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1/71 Questions

Muscle Fatigue sets in due to non-availability of……...
- Actin-binding Site
- Calcium
- ATP
- Mg cofactor

About This Quiz

Biology is the scientific study of life. It is a natural science with a broad scope but has several unifying themes that tie it together as a single, coherent field.
Careful! Only the best of biology students can pass this test!
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Careful! Only The Best Of Biology Students Can Pass This Test! - Quiz

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2.

The energy needed to perform a muscle contraction comes directly from .....
- ATP
- Oxygen
- Glucose
- Calcium
Correct Answer

A. ATP

Explanation

During muscle contraction, ATP (adenosine triphosphate) is the primary source of energy. ATP is a molecule that stores and releases energy when needed. When a muscle contracts, ATP molecules are broken down, releasing energy that is used for muscle contraction. This energy is necessary for the myosin heads to interact with actin filaments, causing muscle fibers to contract. Oxygen and glucose are also important for energy production, but they are not the direct source of energy for muscle contraction. Calcium is involved in the process of muscle contraction, but it does not directly provide the energy needed for the contraction.

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3.

Transverse links of the muscle are formed by the help of …… ions
- Sodium
- Potassium
- Chlorine
- Calcium
Correct Answer

A. Calcium

Explanation

Calcium ions are responsible for the formation of transverse links in muscle. These ions play a crucial role in muscle contraction by binding to proteins like troponin and allowing the interaction between actin and myosin filaments. This interaction leads to the sliding of filaments and muscle contraction. Sodium, potassium, and chlorine ions are important for maintaining the resting membrane potential and transmitting nerve impulses, but they are not directly involved in the formation of transverse links in muscle.

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4.

The disappearance of potential difference on the muscle fiber membrane is due to -------
- Entry of calcium ions
- Entry of sodium ions
- Exit of calcium ions
- Exit of potassium ions
Correct Answer

A. Entry of sodium ions

Explanation

The disappearance of potential difference on the muscle fiber membrane is due to the entry of sodium ions. When a muscle fiber is at rest, the inside of the cell is negatively charged compared to the outside. This is maintained by the sodium-potassium pump, which actively transports sodium ions out of the cell and potassium ions into the cell. However, when a muscle is stimulated, sodium channels open, allowing sodium ions to rush into the cell. This causes a change in the electrical potential of the membrane, leading to the disappearance of the potential difference.

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5.

If a muscle fiber contains six Z-lines and five H-zones, then how many sarcomeres are there in that fiber?
- Seven
- Six
- Five
- Four
Correct Answer

A. Five

Explanation

If a muscle fiber contains six Z-lines and five H-zones, then there must be five sarcomeres in that fiber. Each sarcomere is defined by the presence of a Z-line at each end and an H-zone in the middle. Since there are six Z-lines and each sarcomere has two Z-lines, there must be a total of three sarcomeres. However, since there are only five H-zones, this means that one of the sarcomeres does not have an H-zone, resulting in a total of five sarcomeres in the fiber.

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6.

A muscle consists of 300 muscle fibers. What is the least number of motor neurons that can supply it?
- 1
- 3
- 60
- 200
Correct Answer

A. 3

Explanation

Each muscle fiber is innervated by a single motor neuron. Therefore, the least number of motor neurons that can supply 300 muscle fibers is 300.

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7.

When a muscle gets shorter and thicker It Is a(an) _______ muscle.
- Involuntary
- Relaxing
- Skeletal
- Contracting
Correct Answer

A. Contracting

Explanation

When a muscle gets shorter and thicker, it is contracting. Muscle contraction occurs when the muscle fibers generate force by pulling on the tendons, resulting in movement. This process involves the sliding of actin and myosin filaments within the muscle fibers, causing the muscle to shorten and thicken. Therefore, the correct answer is contracting.

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8.

Which of the following does NOT occur during skeletal muscle contraction?
- Calcium binds to myosin heads.
- ATP is hydrolyzed.
- Myosin heads bind to actin.
- The I-bands shorten and H-zones disappear.
Correct Answer

A. Calcium binds to myosin heads.

Explanation

During skeletal muscle contraction, calcium binds to troponin, not myosin heads. Calcium binding to troponin causes a conformational change that allows myosin heads to bind to actin, leading to muscle contraction. ATP is hydrolyzed to provide energy for the myosin heads to move along the actin filaments. As a result of muscle contraction, the I-bands shorten and the H-zones disappear.

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9.

Shortage of oxygen in the muscle stimulates the muscle to convert glycogen to glucose for the production of energy leading to the accumulation of ……., which causes muscle fatigue.
- Acetic acid
- Pyruvic acid
- Lactic acid
- Ethanol
Correct Answer

A. Lactic acid

Explanation

Shortage of oxygen in the muscle leads to anaerobic respiration, where glycogen is converted to glucose for energy production. This process produces lactic acid as a byproduct, which accumulates in the muscle and causes muscle fatigue.

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10.

Muscle contraction occurs when …..
- Depolarization changes to polarization
- The fiber membrane becomes permeable to Na ⁺ ions
- Potassium ions enter inside the sarcoplasm with great quantities
- No chemical transmitters reach the fiber membrane
Correct Answer

A. The fiber membrane becomes permeable to Na ⁺ ions

Explanation

During muscle contraction, the fiber membrane becomes permeable to Na+ ions. This allows the Na+ ions to enter the muscle fiber, which triggers a series of events leading to muscle contraction. This change in permeability is due to the opening of ion channels in the fiber membrane, specifically sodium channels. The influx of Na+ ions leads to depolarization of the muscle fiber, which ultimately results in the contraction of the muscle.

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1
11.

Which of the following is controlled by skeletal muscles?
- Eye movement
- Heart beats
- Dilatation of the eye pupil
- Dilatation of blood vessels
Correct Answer

A. Eye movement

Explanation

Skeletal muscles are responsible for the voluntary movement of the body. Eye movement is controlled by skeletal muscles, allowing us to move our eyes in different directions. The other options, such as heart beats, dilatation of the eye pupil, and dilatation of blood vessels, are controlled by smooth muscles or involuntary muscles, not skeletal muscles.

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12.

The region which its length does not change when the muscle fiber contracts is …….
- Z
- H
- A
- I
Correct Answer

A. A

Explanation

The region which its length does not change when the muscle fiber contracts is A.

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13.

For the contraction of skeletal muscles, the presence of ------ is necessary
- Glucose, glycogen and cholinesterase
- ATP and calcium ions
- ATP and Cholinesterase
- Glucose and calcium ions
Correct Answer

A. ATP and calcium ions

Explanation

For the contraction of skeletal muscles to occur, both ATP and calcium ions are necessary. ATP provides the energy needed for muscle contraction, while calcium ions are responsible for triggering the contraction process by binding to specific proteins in the muscle fibers. Without ATP, the muscles would not have the energy required to contract, and without calcium ions, the contraction process would not be initiated. Therefore, both ATP and calcium ions are essential for skeletal muscle contraction.

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14.

When a contracted skeletal muscle is relaxed, the two regions …….. and …….. increase in length.
- H / I
- H / A
- A / I
- A / Z-Z
Correct Answer

A. H / I

Explanation

When a contracted skeletal muscle is relaxed, the two regions H and I increase in length.

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15.

What is the number of neuromuscular junctions that can be found in a muscle consisting of 5 muscle bundles where each bundle contains 40 muscle fibers?
- 200
- 100
- 50
- 5
Correct Answer

A. 200

Explanation

In a muscle consisting of 5 muscle bundles, each containing 40 muscle fibers, the number of neuromuscular junctions can be calculated by multiplying the number of muscle bundles (5) by the number of muscle fibers in each bundle (40). Therefore, the total number of neuromuscular junctions in the muscle is 5 x 40 = 200.

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16.

A muscle consists of 300 muscle fibers. What is the greatest number of motor neurons that can supply it?
- 1
- 3
- 60
- 200
Correct Answer

A. 60

Explanation

Each muscle fiber is innervated by one motor neuron. Therefore, the maximum number of motor neurons that can supply the muscle is equal to the number of muscle fibers, which is 300.

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17.

If a human skeletal muscle consists of 10 muscle bundles, and each bundle consists of 50 muscle fibers. If each muscle fiber consists of 1000 – 2000 myofibrils, what is the least number of myofibrils that the muscle contains?
- 500,000
- 600,000
- 900,000
- 1000,000
Correct Answer

A. 500,000

Explanation

The least number of myofibrils that the muscle contains can be calculated by multiplying the number of muscle bundles, muscle fibers per bundle, and myofibrils per fiber. In this case, the muscle has 10 bundles, each containing 50 muscle fibers, and each fiber has 1000-2000 myofibrils. To find the least number, we can assume that each fiber has the minimum number of myofibrils, which is 1000. Therefore, the total number of myofibrils in the muscle would be 10 x 50 x 1000 = 500,000.

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18.

What happens during movement of limbs in Man?
- Limbs are supported by the skeletal system during movement
- Muscles of limbs contract and relax by taking an order from the nervous system
- Movement of limbs is done by the contraction and relaxation of the muscles
- All of the above
Correct Answer

A. All of the above

Explanation

During the movement of limbs in humans, all of the above mentioned statements are true. The limbs are supported by the skeletal system, which provides a framework for movement. The muscles of the limbs contract and relax in response to signals from the nervous system, allowing for movement. Therefore, the movement of limbs is indeed accomplished through the contraction and relaxation of muscles, which are supported by the skeletal system and controlled by the nervous system.

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19.

The organelle that contains actin and myosin is .........
- Tendon
- Sarcolemma
- Myofibril
- Fiber
Correct Answer

A. Myofibril

Explanation

The myofibril is the correct answer because it is a specialized organelle found in muscle cells that contains actin and myosin. Actin and myosin are proteins that are responsible for muscle contraction and movement. The myofibril is composed of repeating units called sarcomeres, which are the functional units of muscle contraction. Therefore, the myofibril is the organelle that contains actin and myosin.

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20.

An entire skeletal muscle is surrounded by ______.
- Endomysium.
- Sarcolemma
- Epimysium
- Perimysium
Correct Answer

A. Epimysium

Explanation

The correct answer is Epimysium. The epimysium is the connective tissue layer that surrounds the entire skeletal muscle. It provides support and protection to the muscle fibers and helps to maintain the shape and structure of the muscle.

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21.

The functional unit of contractile system in a striated muscle is …..
- Sarcomere
- A-band
- Myofibril
- I-band
Correct Answer

A. Sarcomere

Explanation

The correct answer is Sarcomere. The sarcomere is the functional unit of the contractile system in a striated muscle. It is the basic unit of muscle contraction and is composed of overlapping thick and thin filaments. The sarcomere is responsible for the muscle's ability to generate force and produce movement.

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22.

Which statement is correct for muscle contraction?
- Length of I-band remains constant
- Length of A-band remains constant
- Length of sarcomere remains constant
- Size of H- zone remains constant
Correct Answer

A. Length of A-band remains constant

Explanation

During muscle contraction, the length of the A-band remains constant. The A-band represents the dark region in the middle of the sarcomere that contains overlapping thick and thin filaments. As the muscle contracts, the thin filaments slide over the thick filaments, causing the sarcomere to shorten. However, the length of the A-band remains constant because the thick filaments do not change in length during contraction.

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23.

Intercostal muscles are found in ….
- Thigh
- Diaphragm
- Ribs
- Abdomen
Correct Answer

A. Ribs

Explanation

Intercostal muscles are found in the ribs. These muscles are located between the ribs and play a crucial role in the process of breathing. They help in expanding and contracting the ribcage, allowing for the movement of the chest during inhalation and exhalation.

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1
24.

What are dark bands that define the two ends of each sacromere called?
- Z-Lines
- Myosin
- Sarcomeres
- Actin
Correct Answer

A. Z-Lines

Explanation

Z-lines are the dark bands that define the two ends of each sarcomere. They are made up of specialized proteins and act as anchoring points for the thin filaments of actin. The Z-lines help to maintain the structural integrity of the sarcomere and play a crucial role in muscle contraction.

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1
25.

The Functional Unit of the contractile system in Striated Muscles is ……
- Z-Band
- Sarcomere
- Myofibril
- Cross bridges
Correct Answer

A. Sarcomere

Explanation

The sarcomere is the functional unit of the contractile system in striated muscles. It is the basic structural and functional unit of a muscle fiber, consisting of overlapping actin and myosin filaments. When a muscle contracts, the sarcomeres within the muscle fibers shorten, resulting in muscle contraction. The Z-bands, myofibrils, and cross bridges are all components of the sarcomere, but the sarcomere itself is the specific unit responsible for muscle contraction.

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26.

Smooth Muscle is not cross striated because ……
- Of the regular arrangement of actin and myosin filaments
- Myosin and actin filaments are organized into well-ordered sarcomeres and myofibrils.
- Myosin and actin fibers are arranged an angles to each other as they run through the cell.
- Globular heads protruding from myosin filaments do not attach with actin filaments to form cross bridges
Correct Answer

A. Myosin and actin fibers are arranged an angles to each other as they run through the cell.

Explanation

Smooth muscle is not cross striated because myosin and actin fibers are arranged at angles to each other as they run through the cell. In cross-striated muscles, such as skeletal muscle, the myosin and actin filaments are organized into well-ordered sarcomeres and myofibrils. However, in smooth muscle, the arrangement is more irregular, with the fibers running in different directions. This lack of regular arrangement is what gives smooth muscle its characteristic smooth appearance under a microscope.

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27.

Intercaled discs are most likely to be observed in.........
- Longitudinal section of skeletal muscle
- Transverse section of skeletal muscle
- Transverse section of cardiac muscle
- Longitudinal section of cardiac muscle
Correct Answer

A. Longitudinal section of cardiac muscle

Explanation

Intercalated discs are specialized cell junctions found in cardiac muscle tissue. These discs play a crucial role in connecting individual cardiac muscle cells, allowing them to function as a coordinated unit. Intercalated discs are most likely to be observed in a longitudinal section of cardiac muscle because this section provides a view of the muscle fibers running parallel to the long axis of the heart. In contrast, a transverse section of cardiac muscle would provide a cross-sectional view of the muscle fibers, which may not clearly show the intercalated discs.

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28.

When skeletal muscle contracts an arrangement of the alternating light and dark bands traversing each skeletal muscle cell changes. Which of the following statements is not correct?
- The dark A-bands will remain a constant length
- The space occupied by the H-zone will not change
- The light I-bands will shorten
- The z-lines come closer together
Correct Answer

A. The space occupied by the H-zone will not change

Explanation

During skeletal muscle contraction, the A-bands, which are the dark bands, will remain a constant length. The H-zone, which is the space occupied by only thick filaments, will actually shorten as the thin filaments slide over the thick filaments. The I-bands, which are the light bands, will also shorten as the thin filaments overlap with the thick filaments. Additionally, the z-lines, which mark the boundaries of sarcomeres, will come closer together as the sarcomeres shorten. Therefore, the statement that is not correct is that the space occupied by the H-zone will not change.

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29.

The direct energy store for the muscle is ……
- ATP
- Glycogen
- Glucose
- Lactic acid
Correct Answer

A. ATP

Explanation

ATP (adenosine triphosphate) is the direct energy store for muscles. It is a molecule that provides the necessary energy for muscle contraction. When ATP is broken down, it releases energy that is used by the muscles for various activities. ATP is constantly being produced and used in muscle cells to support their function. Glycogen and glucose are energy sources that can be converted into ATP, but they are not the direct energy stores. Lactic acid is a byproduct of anaerobic metabolism and is not directly involved in providing energy for muscle contraction.

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30.

Each skeletal muscle fiber is controlled by a neuron at a single _______.
- Synaptic cleft
- Neuromuscular junction
- Synaptic knob
- Sarcomere
Correct Answer

A. Neuromuscular junction

Explanation

Each skeletal muscle fiber is controlled by a neuron at a single neuromuscular junction. This is where the neuron releases neurotransmitters that bind to receptors on the muscle fiber, initiating muscle contraction. The synaptic cleft is the small gap between the neuron and the muscle fiber, while the synaptic knob is the swollen end of the neuron that contains vesicles with neurotransmitters. The sarcomere is the basic unit of muscle contraction.

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31.

Which of the following statements is INCORRECT?
- Skeletal muscles are responsible for the pumping action of the heart.
- Skeletal muscles support the weight of some internal organs.
- Skeletal muscles form valves regulating the passage of substances through internal openings of the digestive tract.
- The contractions of skeletal muscles pull on tendons and move elements of the skeleton
Correct Answer

A. Skeletal muscles are responsible for the pumping action of the heart.

Explanation

The correct answer is "Skeletal muscles are responsible for the pumping action of the heart." This statement is incorrect because the heart is primarily composed of cardiac muscle, not skeletal muscle. Cardiac muscle is a specialized type of muscle that is responsible for the pumping action of the heart, while skeletal muscles are responsible for voluntary movements and support the skeleton.

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32.

Which of the following is NOT a characteristic of skeletal muscle contraction?
- It contracts rapidly.
- It is voluntary.
- It can contract for long periods of time without tiring.
- It can exert tremendous power.
Correct Answer

A. It can contract for long periods of time without tiring.

Explanation

Skeletal muscle contraction is characterized by its rapidity, voluntary control, and ability to exert tremendous power. However, it cannot contract for long periods of time without tiring. Skeletal muscles rely on the breakdown of ATP for energy, and prolonged contraction leads to the depletion of ATP and the buildup of metabolic waste products, causing fatigue.

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33.

Which of the following is not correct regarding the structure of the motor unit?
- A motor unit is made up of one neuron that supplies a single muscle fiber
- Each skeletal muscle fiber is controlled by a single motor neuron
- Groups of motor units often work together to coordinate the contractions of a single muscle
- Each motor neuron synapses with multiple muscle fibers.
Correct Answer

A. A motor unit is made up of one neuron that supplies a single muscle fiber

Explanation

The correct answer is "A motor unit is made up of one neuron that supplies a single muscle fiber." This statement is not correct because a motor unit is actually made up of one motor neuron and multiple muscle fibers. Each motor neuron branches out and forms connections with multiple muscle fibers, allowing for coordinated contractions of a single muscle.

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34.

During muscle contraction, the transverse links pull the ……….
- Acetyl choline
- Actin
- Myosin
- Sarcoplasm
Correct Answer

A. Actin

Explanation

During muscle contraction, the transverse links, also known as cross-bridges, pull the actin filaments towards the center of the sarcomere. Actin and myosin are the two main proteins involved in muscle contraction. Actin is the thin filament that forms the backbone of the sarcomere, while myosin is the thick filament that contains the heads which interact with actin to generate force and cause muscle contraction. Acetyl choline is a neurotransmitter that is released at the neuromuscular junction to initiate muscle contraction, and sarcoplasm is the cytoplasm of muscle cells.

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35.

The shortage of ATP in the muscle prevents the separation of …….
- The transverse links from the myosin filaments
- The transverse links from the actin filaments
- The choline group from the acetyl choline
- The linkage between the actin and the z-lines
Correct Answer

A. The transverse links from the actin filaments
36.

Sliding filament’s theory did not explain the mechanism of contraction in……
- Muscles of small intestine
- Muscles of the heart
- Intercostal muscles
- Gastrocnemius muscle
Correct Answer

A. Muscles of small intestine

Explanation

The sliding filament theory is a widely accepted explanation for muscle contraction, but it does not fully explain the mechanism of contraction in the muscles of the small intestine. The muscles of the small intestine exhibit a unique pattern of contraction known as peristalsis, which involves coordinated waves of contraction and relaxation to propel food through the digestive system. This mechanism is not fully accounted for by the sliding filament theory, which primarily focuses on the interaction between actin and myosin filaments in muscle fibers.

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37.

When the neuro-chemical transmitters reach the muscle fiber through the synaptic cleft, the muscle fiber is ……
- Polarized
- Depolarized
- Repolarized
- Hyperpolarized
Correct Answer

A. Depolarized

Explanation

When the neuro-chemical transmitters reach the muscle fiber through the synaptic cleft, they bind to receptors on the muscle fiber membrane. This binding causes a change in the electrical charge of the membrane, leading to the opening of ion channels. The opening of these ion channels allows the flow of positively charged ions into the muscle fiber, which depolarizes the membrane. Depolarization is a necessary step for the muscle fiber to generate an action potential and ultimately contract. Therefore, the correct answer is depolarized.

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38.

The increase in permeability of the sarcolemma to …….… ions lead to the depolarization of the sarcolemma.
- Potassium
- Magnesium
- Sodium
- Calcium
Correct Answer

A. Sodium

Explanation

The increase in permeability of the sarcolemma to sodium ions leads to the depolarization of the sarcolemma. When the sarcolemma becomes more permeable to sodium ions, they are able to enter the muscle cell more easily. This influx of sodium ions causes a change in the electrical charge of the sarcolemma, leading to depolarization. This depolarization is an important step in the generation of an action potential, which ultimately leads to muscle contraction.

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39.

The ions that are responsible for the transmission of the impulse across synapse to the muscle fiber are ….... ions
- Potassium
- Sodium
- Chlorine
- Calcium
Correct Answer

A. Calcium

Explanation

Calcium ions are responsible for the transmission of the impulse across synapse to the muscle fiber. When an action potential arrives at the presynaptic terminal, it triggers the release of calcium ions into the synaptic cleft. These calcium ions then bind to proteins on the presynaptic membrane, causing the synaptic vesicles to fuse with the membrane and release neurotransmitters into the synaptic cleft. The neurotransmitters then bind to receptors on the postsynaptic membrane, initiating a new action potential in the muscle fiber.

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40.

The muscle fiber responds to the stimulus (becomes depolarized) in the presence of ..……. ions
- Sodium
- Potassium
- Calcium
- Chlorine
Correct Answer

A. Sodium

Explanation

Muscle fibers respond to stimuli by becoming depolarized, which means that the electrical charge inside the cell becomes more positive. This depolarization is caused by the movement of ions across the cell membrane. In this case, the correct answer is sodium because the movement of sodium ions into the cell is responsible for the initial depolarization of the muscle fiber. Sodium ions rush into the cell through channels in the cell membrane, causing an influx of positive charge and triggering a muscle contraction.

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41.

In the sliding filament theory of muscle contraction, what is the primary role of calcium ions?
- To provide the energy required to return the myosin heads back to their normal position
- To initiate the release of a molecule of ADP as the myosin heads pull the actin filament along
- To stimulate the detachment of the myosin heads from the actin binding sites
- To bind to tropomyosin, changing its shape and moving it away from myosin binding sites
Correct Answer

A. To bind to tropomyosin, changing its shape and moving it away from myosin binding sites

Explanation

Calcium ions play a crucial role in muscle contraction by binding to tropomyosin, a protein that covers the myosin binding sites on the actin filament. When calcium ions bind to tropomyosin, it changes its shape and allows the myosin heads to attach to the actin filament, initiating muscle contraction. Therefore, the primary role of calcium ions in the sliding filament theory of muscle contraction is to bind to tropomyosin, changing its shape and moving it away from the myosin binding sites.

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42.

Red muscles are rich in …..
- Hemoglobin and glucose
- Actin only
- Hemoglobin and lactic acid
- Myoglobin and cytochromes
Correct Answer

A. Myoglobin and cytochromes

Explanation

Red muscles are rich in myoglobin and cytochromes. Myoglobin is a protein that stores oxygen in muscle cells, allowing for sustained aerobic respiration. Cytochromes are proteins involved in the electron transport chain, which is essential for generating ATP, the energy currency of cells. These two substances are responsible for the red color of these muscles and their ability to sustain prolonged activity.

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43.

What does the area (R) represent in the following figure?
- Neuro-muscular junction
- Motor end plate
- Motor unit
- Myofibrils
Correct Answer

A. Motor end plate

Explanation

The area (R) in the figure represents the motor end plate. The motor end plate is a specialized region of the muscle fiber membrane that forms the synapse with the motor neuron. It is where the neurotransmitter acetylcholine is released from the motor neuron and binds to receptors on the motor end plate, initiating muscle contraction.

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44.

What is the importance of calcium ions in muscular contraction?
- Causes ATP binding to actin.
- Increases the action potential along the sarcolemma.
- Binds to protein receptors on the sarcolemma.
- Activates the binding of myosin to actin.
Correct Answer

A. Activates the binding of myosin to actin.

Explanation

Calcium ions play a crucial role in muscular contraction by activating the binding of myosin to actin. Myosin is a protein that interacts with actin to generate the force required for muscle contraction. When calcium ions are released into the muscle cell, they bind to a protein called troponin, causing a conformational change that exposes the binding sites on actin. This allows myosin to bind to actin, forming cross-bridges and initiating the sliding of actin filaments over myosin filaments, leading to muscle contraction. Therefore, the activation of myosin binding to actin is an important step in the process of muscular contraction.

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45.

A muscle consists of 1000 muscle fiber, what is the least and the greatest numbers of motor neurons that can supply this muscle respectively?
- 10 – 100
- 5 – 100
- 10 - 200
- 5 - 500
Correct Answer

A. 10 - 200

Explanation

A muscle consists of many muscle fibers, and each muscle fiber is innervated by a motor neuron. The least number of motor neurons that can supply the muscle would be equal to the number of muscle fibers, which is 1000. However, a single motor neuron can innervate multiple muscle fibers, so the greatest number of motor neurons that can supply the muscle would be less than or equal to the number of muscle fibers. Therefore, the range of possible numbers of motor neurons is 10 to 200.

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46.

Sarcolemma is the membrane which covers …..
- Muscle bundle
- Nerve fiber
- Muscle fiber
- Muscle fibril
Correct Answer

A. Muscle fiber

Explanation

The sarcolemma is the membrane that covers the muscle fiber. It is a specialized plasma membrane that surrounds each individual muscle cell, allowing for the exchange of nutrients and waste products. The sarcolemma is essential for the proper functioning of the muscle fiber and plays a crucial role in muscle contraction and relaxation.

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47.

Concerning Cardiac and Skeletal muscle, which statement is accurate?
- Cardiac muscle fibers are not striated whereas skeletal muscle fibers are striated.
- Cardiac myofibril nuclei are placed away from the center, whereas skeletal myofibril nuclei are centrally placed.
- Skeletal muscle fibers exhibit more branching than cardiac muscle fibers
- Cardiac muscle contains structures known as intercalated discs
Correct Answer

A. Cardiac muscle contains structures known as intercalated discs

Explanation

Cardiac muscle contains structures known as intercalated discs, which are specialized junctions between cardiac muscle cells. These discs play a crucial role in allowing the cells to communicate and contract together as a coordinated unit. Intercalated discs contain gap junctions, which allow for the rapid spread of electrical impulses between cells, and desmosomes, which provide structural support and prevent the cells from separating during contraction. This unique feature of intercalated discs is not present in skeletal muscle, making the statement accurate.

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48.

Which of the following statements is correct for different degrees of muscle tension shown in the figure below?
- At (A) maximum binding of myosin and actin can take place, and so contraction is possible.
- At (B) binding between myosin and actin is blocked, and so no contraction is possible.
- At (C) the actin filaments do not overlap the myosin ones, no cross bridges can form and so contraction is not possible.
- All are correct.
Correct Answer

A. All are correct.

Explanation

The given question asks which statement is correct for different degrees of muscle tension shown in the figure. The correct answer states that all of the given statements are correct. This means that at maximum muscle tension (A), there is maximum binding of myosin and actin, allowing for contraction. At minimum muscle tension (B), the binding between myosin and actin is blocked, preventing contraction. And at an intermediate level of muscle tension (C), the actin filaments do not overlap the myosin ones, preventing the formation of cross bridges and therefore contraction.

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49.

In the following graph, the curve (A) represents a nerve impulse in an axon. While curve (B) represents a muscular contraction, from the graph we can conclude that …….
- The nerve impulse takes longer time than muscle contraction
- The muscle contraction does not occur unless, the nerve impulse is generated
- The nerve impulse and muscle contraction are not related to each other
- The muscle remains contracted while there is no nerve impulse generated
Correct Answer

A. The muscle contraction does not occur unless, the nerve impulse is generated

Explanation

From the graph, we can see that the muscle contraction (curve B) only occurs when there is a nerve impulse (curve A) present. This indicates that the nerve impulse is necessary for the muscle contraction to happen. Therefore, the correct answer is that the muscle contraction does not occur unless the nerve impulse is generated.

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Mar 21, 2023

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May 25, 2021

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Muscle Fatigue sets in due to non-availability of……...

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The energy needed to perform a muscle contraction comes directly from .....

Transverse links of the muscle are formed by the help of …… ions

The disappearance of potential difference on the muscle fiber membrane is due to -------

If a muscle fiber contains six Z-lines and five H-zones, then how many sarcomeres are there in that fiber?

A muscle consists of 300 muscle fibers. What is the least number of motor neurons that can supply it?

When a muscle gets shorter and thicker It Is a(an) _______ muscle.

Which of the following does NOT occur during skeletal muscle contraction?

Shortage of oxygen in the muscle stimulates the muscle to convert glycogen to glucose for the production of energy leading to the accumulation of ……., which causes muscle fatigue.

Muscle contraction occurs when …..

Which of the following is controlled by skeletal muscles?

The region which its length does not change when the muscle fiber contracts is …….

For the contraction of skeletal muscles, the presence of ------ is necessary

When a contracted skeletal muscle is relaxed, the two regions …….. and …….. increase in length.

What is the number of neuromuscular junctions that can be found in a muscle consisting of 5 muscle bundles where each bundle contains 40 muscle fibers?

A muscle consists of 300 muscle fibers. What is the greatest number of motor neurons that can supply it?

If a human skeletal muscle consists of 10 muscle bundles, and each bundle consists of 50 muscle fibers. If each muscle fiber consists of 1000 – 2000 myofibrils, what is the least number of myofibrils that the muscle contains?

What happens during movement of limbs in Man?

The organelle that contains actin and myosin is .........

An entire skeletal muscle is surrounded by ______.

The functional unit of contractile system in a striated muscle is …..

Which statement is correct for muscle contraction?

Intercostal muscles are found in ….

What are dark bands that define the two ends of each sacromere called?

The Functional Unit of the contractile system in Striated Muscles is ……

Smooth Muscle is not cross striated because ……

Intercaled discs are most likely to be observed in.........

When skeletal muscle contracts an arrangement of the alternating light and dark bands traversing each skeletal muscle cell changes. Which of the following statements is not correct?

The direct energy store for the muscle is ……

Each skeletal muscle fiber is controlled by a neuron at a single _______.

Which of the following statements is INCORRECT?

Which of the following is NOT a characteristic of skeletal muscle contraction?

Which of the following is not correct regarding the structure of the motor unit?

During muscle contraction, the transverse links pull the ……….

The shortage of ATP in the muscle prevents the separation of …….

Sliding filament’s theory did not explain the mechanism of contraction in……

When the neuro-chemical transmitters reach the muscle fiber through the synaptic cleft, the muscle fiber is ……

The increase in permeability of the sarcolemma to …….… ions lead to the depolarization of the sarcolemma.

The ions that are responsible for the transmission of the impulse across synapse to the muscle fiber are ….... ions

The muscle fiber responds to the stimulus (becomes depolarized) in the presence of ..……. ions

In the sliding filament theory of muscle contraction, what is the primary role of calcium ions?

Red muscles are rich in …..

What does the area (R) represent in the following figure?

What is the importance of calcium ions in muscular contraction?

A muscle consists of 1000 muscle fiber, what is the least and the greatest numbers of motor neurons that can supply this muscle respectively?

Sarcolemma is the membrane which covers …..

Concerning Cardiac and Skeletal muscle, which statement is accurate?

Which of the following statements is correct for different degrees of muscle tension shown in the figure below?

In the following graph, the curve (A) represents a nerve impulse in an axon. While curve (B) represents a muscular contraction, from the graph we can conclude that …….