Muscle Physiology Flashcards

1
Q

describe muscles in a simple manner

A

excitable tissues (like neurons)

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2
Q

how does the action potential affect muscles

A

induces contractions to generate force for movement

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3
Q

what are the types of muscles

A
  • smooth
  • cardiac
  • skeletal
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4
Q

what are the main parts of a skeletal muscle structure

A
  • tendons
  • epimysium
  • fascicles
  • perimysium
  • muscle fibres
  • endomysium
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5
Q

describe tendons

A

thick connective tissue that connects to bones

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6
Q

describe epimysium

A
  • continuation of tendon
  • thin outer covering of entire muscle
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7
Q

describe fascicles

A

bundles of muscle fibres

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8
Q

describe perimysium

A

covering of fascicle

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9
Q

describe muscle fibres

A

= muscle cells

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10
Q

describe endomysium

A

covering of muscle fibres

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11
Q

what is gross muscle made of

A

bundles of fascicles

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12
Q

what are the main components of a muscle fibre

A
  • sarcolemma
  • sarcoplasm
  • sarcoplasmic reticulum
  • transverse (T) tubules
  • (multi)nuclei
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13
Q

describe the sarcolemma

A

muscle plasma membrane

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14
Q

describe the sarcoplasm; what does it consist of

A

muscle cell cytoplasm; consists of mitochondria and myofibrils

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15
Q

describe the sarcoplasmic reticulum; what does it consist of

A

muscle ER; consists of lateral sacs/terminal cisternae

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16
Q

what is a triad and what does it do

A

1 t-tubule in middle and 2 terminal cisternae at ends (swelling), which plays a role with propagating AP leading to muscle contraction

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17
Q

draw out the structure of sarcolemma to triad

A

…..

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18
Q

draw out the components of a muscle fibre

A

…..

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19
Q

draw out the skeletal muscle structure

A

…..

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20
Q

how do the SR and terminal cisternae work together

A

calcium pumps on SR membrane which allows for active transport of calcium ions into SR for storage in TC

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21
Q

how do SR and T-tubules work together

A

activate muscle contractions (propagating AP); transmit signals from sarcolemma to myofibrils

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22
Q

describe myofibrils; what protein fibres does it contain

A

lowest level of bundles (molecular level) and contains actin and myosin protein fibres

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23
Q

describe the functional unit of myofibril

A

sarcomere; has A and I bands, M and Z (start and end) lines, H zone

24
Q

describe the arrangement of muscle that makes it look the way it does

A

thick and thin filaments arranged in a manner that gives stripey appearance

25
Q

what type of a filament is myosin; actin?

A

thick; thin

26
Q

draw out a myofibril

A

….

27
Q

what is the Z-line

A

the area where thin filaments are held together (edge of sarcomere)

28
Q

what is the M-line

A

middle of sarcomere where thick filaments are linked together

29
Q

what is the I-band

A

area of sarcomere with only thin filaments (light in colour)

30
Q

what is the H-zone

A

area of sarcomere with only thick filaments

31
Q

what is the A-band

A

area of sarcomere with mainly thick filaments with overlap of thin filaments at edges (dark in colour)

32
Q

what are the main parts of thin filament structure

A

G-actin with binding site making actin protein making F-actin making thin filament

33
Q

what are the regulatory proteins of the thin filaments

A

tropomyosin, troponin

34
Q

what is the role of tropomyosin

A

overlaps myosin binding sites on actin

35
Q

what is the role of troponin

A

complex of 3 proteins; attaches to actin and tropomyosin which then binds Ca (reversibly) and allows for regulation of skeletal muscle contraction

36
Q

describe the thin filament structure shape

A

double stranded, helical/twining

37
Q

describe the thick filament structure shape

A

many hockey stick structures bound together, each end of hockey stick is myosin head binding site (crossbridge)

38
Q

what do the myosin heads bind for

A

actin and ATPase

39
Q

draw flow of main parts of sarcomere structure at the molecular level

A

z-line -> titin -> thick and thin filaments overlapped -> z-line

40
Q

what is titin

A
  • elastic and structurally supportive protein
  • when muscle contracts and expands, titin produces elastic force allowing sarcomere to stretch and return back to shape
41
Q

list the mechanisms of generating force in muscles

A
  • sliding filament model
  • crossbridge cycle
  • excitation-contraction coupling
42
Q

describe the sliding filament model

A
  • thin and thick filaments overlap
  • slide past e/o
  • individual filaments do not shorten but appearance turns short of muscle
43
Q

how does sliding happen

A

cyclical formation and breaking of crossbridges

44
Q

describe the steps of crossbridge cycle

A
  • myosin head goes through conformation change due to ATP hydrolysis
  • cyclic binding/unbinding of crossbridges to thin filaments
  • results in thin filaments moving toward M line of sarcomere
45
Q

the crossbridge cycle alters the energy content of myosin molecules. describe the energy forms

A
  • high energy: ADP + P bound to myosin so it stores energy (high affinity for actin)
  • low energy: ATP bound to myosin (low affinity for actin)
46
Q

draw out the crossbridge cycle

A

…..

47
Q

why are crossbridges out of sync but go through the cycle simultaneously

A

to allow for gradual movement

48
Q

what would happen if crossbridges were in sync

A

inefficient use/generation of power

49
Q

describe excitation-contraction coupling

A
  • explains how muscle contractions turn on and off
  • sequence of events where an AP in the sarcolemma cause contraction
  • dependent on neural input from motor neuron
  • requires Ca release from SR
50
Q

describe the role of the neuromuscular junction

A
  • nerves and muscle fibres meet here
  • essential synapse for muscle contraction and movement
  • motor neuron innervates several muscle cells which releases acetylcholine
  • potential generated in end plate to trigger AP in muscle cell
51
Q

motor neuron AP ______ creates muscle cell AP

A

always

52
Q

what are the roles of Ca, troponin and tropomyosin in excitation-contraction coupling

A
  • low/no Ca: troponin holds tropomyosin over myosin binding sites on actin
  • Ca present: binds to troponin causing movement of troponin then tropomyosin and exposes binding sites for myosin on actin
  • cycle occurs and muscle contracts
53
Q

draw a diagram of excitation-contraction coupling

A

….

54
Q

what are the receptors and releases that cause AP in T-tubule membrane to lead to calcium release from SR membrane

A
  • DHP and ryanodine receptors
  • calcium-induced calcium release
55
Q

draw gating of SR calcium channels before and after AP

A

….