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Anatomy and Physiology > Muscles and Muscle Tissues (Chapter 9) > Flashcards

Muscles and Muscle Tissues (Chapter 9) Flashcards

1
Q

What is the function of muscle tissue?

A

Transform chemical energy (ATP) into mechanical energy

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2
Q

Smooth Muscle Structure/Function/Location

A

Structure: no visible striations, spindle-shaped uninucleate cells; Function: propels substances along internal passageways, involuntary; Location: walls of hollow organs such as stomach, small/large intestines, blood vessels

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3
Q

Cardiac Muscle Structure/Function/Location

A

Structure: branching striated fibers with 1-2 nuclei per cell, intercalated discs at junction of adjacent cells; Function: propels blood throughout body, involuntary (ANS can speed up or slow down rate of contraction); Location: Walls of heart

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4
Q

Skeletal Muscle Structure/Function/Location

A

Structure: striated, multinucleated long cylindrical cells; Function: movement of body parts, heat generation, voluntary; Location: attached to bones and occasionally skin

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5
Q

Primary Functions of Muscles

A

Stabilize joints, muscle contractions oppose gravity -> maintain upright posture, muscle contractions produce movements within body and of body, muscle contractions generate heat via thermogenesis

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6
Q

First Characteristic of Muscle Tissue

A

Electrical Excitability: ability to produce electrical signals (action potentials) in response to stimuli

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7
Q

Second Characteristic of Muscle Tissue

A

Contractibility: ability to shorten when stimulated by AP

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8
Q

Third Characteristic of Muscle Tissue

A

Extensibility: ability to stretch without being damaged

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9
Q

Fourth Characteristic of Muscle Tissue

A

Elasticity: ability to return to original length and shape after stretching or contraction

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10
Q

Superficial Fascia

A

Separates muscle from skin, composition: areolar and adipose CT; contains blood vessels, lymphatics, and nerves

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11
Q

Deep Fascia

A

Lines body walls, holds muscles together with similar functions, allows free movement of muscle groups, composition: primarily dense irregular CT; contains: blood vessels, lymphatics, and nerves

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12
Q

3 Layers of Deep Fascia

A

Epimysium: outermost layer -> surrounds entire muscle, composition: dense, irregular CT; Perimysium: surrounds 10-100+ individual muscle fibers -> form fascicles, composition: dense, irregular CT; Endomysium: surrounds individual muscle fibers withing fascicle, composition: thin layer of areolar CT

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13
Q

Muscle Attachments

A

Tendons: attach muscles to periosteum, composition: bundles/cords of dense regular CT; Aponeuroses: sheet-like tendons, composition: sheets of dense regular CT

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14
Q

Nerve and Blood Supply

A

Each muscle -> a nerve, artery, and 1-2 veins; Nerve branches supply each fiber -> stimulates contraction; Each muscle cell is in loose contact with multiple capillaries -> highly vascularized; Contracting muscle fibers require large amounts of oxygen and nutrients; Also need carbon dioxide and waste products removed quickly

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15
Q

Motor Unit of NMJ

A

Somatic motor neuron, all muscle fibers innervated by motor neuron (4 to several hundred)

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16
Q

Neuromuscular Junction

A

Contact site between skeletal muscle fiber and axon branch of somatic motor neuron; Occurs about midway down skeletal muscle fiber; Axon branches many times; Each branch typically innervates one muscle fiber; Axon branch subdivides to form axon terminals; Axon terminals expand to form synaptic end bulbs; Location of vesicles filled with neurotransmitters

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17
Q

Embryonic Development

A

Myoblasts; Derived from embryonic mesodermal cells; 100+ fuse to form multinucleated skeletal muscle fiber; Lose mitotic ability once fused; At birth, number of muscle fibers/muscle is already determined; Muscle growth: hypertrophy vs. hyperplasia -> enlargement of fibers; Satellite Cells: myoblast that persist as stem cells for skeletal muscle in mature muscle

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18
Q

Sarcolemma

A

muscle cell plasma membrane

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19
Q

T-Tubules

A

Formed by tiny invagination of sarcolemma -> extend in center of fiber; Filled with tissue fluid; Thousands of t-tubules per fiber; Function: transmit muscle APs into muscle fiber, all parts of muscle fiber stimulated at same time

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20
Q

Sarcoplasm

A

Muscle cell cytoplasm; Abundant glycogen granules -> ATP production; Myoglobin: red-pigmented protein containing heme group, found only in muscle cells, function: binds O2 into cell -> releases O2 as needed by mitochondria for ATP production, MT lie in rows throughout muscle fiber -> close to proteins requiring ATP during muscle contraction

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21
Q

Sarcoplasmic Reticulum

A

Intracellular system of tubules, similar to SER surround contractile proteins within muscle fiber; Function: regulate intracellular Ca+2 levels -> stores Ca+2 when fiber is relaxed and releases Ca+2 when fibers are stimulated to contract

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22
Q

Myofibrils

A

Groups of contractile proteins within muscle fibers -> 80% cell volume, extend entire length of muscle fiber, organelles are squished around them

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23
Q

Myofilaments

A

Do not extend entire length of muscle fiber, arranged into functional units -> sarcomeres, Actin: main component of thin filaments, Myosin: main component of thick filaments

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24
Q

Sarcomere Structure

A

Z disc, A Band, I Band, H Zone, M Line

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25
Q

Z Disc

A

Region of dense material separating sarcomeres, site of actin attachment

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26
Q

A Band

A

Regions of myosin and actin overlap, forms “dark” band

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27
Q

I Band

A

Region of actin only, forms “light” band

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28
Q

H Zone

A

Regions of myosin only -> central, narrow region of A band

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29
Q

M Line

A

Site of support proteins anchoring myosin at H zone

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30
Q

Myosin

A

Function: motor protein, convert chemical energy (ATP) into mechanical energy (movement); Structure: 300 myosin proteins per thick filament, tails: pointed toward M line -> parallel, heads: extend toward thin filaments -> spirally arranged, form cross bridges during contraction, contain: ATP binding site, ATPase, Actin binding site

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31
Q

Actin and Regulatory Proteins

A

Actin: thin filaments -> numerous actin subunits, each subunit contains 1 myosin binding site, actin filament folds back on itself forming a helix; Tropomyosin: blocks myosin binding site on actin when muscle is relaxed; Troponin: attaches to actin (holds tropomyosin in place), TnL subunit - binds actin (inhibits actomyosin ATPase activity associated with myosin head, TnT subunit - binds tropomyosin, TnC subunit - binds up to 4 Ca+2

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32
Q

Sarcomere-Associated Structural Proteins

A

Titin: extends from Z disc to M line, anchors thick filaments and contributes to elasticity and extensibility; Myomesin: forms M line, binds titin and anchors adjacent thick filaments; Dystrophin: anchors thin filaments to TM proteins in sarcolemma -> TM proteins anchored to proteins in ECM

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33
Q

Sliding Filament Model of Contraction

A

Thin filaments slide past thick filaments, thin overlap thick when fully contracted, I band shortens and H zone disappears, A band width stays the same

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34
Q

Contraction Cycle: ATP Hydrolysis

A

ATP bound to myosin head, myosin heads break down ATP via ATPase -> ADP + Pi + energy, head reorients -> actin binding site faces actin subunit, head is energized

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35
Q

Contraction Cycle: Attachment of myosin to actin to form cross bridges

A

Energized myosin head attaches to myosin binding site on actin subunit, Pi group is released -> triggers power stroke

36
Q

Contraction Cycle: Power/Working Stroke

A

Pocket containing ADP opens up, myosin head rotates toward center of sarcomere and releases ADP, thin filaments slides past thick filament towards M line

37
Q

Contraction Cycle: Detachment of myosin from actin

A

ATP binds to myosin head, binding of ATP causes head to detach from actin -> breaks cross bridge

38
Q

Excitation-Contraction Coupling: Generation of AP in sarcolemma

A

Nerve impulse triggers release of acetylcholine from synaptic end bulbs of somatic motor neuron, Ach binds to receptors in sarcolemma and stimulates AP in sarcolemma -> t-tubules

39
Q

Excitation-Contraction Coupling: Release of Ca+2 from SR

A

AP stimulates release of Ca+2 from SR by opening Ca+2 channels in SR membrane

40
Q

Excitation-Contraction Coupling: Binding of Ca+2 to TnC of Troponin

A

Ca+2 binds to TnC subunit which changes shape of troponin-tropomyosin complex, tropomyosin rolls away from myosin binding site on actin

41
Q

Excitation-Contraction Coupling: Cross-Bridge formation leading to contraction

A

Myosin heads alternately attach to/detach from actin, actin filaments are pulled toward M line, ATP and Ca+2 required for cycle to continue

42
Q

Excitation-Contraction Coupling: Removal of Ca+2 from Sarcoplasm

A

After AP ends, Ca+2 pumped back into SR via Ca+2 active transport pumps, Ca+2 release channels also close

43
Q

Excitation-Contraction Coupling: Cross-Bridge inhibition by tropomyosin leading to relaxation

A

Occurs as Ca+2 levels drop, troponin-tropomyosin complex rolls back into place, myosin binding sites on actin blocked -> relaxation

44
Q

Rigor Mortis

A

Dying cells can’t keep out Ca+2 in TF -> Ca+2 rushes into muscle cells, Ca+2 also leaks out of SR -> increased intracellular Ca+2 myosin binds to actin -> muscles contract, once breathing stops ATP synthesis stops due to lack of oxygen, without ATP myosin cannot detach from actin and myosin is now irreversibly bound to actin and muscles cannot relax (body appears stiff)

45
Q

Neuromuscular Junction: Motor End Plate

A

Region of sarcolemma opposite to synaptic end bulb; Axon Terminals: branches of motor neuron, each terminates as a synaptic end bulb; Synaptic Cleft: space between axon PM and sarcolemma, filled with TF, Ach receptors are found in folds of sarcolemma -> motor end plate

46
Q

Gated Ion Channels within Sarcolemma

A

Chemically-Gated Ion Channel: Na+/K+ channels (binding of chemical messengers); Voltage-Gated Ion Channel: Na+ channels and K+ channels (changes in membrane potential)

47
Q

Generation of APs at NMJ: Release of Acetylcholine

A

1 nerve impulse -> Ca+2 channels open in axon PM, Ca+2 influx stimulates exocytosis of vesicles containing Ach

48
Q

Generation of APs at NMJ: Activation of Ach Receptors

A

Ach diffuses across synaptic cleft and binds to Ach receptors in motor end plate, 2 Ach molecules open the Na+/K+ channel associated with receptor and Na+ diffuse into sarcoplasm and K+ out

49
Q

Generation of APs at NMJ: Production of Muscle Action Potential

A
50
Q

Generation of APs at NMJ: Termination of Ach Activity

A

Diffusion away from synaptic cleft, acetylcholinesterase (ACase) associated with sarcolemma, Ach -> acetic acid and choline

51
Q

Depolarization of Sarcolemma

A

Outside sarcolemma [Na+] hi, [K+] lo / inside of sarcolemma [Na+] lo, [K+] hi, Na+/K+ channels open (chemically-gated ion channels), more Na+ rush in than K+ rush out and membrane polarity changes, adjacent voltage-gated Na+ channels open and initiates wave of depolarization in sarcolemma -> action potential

52
Q

Repolarization of Sarcolemma

A

Na+ channels begin to close, K+ ion channels begin to open and K+ diffuse out of sarcoplasm (reestablishes polarity of sarcolemma), Na+/K+ active transport pumps are activated -> Na+ pumped out and K+ pumped in, reestablishes resting ion contractions

53
Q

Factors that increase the force of skeletal muscle contraction

A

Frequency (rapid stimulation), Number of fibers, Size of fibers, Degree of stretch

54
Q

Visualizing Muscle Contractions: Electromyography

A

Allows visualization of muscle contractions via myogram, uses isolated muscles attached to apparatus that measures muscle tension in response to a stimulus

55
Q

Visualizing Muscle Contractions: Muscle Twitch

A

Latent Period: initiation of excitation-contraction coupling, Ca+2 released from SR and cross bridges begin to form, no force evident yet; Contraction Period: cross bridges actively form between actin and myosin, muscle contracts

56
Q

Refractory Period

A

Refers to period during which a muscle fiber cannot be re-stimulated, represents time during which sarcolemma is repolarized, Na+ channels close and K+ channels open -> membrane polarity re-established, Na+/K+ pumps are activated -> correct ion concentrations re-established just inside/outside membrane

57
Q

Muscle Twitch in Different Muscles

A

Enzyme variations, myofibril metabolism, ATP hydrolysis, pathway used for ATP production

58
Q

Unfused Tetanus

A

Increased rate of stimulation (20-30 per second), decreased relaxation time: produces a wavering yet sustained contraction, 3-4x greater strength than single twitch, sufficient for everyday tasks

59
Q

Fused Tetanus

A

Increased rate of stimulation (8-100x per second), no detectable relaxation time: not all Ca+2 returns to SR, allows increased strength of contraction, produces a smooth sustained contraction, typically used when maximum force required

60
Q

Muscle Fatigue

A

Often occurs due to prolonged activities, ATP production cannot keep up with ATP usage, gradual decreases in ability of muscles to generate force/contractions, protective mechanisms to prevent injury, reversed with rest

61
Q

Methods of ATP Production: Conversion of Creatine-Phosphate

A

Stored ATP: 4-6 sec of activity, at rest muscle cells produce more ATP than needed for resting metabolism, excess ATP converted to creatine-phosphate, 3-6x more CP stored than ATP, CP only found in muscle fibers, replenished during inactivity from excess ATP produced, no O2 required for CP conversion to ATP, 1 CP + ADP -> 1 ATP + creatine

62
Q

Methods of ATP Production: Anaerobic Mechanisms

A

Glycolysis and lactic acid formation, occurs in cytoplasm, glucose -> 2 pyruvate + 2 ATP (net gain), insufficient O2 -> pyruvate converted into lactic acid, requires lots of glucose to produce sufficient amounts of ATP (1 glucose -> 2 ATP)

63
Q

Methods of ATP Production: Aerobic Cellular Respiration

A

Occurs in mitochondria when O2 is present, converts glucose, fatty acids, and amino acids into ATP (1 glucose -> 32 ATP, 1 fatty acid -> 100 ATP), slower process, requires constant supply of O2 and nutrients

64
Q

Oxygen Debt

A

Refers to temporary oxygen shortage in body tissues after exercise, increased intake of O2 required; Restores homeostasis, converts lactic acid back to glycogen in liver, resynthesizes Cp and ATP in muscle fibers, replaces O2 removed from hemoglobin

65
Q

Cardiac Muscle

A

CT sheets lie between layers of cardiac muscle fibers, contains blood vessels, nerves, and heart conduction system fibers; intercalated discs: desmosomes hold adjacent cardiac muscle fibers together, gap junctions: TM connexons -> form passageways between adjacent cells which enables cardiac muscle APs to spread quickly

66
Q

Cardiac Muscle: Response to APs

A

Cardiac muscle remains contracted 10-15x longer than skeletal muscle due to increased levels of Ca+2, due to prolonged Ca+2 into sarcoplasm

67
Q

Cardiac Muscle: Stimulation by Autorhythmic Cardiac Muscle Fibers

A

Cardiac muscle contracts when stimulated by its own authorhythmic fibers

68
Q

Smooth Muscle

A

Thick and thin filaments longer in length, ratio of thick and thin filaments differ, arranged diagonally and not longitudinally, no striations

69
Q

Smooth Muscle: Dense Bodies and Intermediate Filaments

A

Bundles of intermediate filaments attach to dense bodies within sarcoplasm and sarcolemma, dense bodies attach to thin filaments

70
Q

Smooth Muscle: Response to AP

A

Sliding of thick and thin filaments during contraction pulls on dense bodies and intermediate filaments, muscle fibers shorten and rotating as a corkscrew into a helix and untwists when in relaxes

71
Q

ANS and Other Factors

A

Conduction of nerve impulses, stretching, hormones, changes in pH and O2/CO2 levels, temperature

72
Q

Regeneration of Skeletal Muscle

A

Satellite Cells: divide slowly and fuse with existing fibers to assist in muscle growth and repair of damaged fibers, not enough to compensate for significant damage or degeneration, fibrosis - replacement of muscle fibers with fibrous scar tissue

73
Q

Hypertrophy and Hyperplasia

A
74
Q

Myasthenia Gravis

A
75
Q

Duchenne Muscular Dystrophy

A
76
Q

Myotonic Dystrophy

A
77
Q

Myofascial Pain Syndrome

A
78
Q

Fibromyalgia

A
79
Q

Muscle Strain

A
80
Q

Disuse Atrophy

A
81
Q

Tetanus

A
82
Q

Aerobic Training

A
83
Q

Strength/Resistance Training

A
84
Q

Interval Training

A
85
Q

Anabolic Steroids

A

Anatomy and Physiology (29 decks)

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