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BIOL 1190 > Chapter 10: Muscular Tissue > Flashcards

Chapter 10: Muscular Tissue Flashcards

1
Q

Three types of muscular tissue

A
  • skeletal
  • cardiac
  • smooth (visceral)
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2
Q

Functions of muscular tissue

A
  • producing body movements
  • stabilizing body positions
  • storing and mobilizing substance within the body
  • generating heat ex; “shivering”
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3
Q

Properties of muscular tissue

A
  • electrical excitability (when its “on” muscle shorter, when its “off” it relaxes and lengthens
  • contractility (when you contract biceps; triceps relax and vice versa)
  • extensibility
  • elasticity
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4
Q

How are muscles formed?

A

fusion of myoblasts into skeletal muscle

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5
Q

Muscle cell nucleus and length

A
  • muscles cells are very long and therefore are multinucleated.
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6
Q

Myofibrils

A
  • protein filaments that run parallel along the length of the muscle cell
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7
Q

Muscle connects to

A

bones by tendons

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8
Q

Muscle fascicle

A

muscle cells are arranged in bundles called muscle fascicle

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9
Q

Endomysium

A

layer of connective tissue that wraps around the sarcolemma (membrane that surrounds muscle cells)

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10
Q

Perimysium

A

surrounds each muscle fascicle

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11
Q

Epymysium

A

a whole muscle is surrounded by epimysium

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12
Q

The more muscle cells a person has…

A

the more strength the person has (myofibrils in specific)

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13
Q

Function of T-tubules

A

they fold inward to allow membrane proteins to get close to the sarcoplasmic reticulum

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14
Q

Glycogen granules in muscle cells

A
  • muscle cells carry their own energy all the time
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15
Q

Myoglobin

A

protein found only in muscle cells and caries oxygen

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16
Q

Dystrophin

A
  • accessory protein
  • functions to anchor the length of the cells
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17
Q

Muscular hypertrophy

A
  • enlargement of EXISTING muscle fibers
  • due to increased production of myofibrils, mitochondria, sarcoplasmic reticulum, and other organelles
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18
Q

Muscular atrophy

A

decrease in size of muscle fibers due to loss of myofibrils
- occurs as a result of aging or disuse

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19
Q

What causes striations in muscle cells

A
  • there are regions in skeletal fibers where it looks darker and lighter through microscope because i band has only thin filaments whereas A band has thick filaments
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20
Q

Z discs

A

Narrow, plate-shaped regions of dense material that separate one sarcomere from the next

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21
Q

A band

A

dark, muddle part of sarcomere that extends entire length of thick filaments and includes those parts of thin filaments that overlap thick filaments

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22
Q

I (i) band

A

lighter, less dense area of sarcomere that contains remainder of thin filaments but no thick filaments.
- a Z disc passes through the center of each i band

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23
Q

H band

A

narrow region in center of each A band that contains thick filaments but no thin filaments

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24
Q

M line

A

region in center of H band that contains proteins that hold thick filaments together at the center of the sarcomere

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25
Q

As a sarcomere shortens…

A

the zone of overlap increases and i band disappears

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26
Q

Thick filaments

A

myosin

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27
Q

Thin filaments

A

actin
- connected to Z discs and myosin

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28
Q

Contraction simple explained

A

myosin pulls actin filaments therefore, pulling z discs causing sarcomere and entire myofibril to shorten (contract)

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29
Q

What are contractile proteins

A

myosin and actin

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30
Q

Myosin descrption

A

contractile protein that makes up thick filament; molecule consists of a tail and two myosin heads, which bind to myosin-binding sites on actin molecules of thin filament during muscle contraction

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31
Q

Actin description

A

Contractile protein that is the main component of thin filament; each actin molecule has a myosin-binding site where myosin head of thick filament binds during muscle contraction

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32
Q

Regulatory proteins in myofibrils

A
  • Tropomyosin
  • Troponin
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33
Q

Tropomyosin description

A

regulatory protein that is a component of thin filament; when skeletal muscle fiber is relaxed, tropomyosin covers myosin-binding sites on actin molecules, thereby preventing myosin from binding to actin

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34
Q

Troponin description

A

Regulatory protein that is a component of thin filament; when calcium ions (Ca+) bind to troponin, it changes shape; this conformational change moves tropomyosin away from myosin-binding sites on actin molecules, and muscle contraction subsequently begins as myosin binds to actin

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35
Q

Structural proteins of myfibrils

A
  • Titin
  • a (alpha) actinin
  • Myomesin
  • Nebulin
  • Dystrophin
36
Q

Titin (structural protein)

A

structural protein that connects Z discs to M line of sarcomere, thereby helping to stabilize thick filament position; can stretch and then spring back unharmed, and thus accounts for much of the elasticity and extensibility of myofibrils

(holds sarcomere structure)

37
Q

a Actinin (alpha)

A

Structural protein of Z discs that attaches to actin molecules of thin filaments and to titin molecules

38
Q

Dystrophin

A
  • links edge of sarcomere to sarcolemma
  • muscular dystrophy lacks dystrophin
39
Q

The contraction cycle; step 0

A
  • before you contract a sarcomere you must release calcium to each myofibril
40
Q

The contraction cycle; step 1

A
  • myosin head hydrolyzes ATP and becomes energized and oriented
  • myosin head winds back (changes orientation) using ATP hydrolysis
41
Q

The contraction cycle; step 2

A
  • myosin head binds to actin, forming a cross bridge (connection between myosin + actin)
  • phosphate leaves and myosin head goes back and pulls actin back with it
42
Q

The contraction cycle: step 3

A
  • myosin head pivots, pulling the thin filament past the thick filament toward center of the sarcomere (power stroke)
  • ADP leaves
43
Q

The contraction cycle; step 4

A
  • as myosin head binds ATP, the cross bridge detaches from actin
    and the cycle repeats
44
Q

When the contraction cycle repeats the myosin grabs..

A

a new position making the sarcomere shorter until it can’t contract anymore

45
Q

ATP hydrolysis?

A

when ATP turns into ADP

46
Q

What happens when there is no ATP you cannot release the cross bridge

A

the muscle stays contracted (occurs when a person dies)
- after 24 hours the body starts to relax because the proteins get broken down.

47
Q

Rigor mortis (what happens)

A

state of rigidity in muscles that occurs after 3-4 hours after death
- calcium leaks out of sarcoplasmic reticulum
- myosin heads to bind to actin forming cross-bridge
- cross bridge can’t detach since ATP synthesis has ceased

48
Q

When does rigor mortis disappear

A

disappears after 24 hours as proteolytic enzymes digest the cross-bridge

49
Q

Length-tension relationship

A
  • the force of a muscle contraction depends on the length of the sarcomeres in a muscle prior to contraction
50
Q

What does neuromuscular junction or neuromuscular synapse produce

A

produces a muscle action potential

51
Q

Steps of NMJ or NMS

A
  1. voltage-gated calcium channels in a neurons synaptic end bulb open
  2. Ach binds to Ach receptor
  3. Muscle depolarization and calcium releases from the sarcoplasmic reticulum
  4. Ach gets broken down by acetylcholinesterase
52
Q

Step 1 in NMJ or NMS

A

1: voltage-gated calcium channels in a neuron’s synaptic end bulb open
- resulting in calcium influx
- this causes exocytosis of the neurotransmitter acetylcholine (Ach) into synaptic cleft

53
Q

What does acetylcholine do

A

turns on muscle cells

54
Q

Step 2 in NMJ or NMS

A

Ach binds to Ach receptor on the motor endplate, which causes an influx of NA+ into muscle (action potential)
- sodium rushes from outside of muscle cell into the cell. Eventually you reach action potential

55
Q

Step 3 in NMJ or NMS

A

The muscle is now depolarized and it results in Ca to be released from the sarcoplasmic reticulum

56
Q

Step 4 in NMJ or NMS

A

Ach gets broken down by acetylcholinesterase
- should be able to turn off the cell and not be contracted all the time

57
Q

What does acetylcholinesterase do

A

breaks down Ach and it prevents prolonged muscle contraction

58
Q

Motor neuron to skeletal muscle cell ratio

A

1 motor neuron can connect to several skeletal muscle cells

59
Q

Only contraction uses..

A

ATP not relaxing because relaxing is passive

60
Q

3 ways that muscles produce ATP

A
  • Creatine phosphate (least)
  • Anaerobic glycolysis (middle)
  • Aerobic respiration (most)
61
Q

Creatine phosphate explained

A
  • happens during periods of rest
  • Creatine kinase catalyzes the transfer of a phosphate group from creatine phosphate to ADP to rapidly yield ATP
  • myosin is always hydrolyzing ATP
62
Q

Anaerobic glycolysis explained

A
  • when creatine phosphate stores are depleted, glucose is converted into pyruvic acid to generate ATP
  • glycolysis produces 2 ATP by pushing pyruvate away from mitochondria through the lactate dehydrogenase reaction
63
Q

Aerobic respiration explained

A
  • under aerobic conditions, pyruvic acid can enter the mitochondria and undergo a series of oxygen-requiring reactions to generate large amounts of ATP
  • 4 molecules of ATP are produced per glucose
64
Q

Central fatigue

A
  • occurs due to changes in the central nervous system (brain) and generally results in cessation of exercise
  • protective mechanism to prevent the overuse of muscles
65
Q

Muscle fatigue

A
  • inability to maintain force of contraction after prolonged activity
66
Q

Reason for onset of muscle fatigue

A
  • inadequate release of Ca+ from the sarcoplasmic reticulum
  • depletion of creatine phosphate, oxygen and nutrients
  • build up of lactic acid and ADP
  • insufficient release of acetylcholine at the neuromuscular junction
67
Q

Why do you continue to breathe heavily for a period of time after stopping exercise

A

to allow your body to recover

68
Q

The extra oxygen when breathing heavily after exercise goes toward

A
  • replenishing creatine phosphate stores
  • converting lactate into pyruvic acid (pyruvic acid is used for ATP production via aerobic respiration)
  • reloading O2 onto myoglobin
69
Q

Other reasons the body needs extra oxygen after exercise

A
  • increased rate of chemical reactions that is accompanied by elevated body temperature
  • increased consumption of oxygen from the heart and respiratory muscle tissues
  • tissue repair processes are occurring at an increased pace.
70
Q

The strength of a muscle contraction depends on

A

how many motor units are activated

71
Q

What does a motor unit consist of

A

consists of a somatic motor neuron and the muscle fiber it innervates
- activating only few motor units will generally result in a weak contraction, activating many will generally result in a strong muscle contraction

72
Q

Wave summation

A

occurs when a second action potential triggers muscle contractions before the first contraction has finished and the skeletal muscle fiber has relaxed
- the second stimulus occurs after the refractory period but before the skeletal muscle has relaxed

73
Q

Unfused tetanus

A

when the muscle fibers do not completely relax before the next stimulus because they are being stimulated at a fast rate

74
Q

Fused tetanus

A

no relaxation period between muscle contractions

75
Q

Motor unit recruitment

A
  • weakest are recruited first, followed by stronger motor units
  • motor units contract alternately to sustain contractions for longer periods of time (they do not all relax at the same time)
76
Q

Muscle tone; even when at rest, a skeletal muscle exhibits

A

a small amount of taughtness or tension, called muscle tone

77
Q

What is muscle tone established by

A

neurons in the brain and spinal cord that excite the muscle’s motor neurons

78
Q

What happens when a motor neuron thats serving skeletal muscle gets damaged or cut

A

the muscle becomes flaccid

79
Q

Isotonic contractions

A

tension is constant while muscle length changes
- concentric: muscle length shortens
- eccentric: muscle length lengthens

80
Q

Isometric contractions

A
  • does not change length of the muscle
  • tension generated is not enough to exceed the resistance so the muscle length does not change
    (generates just enough to keep balance of objects)
81
Q

Intercalated discs function in cardiac muscle

A
  • contain desmosomes that hold the cardiac muscle fibers together
  • contain gap junctions that allow muscle action potentials to spread from one cardiac muscle fiber to another
82
Q

Cardiac muscle cells have more…

A

mitochondria and their contractions last 10-15 times longer than skeletal muscle contractions

83
Q

What type of ATP does cardiac muscle use

A

uses aerobic respiration

84
Q

Somatic motor neurons connect to

A

skeletal muscle to provide voluntary movements

85
Q

Autonomic motor neurons connect to

A

smooth muscle and allows involuntary movements

86
Q

Smooth muscle contractions

A

start more slowly and last longer than skeletal and cardiac muscle contractions

87
Q

Smooth muscle can shorten and stretch to a greater extent than

A

skeletal and cardiac muscle

BIOL 1190 (16 decks)

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