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Anatomy & Physiology 207 > Muscle and Muscle Tissue > Flashcards

Muscle and Muscle Tissue Flashcards

1
Q

Muscle Tissue

A
  • nearly half of body’s mass
  • capable of transforming chemical energy (ATP) into directed mechanical energy
  • mechanical energy is capable of exerting force
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2
Q

3 types of muscle tissue

A
  • skeletal
  • smooth
  • cardiac
    *both skeletal and smooth muscle cells are elongated and referred to as “muscle fibers”
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3
Q

skeletal muscle tissue - voluntary muscle

A
  • organs attached to bones and skin
  • longest and have striations
  • contract rapidly and powerfully but tire easily
  • remarkably adaptable
  • subject to conscious control and voluntary movement
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4
Q

cardiac muscle tissue

A
  • only in heart; makes up bulk of heart walls
  • striated
  • involuntarily controlled; contracts @ steady rate due to heart’s own pacemaker
  • nervous system can alter heart rate, but it is not consciously controlled
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5
Q

Four characteristics of all muscle tissue

A
  • excitability (responsiveness)
  • contractibility
  • extensibility
  • elasticity
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6
Q

excitability (responsiveness)

A

ability to receive/respond to stimuli by changing its membrane potential

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7
Q

contractibility

A

ability to forcibly shorten when stimulated

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8
Q

extensibility

A

ability to stretch or extend - even beyond resting length

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9
Q

elasticity

A

ability to recoil to resting length

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10
Q

four functions of muscle tissue

A
  • produce movement
    • locomotion & manipulation
    • contraction of the heart
    • blood vessel dilation/constriction
    • movement of all fluids/substances
      through tracts
  • maintain posture and body position
  • stabilize joints
  • generate heat
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11
Q

anatomy and features of a skeletal muscle

A

each skeletal muscle is an organ made of different tissues
features
- nerve and blood supply
- connective tissue sheaths
- attachments

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12
Q

nerve and blood supply

A
  • each muscle receives a nerve, arteries, and veins
  • consciously controlled skeletal muscle have nerves supplying every muscle fiber
  • contracting muscle requires huge amounts of oxygen and nutrients + quick removal of waste
  • cellular respiration: C6H12O6 + 6O2 –> 6CO2 + 6H2O + ATP
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13
Q

connective tissue sheaths

A

every skeletal muscle and muscle fiber is covered in connective tissue
- support muscle cells and reinforce whole muscle
- become the tendons that join muscles to bones
3 parts:
- epimysium
- perimysium
- endomysium

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14
Q

epimysium (connective tissue sheath)

A

most external; dense irregular connective tissue surrounding the entire muscle; may blend with fascia

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15
Q

perimysium (connective tissue sheath)

A

fibrous connective tissue surrounding fascicles (groups of muscle fibers)

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16
Q

endomysium

A

most internal; fine areolar connective tissue surrounding each muscle fiber

17
Q

attachments

A

muscles span joints and attach to bones
- muscles attach in at least to places
- origin: immoveable/less moveable bone
- insertion: moveable bone
- attachments can be direct or indirect
- direct (fleshy): epimysium fused to periosteum or perichondrium
- indirect: connective tissue wrappings extend beyond a muscle as ropelike tendon or sheetlike aponeurosis (more common)

18
Q

muscle fiber microanatomy

A
  • long cylindrical cells w multiple nuclei
  • sarcolemma & sarcoplasm
  • specialized organelles:
    • myofibrils
    • sarcoplasmic reticulum
    • t-tubules
19
Q

sarcolemma

A

plasma membrane of a muscle fiber

20
Q

sarcoplasm

A

cytoplasm of a muscle fiber
- contains many glycosomes - granules of stored glycogen - and myoglobin - a red pigment that stores oxygen

21
Q

myofibrils

A

densely packed, rodlike elements
- single muscle fiber can contain 1000s
- accounts for 80% of muscle cell volume
- made of chains of sarcomeres

22
Q

parts of myofibrils

A
  • striations: stripes formed from repeating series of dark and light bans along the length of each myofibril
  • a bands: dark regions
    • h zone: lighter region in the middle of the dark a band
    • m line: dark line of protein (myomesin) that bisects the H zone vertically
  • i bands: lighter regions
    • z disc/line: sheet of proteins on midline of light i band
23
Q

sarcomere

A

muscle segment
- smallest contractile unit of a muscle fiber
- contains a band with half of an i band at each end - the area between z discs
- individual sarcomeres align end-end along myofibril

24
Q

myofilaments

A
  • contain actin and myosin
  • arranged in an orderly pattern within a sarcomere
  • actin myofilaments = thin filaments
  • myosin myofilamets = thick filaments
25
actin myofilaments
- thin filaments - lateral, extend across i band - partway into a band - anchored by z discs
26
myosin myofilaments
- thick filaments - central, extend length of a band - connected at m line
27
thick filaments
composed of the protein myosin, each myosin molecule contains 2 heavy and 4 light polypeptide chains - heavy chains intertwine to form myosin heads - light chains form globular myosin heads during contraction, myosin heads link thick+thin filaments to form cross bridges - myosins are often offset from each other - staggered array of heads along thick filament
28
regulatory proteins
tropomyosin and troponin - bound to actin that control muscle contraction
29
tropomyosin
rod-shaped protein, spiral about the actin core and block myosin-binding sites
30
troponin
gloular protein, able to bind to 1-actin, 2-tropomyosin, 3-calcium
31
other proteins in myofibril
- elastic filament: composed of protein titin; holds thick filaments in place; helps to resist excessive stretch and assists with recoil - dystrophin: structural protein that links the thin filaments to the integral proteins of the sarcolemma - nebulin, myomesin, c proteins: bind filaments or sarcomeres together; maintain alignment of the sarcomere
32
duchenne muscular dystrophy
caused by defective gene for dystrophin - a protein that links thin filaments to extracellular matrix and stabilizes sarcolemma - loss of muscle mass over time from apoptosis of muscle cells (falling and weakness)
33
sarcoplasmic reticulum
network of smooth endoplasmic reticulum tubules surrounding each myofibril - stores and releases calcium on demand - functions in regulation of intracellular calcium levels - most tubules run longitudinally - terminal cisterns: SR tubules that form perpendicular cross channels at the a-i band junction; always occur in pairs
34
t (transverse) tubules
- tube formed by protrusion of the sarcolemma deep into the cell's interior - pass from 1 myofibril to another - occur at a-i band junction - between terminal cisterns - t tubule lumen is continuous with extracellular space, greatly increases the muscle fiber's surface area - allow electrical nerve transmissions to reach deep into the interior of each muscle fiber and trigger the release of calcium - triad: area formed from the terminal cistern of one sarcomere, a t tubule, and the terminal cistern of the neighboring sarcomere
35
triad relationships
- t tubules are a rapid messaging system - work to ensure every myofibril in the muscle fiber contracts simultaneously - t tubules and SR are linked together via membrane spanning proteins - protruding proteins from the t tubules act as voltage sensors - change shape in response to an electrical current - protruding proteins from the SR form gated channels through which calcium can be released - when an electrical impulse passes by, t tubule proteins change shape, and calcium is released into the cytoplasm
36
contraction
the activation of myosin's cross bridges to generate force
37
sliding filament model of muscle contraction part 1
muscle fiber shortening only occurs if the cross bridges generate enough tension on the thin filaments to exceed the forces that oppose shortening - ex. lifting a bowling ball - contraction ends when cross bridges become inactive, tension decline, and the muscle fiber relaxes
38
sliding filament model of muscle contraction part 2
- in relaxed state, thin + thick filaments overlap only slightly at the ends of the a band - during contraction, thin filaments slide past thick filaments - actin and myosin overlap more - actin + myosin don't change their length - when nervous system stimulates a muscle fiber, myosin heads are allowed to bind to actin, cross bridges are formed, and the sliding process begins
39
sliding filament model of muscle contraction part 3
cross bridge attachments form and break several times, each time pulling the thin filaments a little closer towards the center of the sarcomere - ratcheting action shortens the muscle fiber - z discs are pulled toward the m line - i bands shorten - h zones disappear - a bands move closer together

Anatomy & Physiology 207 (44 decks)

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