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Biology > Chapter 10 Muscular Tissue > Flashcards

Chapter 10 Muscular Tissue Flashcards

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0
Q

Muscular tissue and homeostasis

A

Contributes by

  • Producing movement
  • Moving substances through body
  • Producing heat to maintain body temperature
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1
Q

Study of muscles

A

Myology

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2
Q

Three types of muscle tissue

A

Skeletal
Cardiac
Smooth

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3
Q

Skeletal muscle tissue..

A

Move bones
Striated (alternating light and dark)
Mainly voluntary

Subconsciously (diaphragm to breathe)

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4
Q

Cardiac muscle tissue..

A 
Only in heart
Most of heart wall
Striated
Involuntary
Has natural pacemaker
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5
Q

Autorhythmicity

A

Built in rhythm in pacemaker

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6
Q

Smooth muscle tissue..

A

Located in walls of hollow internal structures (like blood vessels)
Nonstriated
Usually involuntary

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7
Q

Muscular tissue four main functions

A
  • Produce body movements
  • Stabilizing body positions
  • Storing and moving substances within the body
  • Generating heat
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8
Q

Producing body movements

A

Movements of the whole body and localized movements..

Requires muscular contractions,
Which rely on integrated functioning of skeletal muscles, bones, and joints

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9
Q

Stabilizing body positions

A

Skeletal muscle contractions stabilize joints and help maintain body positions

Postural muscles contract continuously when awake, like holding the head upright

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10
Q

Storing and moving substances within the body

A

-Storage held by sphincters
-Cardiac muscle contractions pump blood
-smooth: sperm, oocytes, bile and enzymes (GI), urine
Skeletal: lymph flow, return of blood to heart

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11
Q

Generating heat

A

As muscular tissue contracts, it produces heat (thermogenesis)

Maintain normal body temperature
Involuntary (shivering)

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12
Q

Properties of muscular tissue

A

Electrical excitability
Contractility
Extensibility
Elasticity

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13
Q

Electrical excitability

A

Ability to respond to certain stimuli by producing electrical signals called ‘action potentials (impulses)’

In muscles: muscle action potentials
In nerve: nerve “ “

Autorhythmic electrical signals arising in muscular tissue

Chemical stimuli, such as neurotransmitter a released by neurons, hormones distributed by blood, or even local changes in pH.

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14
Q

Contractility

A

Ability of muscular tissue to contract forcefully when stimulated by an action potential

When a skeletal muscle contracts, it generates tension while pulling on its attachment points

In some muscle contractions, the muscle develops tension but does not shorten

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15
Q

Extensibility

A

Ability of muscular tissue to stretch, within limits, without being damaged

The connective tissue within muscle limits the range of extensibility and keeps within contractile range of muscle cells

Smooth muscle is normally subject to the greatest amount of stretching

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16
Q

Elasticity

A

Ability of muscular tissue to return to its original length and shape after contraction or extension

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17
Q

Skeletal muscle tissue

A

Each skeletal muscle - separate organ
composed of hundreds to thousands of cells, called muscle fibers

Muscle cell = muscle fiber

Skeletal muscle contain connective tissue surrounding muscle fibers and whole muscles and blood vessels and nerves

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18
Q 
Subcutaneous layer (hypodermis)
Aid in muscle function..
A
  • Separates muscle from skin
  • areolar and adipose tissue
  • Pathway for nerves, bv’s, lymphatic vessels to enter in/out of muscles
  • adipose stores most of triglycerides in body
  • insulating layer/protects muscles from trauma
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19
Q

Fascia

A

Dense sheet or broad band of irregular connective tissue that lines the body wall and limbs and supports and surrounds muscles and other organs

Holds muscles with similar movements together

Allows free movement of muscles

Carries nerves, blood vessels, and lymphatic vessels

Fills spaces between muscles

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20
Q

Three layers of connective tissue extend from fascia to protect and strengthen skeletal muscle

A

Epimysium
Perimysium
Endomysium

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21
Q

Epimysium

A

Outer layer encircling entire muscle.

Dense irregular connective tissue

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22
Q

Perimysium

A

Surrounds groups of 10 to 100 or more muscle fibers, separating them into bundles called fascicles

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23
Q

Endomysium

A

Penetrates the interior of each fascicle and separates individual muscle fibers from one another.

Mostly reticular fibers.

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24
Q

Aponeurosis

A

Connective tissue elements extend as a broad, flat sheet

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25
Q

Fibromyalgia

A

Chronic, painful, nonarticular rheumatic disorder that affects the fibrous connective tissue components of muscles, tendons, and ligaments.

Tender points

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26
Q

Somatic motor neuron

A

Stimulate skeletal muscle contractions

Has threadlike axon that extends from the brain or spinal cord to a group of skeletal muscle fibers

Branching to different skeletal muscle fibers

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27
Q

Blood capillaries in muscular tissue

A

Plentiful

Bring in oxygen and nutrients and remove heat and waste products of muscle metabolism

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28
Q

Sarcolemma

A

Plasma membrane of muscle cell

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29
Q

Transverse tubules

A

Thousand of tiny invaginations of sarcolemma, tunneling from surface toward center of each muscle fiber

Filled with interstitial fluid
Muscle action potentials travel along sarcolemma and through T tubules
-ensures action potential excites all parts of the muscle fiber

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30
Q

Sarcoplasm

A

Cytoplasm of the muscle fiber
Includes substantial amount of glycogen
-for synthesis of ATP

Contains red colored protein (myoglobin)
-only in muscles/binds oxygen molecules that diffuse into muscle fibers from interstitial fluid

Myoglobin releases oxygen needed by mitochondria for ATP production

Mitochondria lie in rows throughout muscle fiber, strategically close to contractile muscle that use ATP during contraction so that ATP can be produced quickly

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31
Q

Myofibrils

A

“Little threads in sarcoplasm”

The contractile organelles of skeletal muscle

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32
Q

Sarcoplasmic reticulum

A

Fluid filled system of membranous sacs, encircling each myofibril

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33
Q

Terminal cisterns

A

Dilated end sacs of the Sarcoplasmic reticulum

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34
Q

Triad

A

Formation of a transverse tubule and the two terminal cisterns on either side of it

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35
Q

Denervation atrophy

A

If nerve supply is disrupted or cut

Over a period of 6 months to 2 years, the muscle shrinks to about 1/4 the original size and it’s fibers are irreversibly replaced by fibrous connective tissue

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36
Q

Microscopic organization of skeletal muscle

A

During embryonic development

  • myoblasts form muscle fiber
  • loses ability to cell divide, except satellite cells
  • sarcolemma encloses sarcoplasm and myofibrils
  • Sarcoplasmic reticulum wraps around each myofibril
  • thousands of T tubules invaginate from sarcolemma to center of muscle
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37
Q

Filaments

A

Within myofibrils
Involved in contractile process
Around compartments (sacromeres)
-z discs separate sacromeres

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38
Q

A band

A

Darker middle part of sacromere

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39
Q

I band

A

Lighter less dense area than A band containing the rest of thin filaments but no thick filaments

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40
Q

H zone

A

Narrow, in center of A band, contains thick but no thin filaments

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41
Q

M Line

A

Center of H zone

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42
Q

Proteins of myofibrils

A

Contractile proteins - generate force during contraction

Regulatory proteins - help switch the contraction process on and off

Structural proteins - keep thick and thin filaments in proper alignment, give elasticity and extensibility, and link the myofibrils to sarcolemma and extra cellular matrix

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43
Q

Two contractile proteins

A

Myosin - main component of thick filaments and functions as a motor protein in all three types of muscle tissue
Heads point to M line

Actin - main component of thin filaments, has myosin-binding site where myosin heads bind during contraction

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44
Q

Regulatory proteins

A

Tropomyosin - tropomyosin blocks myosin from binding to actin by covering myosin binding site

Tropomyosin strands are held in place by troponin molecules

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45
Q

Structural proteins

A 
Titin
a-Actinin
Myomesin
Nebulin
Dystrophin
46
Q

Titin

A

Connects Z disc to M line
Stabilize thick filament position
Stretch and spring back

47
Q

a-Actinin

A

In Z disc

Connects actin molecules to Titin

48
Q

Myomesin

A

Form M line

Bind Titin and adjacent thick filaments

49
Q

Nebulin

A

Wraps around thin filament
Anchor thin filament to Z discs
Regulates length of thin filament

50
Q

Dystrophin

A

Links thin filaments to integral membrane proteins in sarcolemma
- which are attached to CT matrix surrounding muscle fibers

Thought to help reinforce sarcolemma and help transmit tension generated by sacromeres to tendons

51
Q

Sliding filament mechanism

A

Myosin heads attach and walk along the thin filaments and both ends of a sacromere

I band and H zone disappear

52
Q

Contraction cycle

A

At onset of contraction
The Sarcoplasmic reticulum release Calcium ions into sarcoplasm
They bind to troponin
-cause tropomyosin to move away from myosin binding sites on actin

53
Q

Contraction cycle steps

A

ATP hydrolysis
Attachment of myosin to actin to form cross-bridges
Power stroke
Detachment of myosin from actin

54
Q

ATP hydrolysis

A

Myosin head includes ATP binding site and an ATPase, an enzyme that hydrolyzes ATP into ADP and a phosphate group

Reorients and energizes myosin head

55
Q

Attachment of myosin to actin to form cross-bridges

A

Energized myosin head attaches to myosin binding site on actin and releases the previously hydrolyzed phosphate group

When myosin heads attach to actin during contraction, they are referred to as cross-bridges

56
Q

Power stroke

A

The site on the cross-bridge where ADP is still bound opens.
As a result, the cross bridge opens and releases the ADP.
The cross-bridge generates force as it rotates towards the center of the sacromere, sliding the thin filament past the thick filament toward the M line.

57
Q

Detachment of myosin from actin

A

At the end of the power stroke, the cross bridge remains firmly attached to actin until it binds another molecule of ATP, causing myosin head to detach from actin

58
Q

Excitation-contraction coupling

A

As muscle action potential propagates along the sarcolemma and into T tubules,
It causes Calcium release channels in SR membrane to open.
-Ca2+ flows out SR to sarcoplasm
Ca2+ rises 10fold
Ca ions combine w/ troponin causing a change in its shape
-moves tropomyosin to move away from myosin-binding sites on actin

59
Q

Ca2+ active transport pumps

A

Use ATP to move Ca2+ constantly from sarcoplasm into SR

60
Q

Calsequestrin

A

Molecules of calcium-binding protein inside the SR.

61
Q

Rigor mortis

A

After death cell membranes leak
Ca2+ leak from SR to sarcoplasm
-allow myosin heads to bind to actin

ATP synthesis ceases shortly after breathing stops (cross bridge cannot detach from actin)

Muscles in a state of rigidity

Begins 3-4 hours after death
Lasts about 24 hours

Disappears as proteolytic enzymes from lysosomes digest the cross-bridge

62
Q

Length-tension relationship

A

Indicates how the forcefulness of muscle contraction depends on the length of sarcomeres within a muscle before contraction begins

63
Q

Neuromuscular junction

NMJ

A

Synapse between a somatic motor neuron and a skeletal muscle fiber

Where muscle action potentials rise

64
Q

Synapse

A

Region where communication occurs between two neurons or between a neuron and a target cell

65
Q

Synaptic cleft

A

Small gap separating two cells at most synapses

Because the cells do not touch, the action potential cannot ‘jump’ between the two
-instead, the first cell communicates with the other by releasing a chemical messenger called a neurotransmitter

66
Q

Axon terminal

A

At NMJ, end of motor neuron

Divides into cluster of synaptic end bulbs
Synaptic vesicles - hundreds of membrane enclosed sacs in the cytosol
Inside each synaptic bulb are thousands of molecules of Acetylcholine (the neurotransmitter released at the NMJ)

67
Q

Motor end plate

A

Region opposite the synaptic end bulbs
Muscle fiber part of NMJ

Within are 30-40 million acetylcholine receptors

68
Q

Nerve impulse (nerve action potential) elicits a muscle action in the following way

A

Release of acetylcholine
Activation of ACh receptors
Production of muscle action potential
Termination of ACh

69
Q

Release of acetylcholine

A

Nerve impulse at synaptic end bulb stimulates voltage-gated channels to open
Ca2+ flows inward through open channels (ions more concentrated in extra cellular fluid)
-stimulates synaptic vesicles to undergo exocytosis
–synaptic vesicles fuse with motor neurons plasma membrane, liberating ACh into synaptic cleft
—ACh diffuses across synaptic cleft between motor neuron and motor end plate

70
Q

Activation of ACh receptors

A

Binding of two molecules of ACh to the receptor on the motor end plate opens an ion channel in the ACh receptor

Once the channel is open, small cations, most importantly Na+, can flow across the membrane

71
Q

Production of muscle action potential

A

The inflow of Na+ makes the muscle fiber more positively charged
This change in the membrane potential triggers a muscle action potential
Each nerve impulse normally elicits one action potential
The muscle action potential then propagates along the sarcolemma into the system of T tubules
This causes sarcoplasmic reticulum to release it’s stored Ca2+ into the sarcoplasm and the muscle fiber subsequently contracts

72
Q

Termination of ACh activity

A

The affect of ACh binding lasts only briefly because ACh is rapidly broken down by an enzyme called acetlycholinesterase
This enzyme is attached to collagen fibers in the extracellular matrix of the synaptic cleft
AChE breaks down ACh into acetyl and choline, products that cannot activate the ACh receptor

73
Q

Electromyography

A

A test that measures the electrical activity in resting and contracting muscles
Resting produce less activity
Needle inserted into muscle
-played through loudspeaker
Determine if weakness is due malfunction of the muscle or the nerves supplying the muscle

74
Q

Botulinum toxin

Curare

A

Botox* - blocks exocytosis of synaptic vesicles at the NMJ

Poison used South American Indians in blow darts - causes muscle paralysis by binding to and blocking ACh receptors

75
Q

Ways for muscle fibers to produce ATP

A

From creating phosphate
By anaerobic glycolysis
By anaerobic respiration

76
Q

Creating phosphate

A

High energy-rich molecule that is found in muscle fibers

Comes from excess ATP produced while muscle fibers are relaxed

Enzyme creating kinase catalyze a the transfer of one of the high energy phosphate groups from ATP to creatine, forming creatine phosphate

77
Q

Creatine

A

Amino-acid like molecule that is synthesized in the liver, kidneys, and pancreas and then transported to muscle fibers

78
Q

Anaerobic glycolysis

A

Process of the breakdown of glucose to give rise to lactic acid when oxygen is absent or at low concentration

1 glucose molecule -> 2 lactic acid + 2 ATP

  • most lactic acid diffuses into blood
  • liver cells convert back to glucose
  • -reduces acidity of blood

Provides enough energy for two minutes of maximal muscle activity

Breaks down glucose into 2 pyruvic acid molecules

79
Q

Aerobic respiration

A

A series of oxygen-requiring reactions that produce ATP, carbon dioxide, water, and heat
(When pyruvic acid enters mitochondria)
If enough oxygen is present

1 molecule glucose -> 30-32 of ATP

80
Q

Myoglobin + hemoglobin

Oxygen sources

A

Myoglobin - only in muscle cells

Hemoglobin - only in red blood cells

Oxygen binding proteins that bind when it’s plentiful and release when it’s scarce

81
Q

Muscle fatigue

A

Inability of a muscle to maintain force of contraction after prolonged activity

Central fatigue - tiredness before actual fatigue

82
Q

Oxygen debt

Recovery Oxygen uptake

A

After heavy exercise, heavy breathing -> pay back oxygen

For..
•Convert lactic acid back into glycogen stores in the liver
•Resynthesize creatine phosphate and ATP in muscle fiber
•Replace the oxygen removed from myoglobin

83
Q

Motor unit

A

Consists of a somatic motor neuron and all of the skeletal muscle fibers it stimulates

84
Q

Twitch contraction

A

Brief contraction of all muscle fibers in a motor unit responsible to a single action potential in its motor neuron

Myogram - record of muscle contraction

Last 20-200msec
Action potential only 1-2msec

85
Q

Latent period

A

2msec delay in beginning of twitch contraction

86
Q

Contraction period

A

Second phase of twitch contraction

Lasts 10-100msec

87
Q

Relaxation period

A

Third phase of twitch contraction

10-100msec

88
Q

Refractory period

A

Period of lost excitability

When a muscle receives enough stimulation to contract

89
Q

Wave summation

A

When a second stimulus occurs after the refractory period of the first stimulus is over, but before the skeletal muscle fiber has relaxed, the second contraction will be stronger. This is what it’s called.

Occur when additional Ca2+ is released from the sarcoplasmic reticulum by subsequent stimuli while the levels of Ca2+ in the sarcoplasm are still elevated from the first stimulus.

90
Q

Unfused tetanus

A

Muscle fiber is stimulated at a rate of 20-30 times per second, and can only partially relax

91
Q

Fused tetanus

A

Skeletal muscle is stimulated at a higher rate of 80-100 times per second, does not relax at all

Individual twitches cannot be detected

92
Q

Motor unit recruitment

A

Process in which the number of active motor units increases

Weakest motor units are recruited first
Progressively stronger added if task requires

93
Q

Hypertonia

A

Increased muscle tone

Spasticity - stiffness, increase tendon reflexes

Rigidity - increase muscle tone not affecting reflexes (tetanus)

94
Q

Isotonic contraction

A

Concentric - great enough to overcome the resistance of the object to be moved, muscle gets shorter

Eccentric - resists movement of the load, muscle gets longer

95
Q

Isometric contraction

A

Not enough to exceed resistance of the object to be moved, muscle does not change in length

96
Q

Red muscle fibers

A

High hemoglobin content of skeletal muscle fibers

(Dark meat in chicken legs and thighs)

More mitochondria and capillaries

97
Q

White muscle fibers

A

Low hemoglobin content of skeletal muscle fibers

White meat in chicken breasts

98
Q

Muscle fiber speed groups

A

Slow oxidative fibers
Fast oxidative-glycolytic fibers
Fast glycolytic fibers

99
Q

Slow oxidative fibers

SO

A

Appear dark red - many capillaries and myoglobin
Generate ATP mainly by aerobic respiration

ATPase hydrolyzes ATP slowly

Resistant to fatigue
Capable of prolonged sustained contractions for many hours,
-posture, aerobic activities

100
Q

Fast oxidative-glycolytic fibers

FOG

A

Many capillaries and myoglobin
Generate considerable ATP
Higher intercellular glycogen = generate ATP by anaerobic glycolysis

ATPase in myosin heads hydrolyzes ATP 3-5 times faster than in SO

*walking and sprinting

101
Q

Fast glycolytic fibers

FG

A

Low myoglobin, few capillaries
Few mitochondria
Appear white in color
Ability to hydrolyze ATP rapidly = intense anaerobic movements of short duration

102
Q

Intercalated discs

A

Irregular transverse thickenings of sarcolemma that connect ends of cardiac muscle fibers to one another

Contains desmosomes which hold the fibers together

Contains gap junctions which allow muscle action potentials to spread from one cardiac muscle fiber to another

103
Q

Cardiac muscle tissue

A

Contain intercalated discs
Has endomysium and perimysium, but to epimysium

Contraction lasts longer than skeletal muscle because Ca2+ in interstitial fluid

104
Q

Physiological enlarged heart

A

Cardiac muscle hypertrophy due to increased workload.

105
Q

Smooth muscle tissue

A

Usually involuntary

Two types:
Visceral (single-unit) smooth muscle tissue
Multiunit smooth muscle tissue

106
Q

Visceral (single-unit) smooth muscle tissue

A

In skin, arteries, veins, hollow organs
Autorhythmic
Fibers connect through gap junctions
-where action potentials spread

107
Q

Multiunit smooth muscle tissue

A

Individual fibers with own motor neuron terminals, few gap junctions
Stimulation of one Multiunit fiber causes contraction of that fiber only

In walls of large arteries
- airways of lungs, arrector pili, muscles of iris, ciliary body

108
Q

Dense bodies

A

Structures that thin filaments attach to, in smooth muscle fibers

Functionally similar to z discs in striated muscle fibers

109
Q

Caveolae

A

Small pouch like invaginations of the plasma membrane in smooth muscle

Like ‘transverse tubules’

110
Q

Physiology of smooth muscle

A

Contractions Start more slowly and lasts longer than skeletal and cardiac

Can shorten and stretch to greater extent

Increase in Ca2+ concentration in cytosol initiates contraction

No transverse tubules = takes longer for Ca2+ to reach filaments
-slow contraction onset

111
Q

Calmodulin

A

Regulatory protein in smooth muscle

Binds to Ca2+ in cytosol, activates enzyme myosin light chain kinase -> then uses ATP to add a phosphate group to a portion of the myosin head

112
Q

Smooth muscle tone

A

A state of continued partial contraction

from the prolonged presence of Ca2+ in the cytosol

113
Q

Where most muscles are derived.

A

From the mesoderm

Biology (8 decks)

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