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CH10A&PMuscle tissue
| Term | Definition |
|---|---|
| The primary function of muscle is to | change chemical energy into mechanical energy to produce body movement. |
| The three types of muscle tissue are | skeletal cardiac smooth |
| Skeletal muscle tissue is | striated, under voluntary control, and functions to move bones of the skeleton |
| Cardiac muscle tissue is | s striated, under involuntary control, has autorhythmicity, and is found only in the heart. |
| Smooth muscle tissue is | nonstriated, under involuntary control, and is located in the walls of hollow internal structures. |
| Muscle tissue has four important functions | : producing body movements, stabilizing body positions, moving substances within the body, and producing heat. |
| Muscle tissue has four special properties | electrical excitability, contractility, extensibility, and elasticity. |
| A skeletal muscle is | an organ composed of elongated muscle fibers plus associated nerves, blood vessels, and connective tissues. |
| Hypodermis | separates muscle from skin |
| Fascia | unites muscles with similar functions, carries nerves and vessels, and fills spaces between muscles |
| 3 layers of connective tissue | epimysium perimysium endomysium protect and strengthen skeletal muscle: These three layers may extend beyond the muscle to form a tendon, or a broad flat aponeurosis |
| epimysium | the outermost layer encircles the muscle |
| perimysium | bundles together groups of muscle fibers into fascicles |
| endomysium | the innermost layer, surrounds each muscle fiber |
| Tendons and aponeuroses | attach a muscle to bone |
| One artery and one or two veins supply each | skeletal muscle |
| Motor ________stimulate muscle fibers through processes called _______. | neurons, axons |
| Skeletal, cardiac, and smooth muscle tissues differ in | location, structure, and function |
| skeletal muscles are? | surrounded by connective tissues and are well supplied with nerves and blood vessels |
| Each skeletal muscle fiber is covered by? | a sarcolemma; each of its myofibrils is surrounded by sarcoplasmic reticulum and contains sarcomeres |
| Embryonic development of skeletal muscle fibers arises from? | fusion of myoblasts into one elongated, multinucleate, amitotic muscle fiber |
| Some myoblasts persist as | satellite cells in mature skeletal muscle that can fuse and regenerate muscle fibers in damaged tissue. Extensive damage involves fibrosis |
| fibrosis | the replacement of muscle fibers with scar tissue. |
| Aƞer birth, muscle growth occurs from | enlargement of existing muscle fibers, termed hypertrophy, stimulated by human growth hormone, testosterone, and other hormones. |
| hypertrophy | the enlargement of existing muscle fibers |
| The sarcolemma has many invaginated, tunnel-like extensions called | sverse (T) tubules that are also open to the cell’s exterior. |
| The sarcoplasm contains glycogen, and a red protein, called | myoglobin, that binds oxygen molecules for use in ATP synthesis |
| The sarcoplasm is full of long contractile elements, called | myofibrils, which give the fiber its striated appearance |
| sarcoplasmic reticulum (SR) | wraps around each myofibril. The SR stores and releases Ca . The dilated end sacs of the SR, called terminal cisterns, lie on each side of one T tubule, forming a triad. |
| terminal cysterns | dilated end sacs of the SR, lie on each side of one T tubule, forming a triad. |
| Myofibrils contain thin filaments and thick filaments arranged in basic functional units called | sarcomeres |
| Sarcomeres in a myofibril are separated from one another by | Z discs |
| A darker middle part of the sarcomere containing thick and thin overlapping filaments is the | A band |
| at the center of A band is a narrow H zone containing | only thick myofilaments. |
| I bands | contain only thin filaments and are located near the Z discs at the ends of a sarcomere |
| The contractile proteins, myosin and actin, are located inside | myofibrils |
| Myosin | the main component of thick filaments, converts chemical energy in ATP to the mechanical energy of motion. |
| Actin | has a myosin-binding site where the myosin head can attach. |
| Two regulatory proteins, are also part of the thin filament, and help switch contraction on and off. | tropomyosin and troponin |
| In addition to contractile and regulatory proteins, muscle contains structural proteins such as | titin and dystrophin |
| titin | helps anchor a Z disc to the M line |
| dysrophin | links thin filaments of the sarcomere to the sarcolemma. |
| The neuromuscular junction is | where a muscle action potential is initiated |
| Muscle action potentials arise at the________ , the _______between a motor neuron and a skeletal muscle fiber. | neuromuscular junction, synapse |
| The synaptic end bulbs have synaptic vesicles containing the neurotransmitter | acetylcholine (ACh). |
| The motor neuron releases ______ into the synaptic cleft; ACh binds to___________on the motor end plate region of the sarcolemma of the muscle fiber | ACh, acetylcholine receptors 2+ |
| Events in the excitation of a skeletal muscle fiber include the following | release of acetylcholine as an impulse from the brain or spinal cord reaches the synaptic end bulbs; activation of ACh receptors when ACh binds to a motor end plate ACh receptor, which opens ion channels; generation of a muscle action potential that stim |
| An action potential releases calcium ions that allow thick filaments to bind to and pull thin filaments toward the center of the sarcomere | |
| An action potential releases ______ that allow thick filaments to bind to and pull thin filaments toward the center of the_________ | calcium ions, sarcomere |
| The sliding filament mechanism of muscle contraction involves | thin filaments at both ends of the sarcomere being pulled to the center of the sarcomere by myosin head activity. Z discs come closer together and the sarcomere shortens |
| When a muscle action potential propagates along the sarcolemma and T tubules, it opens | Ca2+ release channels in the SR membrane |
| Ca flows into the sarcoplasm and combines with | troponin, moving the troponin–tropomyosin complex away from myosin-binding sites on actin |
| Myosin heads | then bind to actin. |
| The contraction cycle consists of four steps. 1st step | ATP splits on the myosin head to reorient and energize it |
| The contraction cycle consists of four steps, 2nd step | myosin attaches to actin when the energized myosin head attaches to the myosin-binding site on actin |
| The contraction cycle consists of four steps 3rd step | myosin attaches to actin when the energized myosin head attaches to the myosin-binding site onactin; the power stroke occurs when the energized myosin head releases the phosphate group, triggering ADP release and myosin rotation, which slides the thin fil |
| The contraction cycle consists of four steps 4th step | myosin detaches from actin as ATP binds to the myosin head. ATPase splits ATP on the myosin head, and energy is transferred to the myosin head as it is energized and reoriented in position |
| The contraction cycle repeats as successive power strokes result in | shortening of the sarcomeres |
| As Z discs pull on adjacent sarcomeres, the whole muscle fiber | shortens, and, ultimately, the entire muscle shortens |
| Cessation of impulses in the motor neuron stops | ACh release |
| AChE breaks down any ACh in the | synaptic cleft |
| Ion channels close, action potentials stop, and Ca active transport pumps use ATP to | move Ca back into the SR |
| The troponin–tropomyosin complexes slide back to cover myosinbinding | sites of actin, and thin filaments return to their relaxed positions. |
| Muscle tension is controlled by | stimulation frequency and motor unit recruitment |
| A single impulse in a motor neuron elicits a single muscle twitch contraction in | all muscle fibers that it innervates. |
| The frequency of stimulation governs the | total tension that can be produced by a single muscle fiber. |
| The total tension produced in a whole muscle depends on | the number of fibers contracting in unison. |
| motor unit | is one motor neuron and all skeletal muscle fibers the motor neuron stimulates. |
| Muscles controlling small, precise movements are innervated by | many small motor units |
| muscles controlling large, powerful movements have | fewer, large motor units |
| The size of a muscle’s motor units and the number of motor units activated contribute to the | contraction strength. |
| The response of a motor unit to a single impulse in its motor neuron is a | twitch contraction |
| . The three phases of a twitch contraction are | latent contraction relaxation |
| latent period | cell events leading up to contraction |
| contraction period | power strokes generating tension |
| relaxation period | the muscle is allowed to resume its original length |
| Multiple stimuli that arrive before the muscle fiber has fully relaxed lead to | wave summation |
| When the frequency of stimulation allows partial relaxation it is called______ or ________. | unfused tetanus, incomplete tetanus |
| rapid frequency of stimulation and sustained contraction is called ________or_____________. | fused tetanus, complete tetanus |
| Motor unit recruitment is | the process of increasing the number of contracting motor units. |
| A muscle at rest exhibits________, a small amount of tension due to involuntary alternating contractions of a small number of its motor units that do not produce movement | muscle tone |
| Damaged motor neurons that cannot maintain muscle tone cause a muscle to become | flaccid |
| Isotonic contractions involve | a change in muscle length without a change in its tension. |
| There are two types of Isotonic contractions | concentric isotonic contractions eccentric isotonic contractions |
| concentric isotonic contractions | occur when the muscle shortens |
| eccentric isotonic contractions | occur when the muscle lengthens |
| isometric contraction | occurs when the load equals or exceeds the muscle tension, and the muscle does not lengthen or shorten |
| is the only direct source of energy for muscle contraction | ATP |
| Muscle fibers have three ways to produce ATP: | from creatine phosphate, by anaerobic glycolysis, and by aerobic respiration |
| Muscle fibers break down excess ATP and transfer a phosphate group to creatine, forming | creatine phosphate and ADP |
| During contraction, muscle fibers transfer the phosphate group from creatine phosphate to ADP, forming | ATP |
| A muscle at peak activity quickly depletes available ATP and creatine phosphate, and it will then | catabolize glucose molecules from glycogen |
| is the initial pathway in glucose breakdown and yields two ATP molecules and two pyruvic acid molecules | Glycolysis |
| When oxygen is unavailable, anaerobic reactions convert pyruvic acid to | lactic acid |
| Blood removes lactic acid from skeletal muscle and carries much of it to the | liver for reconversion to glucose. |
| When oxygen is available, the pyruvic acid molecules from glycolysis enter the ___________ , where aerobic respiration completely oxidizes each molecule of glucose to generate ________ATP molecules. | mitochondria, 30 or 32 |
| the inability of muscle to contract forcefully after prolonged activity. | Muscle fatigue |
| Heavy breathing after prolonged muscle activity helps to repay the oxygen debt, more accurately referred to as | recovery oxygen uptake |
| This increased oxygen intake helps to restore metabolic This increased oxygen intake helps to restore metabolic conditions to the resting level by conversion of lactic acid to | glycogen, resynthesis of creatine phosphate and ATP, and replacement of oxygen in muscle fibers. |
| 1. Skeletal muscle fibers with low myoglobin content appear pale and are called | white muscle fibers |
| skeletal muscle fibers with high myoglobin content have a dark, reddish appearance and are called | red muscle fibers |
| Skeletal muscle fibers are classified as | slow oxidative, fast oxidative–glycolytic, and fast glycolytic. |
| Slow oxidative fibers | use aerobic respiration, have a slow speed of contraction, and are fatigue resistant. These fibers are beneficial for posture and endurance activities. |
| Fast oxidative–glycolytic fibers | use aerobic respiration and glycolysis, have fast speeds of contraction, and are moderately fatigue-resistant. These fibers are used for walking and sprinting. |
| . Fast glycolytic fibers | mainly use glycolysis, contract strongly and rapidly, and are adapted for intense bursts of anaerobic movements, but they fatigue rapidly. |
| Most skeletal muscles in the body are | a mixture of all three types of muscle fibers |
| Training, genetics, and muscle action can | slightly alter proportions of the fiber types. |
| Cardiac muscle tissue is found in | the wall of the heart |
| Cardiac muscle fibers have | one nucleus and are branched and striated |
| Cardiac muscle fibers interconnect by | intercalated discs containing desmosomes and gap junctions |
| Long, sustained contractions are supported by | inflow of Ca2+ into the sarcoplasm |
| Specialized cardiac muscle fibers have | autorhythmicity |
| is needed for the continuous contraction–relaxation cycle that occurs in cardiac muscle fibers. | A constant supply of oxygen and nutrients |
| There are two types of smooth muscle tissue | (1) visceral (single-unit) smooth muscle tissue (2) multiunit smooth muscle tissue |
| visceral (single-unit) smooth muscle tissue | is autorhythmic, and the fibers are connected by gap junctions allowing action potentials to spread throughout the network so that cells contract as a single unit |
| multiunit smooth muscle tissue | acts independently, has few gap junctions, and lacks autorhythmicity. |
| Smooth muscle fibers | have tapered ends, one central nucleus, are nonstriated, and lack sarcomeres. Intermediate filaments form bundles that stretch between dense bodies |
| Thin and thick filaments of smooth muscle have a | sliding mechanism that generates tension, resulting in lengthwise shortening of the fiber |
| Smooth muscle contraction | starts slowly and lasts an extended time. |
| Smooth muscle is | involuntary and responds to autonomic nervous system impulses, hormones, and local factors |
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