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Z -Biol 151 > Muscular System > Flashcards

Muscular System Flashcards

1
Q

activation gates

A

closed at rest; open with depolarization, allowing Na+ to enter cell

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2
Q

inactivation gates

A

open at rest; block channel once it is open to prevent more Na+ from entering cell

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3
Q

excitation-contraction coupling

A
  • AP from motor end plate to t-tubules to sarcoplasm
  • AP stimulate voltage gates open; linked to Ca channels in terminal cisternae (SR)
  • Ca is released and diffuse out of cytoplasm
  • Ca bind to troponin, cause troponin-tropomyosin to change shape and rest on actin
  • actin activation sites now available to bind to myosin heads and contract
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4
Q

cross bridge movement

A

attach: lose P and ADP attaches to myosin head to actin

power stroke: myosin head attached to actin stroke forward from preexisting energy in the heads

release: ATP arrives and removes the myosin head from the actin

recovery: ATP broken into ADP and P; energy released stored in myosin heads

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5
Q

relaxation

A
  • Ca back into sarcoplasmic reticulum via active transport (pay w ATP)
  • use ATP to move Ca from troponin-tropomyosin complex
  • troponin-tropomyosin complex reestablishes position and block binding sites
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6
Q

muscle twitch

A

Muscle contraction in response to a stimulus that causes action potential in one or more muscle fibers
-lag/latent phase
- contraction phase
- relaxation phase

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7
Q

lag (latent) phase

A
  • AP arrive at presynaptic terminal and causes its permeability to increase
  • Ca diffuse in and sends ACh vesicles across synaptic cleft to be received by ACh receptor molecules
    -ACh binding to receptor = open Na ligand channels
  • Na diffuse in > depolarize > conduct AP
  • acetylcholinestrease is working and causes presynaptic AP to cause postsynaptic AP
  • AP in t tubules allows Ca in from SR to sarcoplasm
  • Ca bind to troponin > change shape of troponin-tropomyosin complex > expose actin active sites
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8
Q

contraction phase

A

cross bridge formation and filament movement (attach, power stroke, release, recovery)

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9
Q

relaxation phase

A
  • Ca actively transported from sarcoplasm to SR
  • troponin-tropomyosin complex inhibits against cross bridge formation
  • muscle fibers lengthen passively
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10
Q

titan

A

a protein the length of a sarcomere that allows muscle fiber to rebound to normal length after being stretched/compressed

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11
Q

contraction of whole muscle

A
  • Strength of contraction is graded: ranges from weak to strong depending on stimulus strength
  • multiple motor unit summation: strength of contraction depends on recruitment of motor units
    (submaximal stimulus, maximal stimulus, supramaximal stimulus)
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12
Q

multiple wave summation

A

muscle tension increases as contraction frequencies increase
- incomplete tetanus: muscle fibers relax btwn contractions
- complete tetanus: no relax btwn contractions

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13
Q

treppe

A

each successive twitch contracts more forcefully than the previous one until all equal after a few stimuli
- occurs in long rested muscle
- Ca in sarcoplasm and not SR

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14
Q

isometric contraction

A

Muscle contracts but there is no movement, muscle stays the same length (“same” “length”)
- push/pull and hold

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15
Q

isotonic contraction

A

change in muscle fiber length but tension is constant (“same” “tension”)
- concentric: overcome opposing resistance, muscle shortens
- eccentric: tension maintained but muscle lengthens

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16
Q

muscle tone

A

the state of balanced muscle tension that makes normal posture, coordination, and movement possible

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17
Q

multiple wave summation

A

muscle tension increases as contraction frequencies increase
- incomplete tetanus: muscle fibers relax btwn contractions
- complete tetanus: no relax btwn contractions

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18
Q

Tetanus

A

Muscle contractions in smooth/organized way up until complete contraction

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19
Q

treppe

A

each successive twitch contracts more forcefully than the previous one until all equal after a few stimuli
- occurs in long rested muscle
- Ca in sarcoplasm and not SR

20
Q

isometric contraction

A

Muscle contracts but there is no movement, muscle stays the same length (“same” “length”)
- push/pull and hold
- postural muscles

21
Q

isotonic contraction

A

no change in length but muscle increases (postural muscles), stays the same

22
Q

muscle tone

A
  • Isotonic: change in length but tension constant, same tone
  • Concentric: overcome opposing resistance and muscle shortens
  • Eccentric: tension maintain but muscle lengthens
23
Q

Muscle Tone

A

Constant tension by muscles for long periods of time (full motor unit recruitment)

24
Q

active tension

A

force applied to an object to be lifted when a muscle contracts
- actively move weight (bicep curl)

25
Q

passive tension

A

tension applied to load when a muscle is stretched but not stimulated
- pick up and hold weight (before action)

26
Q

Total Tension

A

Sum of active and passive tension

27
Q

Fatigue

A

decreased capacity to work; reduced performance efficiency
- psychological: depends on each person
- muscular: ATP depletion
- synaptic: not enough ACh in NMJ

28
Q

Physiological contracture

A

State of fatigue where due to lack of ATP neither contraction nor relaxation can occur
- muscles cannot relax and stay contracted as not enough ATP is there to remove myosin head

29
Q

Energy Sources

A

ATP made from:
- creatine phosphate: resting condt stores to make ATP
- anaerobic respiration: w/o oxygen break glucose down into lactic acid and ATP
- aerobic respiration: w oxygen, break glucose into ATP, CO, H2O
-oxygen debt

30
Q

Slow twitch fibers

A

high-oxidative
-Lots of mitochondria
-Myoglobin stores oxygen in muscles (lots)
-Endurance > power
-Contract slowly
-Lots of blood supply (lots of capillaries)
-high aerobic capacity
-Postural muscles
- small fiber diameter

31
Q

Intermediate Twitch Fibers

A
  • intermediate fiber diameter
  • medium myoglobin, mitochondria, capillaries, and aerobic capacity
  • high anaerobic capacity
  • lower body
  • endurance activities
  • traits of both fast and slow twitch fibers
32
Q

fast twitch fibers

A

low-oxidative
- largest fiber diameter
- Contractile phase is fast; contract rapid
-Low myoglobin and low/fewer mitochondria
-Fatigue quickly
-Upper limbs for most people
- low aerobic capacity
- highest anaerobic capacity
- fasted ARP breakdown
- few capillaries

33
Q

Hypertrophy

A

increase in:
- muscles size
- myofibrils
- nuclei due to fusion of satellite cells
- strength (better coordination)
- production of metabolic enzymes
- circulation
- less restriction by fat

34
Q

Atrophy

A

decrease in muscle size
reverse of Hypertrophy except in severe situations cells die

35
Q

Smooth muscle

A

-Not striated; small muscle fibers
-Spindle shaped; single and central nucleus (not produce a lot of ATP)
-no z disks
-more actin and less myosin
-Dense bodies are the z disk of smooth muscle; noncontractile intermediate filaments

36
Q

Relaxation of Smooth muscle

A

is caused by enzyme myosin phosphatase (take P of myosin head so smooth muscle can relax)

37
Q

Caveolae

A

indentations in sarcolemma; act similar to t tubule; electrical signal enter here

Ca makes contractions; bind to calmodulin to regulate myosin kinase

38
Q

smooth muscle contraction

A
  • Hormones create action potentials
  • attach to G-protein + Alpha unit
  • Alpha unit changes GTP to GDP
  • Alpha unit w/ GTP opens Ca2+ channel + Ca2+ enters
  • Ca2+ breaks to Calmodulin
  • Calmodulin excites myosin kinase
  • myosin kinase
    dephosph ATP
  • P goes to myosin head
    Myosin phosphatase remove P from myosin so the muscle can relax
39
Q

visceral smooth muscle

A

-Cells in sheets; function as unit
-Digestive system ; respiratory tracts
-Work as group with lots of gap junctions
-All fire together (autorhythmic)

40
Q

Multiunit smooth muscle

A

cells or groups of cells act as independent units
-Blood vessels (sheets)
-Arrector pili or iris (bundles)
-Capsule of spleen (single cells)
-Partial contractions (autorhythmic)

41
Q

electrical properties of smooth muscle

A
  • not all or none
  • -60mV (reduced amplitude)
  • Slow waves of depolarization and repolarization from cell to cell
    -Depolarization = spontaneous diffusion of Na+ and Ca2+ into cell (none gated leakage channels)
    -Does not follow all-or-none law
    -May have pacemaker cells (spontaneous action potential)
    -Contraction regulated by ANS and by hormones
42
Q

cardiac and skeletal APs

A
  • both have rapid depolarization
  • both have all-or-none principle
    skeletal: 2miliseconds long
    cardiac: 500ms long
  • slow dispersal of CO2+ to bring it back into repolarization = long plateau phase = causes larger action potential
43
Q

smooth muscle functional properties

A
  • Some visceral muscle show autorhythmic contractions
    -Tends to contract in response to sudden stretch but not to slow increase in length
  • constant tension (can maintain contraction for extended amount of period because not all-or-none)
44
Q

smooth muscle regulation

A

*Innervated by ANS
*Neurotransmitters are acetylcholine and norepinephrine
*Hormones important are epinephrine and oxytocin
*Receptors present on plasma membrane which neurotransmitters or hormones bind determines response

45
Q

cardiac muscle

A
  • Found only in the heart and is striated with one nucleus
    *Has intercalated disks and gap junctions (can excite adjacent cells)
    *Autorhythmic cells
    *Action potentials of longer duration and longer refractory period (500ms)
    *Ca2+ regulates contraction

Z -Biol 151 (9 decks)

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