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Exam 2 Anatomy
Muscles
| Term | Definition |
|---|---|
| Skeletal muscle | connects to bone, voluntary (conscious control) |
| Cardiac muscle | make up most of the wall in the heart, and responsible for pumping blood, involuntary |
| Smooth muscle | found in walls of internal organs, involuntary |
| Fascia | thin covering of connective tissue around a muscle |
| Tendon | cord-like mass of connective tissue that connects muscle to bone |
| Aponeurosis | sheet-like mass of connective tissue that connects muscle to bone, skin, or another muscle |
| Epimysium | surrounds who muscle; likes beneath fascia |
| Perimysium | surrounds fascicles within a muscle |
| Endomysium | surrounds muscle fibers (cells) within a fascicle |
| Muscle cell | muscle fiber |
| Sarcolemma | plasma membrane |
| Sarcoplasm | cytoplasm |
| Sarcoplasmic reticulum | endoplasmic reticulum; sequesters calcium ions |
| Transverse (T) tubule | small tube produced by invagination of sarcolemma |
| Triad | group of 3 structures - 2 tubules + cisterna of SR; usually located near Z line |
| Myofibril | small muscle fiber cylinders of sarcomeres within a muscle fiber (cell) |
| Sarcomere | functional unit of skeletal muscle; made up of overlapping actin and myosin filaments |
| Striation pattern | is made by arrangement of myofilaments in myofibrils |
| I band | region straddling a Z line where actin filaments do not overlap myosin filaments (isotropic: look same) |
| A band | central region of sarcomere; encompasses H-zone, M-line and full length of myosin filaments; also contains actin filaments (that overlap with myosin) |
| H- zone | area within A-band; contains M-line and myosin filaments that are not overlapped with actin |
| M line | middle of the sarcomere; cytoskeletal elements to which myosin filaments are anchored |
| Thick filaments | composed of myosin protein, heads form cross bridges with thin filaments |
| thin filaments | composed of actin protein, associated with troponin and tropomyosin, which prevent cross bridge formation when muscle is not contracting |
| Neuromuscular junction | a type of synapse, site where an axon of motor neuron and skeletal muscle fiber interact, skeletal muscle fibers contract only when stimulated by a motor neuron |
| Motor neuron | neuron that controls skeletal muscle fiber |
| Motor end plate | specialized folded portion of skeletal muscle fiber sarcolemma |
| Synaptic cleft | space between neuron and muscle fiber, across which neurotransmitter travels |
| Synaptic vessible | membrane bound sacs containing neurotransmitters |
| neurotransmitters | chemicals released by motor neuron to deliver message to muscle fiber |
| Aceytylcholine (ACh) | neurotransmitter, released from synaptic vessicle, binds to receptors on motor end plate |
| Excitation Contraction coupling | connection between muscle fiber stimulation and muscle contraction |
| Relaxation | Ca2+ ions stored in SR troponin-tropomyosin complexes cover binding sites on actin filament |
| Sliding filament theory | When sarcomeres shorten, thick and thin filaments slide past each other, H zones and I band narrow, Z lines move closer together, thick and thin filaments do not change length, overlap between filaments increase |
| Acetylcholinesterase | enzyme that rapidly decomposes ACh remaining in the synapse during relaxation |
| ATP reserves | first source of energy for muscle contraction, muscle cells store only a small amount |
| Creatine phosphate | initial source of energy to regenerate ATP from ADP and P stores energy in phosphate bond, like ATP, only can fuel ~10 seconds of intense muscle contraction with ATP |
| Cellular respiration | must be used to fuel longer periods of muscle contraction, breaks down glucose to produce ATP, glucose stored as glycogen in muscle cells |
| Anaerobic phase | Glycolysis, occurs in the cytoplasm, produces little ATP |
| Aerobic phase | Citric Acid cycle and electron transport chain, occurs in the mitochondria and produces the most ATP, myoglobin stores extra oxygen in muscles |
| Oxygen debt | During rest or moderate exercise, respiratory and cardiovascular systems supply enough O2 to support aerobic respiration |
| Anaerobic (Lactic acid) threshold | Shift in metabolism from aerobic to anaerobic, during strenuous muscle activity, when the above systems cannot supply the necessary O2 lactic acid is produced, liver converts lactic acid into glucose |
| Isotonic | muscle contracts and changes length, such as lifting weights |
| Isometric | muscle contracts but does not change length, tension develops but parts attached to muscle do not move |
| Slow twitch fibers (type I) | always oxidative, resistant to fatigue, red fibers (abundant in myoglobin) good blood supply, many mitochondria, slow ATPase activity; slow to contract |
| Fast twitch fatigue resistant fibers (type IIa) | intermediate twitch fibers, intermediate oxidative capacity, intermediate amount of myoglobin, white fibers, resistant to fatigue, rapid ATPase activity |
| Fast twitch glycolytic fibers (Type IIb) | anaerobic respiration (glycolysis), white fibers (less myoglobin), poorer blood supply than slow twitch, and fewer mitochondrial than slow twitch, susceptible to fatigue, fast ATPase activity; contract rapidly |
| Muscle tension (whole muscle) | generation capacity is physiological cross-sectional area, orientation/number of fibers, the larger the muscle the more tension it generates |
| Muscle fatigue | inability to contract muscle, common causes include decreased blood flow, ion imbalance across sarcolemma, loss of desire to continue exercise, accumulation of lactic acid |
| Muscle Cramps | sustained, involuntary muscle contraction, may be caused by changes in electrolyte concentration in extracellular fluids in the area |
| Heat production | heat is a by-product of cellular respiration in active cells, muscle cells are major source of body heat, more than half the energy released in cellular respiration becomes heat; less than half is transferred to ATP, heat transported through core |
| Motor Unit | a motor neuron plus all of the muscle fibers it controls, coarse movements are produced with large numbers of fibers, precise movements are produced with fewer muscle fibers in a motor unit |
| Order of motor units | smaller motor units recruited first (fine motor), larger motor units recruited later (smoother muscle contraction) |
| Muscle tone | continuous state of partial contraction in resting muscle (muscle needs less energy to contract) |
| Parrell muscle fibers | produce greater range of motion (less tension) examples are abdominal muscle, and bicep brachii |
| Pennate fibers | can produce greater tension (less range of motion) examples are digital extensor and rectus femoris |
| Physiological cross-sectional area | takes into account fiber direction and direction of force |
| Smooth muscle fiber | short, single centrally located nucleus, elongated with tapering ends, myofilaments randomly organized, lack striations, lack transverse tubules, sarcoplasmic reticulum not well developed |
| Multi-Unit Smooth muscle | cells are less organized, function as separate units, fibers function independently, examples: iris of eye, walls of blood vessels, stimulated by neurons and hormones |
| Visceral smooth muscle | cells respond as a unit, sheet of spindle-shaped muscle fibers, fibers held together by gap junctions, exhibit rhythmicity, conduct peristalsis, examples: walls of most hollow organs more common type |
| Cardiac muscle fiber | located only in the heart, striated muscle cells, muscle fibers joined together by intercalated discs, fibers branch contain single nucleus, network of fibers contracts as a unit, self-exciting and rhythmic, longer refractory period than skeletal muscle |
| Hypertrophy | enlargement of skeletal muscle that is exercised |
| Atrophy | decrease in size and strength of skeletal muscle that is unused |
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