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Anatomy and Physiology I > Chapter 9: Muscles and Muscle Tissue > Flashcards

Chapter 9: Muscles and Muscle Tissue Flashcards

1
Q

Where is skeletal muscle tissue found?

A

packaged into skeletal muscles

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2
Q

What are skeletal muscles?

A

Organs attached to bones and skin

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3
Q

Skeletal muscle fibers: description

A

longest of all muscles and have striations (stripes)

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4
Q

Other name for skeletal muscle

A

voluntary muscle: can be consciously controlled

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5
Q

Skeletal muscle characteristics

A

contract rapidly, tire easily, powerful

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6
Q

Skeletal muscle key words

A

skeletal, striated, voluntary

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7
Q

Where is smooth muscle tissue found?

A

in wall of hollow organs
ex. stomach, urinary bladder, airways

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8
Q

Smooth muscle appearance

A

not striated

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9
Q

Smooth muscle characteristics

A

involuntary: cannot be controlled consciously

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10
Q

Smooth muscle key words

A

visceral, nonstriated, involuntary

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11
Q

Where is cardiac muscle tissue found

A

only in heart (makes up bulk of heart)

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12
Q

Cardiac muscle appearance

A

striated (striped appearance)

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13
Q

Cardiac muscle characteristics

A

involuntary: cannot be controlled consciously
contracts at steady rate due to heart’s own pacemaker, but nervous system can increase rate

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14
Q

Cardiac muscle key words

A

cardiac, striated, involuntary

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15
Q

Sarcolemma: what is it

A

muscle fiber plasma membrane

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16
Q

Sarcoplasmic Reticulum (SR): what is it

A

network of endoplasmic reticulum tubules surrounding each myofibril

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17
Q

Sarcoplasmic Reticulum (SR): what is its purpose

A

regulation of intracellular calcium ion levels (Ca+2)
stores and releases Ca+2: essential for muscle contractions

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18
Q

Sarcoplasm: what is it

A

muscle fiber cytoplasms

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19
Q

Sarcoplasm: important items in it

A
  • glycosomes: store glucose as glycogen for muscle fiber to make ATP
  • myoglobin: oxygen-storing protein, provides oxygen to make ATP
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20
Q

Myofilaments: what are they

A

feature of myofibrils (densely packed, rodlike elements)

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21
Q

What are myofilaments composed of

A

proteins’ actin (thin filaments) and myosin (thick filaments), found within the sarcomere

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22
Q

Sarcomere: what is it

A
  • feature of myofibrils
  • smallest contractile unit (functional unit) of muscle fiber
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23
Q

Where do individual sarcomeres align?

A

end to end along myofibril, like boxcars of a train

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24
Q

4 major steps in skeletal muscle contraction

A
  1. Events at neuromuscular junction
  2. Muscle fiber excitation
  3. Excitation-contraction coupling
  4. Cross-bridge cycling
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25
Q
  1. Events at neuromuscular junction
A

motor neuron releases acetylcholine which stimulates skeletal muscle fiber, causing a depolarization called end plate potential (EPP)

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26
Q
  1. Muscle fiber excitation
A

EPP triggers an AP that travels across sarcolemma of muscle fiber

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27
Q
  1. Excitation-contraction coupling
A

AP in sarcolemma causes release of calcium ions from SR, calcium binds troponin which moves tropomyosin and exposes myosin- binding sites for binding with actin

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28
Q
  1. Cross-bridge cycling
A

actin-myosin cross-bridge cycling results in muscle contraction

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29
Q

Key components of step 4 in skeletal muscle contraction

A
  1. “Grab rope” = cross bridge formation
  2. “Pull” = powerstroke
  3. “Let go” = cross bridge detachment
  4. “Reach forward” = cocking myosin head
30
Q

“Grab rope”

A
  • cross bridge formation
  • energized myosin head attaches to an actin myofilament, forming a cross bridge (attached high energy state)
31
Q

“Pull”

A
  • Power stroke
  • ADP and P released and myosin head pivots and bends, changing to its bent low-energy state.
  • AS a results it pulls actin filament towards the M line (middle)
32
Q

“Let go”

A
  • cross bridge detachment
  • after ATP attaches to myosin, link between myosin and actin weakens, and myosin head detaches
33
Q

“Reach forward”

A
  • cocking myosin head
  • as ATP is hydrolyzed (broken down) to ADP and Phosphate, myosin head returns to its prestrike high -energy, or cocked position
34
Q

Neurotransmitter released in skeletal muscle contraction

A

AP in neuron triggers release of neurotransmitter acetylcholine (ACh) which tells skeletal muscles to contract

35
Q

Rigor Mortis: what is it and when does it occur

A
  • 3-4 hours after death, muscles begin to stiffen; peak rigidity about 12 hours postmortem
36
Q

Rigor Mortis: why does it occur

A
  • in dying muscle cells, intracellular calcium levels increase resulting in cross bridge formation
  • ATP needed for cross bridge detachment; upon death ATP no longer produced
37
Q

Rigor Mortis; how does it occur

A

myosin head stays bound to actin causing constant state of contraction

38
Q

What causes rigor mortis to stop

A

muscles stay contracted until muscle proteins break down, causing cross bridge to break

39
Q

What is recruitment

A

process of activating more motor units to increase strength of muscle contraction (faster and more prolonged)

40
Q

Another name for recruitment

A

multiple unit summation

41
Q

How does recruitment work

A

works on size principle: motor units of small muscle fibers recruited first; as stimulus intensity increases, motor units innervating increasingly larger muscle fibers get recruited

42
Q

Muscles are never 100% relaxed, what is this phenomenon commonly known as

A

muscle tone: all muscles are constantly in a slightly contracted state

43
Q

Why does this occur? (muscles never fully relaxed)

A

due to spinal reflexes (involuntary response to stimuli mediated by spinal cord): stimuli for muscle tone comes from stretch receptors in muscles

44
Q

Purpose of muscles never relaxed phenomenon

A
  • keep muscles firm, healthy, and ready to respond to stimuli
  • does not result in active movement of body
45
Q

What molecules are involved in direct phosphorylation?

A
  • creatine phosphate (CP) + ADP
46
Q

Direct phosphorylation equation (result)

A
  • CP + ADP –> ATP
    Products: 1 ATP per CP, creatine
  • creatine phosphate in muscle fibers donates phosphate to make ATP from ADP
47
Q

Direct phosphorylation: energy source

A

Creatine phosphate

48
Q

Direct phosphorylation: oxygen use

A

none

49
Q

Direct phosphorylation: duration of energy provided

A

15 seconds

50
Q

What molecules are involved in anaerobic pathway?

A
  • Glycolysis ( energy source- glucose- broken down via glycolysis to make ATP)
  • lactic acid formation
51
Q

Anaerobic pathway: oxygen use

A
  • none
  • in absence of O2 (anaerobic) lactic acid is the end product
  • glycolysis does not require oxygen, making it part of the anaerobic pathway
52
Q

Anaerobic pathway: products

A

2 ATP per glucose, lactic acid

53
Q

Anaerobic pathway: duration of energy provided

A

30-40 seconds or slightly more

54
Q

Aerobic pathway: energy source

A
  • glucose, pyruvic acid, free fatty acids from adipose tissue, amino acids from protein catabolism
55
Q

Aerobic pathway: oxygen use

A

required

56
Q

Aerobic pathway: products

A

32 ATP per glucose, CO2, H2O

57
Q

Aerobic pathway: duration of energy provided

A

hours

58
Q

Aerobic pathway vs others

A
  • further breakdown of glucose following glycolysis
  • makes significantly more ATP, but required O2
59
Q

Skeletal vs. Smooth muscle: cell shape

A

Smooth muscle fiber: spindle-shaped, thin and short
Skeletal muscle fiber: cylindrical, wider, longer

60
Q

Skeletal vs. Smooth muscle: sources of calcium for muscle contraction

A

Smooth muscle: extracellular fluid from SR
Skeletal muscle: Sarcoplasmic Reticulum (SR)

61
Q

Organization/Orientation of muscle tissue: Smooth muscle

A
  • unitary muscle in walls of hollow organs, multiunit muscle in intrinsic eye muscles, airways, large arteries
  • lacks connective tissue sheaths, contains endomysium only
  • arranged in sheets or layers; typically found in walls of hollow organs, with 2 primary layers: longitudinal and circular
62
Q

Smooth muscle tissue: longitudinal layer

A

fibers run parallel to long axis of organ; contraction causes organ to shorten

63
Q

Smooth muscle tissue: circular layer

A

fibers run around circumference of organ; contraction causes lumen (inside cavity) of organ to constrict

64
Q

Organization/orientation of skeletal muscle tissue

A
  • attached to bones or (some facial muscles) to skin; composed of long fibers organized into bundles; myofibers (contain several myofibrils)
  • each skeletal muscle surrounded by 3 layers of connective tissue: epimysium, perimysium, and endomysium
65
Q

Mechanism of muscle contraction (filaments and cross-bridge cycling): Smooth muscle

A

involves actin and myosin sliding filaments and cross-bridge cycling in a slower, more sustained manner, smooth muscle filaments are arranged in a crisscross pattern allowing contraction in multiple directions

66
Q

Mechanism of muscle contraction (filaments and cross-bridge cycling): Skeletal muscle

A

uses sliding filament model where actin and myosin filaments form cross-bridges and slide past each other
* myosin heads attach to actin binding sites, creating contraction force through ATP-fueled cycles

67
Q

Calcium ion involvement: smooth muscle

A
  • Ca2+ comes from both the SR and extracellular sources with influx occurring through caveolae and voltage-gated channels on the sarcolemma
  • contraction can be stimulated by mechanical, hormonal, or neural inputs
68
Q

Calcium ion involvement: skeletal muscle

A

Ca2+ released from the SR in response to an AP initiated by ACh binding at neuromuscular junction

69
Q

Regulatory proteins: smooth muscle

A
  • no troponin complex; instead, protein called calmodulin binds calcium ion; calcium ion binds to calmodulin not troponin
  • activated calmodulin leads to cascade of events that results in myosin activation and cross-bridge formation
70
Q

Regulatory proteins: skeletal muscle

A

tropomyosin and troponin: regulatory proteins bound to actin; block actin binding site until muscle contraction is stimulated

Anatomy and Physiology I (7 decks)

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