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Anatomy & Physiology > Muscles (Function and Organization) > Flashcards

Muscles (Function and Organization) Flashcards

1
Q

Skeletal Muscle (description)

A
  • Usually attached to bones
  • Voluntary control
  • Striated
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2
Q

Cardiac Muscle (description)

A
  • Located on in the wall of the heart
  • Muscle fibers joined together by intercalated discs
  • Branched networks of fibers contract as a unit
  • Self-exciting and rhythmic
  • Involuntary
  • Striated
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3
Q

Smooth Muscle (description)

A
  • Located in the lining of hollow organs, blood vessels, and skin
  • Shorter fibers (compared to skeletal muscle fibers)
  • Single, centrally located nucleus
  • Elongated with tapering ends
  • Involuntary
  • Not striated due to random organization of myofilaments
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4
Q

Structure of a Muscle

A
  • Muscle (belly)
  • Fascicles
  • Muscle fibers
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5
Q

Fascia

A

Covers muscle (belly)

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6
Q

Epimysium

A

Covers muscle (belly)

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7
Q

Perimysium

A

Surrounds fascicles

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8
Q

Endomysium

A

Surround individual muscle cells/fibers

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9
Q

Structure of a Muscle Fiber

A
  • Sarcolemma
  • Myofibrils
  • Actin and Myosin
  • Sarcomeres
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10
Q

Sarcolemma

A

Cell membrane of a muscle cell

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11
Q

Myofibrils

A

Make up muscle fibers; fundamental role in muscle contractions

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12
Q

Sarcomeres

A

Structural and functional unit of myofibrils; distance between two Z lines

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13
Q

Thick Filaments

A

Composed of myosin; cross-bridges

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14
Q

Thin Filaments

A

Composed of actin

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15
Q

Motor Unit

A

All the muscle fibers controlled by a single motor neuron

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16
Q

Stimulus for Muscle Contraction

A
  • Motor neuron stimulates the release of Acetylcholine (ACh), a neurotransmitter
  • Occurs in the neuromuscular junction
  • Triggers a chemical reaction in the muscle tissue (muscle impulse)
17
Q

Contraction

A
  • Muscle impulses cause the release of calcium ions into cytoplasm
  • Calcium binds to the actin filaments which changes its shape and exposes the myosin binding sites
  • Actin and myosin filaments bind via myosin cross-bridges
  • Process continues as long as Ca+2 ions and ATP are present
  • ATP is produced by cellular respiration
18
Q

Contraction (Cross-Bridge Cycling)

A
  • Myosin heads pull on actin filament toward center of sarcomere (= power stroke); ADP and phosphate are released from myosin head
  • New ATP binds to myosin; myosin cross-bridge releases
  • New ATP is split; myosin head goes back to original position and is ready to bind again
19
Q

Contraction (Sliding Filament Model)

A

Sarcomeres shorten as myofilaments slide past one another; Z-lines move closer together

20
Q

Relaxation

A
  • Motor neuron stimulus to muscle stops
  • Calcium moves back into sarcoplasmic reticulum
  • ATP binds to myosin head to break cross-bridges
  • In the absence of Ca+2 ions, actin returns to its resting shape and prevents myosin binding
  • Muscle fibers relax and lengthen
21
Q

Muscle Fatigue

A

Inability of muscles to contract and/or relax

22
Q

Muscle Fatigue (causes)

A
  • Decreased blood flow
  • Ion imbalances across the sarcolemma
  • Accumulation of lactic acid
23
Q

Cramp

A

Sustained, involuntary muscle contraction; can result from fatigue

24
Q

Heat Production

A
  • By-product of cellular respiration
  • Skeletal muscles are major sources of body heat
  • Blood distributes heat throughout body
25
Q

Skeletal Muscle (categorization)

A
  • Origin
  • Insertion
  • Prime mover
  • Synergists
  • Antagonist
26
Q

Origin

A

Immovable end of a skeletal muscle

27
Q

Insertion

A

Movable end of a skeletal muscle

28
Q

Prime Mover

A

Primarily responsible for movement of a skeletal muscle

29
Q

Synergists

A

Skeletal muscles that assist the prime mover

30
Q

Antagonist

A

Skeletal muscle that resists prime mover’s action and causes movement in the opposite direction

31
Q

Life-Span Changes

A
  • Myoglobin, ATP, and creatine phosphate (needed for ATP production) decline
  • By age 80, half of muscle mass has atrophied
  • Adipose cells and CT replacement muscle tissue
  • Exercise helps to maintain muscle mass and function

Anatomy & Physiology (8 decks)

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