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Biology 241 > 37.1 Muscles: Biological Motors That Generate Force and Produce Movement > Flashcards

37.1 Muscles: Biological Motors That Generate Force and Produce Movement Flashcards

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1
Q

why are muscles the “biological motors” of the body?

A

because they generate force and produce movement

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2
Q

what does a muscle’s ability to produce movement depend on?

A

the electrically excitable muscle cells containing proteins that can be activated by the nervous system

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3
Q

basic features of muscle organization and function are conserved across the vast diversity of….

A

eukaryotes (cnidarians had the first muscle fibres-jellyfish and sea anemones)

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4
Q

what largely determines how muscles contract to produce force and movement?

A

the geometry and organization of proteins in muscles

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5
Q

fiber

A

in animals, a term for a muscle cell, which produces forces within an animal’s body and exerts forces on the environment

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6
Q

muscles are composed of elongated cells called:

A

muscle fibers

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7
Q

muscle fibres use:

A

ATP generated through cellular respiration to generate force and change length during a contraction

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8
Q

force

A

an interaction that changes the movement of an object, such as a push or pull by one object interacting with another object

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9
Q

the work performed by a muscle is equal to:

A

force times length change

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10
Q

muscles only exert pulling forces, therefore…

A

pairs of muscles are arranged to produce movements in two opposing directions at specific joints of the skeleton

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11
Q

all muscles contain the same contractile proteins that enable them to shorten and produce force, these proteins are:

A

actin and myosin

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12
Q

filament

A

in animals, a thin thread of proteins that interacts with other filaments to cause muscles to shorten. in plants, the part of the stamen that supports the anther

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13
Q

although all muscle fibres have filaments of actin and myosin, in different types of muscles…

A

the filaments are arranged differently

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14
Q

what are the two broad groups of muscles (based on function and appearance)

A

striated muscle and smooth muscle

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15
Q

striated muscle

A

skeletal muscle and cardiac muscle, which appear striped under a light microscope-actin and myosin filaments are arranged in a regularly repeating pattern

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16
Q

skeletal muscle

A

muscle that connects to the body skeleton to move an animal’s limbs and torso (elongated, many nuclei in each cell)

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17
Q

cardiac muscle

A

muscle cells that make up the walls of the atria and ventricles and contract to pump blood through the heart (less elongated when compared to skeletal muscle, tranches, only contain or more nuclei per cell)

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18
Q

smooth muscle

A

the muscle in the walls of arteries, the respiratory system, and the digestive and excretory systems; smooth muscle appears uniform under the light -actin and myosin filaments are irregularly organized

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19
Q

when compared to cardiac and skeletal muscles, smooth muscles contract….

A

slowly

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20
Q

whole muscles are made up of :

A

parallel bundles of individual muscle fibres (muscle cells)

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21
Q

myofibril

A

a long rodlike structure in muscle fibbers that contains parallel arrays of the actin and myosin filaments

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22
Q

each muscle finer contains hundreds of:

A

myofibrils (has a striated appearance due to their regular molecular organization)

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23
Q

each myosin molecule consists of:

A

two long polypeptide chains coiled together, each ending with a globular head

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24
Q

thick filament

A

a parallel grouping of myosin molecules that makes up the myosin filament

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25
Q

thin filament

A

two helically arranged actin filaments twisted together that make up the actin filament

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26
Q

tropomyosin

A

a protein that runs in the grooves formed by the actin helices and blocks the myosin-binding sites

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27
Q

Z disc

A

a protein backbone found regularly spaced along the length of a myofibril

28
Q

sarcomere

A

the region from one Z disc to the next, the basic contractile unit of a muscle

29
Q

what is the functional units of muscles?

A

sarcomeres-the shortening/contraction of a muscle is ultimately the result of the shortening of thousands of sarcomeres along a myofibril

30
Q

titin, a third large protein, what is its function?

A

to help with assembly and protect the sarcomeres from being overstretched, thus contributing to muscle elasticity

31
Q

what contributes to the striated appearance of skeletal muscles?

A

the regular pattern of actin and myosin filaments with sarcomeres along the length of the fibre

32
Q

sliding filament model

A

the hypothesis that muscles produce force and change length by the sliding of actin filaments relative to myosin filaments

33
Q

when myofibrils contracted to short lengths…

A

the sarcomeres had increased actin-myosin overlap

34
Q

when myofibrils were stretched to longer lengths…

A

actin-myosin overlap decreased

35
Q

the length of myosin and actin filaments…

A

never change

36
Q

all of the length change during a muscle contraction results from:

A

the sliding of actin filaments with respect to myosin filaments within individual sarcomeres

37
Q

the length change of the whole muscle fibbers is a sum of:

A

the fractions by which each sarcomere shortens along the fibre’s length

38
Q

longer sarcomeres allow:

A

a greater degree of shortening

39
Q

what causes a muscle finer to shorten and produce force?

A

interactions between the myosin and actin filaments

40
Q

cross-bridge

A

the binding of the head of a myosin molecule to actin at a specific site between the myosin and actin filaments-how the myosin filaments pull the actin filaments toward each other

41
Q

what allows the filaments to slide relative to each other?

A

the ability of the myosin head to undergo a conformational change and pivot back and forth

42
Q

cross-bridge cycle

A

repeated sequential interactions between myosin and actin filaments at cross-bridges that cause a muscle finer to contract

43
Q

movement of the myosin head is powered by:

A

ATP (needs it to detach from actin)

44
Q

outline the steps of muscle contraction:

A
  1. myosin head binds ATP and detaches from actin
  2. myosin head hydrolyzes ATP resulting in a conformational change and myosin head is cocked back, ADP and P remain bound (myosin in in a high energy state)
  3. myosin head binds to actin (cross-bridge)
  4. once bound, ADP and P released, power stroke results
45
Q

power stroke

A

the stage in the cross-bridge cycle in which the myosin head pivots and generates a force, causing the myosin and actin filaments to slide relative to each other

46
Q

individual muscle contractions are the result of:

A

many successive cycles of cross-bridge formation and detachment

47
Q

faster muscle fiber contraction=

A

faster rates of ATP hydrolysis

48
Q

myosin functions as both a:

A

structural protein and an enzyme

49
Q

each thick filament can interact with:

A

6 actin filaments

50
Q

skeletal and smooth muscle fibres are both activated by:

A

the nervous system

51
Q

skeletal muscles are innervated by:

A

the somatic nervous system

52
Q

smooth muscles are innervated by:

A

the autonomic nervous system

53
Q

motor endplate

A

the region on a muscle cell where acetylcholine binds with receptors, triggers opening of sodium channels

54
Q

actin and myosin filaments can only form cross bridges when:

A

the myosin-binding sites on actin are exposed

55
Q

at rest, the myosin-binding sites are blocked by:

A

the protein tropomyosin

56
Q

sarcoplasmic reticulum (SR)

A

a modified form of the endoplasmic reticulum surrounding the myofibrils of muscle cells

57
Q

when the muscle is at rest, the SR contains a large internal concentration of:

A

calcium ions which are transported in by calcium pumps in the membrane

58
Q

a muscular contraction is initiated when depolarization of the muscle fibbers causes:

A

the SR to release calcium ions

59
Q

troponin

A

a protein that moves tropomyosin away from myosin-binding sites, allowing cross-bridges between actin and myosin to form and the muscle to contract-does this when calcium binds to it

60
Q

excitation-contraction coupling

A

the process that produces muscle force and movement, by excitation of the muscle cell coupled to contraction of the muscle

61
Q

the muscle relaxes when:

A

neural stimulation ends-acetylcholine is broken down or reabsorbed, calcium ions actively transported back into sarcoplasmic reticulum, tropomyosin block myosin-binding sites

62
Q

the smooth muscles can also be regulated by:

A

stretch of the muscle, local hormones, and other local factors (ex. pH, oxygen, carbon dioxide) by intracellular signalling

63
Q

in smooth muscle, calcium ions also enter through:

A

voltage-gated and stretch-receptor calcium channels in the cell’s plasma membrane

64
Q

smooth muscle lacks:

A

the troponin-tropomyosin mechanism for regulation contraction

65
Q

calmodulin

A

a protein that binds with calcium ions and activates the enzyme myosin kinase that phosphorylates the smooth muscle myosin heads, causing them to bind to actin and begin the cross-bridge cycle, another enzyme dephosphorylates the myosin head to relax the muscle

66
Q

smooth muscles use less…

A

ATP per unite time, contracts slower compared to skeletal muscle

Biology 241 (31 decks)

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