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PHA112 > Skeletal system - Muscle > Flashcards

Skeletal system - Muscle Flashcards

1
Q

What are the types of muscle?

A
  • Skeletal
  • Cardiac
  • Smooth
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2
Q

Describe each type of muscle?

A
  • Skeletal: movement of bone & body parts, voluntary
  • Cardiac: heart only, develops pressure for arterial blood flow
  • Smooth: grouped in walls of hollow organs, move material in GI & reproductive organs
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3
Q

What is excitability?

A

Ability to receive and respond to stimuli

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4
Q

What is contractility?

A

Ability to shorten when stimulated

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5
Q

What is extensibility?

A

Ability to be stretched

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6
Q

What is elasticity?

A

Ability to recoil to resting length

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7
Q

List the functions of the skeletal muscle

A
  • Producing movement
  • Maintaining posture & body position
  • Supporting soft tissues
  • Guarding body entrance & exits
  • Maintaining body temp
  • Storing nutrients
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8
Q

What is endomysium?

A

Loose connective tissue that surrounds individual muscle fibres

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9
Q

What is epimysium?

A

Dense irregular connective tissue surrounding entire muscle

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10
Q

What is perimysium?

A

Collagen & elastic fibres surrounding a group of muscle fibres called a fascicle

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11
Q

What do motor neurons do?

A

Stimulate muscle fibres to contract

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12
Q

What do capillary beds surrounding muscle fibres require?

A

Large amounts of energy

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13
Q

What is the sarcolemma?

A

cell membrane

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14
Q

What are myofibrils?

A

Cylindrical structures within muscle fibre

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15
Q

What are myofilaments?

A

Bundles of protein filaments

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16
Q

What is the difference between actin & myosin filaments?

A

Actin - thin

Myosin - thick

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17
Q

What is the sarcomere?

A

Smallest contractile unit of a muscle fibre

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18
Q

What is the difference between thick and thin filaments?

What does the Z disc do?

A

1) Thick - run the length of A band
2) Thin - run the length of I band & partway into A band
3) Z - coin shaped sheet that anchors the thin filaments & connects myofibrils to each other

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19
Q

What is tropomyosin?

A

An elongated protein winds along the groove of the F actin double helix

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20
Q

Troponin composed of 3 subunits (Tn-I, Tn-T, Tn-C), what do they bind to?

A
  • Tn-I = binds to actin
  • Tn-T = binds to tropomyosin
  • Tn-C = binds to calcium ions
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21
Q

What is SR?

A

Sarcoplasmic reticulum

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22
Q

A single T-tubule & 2 terminal cisternae form a ?

A

triad

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23
Q

SR stores what when not contracting?

A

Ca 2+

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24
Q

After contraction, SR pumps the Ca 2+ back into?

A

SR

25
Q

What is the neuromuscular junction (NMJ) ?

A

Skeletal muscles stimulated by somatic motor neurons

26
Q

What is released from nerve fibre?

A

ACh

27
Q

What are the components of the NMJ?

A
  • Synaptic knob swollen end - contains ACh
  • Motor end plate
  • Synaptic cleft
28
Q

List the 4 actions involved in muscle

A
  • Excitation
  • Excitation-contraction coupling
  • Contraction
  • Relaxation
29
Q

Describe each action

A
  • Excitation: nerve action potentials lead to action potentials in muscle fibre
  • ECC: action potentials on sarcolemma activate myofilaments
  • Contraction: shortening of muscle fibre
  • Relaxation: return to resting length
30
Q

What is the sliding filament theory?

A

Explains the relationship between thick & thin filaments as contraction proceeds

31
Q

Cyclic process beginning with Ca release from SR. What does Ca bind to?

A

Troponin

32
Q

What does ATP allow?

A

Release of cross bridge

33
Q

ACh binds with nAChR in muscle membrane to allow what to enter?

A

Na+ ions

34
Q

Na+ ions generate what?

A

Action pontential in sarcolemma

35
Q

What happens when action potential cease?

A

Muscles stop contracting

36
Q

What are the functions of ATP in the skeletal muscle contraction?

A
  • Hydrolysis of ATP by myosin
  • Binding of ATP to myosin
  • Energises Ca 2+ pumps actively transport Ca 2+ back into SR
  • Runs the Na+ K+ pump into sarcolemma
37
Q

ATP for muscle contractions, produced from what 3 sources?

A
  • Creatine phosphate ( 1 ATP per CP)
  • Aerobic respiration (36 ATP per glucose)
  • Anaerobic resp (Glycolysis) - breakdown of glucose to yield ATP & lactic acid
38
Q

Velocity & duration of contraction influenced by what?

A
  • Muscle fiber type
  • Load
  • Recruitment
39
Q

How are skeletal muscle fibres classified?

A
  • Speed of contraction

- Metabolic pathways for ATP synthesis

40
Q

What are the 3 types of fibers?

A
  • Slow oxidative fibers
  • Fast oxidative fibers
  • Fast glycolytic fibers
41
Q

What affects influence of load?

A

↑ load - ↑ latent period, decrease contraction & duration

42
Q

What is a muscle twitch?

A

Response of a muscle fibre to a single, brief threshold stimulus

43
Q

What are the 3 phases of a muscle twitch?

A
  • Latent period
  • Contraction phase
  • Relaxation phase
44
Q

What is a motor unit?

A

Motor neuron & all the muscle fibres it supplies

45
Q

List the motor unit ratios

A

Back muscles - 1:100
Finger muscles - 1:10
Eye muscles - 1:1

46
Q

List components of smooth muscle

A
  • More actin than myosin
  • No sarcomeres
  • Caveolae: indentations in sarcolemma
  • Dense bodies instead of Z disks
47
Q

List the groups of smooth muscle

A
  • Longitudinal layer: muscle fibres run parallel to organ’s long axis
    Circular layer: muscle fibres around circumference of organ
48
Q

What is smooth muscle innervated by?

A

Autonomic nervous system (ANS)

49
Q

What is a multiunit?

A

Cells/groups of cells act as independent units

50
Q

What does Ca 2+ interact with to activate myosin?

A

Ca 2+ interacts with calmodulin + myosin light chain kinase (MLCK)

51
Q

Phosphorylated cross bridges interact with _____ to produce _____

A

actin, shortening

52
Q

_____ muscle _____ when intracellular Ca 2+ levels drop

A

Smooth

Relaxes

53
Q

What is cardiac muscle?

A

Involuntary muscle found only in heart wall

54
Q

What are fibers connected by?

A
  • Intercalated discs (thickened cell membranes)

- Gap junctions that allow spread of action potentials

55
Q

What does cardiac muscle not require?

A

Nerve stimulation nerve

56
Q

Cardiac muscle has its own _______

A 
intrinsic pacemaker (conduction system within cardiac muscle)
- Initiates cardiac contraction (auto-rhythmicity)
57
Q

What do intercalated discs with gap junctions do?

A

Transmit action potentials from one muscle to the next

58
Q

What is the H zone?

A

Lighter midregion where filaments do not overlap

59
Q

What is the M line?

A

Line of protein myomesin that holds adjacent thick filaments together

PHA112 (16 decks)

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