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Anatomy > Muscular Tissue > Flashcards

Muscular Tissue Flashcards

1
Q

What are the characteristics of muscles?

A
  1. responsiveness (excitability)
  2. conductivity
  3. contractility
  4. extensibility
  5. elasticity
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2
Q

characteristics of muscles: to chemical signals, stretch, and electrical changes across the plasma membrane

A

responsiveness (excitability)

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3
Q

characteristics of muscles: local electrical change triggers a wave of excitation that travels along the muscle fiber

A

conductivity

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4
Q

characteristics of muscles: shortens when stimulated

A

contractility

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5
Q

characteristics of muscles: capable of being stretched between contractions

A

extensibility

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6
Q

characteristics of muscles: returns to its original resting length after being stretched

A

elasticity

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7
Q

plasma membrane of a muscle fiber

A

sarcolemma

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8
Q

cytoplasm of a muscle fiber

A

sarcoplasm

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9
Q

long protein bundles that occupy the main portion of the sarcoplasm

A

myofibrils

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10
Q

stored in abundance to provide energy with heightened exercise

A

glycogen

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11
Q

red pigment; stores oxygen needed for muscle activity

A

myoglobin

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12
Q

flattened nuclei pressed against the inside of the sarcolemma

A

multiple nuclei

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13
Q

stem cells that fuse to form each muscle fiber

A

myoblasts

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14
Q

unspecialized myoblasts remaining between the muscle fiber and endomysium
-may multiply and produce new muscle fibers to some degree

A

satellite cells

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15
Q

packed into spaces between myofibrils

A

mitochondria

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16
Q

smooth ER that forms a network around each myofibril: calcium reservoir
-calcium activates the muscle contraction process

A

sarcoplasmic reticulum (SR)

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17
Q

dilated end-sacs of SR which cross the muscle fiber from one side to the other

A

terminal cisternae

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18
Q

tubular infoldings of the sarcolemma which penetrate through the cell and emerge on the other side

A

T tubules

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19
Q

a T tubule and two terminal cisterns

A

triad

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20
Q

made of several hundred myosin molecules
-shaped like a golf club
-heads directed outward in a helical array around the bundle

A

thick filaments

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21
Q

What are thin filaments? (3)

A
  1. fibrous (F) actin
  2. tropomyosin molecules
  3. troponin molecule
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22
Q

thin filament: two intertwined strands
-string of globular (G) actin subunits each with an active site that can bind to head of myosin molecule

A

fibrous (F) actin

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23
Q

thin filament: each blocking six or seven active sites on G actin subunits

A

tropomyosin molecules

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24
Q

thin filament: small, calcium-binding protein on each tropomyosin molecule

A

troponin molecule

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25
Q

striations: dark; A stands for anisotropic
-part of A band where thick and thin filaments overlap is especially dark

A

A band

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26
Q

striations: middle of A band; thick filaments only

A

H band

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27
Q

striations: middle of H band

A

M line

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28
Q

striations: alternating lighter band; I stands for isotropic
-the way the bands reflect polarized light

A

I band

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29
Q

striations: provides anchorage for thin filaments and elastic filaments
-bisects I band

A

Z disc

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30
Q

-when sarcromeres shorten, thick and thin filaments slide past one another
-H zones and I bands get narrower
-Z lines move closer
-explains why skeletal muscles are striated and why muscles contract

A

sliding filament theory

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31
Q

segment from Z disc to Z disc
-functional contractile unit of muscle fiber

A

sarcomere

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32
Q

nerve cells whose cell bodies are in the brainstem and spinal cord that serve skeletal muscles

A

somatic motor neurons

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33
Q

their axons that lead to the skeletal muscle
-each nerve fiber branches out to a number of muscle fibers
-each muscle fiber is supplied by only one motor neuron

A

somatic motor fibers

34
Q

one nerve fiber and all the muscle fibers innervated by it

A

motor unit

35
Q

dispersed throughout the muscle
-contract in unison
-produce weak contraction over wide area
-provides ability to sustain long-term contraction as motor units take turns contracting (postural control)
-effective contraction usually requires the contraction of several motor units at once

A

muscle fibers of one motor unit

36
Q

200 muscle fibers for each motor runit

A

average motor unit

37
Q

fine degree of control
-three to six muscle fibers per neuron
-eye and hand muscles

A

small motor units

38
Q

more strength than control
-powerful contractions supplied by large motor units (ex: gastrocnemius has 1,000 muscle fibers per neuron)
-many muscle fibers per motor unit

A

large motor units

39
Q

point where a nerve fibers meets its target cell

A

synapse

40
Q

when target cell is a muscle fiber

A

Neuromuscular junction (NMJ)

41
Q

swollen end of nerve fiber
-contains synaptic vesicles filled with acetylcholine (ACh)

A

synaptic knob

42
Q

tiny gap between synaptic knob and muscle sarcolemma

A

synaptic cleft

43
Q

envelops and isolates all of the NMJ from surrounding tissue fluid

A

schwann cell

44
Q

undergo exocytosis releasing ACh into synaptic cleft

A

synaptic vesicles

45
Q

quick up-and-down voltage shift from the negative RMP to a positive value, and back to the negative value again

A

action potential

46
Q

a state of continual contraction of the muscles; possible suffocation

A

spastic paralysis

47
Q

What are the three major phases of contraction and relaxation?

A
  1. excitation
  2. excitation
  3. contraction
  4. relaxation
48
Q

phase of contraction and relaxation: the process in which nerve action potentials lead to muscle action potentials

A

excitation

49
Q

phase of contraction and relaxation: contraction coupling
-events that link the action potentials on the sarcolemma to activation of the myofilaments, thereby preparing them to contract

A

excitation

50
Q

phase of contraction and relaxation: step in which the muscle fiber develops tension and may shorten

A

contraction

51
Q

phase of contraction and relaxation: when its work is done, a muscle fiber relaxes and returns to its resting length

A

relaxation

52
Q

hardening of muscles and stiffening of body beginning 3 to 4 hours after death
-deteriorating sarcoplasmic reticulum releases Ca^+2
-deteriorating sarcolemma allows Ca^+2 to enter cytosol
-Ca^+2 activates myosin-actin cross-bridging
-muscle contracts, but cannot relax

A

rigor mortis

53
Q

T or F: Rigor mortis peaks about 12 hours after death, then diminishes over the next 48 to 60 hours

A

true

54
Q

-muscle is producing internal tension while an external resistance causes it to stay the same length or become longer
-can be a prelude to movement when tension is absorbed by elastic component of muscle
-important in postural muscle function and antagonistic muscle joint stabilization

A

isometric muscle contraction

55
Q

all muscle contraction depends on what?

A

ATP

56
Q

ATP supply depends on availability of what?

A

oxygen, organic energy sources such as glucose and fatty acids

57
Q

what are the two main pathways of ATP synthesis?

A
  1. anaerobic fermentation
  2. aerobic respiration
58
Q

-enables cells to produce ATP in the absence of oxygen
-yields little ATP and toxic lactic acid, a major factor in muscle fatigue

A

anaerobic fermentation

59
Q

-produces far more ATP
-less toxic end products (CO2 and water)
-requires a continual supply for oxygen

A

aerobic respiration

60
Q

What are the two enzyme systems that control the phosphate transfers?

A
  1. myokinase
  2. creatine kinase
61
Q

transfers Pi from one ADP to another, converting the latter to ATP

A

myokinase

62
Q

obtains Pi from a phosphate-storage molecule creatine phosphate (CP)
-fast-acting system that helps maintain the ATP level which other ATP-generating mechanisms are being activated

A

creatine kinase

63
Q

the pathway from glycogen to lactic acid

A

Glycogen-lactic acid system

64
Q

____ produces 36 ATP per glucose
-efficient means of meeting the ATP demands of prolonged exercise

A

aerobic respiration

65
Q

abundant mitochondria, myoglobin, capillaries: deep red color
-adapted for aerobic respiration and fatigue resistance
-relative long twitch lasting about 100ms
-soleus of calf and postural muscles of the back

A

slow oxidative (SO), slow-twitch, red, or type 1 fibers

66
Q

-fibers are well adapted for quick responses, but not for fatigue resistance
-rich in enzymes of phosphagen and glycogen-lactic acid systems generate lactic acid, causing fatigue
-poor in mitochondria, myoglobin, and blood capillaries which gives pale appearance

A

fast glycolytic (FG), fast-twitch, white, or type 2 fibers

67
Q

what are the three classes of muscle fibers?

A
  1. slow-twitch fibers (type 1)
  2. fast-twitch glycolytic fibers (type 2)
  3. fast-twitch fatigue-resistant fibers (type 2b)
68
Q

classes of muscles:
-always oxidative
-resistant to fatigue
-red fibers
-most myoglobin
-good blood supply

A

slow-twitch fibers (type 1)

69
Q

classes of muscles:
-white fibers (less myoglobin)
-poorer blood supply
-susceptible to fatigue

A

fast-twitch glycolytic fibers (type 2)

70
Q

classes of muscles:
-intermediate fibers
-oxidative
-intermediate amount of myoglobin
-pink to red in color

A

fast-twitch fatigue-resistant fibers (type 2b)

71
Q

What are the properties of the cardiac muscle? (5)

A
  1. Contraction with regular rhythm
  2. Muscle cells of each chamber must contract in unison
  3. Contractions must last long enough to expel blood
  4. Must work in sleep or wakefulness, without fail, and without conscious attention
  5. Must be highly resistant to fatigue
72
Q

characteristics of cardiac muscle

A

striated like skeletal muscle, by myocytes (cardiocytes) are shorter and thicker

73
Q

smooth muscle compared to skeletal muscle fibers is…

A

-shorter
-single nucleus
-elongated with tapering ends
-myofilaments randomly organized
-no striations
-lack transverse tubules
-sarcoplasmic reticula not well developed

74
Q

autoimmune disease in which antibodies attack neuromuscular junctions and bind ACh receptors together in clusters

A

Myasthenia Gravis

75
Q

inability to fixate on the same point with both eyes

A

strabismus

76
Q

Treatments for Myasthenia Gravis

A

-cholinesterase inhibitors retard breakdown of ACh allowing it to stimulate the muscle longer
-immunosuppressive agents suppress the production of antibodies that destroy ACh receptors
-Thymus removal (thymectomy) helps to dampen the overactive immune response that causes myasthenia gravis
-Plasmapheresis

77
Q

technique to remove harmful antibodies from blood plasma

A

plasmapheresis

78
Q

The presence of what causes muscle contraction?

A

Calcium

79
Q

Contraction where the muscle develops tension but does not shorten
- no movement

A

Isometric muscle contraction

80
Q

Contraction where the muscle shortens, tension remains constant
- movement upward

A

Isotonic concentric contraction

81
Q

Contraction where the muscle lengthens while maintaining tension
- movement downwards

A

Isotonic eccentric contraction

Anatomy (10 decks)

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