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Bad Girl's MCAT Club > Biology 11: Muscloskeletal System > Flashcards

Biology 11: Muscloskeletal System Flashcards

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MCAT flashcards
1
Q

what are the three subtypes of muscle

A

skeletal

smooth

cardiac

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2
Q

skeletal muscle

A

muscle responsible for voluntary movement - somatic

striped/striated bc alternating actin and myosin sarcomeres

multinucleated bc individual muscle cells fuse in long rods

nuclei are found at cell periphery

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3
Q

red fibers / slow-twitch fibers

A

fibers in skeletal muscle

have high myoglobin content and derive most of their energy aerobically

have lots of mitochondria to carry out oxidative phosphorylation

numerous in muscles that contract slowly and can sustain activity

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4
Q

white fibers / fast-twitch fibers

A

fibers in skeletal muscle

contain less myoglobin, less iron, lighter color

numerous in muscles that contract rapidly but fatigue quickly

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5
Q

myoglobin

A

an oxygen carrier that uses iron in a heme group to bind O2, imparting a red color

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6
Q

smooth muscle

A

muscle responsible to involuntary action - autonomic

cells have a single nucleus in the center

contain actin and myosin in fibers not well organized - not striated

can do tonic contraction - constant low-level contraction

myogenic activity - responds directly to stretch and other stimuli

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7
Q

myogenic activity

A

the ability of muscle to contract without nervous system input

present in smooth and cardiac muscle

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8
Q

cardiac muscle

A

muscle found in the heart - involuntary - autonomic

appears striated

primarily uninucleated but sometimes w two nuclei

can define and maintain rhythm through myogenic activity

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9
Q

intercalated discs

A

connect cardiac muscle cells and contain gap junctions

gap junctions - connections between the cytoplasm of adjacent cells, allowing for the flow of ions directly between cells

allows for rapid and coordinated muscle cell depolarization and efficient contraction

allows progressive depolarization to spread via ion flow across

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10
Q

pathway of electrical depolarization through the heart

A

sinoatrial node –> atrioventricular node –> bundle of His –> Purkinje fibers

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11
Q

what provides parasympathetic outflow to heart?

A

vagus nerve

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12
Q

what neural innervations increases heart rate?

A

norepinephrine from sympathetic neurons or epinephrine from adrenal medulla binds to adrenergic receptors in heart

increases heart rate and greater contractility

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13
Q

which filament in a sarcomere is composed of actin?

thin or thick

A

thin

thin filaments also consist of troponin and tropomyosin to regulate interaction between the two filaments

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14
Q

which filament in a sarcomere is composed of myosin?

thin or thick

A

thick

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15
Q

titin

A

protein in sarcomeres that acts as a spring and anchors the actin and myosin filaments together

prevents excessive stretching of muscle

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16
Q

M-line

A

line that runs down the center of the sarcomere, through the middle of the myosin filaments

middle of the myosin filaments

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17
Q

Z-line

A

defines the boundaries of each sarcomere

z is the end of the alphabet, the end of the sarcomere

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18
Q

I-band

A

the region containing exclusively thin filaments (actin)

I is a thin layer, thin filaments only

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19
Q

H-zone

A

region containing exclusively thin filaments (myosin)

H is a thick letter, thick filaments only

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20
Q

A-band

A

region that contains the thick filaments in their entirety, including any overlap with thin filaments

all of the thick filament whether overlapping or not

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21
Q

how do the H-zone, I-band, Z-lines, M-lines, A-lines of a sarcomere change during contraction?

A

H zone, I band becomes smaller

distance between Z lines and M lines all become smaller

A band’s size remains constant

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22
Q

myofibrils

A

end-to-end attachment of sarcomeres

surrounded by sarcoplasmic reticulum

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23
Q

sarcoplasmic reticulum

A

a modified endoplasmic reticulum that contains high concentrations of Ca2+ ions

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24
Q

sarcoplasm

A

modified cytoplasm located just outside sarcoplasmic reticulum

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25
Q

sarcolemma

A

cell membrane of a myocyte

capable of propagating an action potential and can distribute the action potential to all sarcomeres through T-tubules

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26
Q

transverse tubules / T tubules

A

tubes oriented perpendicularly to myofibrils

propagates action potentials to all sarcomeres in a muscle

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27
Q

neuromuscular junction

A

site where motor neurons reach muscles

acetylcholine binds to receptors on the sarcolemma, causing depolarization

28
Q

how are muscle contractions initiated?

A
  • acetylcholine release at neuromuscular junction -> depolarization of sarcolemma
  • action potentials reach T-tubule -> sarcoplasmic reticulum
  • Ca2+ released in sarcoplasmic reticulum, bind to troponin, cause conformational change in tropomyosin to expose myosin-binding site on actin
29
Q

how are sarcomeres shortened?

A
  • heads of myosin have ADP + Pi = able to bind to myosin-binding site on actin, forming crossbridge
  • release of ADP and Pi provides energy for powerstroke
  • ATP binds to myosin = release of myosin from actin
  • ATP is hydrolyzed to ADP and Pi, causes myosin to recock for the next powerstroke
30
Q

what causes the relaxation of muscle?

A
  • acetylcholine degraded in synapse by acetylcholinesterase
  • allows sarcolemma to repolarize
  • Ca2+ release decreases, sarcoplasmic reticulum takes up Ca2+ from sarcoplasm
  • ATP binds to myosin heads to free them from actin
  • with no Ca2+, myosin-binding sites are covered by tropomyosin
31
Q

simple twitch

A

the response of a single muscle fiber to a brief stimulus at or above threshold

latent period - contraction period - relaxation period

32
Q

latent period

A

the time between reaching threshold and the onset of contraction

the action potential spreads along the muscle and allows for Ca2+ to be released from the sarchoplasmic reticulum

33
Q

frequency summation

A

muscle exposed to frequent and prolonged stimulation, no time to relax

contractions combine, become stronger and more prolonged

34
Q

tetanus

A

contractions become so frequent that the muscle is unable to relax at all between stimulations

results in muscle fatigue

35
Q

besides O2, what are two extra energy reserves for slow-twitch/red fibers to avoid oxygen debt?

A

creatine phosphate

myoglobin

36
Q

creatine phosphate

A

alternative energy reserve in muscles the case of oxygen debt

can transfer a phosphate group to ADP, creating ATP

37
Q

myoglobin

A

heme-containing protein

muscular O2 reserve, binds O2 with high affinity

38
Q

what’s the difference between endoskeletons and exoskeletons?

A

exoskeletons - encase organisms, protect soft tissue underneath; must be shed with growth

endoskeletons - internal, can’t protect but are able to accomodate growth

39
Q

from which gastrulation layer is bone derived from?

A

mesoderm

40
Q

compact bone

A

type of bone

is dense and strong

41
Q

spongy / cancellous bone

A

type of bone

has a lattice-like structure of bony spicules - trabeculae

cavities are filled with bone marrow

42
Q

what is the difference between red marrow and yellow marrow?

A

red marrow - filled with hematopoietic stem cells

yellow marrow - composed primarily of fat and relatively inactive

43
Q

periosteum

A

fibrous sheath that surrounds the long bone to protect it and serve as a site of muscle attachment

cells may differentiate into osteoblasts

44
Q

what is the difference between a tendon and a ligament?

A

tendons attach muscle to bone

ligaments hold bone together at joints

45
Q

what is the difference between haversian canals and volkmann’s canals?

A

both contain blood vessels, nerve fibers, and lymph vessels that maintain the health of the bone

haversian canals are longitudinal

volkmann’s canals are transverse to the bone

46
Q

where are osteocyes in bone matrix housed?

A

in lacunae between the lamellar rings

47
Q

parathyroid hormone

A

peptide hormone released by parathyroid gland in response to low blood Ca2+

promotes resorption of bone -> increased Ca2+ and PO4- in blood

48
Q

vitamin D

A

activated by parathyroid hormone

promotes resorption of bone, encouraging growth of stronger bone

49
Q

calcitonin

A

peptide hormone released by parafollicular cells of thyroid in response to high blood Ca2+

promotes bone formation, lowering Ca2+ levels

50
Q

chondrin

A

firm but elastic matrix surrounding cartilage

secreted by chondrocytes

51
Q

how is cartilage different from bone?

A
  • cartilage is flexible and cushioning
  • cartilage is avascular and is not innervated
52
Q

endochondral ossification

A

the creation of bone by the hardening of cartilage

creates most long bones in the body

53
Q

intramembranous ossification

A

the replacement of undifferentiated embryonic connective tissue (mesenchymal tissue) by bone

occurs in bones of the skull

54
Q

immovable joints

A

joints made of bones that are fused together to form sutures or fibrous joints

primarily in the head, anchoring bones of the skull together

55
Q

movable joints

A

hinge joints (elbow, knee), ball-and-socket joints (shoulder, hip)

permit bones to shift relative to one another

strengthened by ligaments

synovial capsule - encloses the joint cavity (articular cavity)

56
Q

synovial fluid

A

secreted by synovium - soft tissue layer

lubricates the movement of structures in the joint space

57
Q

what is the difference between the origin and insertion of muscles?

A

origin is the end of the muscle with a larger attachment to bone (usually proximal)

insertion is the end with the smaller attachment to bone (usually distal)

58
Q

what is the difference between a flexor muscle and an extensor muscle?

A

flexor muscle decreases the angle across a joint

extensor muscle increases or straightens the angle

59
Q

what is the difference between an abductor and an adductor?

A

abductor moves a part of the body away from the midline

adductor moves a part of the body toward the midline

60
Q

what is the difference between medial and lateral rotation?

A

a medial rotator rotates the axis of the limb toward the midline

a lateral rotator rotates the axis of the limb away from the midline

61
Q

osteoblasts

A

bone cells involved in the secretion of bone matrix

build bone

62
Q

osteoclasts

A

polynucleated cells actively involved in bone resorption

chew bone

63
Q

where does longitudinal bone groth occur?

A

epiphyseal plate

64
Q

which bones constitute the axial skeleton?

A

skull

vertebral column

ribcage

hyoid bone

65
Q

what bones constitute the appendicular skeleton?

A

limbs

pectoral girdle

pelvis

Bad Girl's MCAT Club (39 decks)

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