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Anatomy > Muscles > Flashcards

Muscles Flashcards

1
Q

Functions of Muscle Tissues

A

Muscle tissue contracts in response to a stimulus from the nervous system. This allows
• Material to move through the body
• Parts of the body to move (including the whole body)
• The generation of heat

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2
Q

Muscle Tissue Types

A
  1. Skeletal muscle
  2. Cardiac muscle
  3. Smooth muscle
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3
Q

Properties of Skeletal muscle

A

Skeletal muscle
• Moves the skeleton
• Under voluntary control
• Is multinucleated
• Long, cylindrical fibers
• Striated
• Accounts for ~40% body weight

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4
Q

Properties of cardiac muscle

A

Cardiac muscle
• Only found in heart wall
• Shorter, branched fibers
• One nucleus per cell
• Striated
• Under involuntary control

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5
Q

Properties of smooth muscle

A

Smooth muscle
• Found in walls of hollow organs (except the heart)
• Small, spindle-shaped cells
• One nucleus per cell
• No striations
• Under involuntary control

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6
Q

What are the four properties of muscle tissue (not types)

A
  1. Excitability
  2. Contractility
  3. Extensibility
  4. Elasticity
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7
Q

What is Excitability?

A
  1. Excitability
    • Nerve signal excites the muscle, causing contraction
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8
Q

What is Contractility

A
  1. Contractility
    • When a muscle contracts, it shortens*
    • This occurs at the microscopic level as myofilaments pull past each other
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9
Q

What is Extensibility

A

Extensibility
• After contraction, the muscle can go back to resting length (by gravity and/or an antagonist)

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10
Q

What is Elasticity?

A

Elasticity
• After being stretched, a muscle recoils passively and resumes its resting length

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11
Q

What runs through muscle?

A

Arteries, Veins, and Nerves Run Through Muscle

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12
Q

Arteries, Veins, and Nerves purpose?

A

• Arteries provide oxygen and nutrients
• Veins remove cellular wastes
• Nerves innervate muscle cells

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13
Q

What subunits are the muscles made of?

A

The whole muscle is made of subunits called fascicles

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14
Q

What are fascicles?

A

The whole muscle is made of subunits called fascicles
• Fascicles are made of individual muscle fibers (cells)
• Muscle fibers can be less than an inch and longer than one foot

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15
Q

What are the connective tissues of muscles?

A

Connective tissues
• Epimysium
• Perimysium
• Endomysium

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16
Q

What/where is Epimysium?

A

Epimysium
• surrounds whole muscle
• Dense irregular CT

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17
Q

What/where is Perimysium?

A

Perimysium
• surrounds fascicles
• Fibrous CT

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18
Q

What/where is Endomysium?

A

Endomysium
• surrounds individual muscle fibers
• Loose CT

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19
Q

What are muscles fibers made of?

A

Skeletal Muscle Anatomy
• Individual muscle fibers are made of cylindrical organelles called myofibrils
- These organelles run parallel to each other and the muscle fiber

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20
Q

What are myofibrils?

A

Myofibrils are made of repeating units called sarcomeres
• Sarcomeres are made of proteins called myofilaments
• Sarcomeres repeat throughout length of muscle fiber
• They line up end to end like box cars of a train

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21
Q

What are Sarcomeres made of?

A

Sarcomeres are made of two types of myofilaments
• Thick filament
• Thin filament
• Elastic filament

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22
Q

What is thick filament?

A

Thick filament (made of protein myosin)
- found in sarcomeres

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23
Q

What is thin filament?

A

• Thin filament (made of 3 proteins: actin, troponin, tropomyosin;
- type of myofilament in sacromeres

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24
Q

What is elastic filament?

A

Elastic filament (titin): attaches Z disc to thick filament; offers elasticity
- found in sacromeres??

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25
Q

What do the three proteins in thin filament do?

A

• Tropomyosin blocks actin’s binding site for myosin head
• Tropomyosin and troponin interact with each other
- when Ca2+ binds to troponin, it causes tropomyosin to unblock actin’s binding site
- Myosin heads can now bind to active site

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26
Q

What are the Sarcomere Striations?

A

• I bands
• A bands
• H zones
• M line

27
Q

What are I bands?

A

• I bands: between thick filaments of adjacent sarcomeres
- Contain Z discs, thin filaments, elastic filament

28
Q

What are A bands?

A

• A bands: length of thick filaments
- Contain both thick and thin filaments

29
Q

What are H zones?

A

H zones: between thin filaments (within single sarcomere)
- Contain only thick filaments

30
Q

What is the M line?

A

• M line: middle of H zone; delicate filaments holding myosin in place

31
Q

What is the Muscle Fiber Anatomy?

A

• Muscle fiber = single muscle cell
• Sarcolemma = plasma membrane of muscle fiber
• Sarcoplasm = cytoplasm of muscle fiber

32
Q

What are T Tubules?

A

• T tubules are extensions of sarcolemma that extend into muscle fiber
- Wrap around myofibrils
- Carry electrical stimulus to myofibrils

33
Q

What is the Sarcoplasmic reticulum?

A

Sarcoplasmic reticulum
• Modified smooth ER
• Stores and releases calcium ions

34
Q

Structure of Fascicles

A
  1. Fascicles are bundles of muscle fibers
  2. Each muscle fiber is made of many myofibrils
  3. Myofibrils are made of sarcomeres
  4. Sarcomeres are made of myofilaments
  5. There are 2 myofilaments: thick filament and thin filament
35
Q

What are motor units?

A

Motor Units
• Within a muscle, muscle fibers work together to perform an action (contraction)
• Motor units allow for a given muscle to exert a great • •All fibers innervated by a single motor neuron contract at the same time
• Activating more motor units within a muscle increases the force exerted by that muscle

36
Q

What is a motor unit = to

A

• Motor unit =1 motor neuron and all the muscle fibers it innervates

37
Q

Small vs Large motor unit

A

• Some large muscles (quadriceps femoris) have motor units with 2000 muscle fibers per motor unit (= large motor unit)
- Powerful contractions
• Smaller muscles (extraocular muscles) can have 10 fibers per motor unit (= small motor unit)
- Fine motor control

38
Q

What is a neuromuscular junction

A

Neuromuscular junction
• Where motor neuron meets muscle fiber
• Stimulation of muscle fiber can occur

39
Q

What causes Sarcomere shortening?

A

When acetylcholine (ACh) is released from the motor neuron, an action potential of excitation stimulates the muscle fiber…this ultimately causes sarcomere shortening

40
Q

Why are muscle fibers arranged how they are?

A

Muscle fibers are arranged in a pattern that provides the most efficient movement for an extended action

41
Q

What does muscle power depend on?

A

• Muscle power depends on the total number of muscle fibers in the muscle
- More fibers –> stronger contraction

42
Q

How much is each muscle fiber able to shorten?

A

• Each muscle fiber is only able to shorten about 1/3 of its resting length
- Longer muscle fibers are able to shorten more

43
Q

What are componets of Parallel muscles

A

Parallel muscles
• Muscle fascicles run parallel to axis of muscle
• Tendon on either end
• Look long and ropelike
• Fewer fibers than other types
• Longer fibers so can shorten more
• Can be fusiform (with a belly, ex. biceps brachii) or strap-like (ex. sartorius)

44
Q

What are the components of Pennate muscles?

A

Pennate muscles
• Tendon runs whole length of muscle
• Fascicles attach to tendon at an angle (resemble a feather)
• Shorter fibers than parallel muscles
• Allows for more fibers so stronger than parallel

45
Q

What are Convergent muscles?

A

Convergent muscles
• Origin of muscle is broad
• Muscle fascicles converge into
tendon at insertion
• Fan shaped
• Relationship to other muscle
types:
- More fibers than parallel
- Longer fibers than pennate

46
Q

What is the ranking of Strength between comparably sized muscles?

A

Strength of comparably sized muscles
Parallel (weakest)
Convergent
Pennate (strongest)

47
Q

What is the ranking of Shortening between comparably sized muscles?

A

Shortening ability of comparably sized muscles
Pennate (least)
Convergent
Parallel (greatest)

48
Q

What are circular muscles?

A

Circular muscles
• Fascicles arranged in a ring
• Sphincter muscles
- When contracted, the muscle constricts an orifice (opening), closing it

49
Q

What is an example of circular muscles?

A

Example = orbicularis oris (mouth)

50
Q

What is an example of convergent muscles?

A

Example = pectoralis major (Pec)

51
Q

What is an example of parallel muscles?

A

Example = sartorius (anterior component of thigh)

52
Q

What are the types of muscle attachments?

A

• Origin
• Insertion
• Action
• Direct
• Indirect

53
Q

What are Direct Muscle Attachments?

A

Direct –> short, dense regular CT
fibers connect muscle to bone

54
Q

What are Indirect Muscle Attachments?

A

Indirect –> long, dense regular CT
fibers connect muscle to bone
• Ex. Tendon and aponeurosis

55
Q

What are origin Muscle Attachments?

A

Origin: attachment site that is not moved, or moved the least during a muscle contraction

56
Q

What are the Insertion Muscle Attachments?

A

Insertion: attachment site that is moved when muscle shortens

57
Q

What are the Action Muscle Attachments?

A

Action: the resulting movement of a muscle contraction

58
Q

What are difference between tendons and Aponeuroses?

A

Tendons
• More rope-like
Aponeuroses
• Flat sheet
- ex: Aponeurosis of the external oblique (nears abs)

59
Q

What are the components of cardiac muscle?

A

Cardiac Muscle
• Striated
• Branched
• Most cells are uninucleate, may have two large nuclei
• Cells have some regenerative ability (recent research has shown that perhaps 1% a year)
• Surrounded by endomysium
• Connected by intercalated discs
• Involuntary control

60
Q

What is the structural components of Intercalated Disc?

A

• Gap junctions
- allow for coordinated contractions by allowing action potentials to quickly spread from cell to cell
• Desmosomes: provide strength, site where intermediate filaments attach

61
Q

What are the components of smooth muscle tissues?

A

• Small, spindle shaped cells
• Uninucleate
• No striations
- They do contain myofilaments but they are not arranged in sarcomeres
• Each cell is covered in endomysium
• Involuntary
• Regenerate

62
Q

What do smooth muscle cells contain?

A

Smooth Muscle Cells
• Intermediate filaments anchor actin and myosin
• A contraction involves myosin and actin filaments moving against one another

63
Q

How is smooth muscle arranged?

A

• Smooth muscle is typically arranged in 2 distinct layers
- Circular layer: closest to lumen of organ
- Longitudinal layer: wraps around circular
layer
• Layers differ in their orientation of cells
- Typically perpendicular to each other

Anatomy (22 decks)

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