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Anatomy & Physiology Lecture > Block 3: Muscular System - Lecture 3.2 > Flashcards

Block 3: Muscular System - Lecture 3.2 Flashcards

1
Q

What is an individual muscle cells called?

A

Myocytes or Muscle Cells

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2
Q

What are the steps to muscle growth?

A

More Exercise –> more nuclei –> more proteins –> more muscle growth!!

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3
Q

How many nuclei are in each myoblast prior to birth?

A

1

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4
Q

What causes the creation of an immature muscle fiber?

A

Fusion of myoblasts

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5
Q

What cells are considered stem cells for muscle and do not fuse with myoblasts?

A

Satellite cells

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6
Q

After an immature muscle fiber is formed, what becomes apparent?

A

Striations become visible and nuclei spread throughout the fiber

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7
Q

What are the 3 structural steps of making muscle fibers PRIOR TO BIRTH?

A

fusion of myoblasts with satellite cells on top –> immature muscle fiber forms –> mature muscle fiber forms with visible striations

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8
Q

What is the job of satellite cells?

A

Regenerate muscle after birth

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9
Q

What is a tendon?

A

Connects muscle to bone

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10
Q

What percentage of muscle is connective tissue?

A

10%

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11
Q

What are the names of the 3 different connective tissues that make up a muscle?

A

1) Epimysium (upon muscle)
2) Perimysium (around fascicles)
3) Endomysium (surrounds individual muscle fibers)

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12
Q

What are the two contractile proteins that make up a myofibril?

A

1) Actin
2) Myosin

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13
Q

From the subcellular level to the organ level, list all the layers that make up a muscle.

A

Subcellular Level
- myofibril
- muscle fiber
- endomysium
- fascicle
- perimysium
- muscle
- epimysium
Organ Level

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14
Q

What is the muscle cell membrane called?

A

Sarcolemma
- phospholipid bilayer of skeletal muscle cells

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15
Q

What connective tissue covers muscle fibers?

A

Endomysium

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16
Q

What connective tissue covers a fascicle?

A

Perimysium

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17
Q

What connective tissue covers a muscle?

A

Epimysium

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18
Q

What percentage of skeletal muscle is intramuscular connective tissue?

A

1 - 10%

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19
Q

As a person gets older, what happens to the Intramuscular CT?

A

Stiffens

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20
Q

What are the functions of Intramuscular CT?

A

1) Transmits forces
- to reach tendons
2) Spring-like properties
- tendons store and release energy
- more exercise = less energy needed

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21
Q

What is Fascia?

A

Connects groups of muscles together and separates them into compartments
- shows continuity (CT) throughout the body

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22
Q

What are the three units of subcellular organization that muscle activation relies on?

A

1) Sarcolemma
2) Sarcoplasmic Reticulum
3) Myofibrils

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23
Q

What is the job of the sarcolemma?

A

Conducts electrical signals
- muscle sheath

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24
Q

What is the job of the sarcoplasmic reticulum?

A

1) Control muscle contraction
2) Store calcium

25
Q

What is the job of myofibrils?

A

Muscle contraction

26
Q

How does conduction work in muscles?

A

T-tubules spread electrical signals to the center of muscle fibers
- surrounded by terminal cisterns, one on each side

Sarcolemma encloses cytoplasm of skeletal muscle fiber

27
Q

How does control work in muscles?

A

Sarcoplasmic Reticulum (SR)
- organelle within muscle fiber that stores calcium
- surrounds myofibrils

28
Q

What is included in the “Triad”?

A

1) Sarcoplasmic Reticulum (SR)
2) T-tubules
3) Terminal Cisterns

29
Q

How does contraction work in muscles?

A

myofibrils arranged into bundles of protein filaments –> muscle shortening by actin & myosin –> actin & myosin are organized into muscle units called sarcomeres

30
Q

Actin forms [thin/thick] filament.

A

Thin

31
Q

Myosin forms [thin/thick] filament.

A

Thick

32
Q

What are 3 basic characteristics of sarcomeres?

A

1) Repeating units within myofibril
- forms striations
2) Functional unit of muscle contraction
3) Basic structural unit of myofibrils

33
Q

What is the function of longitudinal sarcomeres?

A

Force production

34
Q

What is the function of cross sectional sarcomeres?

A

Individual muscle fibers

35
Q

What are the 3 categories of muscle proteins?

A

1) Structural proteins
2) Contractile proteins
3) Regulatory proteins

36
Q

What are the 5 structural proteins?

A

1) α-actinin
2) Nebulin
3) Titin
4) Dystrophin
5) Myomesin

37
Q

What are the 2 contractile proteins?

A

1) Actin
2) Myosin

38
Q

What are the 2 regulatory proteins?

A

1) Troponin
2) Tropomyosin

39
Q

Why are structural proteins so important to skeletal muscle function?

A

mutations/disruptions can cause muscle disease

40
Q

What structure do the two contractile proteins make up?

A

Sarcomere

41
Q

What type of protein is α-actinin and what is its role?

A

Structural Protein
- makes up the z-disk
- binds to actin & tinin

42
Q

What type of protein is Nebulin and what is its role?

A

Structural Protein
- “ruler” for thin filament
- anchors thin filament to z-disks

43
Q

What type of protein is Myosin and what is its role?

A

Contractile Protein
- heads reach up to thin filament to bind to actin
- motor protein in thick filament
- forms crossbridge with thin filament

44
Q

What type of protein is Actin and what is its role?

A

Contractile Protein
- wraps around Nebulin
- thin filaments with myosin binding sites
- forms crossbridge with thick filament

45
Q

What type of protein is Myomesin and what is its role?

A

Structural Protein
- provides structural integrity in the M-line

45
Q

What type of protein is Titin and what is its role?

A

Structural Protein
- stabilizes thick filaments
- spring-like to allow muscle to bring sarcomere back to resting length

46
Q

What type of protein is Tropomyosin and what is its role?

A

Regulatory Protein
- protein on thin filaments
- covers myosin binding sites on actin when muscle is relaxed
- physically turns during muscle contraction to expose myosin binding sites

47
Q

What type of protein is Troponin and what is its role?

A

Regulatory Protein
- protein on thin filaments and attached to tropomyosin
- turns when calcium is present to allow tropomyosin to bind to myosin binding sites
- controls position of tropomyosin
a. relaxed: troponin holds tropomyosin
b. contraction: calcium binds to troponin & causing conformation change to expose myosin binding sites

48
Q

What type of protein is Dystrophin and what is its role?

A

Structural Protein
- relays force/tension from sarcomere to sarcolemma via CT around the muscle fiber and to the tendon
a. sarcomere links thin filament to sarcolemma then anchors to collagen fibers

49
Q

What type of muscle tissue is Dystrophin not present?

A

Smooth muscle tissue

50
Q

What happens when there is no Dystrophin present in the body?

A

weak muscles from not being able to contract
- ex: lose blood flow to cardiac muscle tissue because no dystrophin to allow contraction

51
Q

What do actin molecules have that for crossbridges and actin helicies to form?

A
  • globs of actin molecules with sites for myosin crossbridges
  • actin helicies formed by two strands of connected actin molecules
52
Q

What structure do actin/thin filaments attach to?

A

Z discs

53
Q

What are the two main components of myosin/thick filaments?

A

Myosin heavy chain
- head & tail twisted together
- different forms give rise to different force and velocity production

Myosin ATPase site
- head = energy regulation uses ATP for conformation change of the protein, leading to muscle shortening

54
Q

What two binding sites are on the myosin heads?

A

1) Actin-binding site
2) Myosin ATPase site

55
Q

What structure do thick filaments overlap?

A

Zone of Overlap: overlap with thin filaments
a. may form crossbridges

56
Q

How many molecules of thin filament surround one molecule of thick filament?

A
  • 1 thick filament is surrounded by 6 thin filaments
  • 1 thin filament is surrounded by 3 thick filaments
57
Q

What are the basic steps to single muscle fiber contraction?

A

1) Myosin heads bind to actin & form crossbridges
2) Conformational change (energized by ATP hydrolysis) causes thin filaments to slide along thick filaments
3) Myosin head groups release and form new crossbridges

58
Q

What are the results of basic single muscle fiber contraction?

A

1) Z-line move towards each other
2) Sarcomere decreases in length
3) Myofibril shortens
4) Muscle fibers shorten

Anatomy & Physiology Lecture (13 decks)

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