration, which allows for oxidative phosphorylation. Type 1 muscle fibers allow for low, sustained muscle contraction.
Type 2 muscle fibers are fast twitch, and grossly appear white due to decreased mitochondria and myoglobin concentration. Because of the decreased number of mitochondria, sustained activity of type 2 muscle fibers results in lactic acid accumulation due to anaerobic glycolysis.
Type 1 muscle fibers are slow twitch, and grossly appear red due to increased mitochondria and myoglobin concentration, which allows for oxidative phosphorylation. Type 1 muscle fibers allow for low, sustained muscle contraction.
Which ion is quintessential for muscle contraction in skeletal muscle, but not in smooth muscle?
Which ion is quintessential for muscle contraction in skeletal muscle, but not in smooth muscle?
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The sarcoplasmic reticulum of the muscle fiber is used to store calcium. When an action potential causes depolarization of the T-tubules, adjacent proteins cause the calcium channels of the sarcoplasmic reticulum to open. The released calcium binds to troponin, influencing a change in tropomyosin and allowing myosin to bind the active sites of actin. Without the presence of calcium, tropomyosin remains in place to block myosin binding and contraction cannot occur.
This process, however, does not occur in smooth muscle. Smooth muscle lacks both troponin and tropomyosin, and is thus not reliant on calcium for contraction.
The sarcoplasmic reticulum of the muscle fiber is used to store calcium. When an action potential causes depolarization of the T-tubules, adjacent proteins cause the calcium channels of the sarcoplasmic reticulum to open. The released calcium binds to troponin, influencing a change in tropomyosin and allowing myosin to bind the active sites of actin. Without the presence of calcium, tropomyosin remains in place to block myosin binding and contraction cannot occur.
This process, however, does not occur in smooth muscle. Smooth muscle lacks both troponin and tropomyosin, and is thus not reliant on calcium for contraction.
What process releases the myosin head from actin?
What process releases the myosin head from actin?
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In order for the myosin head to perform a power stroke, an ATP must be cleaved to form ADP and a phosphate. This places the head in a cocked, high energy position. When the phosphate and ADP are expelled from the head, the myosin moves to a low energy position and drags the actin, causing the sarcomere to shorten. Once a new ATP is attached to the myosin, it detaches from the actin filament to begin the process again.
Lack of ATP causes myosin to remain attached to actin. This is the cause of rigor mortis.
In order for the myosin head to perform a power stroke, an ATP must be cleaved to form ADP and a phosphate. This places the head in a cocked, high energy position. When the phosphate and ADP are expelled from the head, the myosin moves to a low energy position and drags the actin, causing the sarcomere to shorten. Once a new ATP is attached to the myosin, it detaches from the actin filament to begin the process again.
Lack of ATP causes myosin to remain attached to actin. This is the cause of rigor mortis.