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bio 2401 chp 9
| Question | Answer |
|---|---|
| motion results from alterating contraction (shortening) and relaxation of muscles; the skeletal system provides | leverage and a supportive framework for this movement |
| the scientific study of muscles is known as | myology |
| skeletal muscle tissue | is primarily attached to bones. it is striated and voluntary |
| cardiac muscle tissue | forms the wall of the heart. it is striated and involuntary, has intercleated discs |
| smooth (visceral) muscle tissue | is located in hollow organs. it is nonstriated (smooth) and involuntary |
| neurotransmitter | ach |
| key muscle functions- production of body_____ | movement |
| key muscle functions- stabilizing body _____ | positions |
| key muscle functions- regulating organ ______ | volume |
| key muscle functioins- moving substances _____ | within the body |
| key muscle functions- generating ___ | heat |
| electrical excitability | is the ability to respond to certain stimuli by producing electrical signals such as action potential (impulse) |
| contractility | is the ability to shorten and thicken (contract) generating force to do work |
| in an isometric contraction, the muscle | develops tension but does not shorten |
| in an isotonic contraction the tension | remains constant while the muscle shortens |
| extensibility | is the ability to be stretched without damaging the tissue |
| elasticity | is the ability to return to original shape after contraction or extension |
| each skeletal muscle is a seperate organ composed of cells called | fibers |
| fascia is a sheet or band of | fibrous connective tissue that is deep to the skin and surrounds muscles ad other organs of the body |
| superficial fascia (or subcutaneous layer) | separates muscle from skin and functions to provide a pathway for nerves and blood vessels, stores fat, insulates, and protects muscle from trauma |
| deep fascia | lines the body wall and limbs and holds muscles with similar functions together, allows free movement of muscles, carries nerves, blood vessels, and lymph vessels, and fills spaces between muscles |
| extensions of deep fascia--epimysium | covering the entire muscle; |
| extensions of deep fascia--perimysium | covering fascicles |
| extensions of deep fascia--endomysium | covering individual muscle fibers (cells) |
| tendons and aponeuroses are extensions of | connective tissue beyond muscle cells that attach muscle to bone or other muscles. |
| tendon (synovial) sheaths | enclose certain tendons and allow them to slide back and forth more easily |
| aponeurosis | is a tendon that extends as a broad, flat layer EX epicranial aponeurosis |
| blood brings | oxygen and nutrients for contraction |
| nerves (containing motor neruons) convey | impulses for muscular contraction |
| during embryonic development, skeletal muscle fibers | arise from myoblasts. |
| a few myoblasts persist in mature skeletal muscle as | satellite cells |
| skeletal muscle consists of fibers (cells) covered by | a cell membrane (sarcolemma) |
| "sarco" | flesh |
| the fibers contain | t tubules and sarcoplasm |
| t tubules are | tiny invaginations of the sarcolemma that quickly spread the muscle action potential to all parts of the muscle fiber |
| sarcoplasm | is the muscle cell cytoplams and contains a large amount of myoglobin for oxygen storage |
| each fiber contains myofibrils that | consist of thin and thick filaments (myofilaments) |
| sarcoplasmic reticulum | encircles each myofibril it is similar to smooth endoplasmic reticulum in on muscle cells and in the relaxed muscle stores calcium ions |
| muscular atrophy | is a wasting away of muscles |
| muscular hypertrophy | is an increase in the diameter of muscle fibers |
| myofibrils | are composed of thick and thin filaments arranged in units called sarcomeres |
| "myo" | muscle |
| calcium is stored in | bone and muscle |
| sarcomeres | are the basic functional units of a myofibril and show distinct dark (A band) and light (l band) areas |
| the darker middle portion, the A band, | is the entire width of the thick filaments with some thin filaments overlapping the thick one |
| the lighter sides are the | I bands that consist of thin filaments only |
| there are two | z discs, one at each end of the sarcomere |
| a narrow | H zone in the center of each A band contains thick but no thin filaments |
| exercise can result in | torn sarcolemma, damaged myofibrils, and disrupted Z discs and results in soreness or pain the next day |
| contractile proteins generate | force during contraction |
| myosin the main component of | thick filaments, functions as a motor protein. |
| motor proteins push or pull their | cargo to achieve movement by converting energy from ATP into mechanical energy of motion or force |
| actin | the main component of thin filaments, connects to the myosin for the sliding together fo the filaments |
| myosin is | thick |
| actin is | thin |
| only striated have | sarcomeres |
| muscle is | protein |
| myosin is | motor protein |
| regulatory proteins help | swith the contractions on and off |
| the regulatory proteins tropomyosin and troponin are a | part of the thin filament |
| in relaxed muscle, | tropomyosin blocks the myosi-binding sites on actin preventing myosin from binding to actin |
| structural proteins keep the thick and thin filaments in the proper alignment, | give the myofibril elasticity and extensibility, and link the myofirbrils to teh sarcolemma and extracellular matrix |
| titin (elastic filaments) | help a sarcomere return to its resting length after a muscle has contracted or been stretched |
| dystrophin reinforces the sarcolemma and helps | transmit the tesion generated by the sarcomeres to the tendons |
| during muscle contraction myosin cross bridges (heads) pull on thin filaments, causing | them to slide inward toward the H zone |
| z discs come toward each other and the sarcomere | shortens, but thick and thin filaments do not change in length. |
| the sliding of filaments and shortening of sarcomeres causes the | shrotening of the whole muscle fiber and ultimately the entire muscle this is called the sliding filament mechanism |
| at the beginning of contraction, the sarcoplasmic reticulum releases | calcium ions which bind ot troponin and cause the tropnin- tropomysium complex to uncover the myosin-binding site on actin. when the binding sites are "free" the contraction cycle begin |
| the contraction cycle is a repeating sequence of events that | causes the filaments to slide. it consists of ATP hydrolysis, attachment of myosin to actin to form cross bridges, the power stroke, and detachment of myosin from actin. |
| an increase in calcium ion | concentration in the cytosol starts muscle contraction; a decrease stops it |
| the muscle action potential releases calcium ions form the sarcoplasmic reticulum that combine with | troponin causing it to pull on tropomyosin to change its orientation, thus exposing myosin-binding sites on actin and allowing the actin and myosin to bind together |
| z discs are like | fingers sliding together |
| ATP is split in | ATP hydrolysis |
| calcium ions causes | contraction to take place |
| for active transport | ATP is needed |
| the use of calcium ions to remove the contraction ihibitor and the joining of actin and myosin constitute the | excitation-contraction coupling, the steps that connect excitation muscle action potential propagation through the T tubules to contraction of the muscle fiber |
| calcum ion active transport | pumps return calcium ions to the sarcoplasmic reticulum |
| rigor mortis | a state of muscular rigidity following death, results from a lack of ATP to split myosin-actin cross bridges |
| muscle action potentials arise at the | neuromuscular junction (NMJ) the synapse between a somatic motor neuron and a skeletal muscle fiber |
| a synapse is a | region of communication between two neurons or a neuron and a target cell |
| target cell = | muscle cell |
| synapses separate cells from | direct physical contact |
| neurotransmitters | bridge that gap |
| the neurotransmitter at a NMJ is | acetylcholine (ACH) |
| a nerve action potential elicits a muscle action potential through the release of | acetycholine activation of ACh receptors, production of a muscle action potential, and termination of ACh activity |
| several plant productions and drugs | selectively block events at the NMJ |
| curare | block acetylocholine binding sites |
| black widow venom | stimulates acetylcholine release |
| during excitation, action potentials in the nerve fiber give | rise to action potentials in the muscle fiber |
| action potentials in the synaptic knob trigger the release of | ACh from synaptic vesicles. ACh is released into the synaptic cleft and is detected by the ligand-gated ion channels in the motor end plate |
| binding of ACh opens the | sodium gated ion channels on the motor end plate |
| sodium ions rush into the muscle cell, which quickly reverses | polarity depolarization (more positive inside) |
| potassium ions rush out, and memrbane polarity is | reestablished (repolarization) |
| during repolarization, a muscle fiber is said to be in a | refactory period because the cell cannot be stimulated again until repolarization is complete |
| this rapid change in polarity at the motor end plate triggers the opening of | voltage gated sodium and potassium ion channels adjacent to the motor end plate, and action potentials spread away from the plate in all directions |
| once initiated the action potential is | unstoppable. it ultimately results in contraction of muscle fiber |
| during excitation-contraction coupling, | action potentials in the muscle fiber lead to activation of the myofilaments (actin and myosin) |
| the wave of action potential travels down the | t tubules and continues to the sarcoplasmic reticulum |
| after the action potential reaches the sarcoplasmic reticulum | it releases a flood of calcium ions into the cytosol |
| calcium ions bind the | troponin of the thin myofilaments, causing the troponin-tropomyosin complex to shift aside, exposing the myosin binding sites on the actin filaments |
| exocitosis requires | ATP |
| the myosin heads can now bind to the | myosin binding sites on actin and initiate contraction |
| during the contraction phase, sliding of the thin myofilaments past the thick ones causes the muscle fiber to | shorten |
| the sliding filament theory suggests that thin filaments slide over | thick ones causing sarcomeres to shorten |
| the head of each myosin molecule contains myosin | ATPase that releases energy from ATP, in preparation for action, the myosin binds and hydrolyzes an ATP molecules, and is now in the "cocked" position |
| when the myosin binding sites on the actin filaent are exposed, the myosin head contacts the active site, releases energy, and performs | a power stroke |
| at the end of a power stroke, myosin binds to a new | ATP, releases the actin, and returns to its original position in a recovery stroke. many myosin heads pull on the actin at once, so the actin does not slip back into its original position |
| the cycle of power stroke and recovery is | repeated many times during muscle contraction |
| when nervous stimulation ceases, the muscle | relaxes |
| acetycholinesterase (AChE) breaks down | ACh so the muscle stops generating its action potentials |
| calcium is carried back to the sarcoplasmic reticulum by | active transport and a protein called calsequestrin |
| rigor mortis is a state of muscular rigidity that begins 3-4 hours after death | and lasts about 24 hours after death |
| CA+2 ions leak out of the SR and allow | myosin heads to bind to actin. since ATP synthesis has ceased, myosin cross bridges cannot detach from actin until proteolytic enzymes begin to digest the decomposing cell |
| active muscle cells require large | quantities of ATP there are there sources of ATP production in muscle cells |
| creatine phosphate and ATP can power maximal muscle contration for about | 15 seconds and is used for maximal short bursts of energy |
| creatine phosphate is | unique to muscle fibers |
| there is a vontroversey regarding the | effectiveness of creatine supplementation |
| the partial catabolism of glucose to generate ATP occurs in | anaerobic cellular respiration. this system can provide enough energy for about 30-40 seconds of maximal muscle acitivty |
| muscular activity lasting more than 30 seconds depends increasingly on | aerobic cellular respiration (reactions requiring oxygen) this system of ATP production involves the complete oxidation of glucose cia cellular respiration (biological oxidation) |
| muscle tissue has two sources of oxygen: | diffusion from blood ad release of myoglobin inside muscle fibers |
| the aerobic system will provide enough ATP for prolonged activity so long as | sufficient oxygen and nutrients are available |
| a state of physiologial inability to contract even though the muscle still may be receiving stimuli is the inability of a | muscle to maintain its strength of contraction or tension is called muscle fatigue. |
| ionic imbalances and an increase in | lactic acid in the muscle are probablt the main causes of fatigue |
| 3 sources of ATP | creatine phosphate, anaerobic pathway, aerobic respiration |
| elevated oxygen use after exersie is called oxygen deficit, for a msucle to return to is resting state | its oxygen reserves must be repleished; the accumulated lactic acid must be reconverted to pyruvic acid; glycogen stores must be replaced, and; ATP and creatine phosphate reserves must be resynthesized |
| when considering the contraction of a whole muscle, the tension it can generate depends on | number of muscle fibers that are contracting in unison |
| a motor neuron | and the muscle fibers it stimulates form a motor unit |
| a single motor unit may innervate as few as | 10 or as many as 2,500 muscle fibers, with an averae of 150 fibers being innervated by each motor neuron |
| a twitch contraction is | a brief contraction of all the muscle fibers in a motor unit in response to a single action potential |
| a record of a muscle contraction is called a | myogram and includes three periods; latent, contraction, and relaxation |
| the refactory period is the time when | a muscle has temporarily lost excitability with skeletal muscles having a short refactory period and cardiac muscle having a long refactory period |
| wave summation is the | increased strength of a contraction resulting from the application of a second stimulus before the muscle has completely relaxed after a previous stimulus. |
| a sustained muscle contraction that permits partial relaxation between stimuli is called | incomplete (unfused) tetanus |
| a sustained muscle contraction that lacks even partial relaxation between stimuli is called | complete (fused) tetanus |
| the process of increasing the number of active motor units is called | recruitment (multiple motor unit summation) |
| MMUS prevents fatigue and helps provide | smooth muscular contraction rather than a series of jerky movements |
| aerobic tranining builds | endurance |
| anaerobic training builds | muscle strength |
| a sustained partial contraction of portions of a relaxed skeletal muscle results in a firmness known as | muscle tone. |
| at any given moment, a few muscle fibers within a muscle are | contracted while most are relaxed. this small amount of contraction is essential for maintaining posture |
| muscle tone | involuntary contraction of a small number of motor units (alternately active and inactive in a constantly shifting pattern) |
| muscle tone keeps muscles | firm even though relaxed |
| muscle tone does not produce | movement |
| muscle tone is essential for | maintaining posture (head upright) |
| muscle tone is important in maintaining | blood pressure because of tone of smooth muscles in walls of blood vessels |
| isotonic contractions | occur when a constant load is moved through the rang of motions possible at a joint and include concentric contractions and eccentric contractions; |
| in a isometric contracion | the muscle does not shorten but tension increases |
| isotonic contractions = a | load is moved |
| concentric contraction = | a muscle shortens to produce force and movement |
| eccentric contractions= | a muscle lengthens while maintaining force and movement |
| isometric contraction= no | movement occurs |
| same length | isometric |
| same tension | isotonic |
| tension is generated without muscle shortening such as while | maintaining posture and supporting objects in a fixed position |
| not all skeletal muscle fibers are | identical in structure or function |
| endurance fibers= | slow oxidative |
| color varies according to the content of | myoglobin, an oxygne-storing reddish pigment. |
| red muscle fibers have high | myoglobin content while the myoglobin content of white muscle fibers is low |
| myoglobin | makes muscles darker--more oxygen |
| fiber diameter varies, as do the cell's | allocations of mitochondria, blood capillaries, and sarcoplasmic reticulum |
| contraction velocity and resistance to fatigue also differ between | fibers |
| on the basis of structure and function, | skeletal muscle fibers are classified as slow oxidative, fast oxidative, and fast glycolytic fibers |
| most skeletal muscles contain a mixture of all three fiber types, their proportions varying with the usual action of the muscle. | all fibers of any one motor unit, however, are the same |
| altough the number of different skeletal muscle fibers does not change, various types of | exercise can alter the characteristic of those present |
| the use of anabolic steroids by athletes to increase muscle size, strength, and endurance | has been shown to have very serious side effects, some of which are life threatening |
| slow oxidative is | red |
| fast oxidative is | pink |
| fast glycolytic is | white |
| cardiac muscle tissue is found only in | the heart wall |
| cardiac muscle fibers are | arranged similarly to skeletal muscle fibers |
| cardiac muscle fibers connect to adjacent fibers by | intercalated discs, which contain desmosomes and gap junctions |
| cardiac muscle contractions last longer than the skeletal muscle twitch due to the | prolonged delivery of calcium ions from the sarcoplasmic reticulum and the extracellular fluid |
| cardiac muscle fibers contract when stimulated by their own | autorhythmic fibers |
| this continuous, rhythmic activity is a major | physiological difference between cardiac and skeletal muscle fibers |
| smooth muscle tissue is | nonstriated and involuntary and is classified into two types |
| visceral (single unit) smooth muscle | is found in the walls of hollow viscera and small blood vessels; the fibers are arranged in a network |
| multiunit smooth muscle | is found in large blood vessels, large airways, arrector pili muscles, and the iris of the eye. the fibers operate singly rather than as a unit |
| the duration of contraction and relaxation of smooth muscle | is longer than in skeletal muscle |
| in smooth muscle, the regulator protein that binds calcium ions in the cytosol is | calmodulin (in place of the role of troponin in striated muscle); |
| calmodulin activates the enzyme | myosin light chain kinase, which facilitates myosin-actin binding and allows contraction to occur at a relativly slow rate |
| the prolonged presence of calcium ions in the cytosol of smooth muscle fibers provides for | smooth muscle tone, a state of continued partial contraction |
| fibrosis | scar tissue formation |
| smooth muscle fibers can stretch considerably without developing tension; this phenomenon is termed the | stress relaxation response |
| smooth muscle lacks | striatioins and have little Sarcoplasmic Reticulum for calcium storage |
| skeletal muscle fibers cannot divide after | 1st year |
| growth is enlargement of existing cells | hypertorphy |
| repair--satellite | cells and bone marrow produce some new cells |
| repair--fibrosis occurs | most often |
| cardiac muscle fibers cannot | divide or regenerate |
| all healing is done by | fibrosis |
| smooth muscle fibers -- | regeneration is possible |
| cells can grow in | size (hypertrophy) |
| some cells (uterus) can | divide (hyperplasia) |
| new fibers can form from | stem cells in blood vessel walls |
| beginning at about 30 years of age, | there is a progressive loss of skeletal muscle, which is replaced by fat |
| there is also a decrease in maximal | strength and a slowing of muscle reflexes |
| neuromuscular disease involves problems wiht | somatic motor neurons, neuromuscular junctions, or muscle fibers |
| myopathy | signifies a disease or disorder of the skeletal muscle tissue itself |
| myasthenia gravis | progressive autoimmune disorder that blocks the ACh receptors at the neuromuscular junction |
| with myasthenia gravis the more receptors that are damaged | the weaker the muscle |
| myasthenia gravis is more common | in in women 20 to 40 |
| myasthenia gravis begins with | double vision and swallowing difficulties and progresses to paralysis of respiratory muscles |
| myasthenia gravis treatments include | inhibitors of acetylcholinesterase and steroids to reduce antibodies against ACh receptors |
| muscular dystrophies is | inherited, muscle-destroying desease |
| muscular dystrophies--when muscle contracts | sarcolemma tears |
| muscular dystrophies is mutated | gene is on X chromosomes so disorder is in Males almost exclusively |
| muscular dystrophies appears by | age 5 in males and by 12 may be unable to walk |
| muscular dystrophies is degeneration of | individual muscle fibers produces atrophy of the skeletal muscle |
| muscular dystrophies is the most common form | ducheone muscular dystrophy |
| intense exercise can cause | muscle damage |
| electron micrographs reveal | torn sarcolemmas, damaged myofibrils and disrupted Z discs |
| increased blood levels of | myoglobin and creatine phosphate found inside the muscle cell |
| delayed onset muscle soreness (DOMS) | 12 to 48 hours after strenuous exercise, stiffness, tenderness and swelling due to microscopic cell damage |
| atrophy | wasting away of muscles, caused by disuse (disuse atrophy) or severing of the nerve supply (denervation) atrophy |
| hypertrophy | increase in the diameter of muscle fibers, results from very forceful, repetitive muscular activity and an increase in myofibrils, SR & mitochondria |
Created by:
morgan8