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Pathophysiology > Muscle Structure, Function And Contraction > Flashcards

Muscle Structure, Function And Contraction Flashcards

1
Q

What are the 3 types of muscle tissue?

A

Cardiac muscle
Skeletal muscle and smooth muscle

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2
Q

Where is cardiac muscle found?

A

In the heart

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3
Q

Where is smooth muscle found?

A

In the walls of organs

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4
Q

Which of the 3 muscle types is multi-nucleated?

A

Skeletal muscle

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5
Q

Which two muscle groups contract involuntary?

A

Cardiac and smooth muscle

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6
Q

What are the names of the 3 key connective tissues in skeletal muscles?

A

Epimysium, perimysium, endomysium

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7
Q

What are the relative sizes of the 3 key layers of connective tissue (in comparison to one another)?

A

Epimysium > perimysium > endomysium

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8
Q

Name 5 functions of muscles

A

Produces body movements
Stabilises body positions
Regulates organ volumes (sphincters)
Movement of substances within the body
Produces heat (shivering)

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9
Q

Name 5 properties of muscle tissue

A

Excitability
Conductivity
Contractibility
Extensibility
Elasticity

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10
Q

Why does skeletal muscle have multiple nuclei?

A

Because during development muscles form from multiple myoblasts fusing together. Each myoblast has its own nucleus therefore when they fuse together you end up with multiple nuclei

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11
Q

Where does skeletal muscle attach to?

A

Bone, skin or fascia
Maybe via tendons/aponeuroses

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12
Q

What happens to left over myoblasts?

A

They become satellite cells

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13
Q

What are satellite cells?

A

Stem cells
When there is some damage to the muscle, the stem cell can divide and assist in repair

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14
Q

Name the 7 functions of skeletal muscle

A

Produce skeletal movement
Maintain body position
Support soft/hard tissues
Guard body openings
Maintain body temperature
Stores nutrient reserves
Proprioception (knowing where your body is in space)

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15
Q

What is epimysium?

A

A sheath of connective fascia that surrounds the whole muscle

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16
Q

What is epimysium connected to?

A

Deep fascia

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17
Q

Which connective tissue separates surrounding muscles from surrounding tissues?

A

Epimysium

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18
Q

Which connective tissue surrounds muscle fibre bundles (fascicles)?

A

Perimysium

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19
Q

Which connective tissue in the muscle contains blood vessels and nerve supply to fascicles?

A

Perimysium

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20
Q

Which connective tissue surrounds individuals muscle cells?

A

Endomysium

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21
Q

Which connective tissue layer contains satellite cells that repair damage and capillaries and nerve fibres contacting muscle cells?

A

Endomysium

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22
Q

What do endomysium, perimysium and epimysium come together at the ends of muscle to form?

A

Connective tissue attachment to bone matrix I.e. tendon (bundle) or aponeurosis (sheet)

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23
Q

Messages from the central nervous system reach the muscle tissue via what nerve?

A

A peripheral nerve

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24
Q

What is a motor unit?

A

One motor nerve and the muscle fibres it supplies

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25
Q

What are skeletal muscle cells called?

A

Fibres

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26
Q

What is the sarcolemma?

A

The cell membrane of a muscle cell

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27
Q

What is the sarcoplasm?

A

Cytoplasm of muscle fibre

28
Q

What do T tubules do?

A

Carry muscle action potentials down into the cell and allow the entire muscle fibre to contract simultaneously

29
Q

What is a T tubule?

A

An invagination of the sarcolemma into the centre of the cell

30
Q

What is the sarcoplasmic reticulum?

A

A membranous structure surrounding each myofibril
It is a system of tubular sacs similar to smooth endoplasmic reticulum in non-muscle cells

31
Q

What does the sarcoplasmic reticulum do?

A

Helps transmit action potential to the myofibrils

32
Q

What do terminal cisternae form?

A

Calcium

33
Q

What does sarcoplasmic reticulum form at each end?

A

Chambers (terminal cisternae)

34
Q

What does sarcoplasmic reticulum do in a relaxed muscle?

A

Stores calcium ions

35
Q

How does sarcoplasmic reticulum trigger muscle contraction?

A

By releasing calcium ions

36
Q

What is a triad made up of?

A

1 T-tubule and 2 terminal cisternae

37
Q

What are myofibrils made up of?

A

Bundles of protein filaments (myofilaments)

38
Q

What are myofilaments?

A

The contractile proteins of muscles

39
Q

What does the sarcoplasm contain?

A

Glycogen and fats for energy as well as mitochondria

40
Q

What does the I band contain?

A

Only thin filaments (actin)

41
Q

What does the A band contain?

A

Thick (myosin) filaments

42
Q

What is a sarcomere?

A

The contractile unit of a muscle

43
Q

What is the importance of titan?

A

It is thought to be quite important in terms of use of eccentric muscle contraction
Titan attaches the myosin filament to the Z line so prevents the muscle from over stretching and it helps it to recoil back to its normal size

44
Q

What are thick filaments composed of?

A

Myosin

45
Q

What are thick filaments held in place by?

A

M line proteins

46
Q

What are thin filaments made up of?

A

Actin, troponin and tropomyosin

47
Q

What is the myosin binding site on each actin molecule covered by in a relaxed muscle?

A

Tropomyosin

48
Q

What are thin filaments held in place by?

A

Z lines

49
Q

What does the M line connect to?

A

Titan and adjacent thick filaments

50
Q

What is nebulin?

A

An in elastic protein that helps align the thin filaments

51
Q

What does dystrophin do?

A

Links thin filaments to sarcolemma and transmits the tension generated by the tendon

52
Q

What type of muscle contraction does the sliding filament mechanism look at specifically?

A

Concentric isotonic muscle contraction

53
Q

For contraction to occur there needs to be some sort of stimulation of the muscle, how is it stimulated?

A

Happens in the form of a nerve impulse or an action potential

54
Q

Describe the stimulation of muscle contraction

A

Nerve impulses reaches an axon terminal
Synaptic vessels release acetyl choline
Acetyl choline diffuses to receptors on the sarcolemma
This causes sodium ion channels to open
Sodium ions rush into the cell
A muscle action potential spreads over the sarcolemma and down into the T tubules
Action potential reaches a triad
Terminal cisternae release calcium ions into the sarcoplasm
Calcium ions bind to troponin and causes troponin-tropomyosin complex to move and reval binding sites on actin
Excitation - contraction coupling
Contraction cycle begins

55
Q

What are the 3 essential components for the contraction cycle to happen?

A

Neural stimulus
Enough calcium ions
Enough ATP

56
Q

What are the 6 steps of the contraction cycle of a muscle?

A

Exposure of active sites on actin
ATP hydrolysis into ADP, Pi and energy
Attachment of myosin to actin to form cross-bridges
Power stroke
Detachment of myosin from actin
Reactivation of myosin

57
Q

What is the contraction cycle of a muscle ?

A

Repeating sequence of events that causes the thin filaments to slide between the thick filaments

58
Q

What is the power stroke?

A

Pivoting of myosin head, pulling in the thin filament

59
Q

What are the 9 steps of relaxation of a muscle?

A

Acetylcholinesterase breaks down acetyl choline within the synaptic cleft
Muscle action potential ceases
Calcium ion channels close
Calcium ions detach from troponin
Active transport pumps calcium ions back into storage in the terminal cisternae of the sarcoplasmic reticulum
Calcium ion concentration falls
Tropomyosin- troponin complex recovers binding site on the actin molecules
Contraction ends
Relaxation occurs, muscle return passively to resting length

60
Q

What is a neuromuscular junction?

A

The site of the signal exchange, this is where the synaptic bulb of an axon terminal and muscle fibre connect

61
Q

What happens when a muscle is above or below optimal length?

A

Fewer cross bridges exist and less force is produced

62
Q

What are the 3 sources of ATP production within a muscle?

A

Creatine phosphate
Anaerobic cellular respiration
Aerobic cellular respiration

63
Q

What is used to form creatine phosphate?

A

Excess ATP within the resting muscle

64
Q

How long does creatine phosphate sustain maximal contraction for?

A

15 seconds

65
Q

How many times more plentiful is creatine phosphate in comparison to ATP within the muscle?

A

3-6 x

66
Q

How long can glycolysis continue to anaerobically provide ATP for?

A

30-40 second of maximal activity

67
Q

How long aerobic respiration provide ATP for?

A

Any activity lasting over 30 seconds

Pathophysiology (14 decks)

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