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Musculoskeletal 1 > Physiology > Flashcards

Physiology Flashcards

1
Q

Skeletal muscle

  • description
  • type of control
  • when does it contract
A
  • somatic effector
  • striated
  • generally voluntary control
  • normally does not contract w/o nervous stimulation
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2
Q

Major diff between connectivity of skeletal m compared to cardiac m

A

lacks anatomical and functional connections between individual muscle fibers

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3
Q

Describe a muscle cell

A
  • aka muscle fiber
  • arranged end to end
  • grouped into parallel bundles
  • derived from myodermal myoblasts (remain in tissue to replace cells)
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4
Q

Satellite cells

- describe

A
  • small, little cytoplasm

- can give rise to more satellite cells OR differentiate to muscle fiber

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5
Q

Proliferation of satellite cells influenced by what

A
  • IGF-1 (insulin like growth factor)

- proliferations to provide growth and repair

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6
Q

Three layers of skeletal muscle tissue

A
  1. epimysium
  2. Perimysium
  3. Endomysium
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7
Q

Epimysium

A
  • external sheath

- septa carry vessels and nerves inward

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8
Q

Perimysium

A
  • thin
  • wraps bundles of muscle fibers to form fascicles (the functional unit)
  • penetrated by vessels and nerves
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9
Q

Endomysium

A
  • very thin

- surrounds each muscle fiber

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10
Q

Define:

  • sarcolemma
  • sarcoplasm
  • sarcoplasmic reticulum
A
  • plasma membrane
  • cytoplasm
  • like endoplasmic reticulum
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11
Q

What is contained in the sarcoplasm

A

myoglobin which holds O2

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12
Q

Describe the sarcoplasmic reticulum

A
  • elaborate
  • surrounds myofibrils
  • contains Ca2+ pumps
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13
Q

Terminal cisterna

A
  • part of the sarcoplasmic reticulum
  • sac-like junctions of SR
  • release calcium
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14
Q

T-tubule

A
  • folds of sarcolemma (increases surface area)
  • encircle myofibrils near A-I junctions
  • depolarization wave runs through t-tubules deep into cell
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15
Q

What is the “triad”

A
  • aka sarcotubular system
  • 2 terminal cistern (sarcoplasmic reticulum) and 1 T-tubule (sarcolemma)
  • links calcium release and depolarization
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16
Q

define myofibril

A
  • filament bundle
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17
Q

A band and I band

A

A band

  • anisotropic
  • thick filaments, myosin

I band

  • isotropic
  • thin filaments, actin
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18
Q

Z band

A
  • region of I band w/o A band overlap
  • appears to bisect I band
  • where actin attach, allows shortening of fiber
  • edge of sarcomere
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19
Q

Sarcomere

A
  • functional unit of myofibril

- Z band to Z band

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20
Q

Thick filament

  • fiber type
  • which band
  • describe
A
  • myosin
  • A bands
  • rod like tail
  • two globular heads
  • head contains ATP binding site and actin binding site
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21
Q

M Line

A
  • in the H zone
  • reversal of polarity of cross bridges
  • she didn’t seem to care much about this…
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22
Q

Thin filament

  • fiber type
  • which bands
A
  • actin, tropomyosin, and troponin

- I bands

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23
Q

Actin

- describe

A
  • composed of G actin subunits

- 2 strands coil to form actin helix

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24
Q

tropomyosin

- describe

A

long filaments that spiral around actin

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25
Q

Troponin

  • describe
  • three types
A
  • located at intervals along tropomyosin
  • TnI: binds actin
  • TnT: binds tropomyosin
  • TnC: binds calcium
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26
Q

Name four additional structural proteins

A
  • Actinin
  • Titin
  • Creatine kinase
  • Myoglobin
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27
Q

Actinin

A
  • binds actin to Z lines
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28
Q

Titin

A
  • connects Z lines to myosin
  • provides structure, stretch, and resistance
  • can coil and stretch
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29
Q

Creatine Kinase

A
  • at M line
  • phosphorylation of ATP from phosphocreatine (holds phosphate so can turn ADP into ATP when needed)
  • provides contractile E source
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30
Q

myoglobin

A
  • holds on O2
  • higher affinity for O2 than hemoglobin
  • O2 will transfer from hemoglobin to myoglobin dt Bohr effect
31
Q

Bohr affect - three factors that affect O2 dissociation

A

will dissociate when:

  • heat
  • low pH
  • increased DPG

*and opposite

32
Q

Very basic overview of muscle excitation

A
  • somatic motor nerve is depolarized
  • releases Ach
  • Ach binds to nicotinic receptor on motor end plate of resting cell (muscle)
33
Q

What is the resting potential of a muscle cell?

What is depolarized membrane potential?

A

-90 mV

30 mV

34
Q

Muscle cell excitation steps

A
  • Ach triggers opening of voltage gated Na+ channels
  • sodium influx
  • local depolarization in all directions along sarcolemma and into T tubules
  • voltage gated calcium channels on SR open, calcium not sarcoplasm
  • contraction of muscle
35
Q

action potential of muscle cells

  • how long does it last
  • can it be partial?
A
  • 1-2 milliseconds

- no, is all or none, once action potential is initiated, full contraction of stimulated cell occurs

36
Q

What happens to calcium after it is released into the sarcoplasm?

A
  • ATP dependent calcium pumps return calcium to sarcoplasmic reticulum
  • another reason muscle contraction is ATP expensive
37
Q

Repolarization

A
  • returns sarcolemma to resting state
  • Na+ gates close
  • K+ gates open, K+ efflux
38
Q

What is the name for the period of time during repolarization

A

refractory period - cannot depolarize

39
Q

When/what returns

  • electrical resting state
  • ionic resting state
A
  • electrical: during repolarization

- ionic: via Na/K pump

40
Q

what is the resting blockade?

A

Myosin binding site on actin is blocked by tropomyosin

41
Q

What happens when calcium binds troponin

A
  • binds to TnC
  • conformational change in tropomyosin
  • myosin binding site on actin exposed
42
Q

Describe steps after myosin binding site of actin is exposed

A
  • myosin head binds myosin binding site on actin (cross bridge attachment)
  • powerstroke
  • repeat until calcium concentration decreases
43
Q

Powerstroke steps

A
  • release of ADP = myosin head pivots (release of energy)
  • draws actin toward
    center of sarcomere
  • head binds ATP, releases actin
  • ATP hydrolysis cocks head to attachment position
44
Q

About how many power strokes per head

A

5

45
Q

What is a motor unit

A
  • motor neuron and all the muscle fibers it supplies
  • one motor nerve has 100s of axons branching to many axonal terminals
  • when nerve fires, all fibers served are stimulated
46
Q

What does it mean that the fibers served by a motor neuron are not clustered?

A

stimulation of a single motor unit causes weak contraction of the entire muscle

47
Q

About how many fibers per motor unit?

A

average is 150 fibers/motor unit

48
Q

Muscle twitch

A
  • single action potential causes brief contraction followed by relaxation
  • there is a small latent period between action potential and start of contraction
  • duration of twitch varies with muscle type
  • can trace on myogram
49
Q

Slow twitch fibers

  • myoglobin
  • cell description
  • myosin ATPase
  • contraction
  • primary E source
  • metabolism type
  • length of contraction
A
  • abundant myoglobin = red
  • thin cells
  • slow acting myosin ATPase (allows for globular head to move, allows contraction)
  • slow contraction
  • fat is primary E source
  • aerobic metabolism
  • can contract for long periods
50
Q

fast twitch fibers

  • myoglobin
  • cell description
  • myosin ATPase
  • contraction
  • primary E source
  • metabolism type
  • length of contraction
A
  • less myoglobin = white
  • large cells
  • fast acting myosin ATPase
  • quick, powerful contraction
  • abundant glycogen reserve
  • glucose is primary fuel
  • anaerobic pathway, lactic acid production
  • quickly fatigued
51
Q

What does graded muscle responses mean?

A

variations in degree of contraction. Depends on

  1. rate at which firing (increased rapidity of stimulus to create contraction)
  2. recruiting increased number of motor units

*muscle contractions are smooth and prolonged, not a muscle twitch

52
Q

Wave summation

A
  • subsequent impulses create a stronger contraction that appears to build on prior contractions
  • when second contraction is stimulated before muscle has completely relaxed
  • creates smooth, continuous muscle contraction
53
Q

Tetany

A
  • no muscle relaxation
  • wave summation results in continue contraction
  • nerve stimulus is in rapid succession
  • fatigue of m eventually occurs (run out of O2, ATP, etc.)
54
Q

Treppe

A
  • staircase effect in contraction, subsequent contractions are greater strength despite same stimulus
  • activity produces heat = enzymes more efficient
  • increases avail of calcium for contraction
  • why warm up before exercise
55
Q

How is force of contraction increased?

A

increased number of motor units stimulated

56
Q

Delicate touch vs. strong grip

A
  • delicate: few motor units
  • Grip: many motor units

*still all or none!!

57
Q

Muscle tone

A
  • relaxed m exhibits certain amt of contraction (tone)
  • involuntary
  • d/t spinal reflexes in response to stretch receptors in muscle/tendon
  • provides joint stability, maintains posture, readiness for stimulation
58
Q

Describe muscle tension

A
  • force exerted by a contracting muscle
59
Q

Describe load

A
  • weight or reciprocal force exerted by objection on muscle
  • thing muscle is trying to move
  • influences velocity and duration of muscle work
60
Q

Describe movement

A

tension overcomes load

- greater the load, longer the latent period, slower the contraction and shorter duration of contraction

61
Q

Isotonic contraction

A
  • tension exceeds load
  • muscle shortens
  • load is moved
  • movement of body
62
Q

Isometric contraction

A
  • tension equals load
  • muscle does not shorten
  • load is not moved
  • posture and balance
63
Q

what type of contraction (isotonic vs. isometric) are most movements?

A

combo of both :)

64
Q

Describe length-tension relationship

A
  • ideal stretch that produces maximal force of contraction (resting length)
  • related to sarcomere length and overlap of myofibrils
  • skeletal m are attached to bones at optimum length, slightly stretched to voice max movement
65
Q

What is required for all muscle contractile events

A

ATP

  • crossbridge stroke and detachment
  • calcium pump, returns calcium to SR
66
Q

How does muscle get ATP?

A

little stored in muscle, most must be generated

67
Q

List two sources of energy for muscle

A
  1. Glucose

2. Fatty Acids

68
Q

Glucose energy source for muscles (2)

A
  • via circulation

- glycogenolysis (from glycogen stored in m tissue)

69
Q

Fatty acid energy source for muscles

A
  • TG in muscle cells and circulation
  • lipolysis from adipose, release FA to circulation, 2 carbon bodies enter Krebs cycle as acetylene-coA

*muscle loves fat as an E source

70
Q

Anerobic respiration for muscle metabolism

A
  • glucose into glycolysis
  • pyruvate is oxidized to relish NADH
  • ATP and lactic acid are produced
  • lactate converted to pyruvate once O2 is available
71
Q

Creatine phosphate

A
  • liver produces creatine from arg, gly, meth
  • creatine kinase phosphorylates creatine into phosphocreatine which is stored in muscle cells
  • CK-MB acts at junction of myosin head/actin to provide phosphate to generate ATP from ADP for contraction
  • can be regenerated
72
Q

what is creatinine

A
  • breakdown product of creatine phosphate

- marker for renal function :)

73
Q

List the energy sources from shortest to longest duration

A
  • ATP
  • creatine phosphate (4 sec)
  • anaerobic glycolysis (2-3 min)
  • aerobic glycolysis (1-2 hours)
  • fatty acid oxidation (many hours)

Musculoskeletal 1 (14 decks)

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