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MCAT Biology > Muscular System > Flashcards

Muscular System Flashcards

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1
Q

skeletal muscle

A
  • voluntary movement
  • somatic NS
  • actin and myosin in repeating units called sarcomeres
  • striated
  • red and white fibers
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2
Q

red fibers

A
  • skeletal muscle slow twitch fibers
  • high myoglobin content, derive energy aerobically
  • contain mitochondria and carry out oxidative phosphorylation
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3
Q

white fibers

A
  • skeletal muscle fibers fast-twitch
  • less myoglobin
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4
Q

smooth muscle

A
  • involuntary action
  • autonomic NS
  • single nucleus at the center of the cell
  • actin and myosin but fibers not as well seen, no striations
  • sustained contractions, tonus
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5
Q

myogenic activity

A
  • smooth and cardiac muscle can contract without NS input
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6
Q

cardiac muscle

A
  • smooth and skeletal muscle types
  • uninucleated primarily, some cells may have two nuclei
  • involuntary contraction, autonomic NS
  • striated
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7
Q

how do cardiac cells communicate?

A
  • they are connected through intercalated discs and contains many gap junctions through which ions flow and allow for rapid depolarization
  • maintain their own rhythm
  • SA node, AV node, bundle of His, Purkinje fibers
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8
Q

how does NS affect heart rate?

A
  • vagus nerve provides sympathetic outflow to the heart and slows HR
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9
Q

how does endocrine system affect HR?

A

NE from sympathetic neurons of Epi from adrenal medulla binds to adrenergic receptors in the heart which causes inc HR and greater contractility

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10
Q

thick filament made of

A

myosin

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11
Q

thin filament made of

A

actin

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12
Q

in a sarcomere, titin acts as a…

A

spring and anchors actin and myosin together to prevent XS stretching

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13
Q

Z line of sarcomere

A

end of sarcomere

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14
Q

M line of sarcomere

A
  • center of sarcomere
  • middle of myosin filaments
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15
Q

I band

A
  • exclusively thin filaments
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16
Q

H zone

A
  • contains only thick filaments
17
Q

A band

A

contains any thick filaments in their entirety including overlap with thin

18
Q

during contraction of a sarcomere…

A
  • H zone and I band become smaller
  • Z lines and M lines get closer
  • A band remains constant
19
Q

sarcomeres attach end to end to form

A

myofibrils

20
Q

myofibrils are surrounded by…

A

sarcoplasmic reticulum

21
Q

sarcoplasm lies…

A

outside the SR

22
Q

cell membrane of a myocyte is known as…

A
  • sarcolemma, capable of propagating an action potential using T-tubules
23
Q

each myocyte consists of…

A

many myofibrils arranged in parallel and can also be called a muscle fiber

24
Q

muscle contraction

A
  • motor neuron sends AP down to the NMJ and releases Ach to attach to the motor end plate
  • Ach binds to sarcolemma receptors causing depolarization
  • AP travels down to T-tubules to the SR, causing Ca2+ release
  • Ca2+ binds to troponin
  • change in tropomyosin which exposes the myosin-binding sites on actin
  • myosin binds to the actin w a hydrolyzed ATP (ADP + Pi) and causes cross-bridge formation, sarcomere shortening
  • power stroke, contraction, ADP + Pi dissociates
  • ATP binds to myosin head and it is now free and relaxation is now achieved
25
Q

each nerve terminal…

A

controls a group of myocytes and this consists of a motor unit

26
Q

muscle cells, like neurons…

A

exhibit an all-or-nothing response

27
Q

simple twitch

A

response of a single muscle fiber to a brief stimulus at or above threshold, consists of a latent period

28
Q

if a muscle fiber is exposed to frequent and prolonged stimulation…

A

it will have insufficient time to relax

29
Q

frequency summation

A

combined strong prolonged contractions due to frequent stimulation

30
Q

tetanus

A
  • if the contractions become so frequent that the muscle is unable to relax at all
  • results in muscle fatigue
31
Q

creatine phosphate

A
  • transferring phosphate group from ATP to creatine during times of rest to
    make it easier to then generate ATP in the reverse rxn
32
Q

what happens to the lactic acid after lactic acid fermentation occurs in both white and red muscle fibers

A

lactic acid then converted into pyruvate to enter the TCA cycle

MCAT Biology (13 decks)

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