Careful! Only The Best Of Biology Students Can Pass This Test!
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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!
Choose your answers wisely and you will get your final score at the end on the quiz!
ALL THE BEST
- 1.
The functional unit of contractile system in a striated muscle is …..
- A.
Sarcomere
- B.
A-band
- C.
Myofibril
- D.
I-band
Correct Answer
A. SarcomereExplanation
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.Rate this question:
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- 2.
Which of the following is the contractile protein of a muscle?
- A.
Myosin
- B.
Actin
- C.
Intercalated disc
- D.
All of the above
Correct Answer
A. MyosinExplanation
Myosin is the contractile protein of a muscle. It is responsible for the movement and contraction of muscles. Actin is also a protein involved in muscle contraction, but the question specifically asks for the contractile protein, which is myosin. Intercalated discs are not contractile proteins, but rather structures found in cardiac muscle cells that help with coordination of muscle contractions. Therefore, the correct answer is myosin.Rate this question:
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- 3.
Which statement is correct for muscle contraction?
- A.
Length of I-band remains constant
- B.
Length of A-band remains constant
- C.
Length of sarcomere remains constant
- D.
Size of H- zone remains constant
Correct Answer
B. Length of A-band remains constantExplanation
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.Rate this question:
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- 4.
Red muscles are rich in …..
- A.
Hemoglobin and glucose
- B.
Actin only
- C.
Hemoglobin and lactic acid
- D.
Myoglobin and cytochromes
Correct Answer
D. Myoglobin and cytochromesExplanation
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.Rate this question:
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- 5.
Sarcolemma is the membrane which covers …..
- A.
Muscle bundle
- B.
Nerve fiber
- C.
Muscle fiber
- D.
Muscle fibril
Correct Answer
C. Muscle fiberExplanation
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.Rate this question:
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- 6.
Intercostal muscles are found in ….
- A.
Thigh
- B.
Diaphragm
- C.
Ribs
- D.
Abdomen
Correct Answer
C. RibsExplanation
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.Rate this question:
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- 7.
When a muscle fiber shortens, the following also shortens.........
- A.
Sarcomere
- B.
Actin filament
- C.
Myosin filament
- D.
Z-line
Correct Answer
A. SarcomereExplanation
When a muscle fiber shortens, the sarcomere, which is the basic unit of muscle contraction, also shortens. The sarcomere is made up of actin and myosin filaments, which slide past each other during muscle contraction. The Z-line, which marks the boundary of each sarcomere, also moves closer together as the sarcomere shortens. Therefore, the correct answer is sarcomere.Rate this question:
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- 8.
What are dark bands that define the two ends of each sacromere called?
- A.
Z-Lines
- B.
Myosin
- C.
Sarcomeres
- D.
Actin
Correct Answer
A. Z-LinesExplanation
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.Rate this question:
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- 9.
The Functional Unit of the contractile system in Striated Muscles is ……
- A.
Z-Band
- B.
Sarcomere
- C.
Myofibril
- D.
Cross bridges
Correct Answer
B. SarcomereExplanation
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.Rate this question:
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- 10.
When a muscle gets shorter and thicker It Is a(an) _______ muscle.
- A.
Involuntary
- B.
Relaxing
- C.
Skeletal
- D.
Contracting
Correct Answer
D. ContractingExplanation
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.Rate this question:
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- 11.
Muscle Fatigue sets in due to non-availability of……...
- A.
Actin-binding Site
- B.
Calcium
- C.
ATP
- D.
Mg cofactor
Correct Answer
C. ATPExplanation
Muscle fatigue sets in due to the non-availability of ATP. ATP, or adenosine triphosphate, is the main source of energy for muscle contractions. During exercise or any physical activity, ATP is broken down into ADP (adenosine diphosphate) and inorganic phosphate, releasing energy that is used for muscle contraction. However, ATP stores in the muscles are limited and can be quickly depleted. When ATP levels decrease, muscle contractions become weaker and less efficient, leading to muscle fatigue.Rate this question:
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- 12.
Light band has which of the following filament proteins?
- A.
Myosin and actin
- B.
Actin
- C.
Myosin
- D.
None of these
Correct Answer
B. ActinExplanation
Actin is the filament protein found in the light band. Myosin is another filament protein found in the dark band. Therefore, the correct answer is Actin.Rate this question:
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- 13.
Smooth Muscle is not cross striated because ……
- A.
Of the regular arrangement of actin and myosin filaments
- B.
Myosin and actin filaments are organized into well-ordered sarcomeres and myofibrils.
- C.
Myosin and actin fibers are arranged an angles to each other as they run through the cell.
- D.
Globular heads protruding from myosin filaments do not attach with actin filaments to form cross bridges
Correct Answer
C. 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.Rate this question:
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- 14.
Intercaled discs are most likely to be observed in.........
- A.
Longitudinal section of skeletal muscle
- B.
Transverse section of skeletal muscle
- C.
Transverse section of cardiac muscle
- D.
Longitudinal section of cardiac muscle
Correct Answer
D. Longitudinal section of cardiac muscleExplanation
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.Rate this question:
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- 15.
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?
- A.
The dark A-bands will remain a constant length
- B.
The space occupied by the H-zone will not change
- C.
The light I-bands will shorten
- D.
The z-lines come closer together
Correct Answer
B. The space occupied by the H-zone will not changeExplanation
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.Rate this question:
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- 16.
Concerning Cardiac and Skeletal muscle, which statement is accurate?
- A.
Cardiac muscle fibers are not striated whereas skeletal muscle fibers are striated.
- B.
Cardiac myofibril nuclei are placed away from the center, whereas skeletal myofibril nuclei are centrally placed.
- C.
Skeletal muscle fibers exhibit more branching than cardiac muscle fibers
- D.
Cardiac muscle contains structures known as intercalated discs
Correct Answer
D. Cardiac muscle contains structures known as intercalated discsExplanation
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.Rate this question:
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- 17.
Which of the following statements is correct?
- A.
A Skeletal muscle fiber consists of numerous skeletal muscle cells joined together by intercalated discs
- B.
Skeletal muscle cells have a fusiform appearance with multinuclei centrally placed
- C.
Smooth muscle has single nuclei that are peripherally placed
- D.
None of the above
Correct Answer
D. None of the aboveExplanation
The given correct answer is "None of the above." The explanation for this is that the statements provided in the options are incorrect. A skeletal muscle fiber is not made up of skeletal muscle cells joined together by intercalated discs; instead, it is made up of individual muscle cells called muscle fibers. Skeletal muscle cells do not have a fusiform appearance with multinuclei centrally placed; instead, they have a cylindrical shape with multiple nuclei located at the periphery. Smooth muscle does not have single nuclei that are peripherally placed; instead, it has a single centrally located nucleus. Therefore, none of the statements provided in the options are correct.Rate this question:
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- 18.
The direct energy store for the muscle is ……
- A.
ATP
- B.
Glycogen
- C.
Glucose
- D.
Lactic acid
Correct Answer
A. ATPExplanation
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.Rate this question:
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- 19.
What happens during movement of limbs in Man?
- A.
Limbs are supported by the skeletal system during movement
- B.
Muscles of limbs contract and relax by taking an order from the nervous system
- C.
Movement of limbs is done by the contraction and relaxation of the muscles
- D.
All of the above
Correct Answer
D. All of the aboveExplanation
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.Rate this question:
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- 20.
What does the area (R) represent in the following figure?
- A.
Neuro-muscular junction
- B.
Motor end plate
- C.
Motor unit
- D.
Myofibrils
Correct Answer
B. Motor end plateExplanation
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.Rate this question:
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- 21.
The specialized part of the cell membrane of the muscle fiber identified as .....
- A.
Motor unit
- B.
Axon Terminal of Motor Neuron
- C.
Motor end plate
- D.
Vesicle
Correct Answer
C. Motor end plateExplanation
The motor end plate is the specialized part of the cell membrane of the muscle fiber that is responsible for transmitting the nerve impulse from the motor neuron to the muscle fiber. It is located at the neuromuscular junction, where the axon terminal of the motor neuron meets the muscle fiber. The motor end plate contains a high concentration of acetylcholine receptors, which allow for the binding of acetylcholine released by the motor neuron, leading to muscle contraction.Rate this question:
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- 22.
The organelle that contains actin and myosin is .........
- A.
Tendon
- B.
Sarcolemma
- C.
Myofibril
- D.
Fiber
Correct Answer
C. MyofibrilExplanation
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.Rate this question:
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- 23.
A bundle of muscle cells is called ……
- A.
Sarcomere
- B.
Fiber
- C.
Fascicle
- D.
Tendon
Correct Answer
C. FascicleExplanation
A bundle of muscle cells is called a fascicle. A fascicle is a small bundle of muscle fibers that are grouped together and surrounded by connective tissue. These fascicles are then further grouped together to form a muscle.Rate this question:
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- 24.
What is the importance of calcium ions in muscular contraction?
- A.
Causes ATP binding to actin.
- B.
Increases the action potential along the sarcolemma.
- C.
Binds to protein receptors on the sarcolemma.
- D.
Activates the binding of myosin to actin.
Correct Answer
D. 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.Rate this question:
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- 25.
The energy needed to perform a muscle contraction comes directly from .....
- A.
ATP
- B.
Oxygen
- C.
Glucose
- D.
Calcium
Correct Answer
A. ATPExplanation
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.Rate this question:
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- 26.
An entire skeletal muscle is surrounded by ______.
- A.
Endomysium.
- B.
Sarcolemma
- C.
Epimysium
- D.
Perimysium
Correct Answer
C. EpimysiumExplanation
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.Rate this question:
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- 27.
Motor neuron and all the muscle fibers it supplies is called a _____.
- A.
Motor end plate
- B.
Synapse
- C.
Motor unit
- D.
Neuro-muscular junction
Correct Answer
C. Motor unitExplanation
A motor unit consists of a motor neuron and all the muscle fibers it innervates. When the motor neuron sends a signal, all the muscle fibers in the motor unit contract simultaneously. Therefore, the correct answer is motor unit.Rate this question:
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- 28.
Which of the following does NOT occur during skeletal muscle contraction?
- A.
Calcium binds to myosin heads.
- B.
ATP is hydrolyzed.
- C.
Myosin heads bind to actin.
- D.
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.Rate this question:
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- 29.
Each skeletal muscle fiber is controlled by a neuron at a single _______.
- A.
Synaptic cleft
- B.
Neuromuscular junction
- C.
Synaptic knob
- D.
Sarcomere
Correct Answer
B. Neuromuscular junctionExplanation
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.Rate this question:
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- 30.
Which of the following statements is INCORRECT?
- A.
Skeletal muscles are responsible for the pumping action of the heart.
- B.
Skeletal muscles support the weight of some internal organs.
- C.
Skeletal muscles form valves regulating the passage of substances through internal openings of the digestive tract.
- D.
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.Rate this question:
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- 31.
Which of the following is NOT a characteristic of skeletal muscle contraction?
- A.
It contracts rapidly.
- B.
It is voluntary.
- C.
It can contract for long periods of time without tiring.
- D.
It can exert tremendous power.
Correct Answer
C. 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.Rate this question:
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- 32.
The ends of the actin filaments are anchored (attached) to the.......
- A.
M-line
- B.
Z-line
- C.
Perimysium
- D.
Sarcoplasm
Correct Answer
B. Z-lineExplanation
The correct answer is Z-line. The Z-line is a protein structure that anchors the actin filaments in a sarcomere, which is the basic unit of a muscle fiber. The actin filaments extend from the Z-line towards the center of the sarcomere, where they overlap with myosin filaments to generate muscle contraction. Therefore, the Z-line serves as an attachment point for the actin filaments and helps maintain the structural integrity of the sarcomere.Rate this question:
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- 33.
The semi-light area in the sarcomere is represented by the letter ….
- A.
A
- B.
H
- C.
I
- D.
Z
Correct Answer
B. HExplanation
The semi-light area in the sarcomere is represented by the letter H.Rate this question:
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- 34.
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.
- A.
Acetic acid
- B.
Pyruvic acid
- C.
Lactic acid
- D.
Ethanol
Correct Answer
C. Lactic acidExplanation
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.Rate this question:
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- 35.
Which of the following is not correct regarding the structure of the motor unit?
- A.
A motor unit is made up of one neuron that supplies a single muscle fiber
- B.
Each skeletal muscle fiber is controlled by a single motor neuron
- C.
Groups of motor units often work together to coordinate the contractions of a single muscle
- D.
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 fiberExplanation
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.Rate this question:
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- 36.
During muscle contraction, the transverse links pull the ……….
- A.
Acetyl choline
- B.
Actin
- C.
Myosin
- D.
Sarcoplasm
Correct Answer
B. ActinExplanation
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.Rate this question:
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- 37.
In the structure below, if (A) represents motor neurons, (B) represents muscle fibers and (C) represents the muscle itself. Which of the following statement is correct?
- A.
Each single (B) is controlled by only one (A)
- B.
The structure (C) is controlled by only one (A)
- C.
Each (A) controls about 1000 to 2000 (C)
- D.
Single (A) with a single (B) form a motor unit
Correct Answer
A. Each single (B) is controlled by only one (A)Explanation
Each muscle fiber (B) is controlled by only one motor neuron (A). This is known as the "one-to-one" principle of motor control, where each motor neuron innervates a single muscle fiber. This allows for precise control and coordination of muscle movements.Rate this question:
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- 38.
The shortage of ATP in the muscle prevents the separation of …….
- A.
The transverse links from the myosin filaments
- B.
The transverse links from the actin filaments
- C.
The choline group from the acetyl choline
- D.
The linkage between the actin and the z-lines
Correct Answer
B. The transverse links from the actin filaments -
- 39.
Transverse links of the muscle are formed by the help of …… ions
- A.
Sodium
- B.
Potassium
- C.
Chlorine
- D.
Calcium
Correct Answer
D. CalciumExplanation
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.Rate this question:
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- 40.
The H-zone is described as a ………
- A.
Dark area
- B.
Light area
- C.
Semi-light
- D.
Sarcomere
Correct Answer
C. Semi-lightExplanation
The H-zone is described as a "semi-light" area. This term refers to a region within a sarcomere, which is the basic unit of muscle contraction. The H-zone is located in the middle of the sarcomere and is characterized by its lighter appearance compared to the surrounding dark areas. It represents the region where only thick filaments are present, with no overlapping thin filaments. This arrangement allows for the sliding of filaments during muscle contraction. Therefore, the correct answer is "Semi-light."Rate this question:
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- 41.
Sliding filament’s theory did not explain the mechanism of contraction in……
- A.
Muscles of small intestine
- B.
Muscles of the heart
- C.
Intercostal muscles
- D.
Gastrocnemius muscle
Correct Answer
A. Muscles of small intestineExplanation
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.Rate this question:
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- 42.
When the neuro-chemical transmitters reach the muscle fiber through the synaptic cleft, the muscle fiber is ……
- A.
Polarized
- B.
Depolarized
- C.
Repolarized
- D.
Hyperpolarized
Correct Answer
B. DepolarizedExplanation
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.Rate this question:
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- 43.
Muscle contraction occurs when …..
- A.
Depolarization changes to polarization
- B.
The fiber membrane becomes permeable to Na + ions
- C.
Potassium ions enter inside the sarcoplasm with great quantities
- D.
No chemical transmitters reach the fiber membrane
Correct Answer
B. The fiber membrane becomes permeable to Na + ionsExplanation
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.Rate this question:
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- 44.
The skeletal muscle contracts when ….
- A.
The two z-lines move away from each other
- B.
The transverse links separate from the actin filaments
- C.
The outer surface of the fiber becomes –ve and the inner +ve
- D.
All of the above.
Correct Answer
C. The outer surface of the fiber becomes –ve and the inner +veExplanation
When a skeletal muscle contracts, the outer surface of the muscle fiber becomes negatively charged (-ve) and the inner surface becomes positively charged (+ve). This change in charge is due to the movement of ions across the muscle cell membrane. The movement of ions creates an electrical potential difference that triggers the contraction of the muscle. The other options mentioned in the question, such as the movement of z-lines and separation of transverse links, are not directly related to the contraction of the muscle.Rate this question:
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- 45.
The increase in permeability of the sarcolemma to …….… ions lead to the depolarization of the sarcolemma.
- A.
Potassium
- B.
Magnesium
- C.
Sodium
- D.
Calcium
Correct Answer
C. SodiumExplanation
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.Rate this question:
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- 46.
According to Huxley theory of muscle contraction in skeletal muscles…… are pulled from both sides towards each other.
- A.
Transverse links
- B.
Actin and myosin
- C.
Myosin filaments
- D.
Actin filaments
Correct Answer
D. Actin filamentsExplanation
According to Huxley's theory of muscle contraction in skeletal muscles, actin filaments are pulled from both sides towards each other. Actin and myosin are the two main proteins involved in muscle contraction, but it is specifically the actin filaments that are pulled towards each other. Myosin filaments, on the other hand, slide along the actin filaments to generate the force that causes muscle contraction. Therefore, the correct answer is actin filaments.Rate this question:
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- 47.
Which of the following is controlled by skeletal muscles?
- A.
Eye movement
- B.
Heart beats
- C.
Dilatation of the eye pupil
- D.
Dilatation of blood vessels
Correct Answer
A. Eye movementExplanation
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.Rate this question:
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- 48.
The number of myofibrils that are present in five muscle fibers ranges between …..
- A.
1000 – 2000
- B.
2000 – 4000
- C.
3000 – 6000
- D.
5000 – 10000
Correct Answer
D. 5000 – 10000Explanation
The number of myofibrils that are present in five muscle fibers can range from 5000 to 10000.Rate this question:
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- 49.
The number of neuro-muscular junctions in a muscle that consists of 50 muscle fibers is about …..
- A.
50
- B.
250
- C.
2500
- D.
25000
Correct Answer
A. 50Explanation
A muscle consists of many muscle fibers, and each muscle fiber has one neuro-muscular junction. Therefore, the number of neuro-muscular junctions in a muscle with 50 muscle fibers would be 50.Rate this question:
-
- 50.
Each motor nerve fiber supplies a group of about ……….. muscle fibers.
- A.
5 – 10
- B.
5 – 20
- C.
5 – 50
- D.
5 – 100
Correct Answer
D. 5 – 100Explanation
Motor nerve fibers are responsible for transmitting signals from the brain or spinal cord to the muscles, allowing them to contract and move. Each motor nerve fiber can innervate a varying number of muscle fibers, depending on the muscle and its function. The range of 5-100 muscle fibers per motor nerve fiber suggests that there is a wide variation in the number of muscle fibers that can be controlled by a single motor nerve fiber. This allows for fine motor control in some muscles (with fewer muscle fibers per nerve fiber) and more gross motor control in others (with more muscle fibers per nerve fiber).Rate this question:
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Mar 21, 2023Quiz Edited by
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May 25, 2021Quiz Created by
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