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What are the main functions of skeletal muscle?
Movement, posture maintenance, protection and support, regulation of material elimination, and heat production.
What are the characteristics of skeletal muscle tissue?
Excitability, conductivity, contractility, extensibility, and elasticity.
What constitutes the gross anatomy of skeletal muscle?
Includes skeletal muscle fibers, connective tissues, blood vessels, and nerves organized into fascicles.
What are the components of connective tissue in skeletal muscle?
Epimysium, perimysium, endomysium, deep fascia, and superficial fascia.
How does excitation-contraction coupling occur?
An action potential triggers calcium release from the sarcoplasmic reticulum, enabling muscle contraction.
What is the process of muscle relaxation?
Re-uptake of calcium ions into the sarcoplasmic reticulum, allowing myosin to detach from actin.
What are the differences between isometric and isotonic contractions?
Isometric: muscle tension increases without length change; Isotonic: muscle tension overcomes resistance leading to movement.
What are the types of skeletal muscle fibers?
Slow-twitch fibers (fatigue resistant) and fast-twitch fibers (powerful but fatigue quickly).
What causes muscle fatigue?
Decreased glycogen and ion imbalances during prolonged exertion.
What are the characteristics of cardiac muscle?
Striated and involuntary, featuring intercalated discs for synchronized contractions.
What is the structure of smooth muscle?
Fusiform shape located in organ systems like blood vessels and intestines, with different contraction mechanisms compared to skeletal muscle.
What is the connective tissue harness of skeletal muscles?
Epimysium surrounds the entire muscle, perimysium wraps around fascicles (bundles of muscle fibers), and endomysium encases individual muscle fibers.
What is the relationship between muscle cell/myofiber, myofibrils, and myofilaments?
A muscle cell (myofiber) contains myofibrils, which are made up of myofilaments (actin and myosin) responsible for contraction.
What is the structure of a myofibril?
A myofibril consists of repeating units called sarcomeres, characterized by structures such as Z-lines, A-bands, I-bands, and H-zones.
What are the key components of a muscle cell?
Key components include sarcolemma (cell membrane), multiple peripheral nuclei (control protein synthesis), sarcoplasmic reticulum (calcium storage), sarcoplasm (cytoplasm), T-tubule triads (conduct impulses), and SR cisternae (terminal storage of calcium).
What is the sliding filament theory of muscle contraction?
The sliding filament theory states that muscle contraction occurs when myosin heads bind to actin, pulling the filaments past each other, resulting in shortened sarcomeres.
What is a motor end unit (neuromuscular junction)?
A motor end unit is the connection point between a motor neuron and a muscle fiber, where signals are transmitted to initiate muscle contraction.
How does a neuron stimulate a muscle to contract?
A neuron releases acetylcholine at the neuromuscular junction, triggering an action potential in the muscle cell that leads to contraction.
What roles do Ca++, troponin, and tropomyosin play in excitation-contraction coupling?
Calcium ions bind to troponin, causing tropomyosin to move and expose binding sites on actin for myosin to attach and start contraction.
What happens during cross bridge cycling in muscle contraction?
During cross bridge cycling, myosin heads attach to actin, pivot to pull actin, release, and reset, with ATP providing energy for these processes.
What is the relationship between motor units, recruitment, and force of contraction?
Motor units consist of a motor neuron and its muscle fibers; recruitment of more motor units increases force of contraction.
What events lead to muscle relaxation?
Muscle relaxation occurs when calcium ions are reabsorbed by the sarcoplasmic reticulum, myosin heads detach from actin, and muscle fibers return to their resting state.
What is tetanus in muscle physiology?
Tetanus refers to a sustained muscle contraction due to rapid stimulation; it is possible in skeletal muscle but not in cardiac muscle which has a longer refractory period.
What is muscle tone?
Muscle tone is the continuous and passive partial contraction of the muscles, which helps maintain posture and readiness to act.
What are isometric and isotonic contractions?
Isometric contractions involve muscle tension without length change; isotonic contractions involve muscle lengthening or shortening while generating force.
What are anaerobic and aerobic pathways of ATP production in skeletal muscle?
Anaerobic pathways produce ATP quickly without oxygen, causing lactic acid buildup; aerobic pathways use oxygen, producing ATP more slowly but efficiently.
What role does creatine phosphate play in muscle metabolism?
Creatine phosphate serves as a quick source of energy by donating a phosphate group to regenerate ATP during high-intensity exertion.
What factors are associated with muscle fatigue?
Muscle fatigue can result from decreased glycogen stores, ion imbalances, accumulation of lactic acid, and insufficient oxygen supply.
What are muscle atrophy and hypertrophy?
Atrophy is the decrease in muscle mass due to disuse or decreased stimuli, while hypertrophy is the increase in muscle size due to increased activity or resistance training.
Compare and contrast cardiac and skeletal muscle tissue.
Cardiac muscle is striated, involuntary, contains intercalated discs; skeletal muscle is also striated but voluntary and does not have intercalated discs.
What is the structure and function of visceral smooth muscle tissue?
Visceral smooth muscle is non-striated, involuntary, found in organs like the intestines, and responsible for peristalsis and other automatic movements.
What is the role of ATP in muscle contraction?
ATP provides the energy required for myosin heads to attach to actin and perform the power stroke during muscle contraction.
What are the effects of stretching on muscle performance?
Stretching can improve flexibility, increase blood flow, and enhance overall muscle performance, reducing the risk of injury.
What is the function of intercalated discs in cardiac muscle?
Intercalated discs connect cardiac muscle cells, allowing for synchronized contraction and efficient heart function.
What is the significance of the sarcoplasmic reticulum in muscle cells?
The sarcoplasmic reticulum stores calcium ions, which are crucial for triggering muscle contraction.
What factors contribute to increased muscle strength?
Increased muscle strength can result from neuromuscular adaptations, muscle hypertrophy, and improved coordination.
What is muscle elasticity?
Muscle elasticity is the ability of muscle tissue to return to its original shape after being stretched or contracted.
What are the energy sources for muscle contraction?
Muscle contraction uses ATP, creatine phosphate, and various energy pathways including aerobic and anaerobic metabolism.
Describe types of muscle fibers based on their oxidative capacity.
Type I fibers (slow-twitch) are more oxidative and fatigue-resistant, while Type II fibers (fast-twitch) are less oxidative and fatigue quickly.
What role does lactic acid play in muscle metabolism?
Lactic acid is produced during anaerobic respiration and can contribute to muscle fatigue when accumulated.
What is the all-or-none principle in muscle contraction?
The all-or-none principle states that a muscle fiber will fully contract or not contract at all when stimulated above a threshold.
