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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
Q

actin myofilaments

A
  • thin filaments
  • lateral, extend across i band - partway into a band
  • anchored by z discs
26
Q

myosin myofilaments

A
  • thick filaments
  • central, extend length of a band
  • connected at m line
27
Q

thick filaments

A

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
Q

regulatory proteins

A

tropomyosin and troponin
- bound to actin that control muscle contraction

29
Q

tropomyosin

A

rod-shaped protein, spiral about the actin core and block myosin-binding sites

30
Q

troponin

A

gloular protein, able to bind to 1-actin, 2-tropomyosin, 3-calcium

31
Q

other proteins in myofibril

A
  • 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
Q

duchenne muscular dystrophy

A

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
Q

sarcoplasmic reticulum

A

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
Q

t (transverse) tubules

A
  • 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
Q

triad relationships

A
  • 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
Q

contraction

A

the activation of myosin’s cross bridges to generate force

37
Q

sliding filament model of muscle contraction part 1

A

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
Q

sliding filament model of muscle contraction part 2

A
  • 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
Q

sliding filament model of muscle contraction part 3

A

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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