Anatomy And Physiology Questions - Muscle Tissue

Tropomyosin and troponin are regulatory proteins that can be found on an actin molecule. Tropomyosin is a long, filamentous protein that wraps around the actin filament and helps regulate muscle contraction by blocking the myosin-binding sites on actin in the absence of calcium ions. Troponin is a complex of three subunits that is bound to tropomyosin. It helps regulate muscle contraction by binding to calcium ions and causing a conformational change in tropomyosin, which allows myosin to bind to actin and initiate muscle contraction.

The mitochondrion is located at position B in the diagram.

In the given diagram, the thick filament is located at position H.

The M line is located at point D in the diagram.

The three different types of muscle tissue (skeletal, cardiac, and smooth) differ from each other in terms of microscopic anatomy, location, and type of control. Skeletal muscle tissue is striated and multinucleated, located attached to bones, and is under voluntary control. Cardiac muscle tissue is striated and uninucleated, found in the walls of the heart, and is under involuntary control. Smooth muscle tissue is non-striated and uninucleated, located in the walls of hollow organs, blood vessels, and the respiratory system, and is under involuntary control. Therefore, the correct answer is A, B, and C.

The sarcoplasmic reticulum is a specialized organelle found in muscle cells that is responsible for storing and releasing calcium ions. Calcium ions are crucial for muscle contraction as they bind to proteins in the muscle fibers, allowing the sliding of actin and myosin filaments and generating muscle force. When a muscle is stimulated, the sarcoplasmic reticulum releases calcium ions into the cytoplasm, triggering muscle contraction. Therefore, the sarcoplasmic reticulum plays a vital role in regulating muscle contraction by storing and releasing calcium ions.

Muscles produce ATP through multiple processes. Creatine phosphate is a quick source of ATP during short bursts of intense activity. Anaerobic cellular respiration occurs when there is not enough oxygen available, and it produces ATP through the breakdown of glucose. Aerobic cellular respiration is the most efficient process and occurs when there is sufficient oxygen, producing ATP through the breakdown of glucose or fatty acids. Therefore, all of the mentioned processes contribute to ATP production in muscles.

Intercalated discs are found in cardiac muscle tissue but not in skeletal muscle tissue. These specialized structures are unique to cardiac muscle and help in coordinating the contraction of cardiac muscle cells. Intercalated discs contain gap junctions, which allow for the rapid transmission of electrical impulses between cells, ensuring synchronized contractions of the heart. This allows the heart to function as a single unit, pumping blood efficiently. In contrast, skeletal muscle tissue does not have intercalated discs and relies on a different mechanism for muscle contraction.

Myofibrils are the contractile organelles of the muscle fiber. They are responsible for the contraction and relaxation of muscles. Made up of thick and thin filaments, myofibrils play a crucial role in muscle movement by sliding past each other during contraction. They are composed of repeating units called sarcomeres, which contain the proteins actin and myosin. The interaction between these proteins allows myofibrils to generate force and produce muscle contractions. Therefore, myofibrils are the correct answer as they are directly involved in muscle contraction.

The correct answer is "All of the above". Myofibrils are the contractile units of muscle cells and they contain various types of proteins. Contractile proteins, such as actin and myosin, are responsible for muscle contraction. Regulatory proteins, such as troponin and tropomyosin, regulate the interaction between actin and myosin. Structural proteins, such as titin and dystrophin, provide support and stability to the myofibrils. Therefore, all three types of proteins - contractile, regulatory, and structural - are present in myofibrils.

Axon terminal clusters at the ends of neuromuscular junctions are referred to as synaptic end bulbs. These bulbs contain synaptic vesicles that store neurotransmitters, which are released into the synaptic cleft to transmit signals to the target muscle cell. The term "synaptic" refers to the connection between neurons, while "end bulbs" describe the bulb-like structures at the end of the axon terminals. Therefore, synaptic end bulbs accurately describe the anatomical features of these structures.

Motor unit recruitment refers to the process of activating additional motor units in a muscle to generate more force. When a muscle needs to exert more force, the nervous system recruits more motor units to contract. This recruitment occurs in a sequential manner, starting with the smallest motor units and progressing to larger ones. By increasing the number of active motor units, the muscle can generate more force and perform stronger contractions.

In the sliding filament mechanism, the thin filament is being pulled towards the M line. The M line is located in the center of the sarcomere and serves as the attachment point for the thick filaments. As the thin filaments slide past the thick filaments during muscle contraction, they are pulled towards the M line, causing the sarcomere to shorten. This movement is essential for muscle contraction and allows for the generation of force.

For the contraction cycle to continue, several factors are required. Calcium ions play a crucial role in muscle contraction as they bind to the troponin protein, which triggers the movement of tropomyosin and allows the myosin heads to bind to actin. ATP (adenosine triphosphate) is needed as an energy source for the contraction process. It provides the energy required for the myosin heads to detach from actin and reset for another contraction. ACh (acetylcholine) is a neurotransmitter that is released at the neuromuscular junction, allowing the muscle fibers to receive the signal to contract. Therefore, all of the above factors are necessary for the contraction cycle to continue.

The signal to excite a muscle cell must cross the synaptic cleft. The synaptic cleft is the small gap between the motor neuron axon and the muscle cell's sarcolemma. When an action potential reaches the end of the motor neuron axon, it triggers the release of acetylcholine from synaptic vesicles into the synaptic cleft. Acetylcholine then diffuses across the synaptic cleft and binds to receptors on the sarcolemma, initiating a series of events that lead to muscle contraction. Therefore, the diffusion of acetylcholine across the synaptic cleft is necessary for the signal to reach the muscle cell.

Inadequate levels of vitamin B is not a factor that can lead to muscle fatigue. Vitamin B is not directly involved in muscle function or energy production. Muscle fatigue is commonly caused by factors such as lactic acid build-up, inadequate levels of creatine phosphate, inadequate levels of oxygen, and inadequate levels of calcium. However, vitamin B deficiency can cause other health issues, but it is not directly related to muscle fatigue.

The correct answer is E because in the diagram, the thick filament is found in all of the mentioned locations: C, E, A, and B.

Cardiac muscle fibers exhibit autorhythmicity, meaning they can generate their own electrical impulses without external stimulation. This allows the heart to beat in a coordinated and rhythmic manner. Unlike other types of muscle fibers, such as actin fibers, multi-unit smooth muscle fibers, and intermediate fibers, cardiac muscle fibers have specialized cells called pacemaker cells that initiate and regulate the electrical signals responsible for heart contractions. Therefore, the correct answer is cardiac muscle fibers.

The terminal cisterns of the sarcoplasmic reticulum are responsible for releasing calcium when stimulated by the T tubules. Calcium release is a crucial step in muscle contraction, as it allows the interaction between actin and myosin filaments, leading to muscle fiber contraction. The terminal cisterns are specialized regions of the sarcoplasmic reticulum that are located adjacent to the T tubules, allowing for efficient communication between these structures. Therefore, the correct answer is the terminal cisterns of the sarcoplasmic reticulum.

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During muscle contraction, the sarcoplasmic reticulum (SR) releases calcium ions into the cytosol. This is necessary for the contraction process to occur. Calcium ions bind to the protein troponin, which causes a conformational change in the tropomyosin-troponin complex. This change exposes the myosin-binding sites on the actin filaments, allowing the myosin heads to attach and initiate the sliding of actin and myosin filaments, resulting in muscle contraction. Therefore, the release of calcium ions from the SR at the beginning of a contraction is crucial for the initiation of muscle contraction.

For every nerve that penetrates a skeletal muscle, there is generally one artery and one or two veins. This means that there is usually one main artery that supplies blood to the muscle, and one or two veins that carry blood away from the muscle. The presence of both arteries and veins is important for the proper functioning of the muscle, as the arteries provide oxygen and nutrients, while the veins remove waste products and deoxygenated blood.

The refractory period is the time during which a neuron or muscle cell is unable to respond to a stimulus, as it is recovering from a previous action potential or contraction. This period is often referred to as the period of lost excitability because the cell is temporarily unable to generate another action potential or contraction. During this time, the cell's ion channels are inactivated and need time to reset before they can be activated again. This ensures that the cell has enough time to recover and prevents excessive stimulation or contraction.

A twitch contraction refers to the brief contraction of all muscle fibers in a motor unit in response to a single action potential. This contraction is a result of the release of calcium ions from the sarcoplasmic reticulum, which triggers the sliding of actin and myosin filaments and leads to muscle contraction. The twitch contraction is a quick and transient response and is often used to study muscle physiology.

The myosin head is energized by the ATP hydrolysis reaction. ATP (adenosine triphosphate) is a molecule that stores and releases energy for cellular processes. During muscle contraction, ATP is hydrolyzed into ADP (adenosine diphosphate) and inorganic phosphate. This hydrolysis reaction releases energy, which is used to power the movement of the myosin head along the actin filaments. Therefore, the ATP hydrolysis reaction provides the necessary energy for the myosin head to perform its function in muscle contraction.

Creatine phosphate and ATP are both energy sources used by muscles during contraction. ATP is the immediate source of energy, but it is quickly depleted. Creatine phosphate can regenerate ATP, allowing for a continuous supply of energy. However, the amount of creatine phosphate stored in muscles is limited, and it can only sustain muscle contraction for a short period of time. Therefore, the correct answer is 15 seconds, as this is the approximate duration that the combined energy from creatine phosphate and ATP can support muscle contraction.

The H zone is located at position D in the diagram.

Excitation is the correct answer because when a muscle is stimulated, a muscle action potential is generated. This action potential travels along the sarcolemma (cell membrane of muscle fibers) and into the T tubules (invaginations of the sarcolemma). This excitation triggers the release of calcium ions from the sarcoplasmic reticulum, leading to muscle contraction. Therefore, the statement accurately describes the process of excitation in muscle cells.

Epimysium is the correct answer because it is a band of connective tissue that surrounds muscles. It is the outermost layer of connective tissue that covers the entire muscle, providing support and protection. It helps to maintain the shape of the muscle and allows for efficient transmission of force generated by the muscle fibers.

An aponeurosis is a type of connective tissue that extends as a broad flat layer. It is different from a tendon, which is a dense connective tissue that attaches muscle to bone. While tendons are rope-like structures, aponeuroses are flat and sheet-like. Therefore, the correct answer for this question is aponeurosis.

Myosin is the correct answer because it is a motor protein that is found in all three types of muscle tissue. It plays a crucial role in muscle contraction by interacting with actin filaments and generating the force necessary for muscle movement. Myosin binds to actin and undergoes a conformational change, causing the actin filaments to slide past each other, resulting in muscle contraction. Therefore, myosin is essential for the functioning of muscles in all three types of muscle tissue.

Hyperplasia refers to an increase in the number of muscle fibers. This means that the overall muscle mass increases as new muscle fibers are formed. It is different from hypertrophy, which refers to an increase in the size of existing muscle fibers. Hyperplasia can occur in response to certain stimuli, such as resistance training or hormonal changes. This process allows the muscle to adapt and become stronger over time.

In the given diagram, the I band is located at position G.

In an isometric contraction, the muscle develops tension but does not shorten. This means that the muscle is contracting and generating force, but there is no change in its length. Isometric contractions are commonly seen in activities such as holding a heavy object or maintaining a static posture. During this type of contraction, the muscle fibers are actively generating force, but the overall length of the muscle remains the same.

The correct order of the four steps in the muscle contraction cycle is as follows: ATP hydrolysis, attachment of myosin to actin forming crossbridges, the powerstroke, and detachment of myosin from actin. ATP hydrolysis provides the energy for the contraction process. The attachment of myosin to actin forms crossbridges, allowing the myosin to pull on the actin. This generates the powerstroke, which is the movement of the actin filament. Finally, the myosin detaches from the actin, preparing for the next contraction cycle.

A motor unit consists of a somatic motor neuron and all the skeletal muscle fibers that it stimulates. When the somatic motor neuron is activated, it sends an electrical signal to the muscle fibers, causing them to contract. This coordinated contraction of multiple muscle fibers allows for precise and controlled movement. The motor unit is the functional unit of muscle contraction, and it plays a crucial role in the overall functioning of the muscular system.

Slow oxidative fibers are the least powerful type of muscle fibers. These fibers are characterized by their ability to contract slowly and sustain contractions for long periods of time. They have a high capacity for aerobic metabolism, meaning they rely on oxygen to produce energy. This allows them to generate energy efficiently, but at a slower rate compared to other muscle fiber types. Slow oxidative fibers are commonly found in muscles that require endurance, such as the muscles used in long-distance running or cycling.

Smooth muscle tone is maintained by the prolonged presence of calcium ions in the cytosol. Calcium ions play a crucial role in smooth muscle contraction by binding to the regulatory protein calmodulin, which then activates the enzyme myosin light chain kinase. This enzyme phosphorylates the myosin light chain, leading to the interaction between actin and myosin and subsequent muscle contraction. Therefore, the presence of calcium ions is essential for maintaining smooth muscle tone.

The zone of overlap in the diagram is at point H.

Extensibility is the property of muscle that allows it to stretch without damage. This means that muscles can be elongated or stretched to their full length without tearing or breaking. This is essential for muscle function, as it allows for movements such as stretching, reaching, and flexing. Without extensibility, muscles would be limited in their range of motion and flexibility.

The basic functional unit of a myofibril is called a sarcomere. It is the structural and functional unit of skeletal muscle and is responsible for muscle contraction. Sarcomeres are made up of actin and myosin filaments, which slide past each other during muscle contraction. Therefore, option F, which represents sarcomere, is the correct answer.

The axon collateral is located at point C in the diagram.

Tetanus refers to a sustained contraction of a muscle caused by rapid and repetitive stimulation of its motor neurons. This results in a continuous and prolonged contraction without any relaxation phase. It is different from a twitch, which is a brief and involuntary contraction of a muscle fiber. Muscle tone refers to the slight tension or firmness present in a muscle at rest, while flaccid describes a muscle that is limp and lacking tone. A myogram is a graphical representation of muscle activity.

Dystrophin is used to reinforce the sarcolemma. The sarcolemma is the cell membrane of a muscle fiber, and it needs to be strong and stable to withstand the force generated during muscle contractions. Dystrophin is a protein that helps anchor the structural components of the muscle fiber to the sarcolemma, providing stability and preventing damage. Mutations in the dystrophin gene can lead to muscular dystrophy, a group of genetic disorders characterized by muscle weakness and degeneration.

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Muscle tissue is responsible for various functions in the body, including generating heat through contractions, promoting movement of body structures, and moving blood throughout the body. However, storing energy is not a major function of muscle tissue. The primary role of muscle tissue is to contract and produce force, allowing for movement and maintaining posture. Energy storage is primarily carried out by adipose tissue in the form of fat cells. Therefore, muscle tissue does not play a significant role in storing energy.

The mitochondria in muscle fibers are arranged closest to the sarcolemma. This arrangement allows for efficient energy production and distribution to the muscle cells. The sarcolemma is the cell membrane of the muscle fiber, and having the mitochondria close to it ensures that ATP, the energy currency of the cell, can be readily supplied to the contractile proteins for muscle contraction. This proximity also facilitates the removal of waste products generated during muscle activity.

The correct answer is 40-50%. Muscle tissue makes up a significant portion of the total body weight in an average adult. This is because muscles are responsible for movement and play a crucial role in maintaining posture and stability. Additionally, muscle tissue is denser than fat tissue, which contributes to its higher percentage in the total body weight.

Motor proteins are proteins that are responsible for generating movement in cells. In the given diagram, option C is the only protein that is depicted with a structure that resembles a motor protein. Therefore, option C is the correct answer as it is the only protein shown in the diagram that can be identified as a motor protein.