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Anatomy & Physiology > Chapter9 > Flashcards

Chapter9 Flashcards

1
Q

types of muscle tissue

A
  1. skeletal
  2. cardiac
  3. smooth
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2
Q
  • Attached to bones and skin
  • multinucleated, long, cylindrical cells
  • Striated
  • voluntary (i.e., conscious control)
A

skeletal muscle tissue

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3
Q
  • Heart muscle
  • Striated; intercalated disks (gap_ junctions)
  • mononucleated_, branched cells
  • Involuntary (i.e., conscious_ control)
A

cardiac muscle tissue

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4
Q
  • In the walls of hollow organs, e.g., stomach , urinary bladder, and airways
  • oblong nucleus, Spindle-shaped cells
  • Not striated
  • Involuntary (i.e., unconscious control)
A

smooth muscle tissue

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5
Q
  • excitability (responsiveness or irritability): ability to receive and respond to stimuli
  • contractibility : ability to shorten when stimulated
  • extensibility : ability to be stretched
  • elasticity : ability to recoil to resting length
A

special characteristics of muscle tissue

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6
Q
  1. Movement of bones or fluids (e.g., GI tract, blood)
  2. maintaining posture and body position
  3. Stabilizing joints
  4. Heat generation (especially skeletal muscle)
A

muscle functions

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7
Q

Each muscle is served by one artery , one nerve , and one or more veins

A

skeletal muscle

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8
Q
  • epimysium : dense regular connective tissue surrounding entire muscle
  • perimysium : fibrous connective tissue surrounding fascicles (groups of muscle fibers)
  • endomysium : fine areolar connective tissue surrounding each muscle fiber
A

connective tissue sheaths of skeletal muscle

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9
Q

fibrous connective tissue surrounding fascicles (groups of muscle fibers)

A

perimysium (connective tissue sheath in skeletal muscle)

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10
Q

dense regular connective tissue surrounding entire muscle

A

epimysium (connective sheath of skeletal muscle)

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11
Q

fine areolar connective tissue surrounding each muscle fiber

A

endomysium (connective tissue sheath of skeletal muscle)

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12
Q
  • ______—epimysium of muscle is fused to the periosteum of bone or perichondrium__ of cartilage
  • ______—connective tissue wrappings extend beyond the muscle_ as a ropelike tendon or sheetlike aponeurosis
A

directly/ indirectly

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13
Q
  • cylindrical_cell 10 to 100um in diameter, up to 30 cm long
  • Many mitochondria [to generate force in skeletal muscle]
  • Multiple peripheral nuclei [to generate myofibrils to develop proteins]
  • Glycosomes for glycogen storage, myoglobin for O2 storage
  • Also contain myofibrils, sarcoplasmic reticulum, and T tubules
A

microscopic anatomy of a skeletal muscle fiber

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14
Q
  • contractile organelle of muscle fiber
  • densely packed, rodlike elements
  • ~80% of cell volume
  • Exhibit striations: perfectly aligned repeating series of dark A bands and light I bands
A

myofibrils

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15
Q
  • Network of smooth endoplasmic reticulum surrounding each myofibril
  • Pairs of terminal cisternae form perpendicular cross channels
  • Functions in the regulation of intracellular Ca2+ levels
A

sarcoplasmic reticulum

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16
Q
  • Continuous with the sarcolemma
  • penetrate the cell’s interior at each A band–I band junction
  • Associate with the paired terminal cisternae to form triads that encircle each sarcomere
A

T(transverse) tubules

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17
Q
  • _ _____ conduct impulses deep into muscle fiber
  • Integral proteins protrude into the intermembrane space from T tubule and SR cisternae membranes
A

t tubules

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18
Q

t tubule proteins : ______ ______

A

voltage sensors

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19
Q

gated channels that regulate Ca2+ release from the cisternae

A

SR foot proteins

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20
Q

Shortening occurs when tension generated by cross bridges of the two contractile proteins: ____ and ____

A

actin and myosin

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21
Q
  • Composed of the protein myosin
  • Myosin heads contain:
    • 2 smaller, light polypeptide chains form cross bridges
    • Binding sites for actin of thin filaments
    • Binding sites for ATP
    • ATPase enzymes
A

ultrastructure of THICK filament

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22
Q
  • Composed of the protein_ actin
  • Composed of two regulatory proteins:
    • Troponin (bind Ca+2)
    • tropomyosin (cover crossbridge binding site
A

ultrastructure of THIN filament

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23
Q
  • Smallest contractile unit (functional unit) of a muscle fiber
  • The region of a myofibril_ between two successive Z discs
  • Composed of thick and thin myofilaments made of contractile proteins
A

sacromere

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24
Q
  • thick filaments: run the entire length of an A band
  • Thin filaments : run the length of the I band and partway into the A band
  • Z disc: coin-shaped sheet of proteins that anchors the thin filaments and connects myofibrils to one another
  • M line: line of protein myomesin_ that holds adjacent thick filaments together (structural protein)
A

features of sarcomere

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25
Q

In what state does thin and thick filaments overlap only slightly

A

relaxed state

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26
Q

during ______, myosin heads bind to actin , detach , and bind again, to propel the thin filaments toward the M line

A

contraction

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27
Q

As _ zones shorten and disappear, sarcomeres shorten, muscle cells shorten, and the whole muscle shortens

A

H

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28
Q
  1. activation : neural stimulation at aneuromuscular junction
  2. Excitation-contraction coupling:
  • generation and propagation of an action potential along the sarcolemma
  • final trigger: a brief rise in intracellular Ca2+ levels
A

Requirements for Skeletal Muscle Contraction

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29
Q
  • skeletal muscles are stimulated by somatic motor neurons
  • Axons of _motor__ neurons _travel_ from the central __nervous_ system via nerves to skeletal muscles
  • Each axon forms several branches as it enters a muscle
  • Each _axon_ ending forms a _neuromuscular__ junction with a single muscle_ fiber
A

events at the neuromuscular junction

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30
Q
  • situated midway along the length of a muscle_fiber
  • Axon terminal and muscle fiber are separated by a gel-filled space called the synaptic cleft
  • synaptic vesicles of axon vesicles contain the neurotransmitter _acetylcholine (ACh)
  • juntional folds of the sarcolemma contain ACh
A

neurmuscular junction

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31
Q
  • nerve_ impulse arrives at axon _terminal__
  • ACh is released and binds with _receptors__ on the sarcolemma_
  • Electrical events lead to the generation of an action potential
A

events at neuromuscular junction

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32
Q
  • ACh effects are quickly rteerminated_ by the enzyme acetylcholinesterase_
  • Prevents continued muscle fiber contraction_ in the absence of additional stiumulation
A

destruction of acetylcholine

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33
Q

the 2 light polypeptide chains in a myosin molecules head link the thick and thin filaments together, forming __, and swivel around their point of attachment during contraction

A

cross bridges

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34
Q

Sequence of events_ by which _transmission__ of an AP along the sarcolemma leads to sliding of the myofilaments

A

Excitation-Contraction (E-C) Coupling

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35
Q

Latent period:
time__ when E-C coupling events occur
Time between AP initiation and the beginning of contraction

A

excitation contraction coupling LATENT PERIOD

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36
Q
  • Continues as long as the Ca2+ signal_ and adequate _ATP_ are present
  • cross_ bridge formation — high-energy myosin_ head attaches to thin filament
  • Power stroke — _mysosin_ head pivots and pulls thin filament toward M line
A

cross bridge cycle

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37
Q

ATP attaches to myosin head and the cross bridge detaches

A

cross bridge detachment

38
Q

energy from the hydrolysis of ATP cocks the myosin head into the high energy state

A

cocking of the myosin head

39
Q
  • no shortening; muscle tension increases but does not exceed the load
  • once sufficient tension develops , tension remains relatively constant through rest of contractile period
A

isometric contraction

40
Q

muscle shortens because muscle tension exceeds the load

A

isotonic contraction

41
Q
  1. Same principles apply to contraction of a single fiber and a whole muscle
  2. contraction_produces tension , the force exerted on the load or object to be moved
  3. Contraction does not always shorten a muscle:
  • isometric contraction: no shortening; muscle tension increases but does not exceed the load
  • isotonic contraction: muscle shortens because muscle tension exceeds the load

4.Force and duration of contraction vary in response to stimuli of different frequencies and intensities

A

principles of muscle mechanics

42
Q

a motor neuron and all (four to several hundred) muscle fibers it supplies

A

motor unit : the nerve muscle functional unit

43
Q

____ motor units in muscles that control fine movements (fingers , eyes)

A

small

44
Q

______ motor units in large weight-bearing muscles (thighs, hips)

A

large

45
Q
  • Muscle fibers from a ___ ___are spread throughout the muscle so that a single motor unit causes weak contraction of entire muscle
  • Motor units in a muscle usually contract asynchronously ; helps prevent fatigue
A

motor unit

46
Q

Response of a muscle to a single, brief threshold stimulus
simplest contraction observable in the lab (recorded as a myogram)

A

muscle twitch

47
Q
  • Latent period: events of excitation-contraction coupling
  • Period of contraction: cross bridge formation; tension increases
  • Period of relaxation : Ca2+ reentry into the SR; tension declines to zero
A

3 phases of a twitch

48
Q

Different strength and duration of twitches are due to

A

variations in metabolic properties and enzymes btw muscles

49
Q
  • Variations in the degree of muscle contraction
  • Required for proper control of skeletal movement

Responses are graded by:

  1. Changing the frequency of stimulation
  2. Changing the strength of the stimulus
A

graded muscle responses

50
Q

a single stimulus results in a single contractile response- muscle twitch

A

response to change in stimulus frequency

51
Q

Ca2+ release stimulates further contraction /further increase in stimulus frequency

A

temporal (wave) summation/ unfused (incomplete) tetanus

52
Q

motor neuron action potential, neurotransmitter release, muscle cell action potential, release of calcium ions from SR, ATP-driven power stroke, sliding of myofilaments

A

sequence of events for muscle contractions

53
Q

funtional unit of a skeletal muscle is called

A

sarcomere

54
Q

contractile units of skeletal muscle

A

myofibrils

55
Q

surrounds the individual muscle cell?

A

endomysium

56
Q

composed of myosin

A

thick filaments

57
Q

During muscle contraction, myosin cross bridges attach to which active sites

A

actin filaments

58
Q

What produces the striations of a skeletal muscle cell?

A

arrangement of myofilaments

59
Q

The major function of the sarcoplasmic reticulum in muscle contraction is to ________.

A

regulate intracellular calcium concentration

60
Q

What structure in skeletal muscle cells functions in calcium storage?

A

sarcoplasmic reticulum

61
Q

Which muscle cells have the greatest ability to regenerate?

A

smooth

62
Q

What is the role of tropomyosin in skeletal muscles?

A

Tropomyosin serves as a contraction inhibitor by blocking the myosin binding sites on the actin molecules.

63
Q

When a muscle fiber _____, the I bands diminish in size, the H zones disappear, and the A bands move closer together but do not diminish in length.

A

contracts

64
Q

The effect of a ______on the muscle cell membrane is to modify its ion permeability properties temporarily.

A

neurotransmitter

65
Q

An increase in the calcium ion level in the sarcoplasm starts the sliding of the thin filaments. When the level of calcium ions declines, ___ ___

A

sliding stops

66
Q

stimulus stength at which the first observable muscle contraction occurs

A

threshold stimulus

67
Q

contraction force is precisely controlled by _______ , which brings more and more muscle fibers into action

A

recruitment (multiple motor unit summation)

68
Q
  • Constant, slightly contracted_ state of all muscles
  • Due to spinal reflexes that activate groups of motor units alternately in response to input from stretch receptors in muscles
  • Keeps muscles firm, healthy, and ready to respond
A

muscle tone

69
Q

isotonic contractions are either ____ or _____

A
  • concentric contractions—the muscle shortens and does work
  • eccentric contractions—the muscle contracts as it lengthens
70
Q
  • The load is greater than the tension the muscle is able to develop
  • tension_ increases to the muscle’s capacity, but the muscle neither shortens nor lengthens
A

isometric contractions

71
Q
  • Direct phosphorylation of ADP by creatine phosphate (CP)
  • Anaerobic pathway (glycolysis )
  • aerobic respiration
A

how ATP is regenerated by

72
Q

glycolysis in cytosol, pyruvic acid, lactic acid released to blood

A

anaerobic pathway

73
Q

this pathway :

  • Produces 95% of ATP during rest and light to moderate exercise
  • Fuels: stored glycogen , then bloodborne glucose, pyruvic acid from glycolysis , and free fatty acids
A

aerobic pathway

74
Q
  • physiological inability to contract

Occurs when:

  • ionic imbalances (K+, Ca2+, Pi) interfere with E-C coupling
  • Prolonged exercise damages the SR and inteferes with Ca2+ regulation and release
  • Total lack of ATP occurs rarely, during states of continuous conraction , and causes contractures (continuous contractions )
A

muscle fatigue

75
Q
  • Extra O2 needed after exercise for:
  • Replenishment of oxygen_ reserves, glycogen stores,ATP and CP reserves, Conversion of lactic acid to pyruvic acid, glucose, and glycogen
A

oxygen deficit

76
Q

______ __ _____ is affected by:
number of muscle fibers stimulated (recruitment )
Relative size of the fibers—hypertrophy of cells increase strength

  • Frequency of stimulation —increase frequency allows time for more effective transfer of tension to noncontractile components
  • Length-tension relationship—muscles contract most strongly when muscle fibers are 80–120% of their normal resting length
A

force of contraction

77
Q

velocity and duration of contraction influenced by…

A

muscle fiber type, load, recruitment

78
Q

1.Speed of contraction : slow or fast, according to:

  • speed at which myosin ATPases split ATP
  • Pattern of electrical activity of the motor neurons

2.Metabolic pathways for ATP synthesis:

  • Oxidative fibers—use aerobic pathways
  • Glycolytic fibers—use anaerobic glycolysis
A

classification of muscle fiber according to these 2 characteristics

79
Q

aerobic (endurance ) exercise leads to increased….

A
  • muscle capillaries
  • number of mitochondria
  • myoglobin synthesis
  • results in greater endurance, strength, resistance to fatigue
80
Q

Resistance exercise (typically anaerobic) results in:

A
  • Muscle hypertrophy (due to increase in fiber size)
  • Increased mitochondria , myofilaments, glycogen stores, and connective tissue
81
Q
  • _______layer contracts; organ dilates and shortens
  • _____ layer contracts_ ; organ constricts and elongates
A

longitudinal/ circular

82
Q

_______ nerve fibers innervate smooth muscle at diffuse junctions

A

autonomic

83
Q

______ are (bulbous swellings) of nerve fibers store and release neurotransmitters

A

varicosities

84
Q
  • Ratio of thick to thin filaments (1:13) is much lower than in skeletal muscle (1:2)
  • thick filaments have heads along their entire length
  • No troponin complex; protein calmodulin binds Ca2+
  • Myofilaments are spirally arranged, causing smooth muscle to contract in a corkscrew manner
  • Dense bodies: proteins that anchor noncontractile_ intermediate filaments to sarcolemma at regular intervals
A

mylofilaments in smooth muscle

85
Q
  • Slow, synchronized contractions
  • Cells are electrically coupled by gap junctions
  • Some cells are self-excitatory (depolarize without external stimuli); act as pacemakers for sheets of muscle
  • Rate and intensity of contraction may be modified by neural and chemical stimuli
A

contraction of smooth muscle

86
Q
  • Stress-relaxation response:
    • responds to stretch only briefly, then adapts to new length
    • Retains ability to contract on demand
    • enables organs such as the stomach and bladder to temporarily store contents
  • Length and tension changes:
    • Can contract when between half and twice its resting length
A

special features of smooth muscle contraction

87
Q
  • sheets contract rhymthmically as a unit (gap junctions)
  • Often exhibit spontaneous action potentials
  • Arranged in opposing sheets and exhibit stress-relaxation response
A

single unit visceral smooth muscle

88
Q
  • located in large airways, large arteries , arrector pili muscles, and iris of eye
  • gap junctions are rare
  • Arranged in motor units
  • Graded contractions occur in response to neural stimuli
A

multiunit smooth muscle

89
Q

in excitation contraction coupling the action potential is propagted down the _ ______ causing calcium to en released from the SR into the cytosol

A

t tubules

90
Q
A

Anatomy & Physiology (19 decks)

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