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MCAT Biology > Chapter 11: The Musculoskeletal System > Flashcards

Chapter 11: The Musculoskeletal System Flashcards

1
Q

What are the 3 types of muscle?

A
  1. skeletal
  2. smooth
  3. cardiac
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2
Q

Sarcomeres are repeating units of ________ and ____________.

A

actin; myosin

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3
Q

____ fibers, also known as ____-________ fibers, have high myoglobin content and primarily derive their energy aerobically.

A

red; slow-twitch

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4
Q

____________ is an oxygen carrier that uses iron in a heme group to bind oxygen.

A

myoglobin

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5
Q

________ fibers, known as ________-________ fibers, contain much less myoglobin.

A

white; fast-twitch

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6
Q

Muscles that contract slowly, but can sustain activity, contain a predominance of ____ fibers.

A

red

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7
Q

Muscles that contract rapidly but fatigue quickly contain mostly ____ fibers.

A

white

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8
Q

Compared to skeletal muscle, smooth muscle is capable of more sustained contractions; a constant state of low-level contraction, as may be seen in the blood vessels, is called ________.

A

tonus

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9
Q

smooth muscle can contract without nervous system input in what is known as ____________ activity; the muscle cells contract in response to stretch or other stimuli

A

myogenic

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10
Q

Cardiac muscle has characteristics of what?

A

Both smooth and skeletal muscle types

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11
Q

Cardiac muscle cells are connected by ____________ ________, which contain many gap junctions.

A

intercalated discs

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12
Q

Gap junctions (connections between cytoplasm) in cardiac muscle allow for what?

A

Flow of ions directly between cells; allows for rapid and coordinated depolarization of muscle cells and efficient contraction

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13
Q

Starting at the ____________ node, depolarization spreads using conudction pathways to the ________________ node.

A

sinoatrial; atrioventricular

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14
Q

From the AV node, depolarization spreads to the ________ of ____ and its branches, and then to the ________ fibers.

A

bundle of His; Purkinje

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15
Q

The ________ nerve provides parasympathetic outflow to the heart and slows the heart rate.

A

vagus

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16
Q

____________ from sympathetic neurons or ____________ from the adrenal medulla binds to adrenergic receptors in the heart, causing increased HR and greater contractility.

A

norepinephrine; epinephrine

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17
Q

Epinephrine increases heart rate by doing what?

A

Increasing intracellular calcium levels within cardiac myocytes

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18
Q

Cardiac contraction, like all types of muscle, relies on ________.

A

calcium

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19
Q

The ____________ is the basic contractile unit of skeletal muscle.

A

sarcomere

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20
Q

Sarcomeres are made of ________ and ________ filaments.

A

thick; thin

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21
Q

The thick filaments are organized bundles of ____________, whereas the thin filaments are made of ________ along with 2 other proteins, which are?

A

myosin; actin; troponin and tropomyosin

acTin with a T for troponin and tropomyosin

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22
Q

Another protein, ________, acts as a spring and anchors the actin and myosin filaments together, preventing excessive stretching of the muscle.

A

titin

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23
Q

____-lines define the boundaries of each sarcomere.

A

Z-lines

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24
Q

The ____-line runs down the center of the sarcomere, through the middle of the myosin filaments.

A

M

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25
Q

The ____-band is the region containing exclusively thin filaments, whereas the ____-zone contains only thick filaments.

A

I; H

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26
Q

The ____-band contains the thick filaments in their entirety, including any overlap with thin filaments.

A

A

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27
Q

Sarcomere are attached end-to-end to form ____________.

A

myofibrils

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28
Q

Myofibrils are surrounded by a covering known as the ________________ ____________, a modified endoplasmic reticulum that contains a high concentration of Ca2+ ions.

A

sarcoplasmic reticulum

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29
Q

The ____________ is a modified cytoplsm just outside the sarcoplasmic reticulum.

A

sarcoplasm

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30
Q

The cell membrane of a myocyte is known as the ________________.

A

sarcolemma

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31
Q

What does the sarcolemma do?

A

Propagates an action potential and distributes AP to all sarcomeres

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32
Q

The sarcolemma distributes AP to all sarcomeres in a muscle using a system of ____________ ____________ that are oriented perpendicularly to the myofibrils.

A

transverse tubules

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33
Q

Each ____________, or muscle cell, contains many myofibrils arranged in parallel and can also be called a ________ ________.

A

myocyte; muscle fiber

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34
Q

Contraction starts at the ____________ ________, where the nervous system communicates with muscles via ________ ____________.

A

neuromuscular junction; motor neurons

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35
Q

The signal from the neuromuscular junction travels down the neuron until it reaches the ________ ____________, or ____________ ________.

A

nerve terminal (synaptic bouton)

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36
Q

At the nerve terminal, ____________ is released into the synapse.

A

acetylcholine

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37
Q

In the case of the neuromuscular junction, the nerve terminal can also be called the ________ ____ ________.

A

motor end plate

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38
Q

Acetylcholine binds to receptors on the ____________, causing depolarization.

A

sarcolemma

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39
Q

Each nerve terminal controls a group of myocytes. Together, the nerve terminal and its myocytes constitute a ________ ________

A

motor unit

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40
Q

Depolarization triggers an AP. What order does it pass through?

A
  1. Sarcolemma
  2. T-tubules
  3. Muscle tissues
  4. Sarcoplasmic reticulum
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41
Q

What happens after an action potential reaches the sarcoplasmic reticulum?

A

Ca2+ is released

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42
Q

After Ca2+ is released, what do they bind to? What happens next?

A

Troponin; since troponin is bound to tropomyosin, tropomyosin undergoes a confirmational change

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43
Q

What happens when tropomyosin changes?

A

Myosin-binding sites are exposed on the actin thin filament

44
Q

What recocks the myosin head for the next actin-myosin cross-bridge cycle?

A

hydrolysis of ATP to ADP and Pi

45
Q

The repetitive binding and releasing of myosin heads on actin filaments causing the sliding of the thin filament across the thick filament is known as what?

A

sliding filament model

46
Q

Actin filaments are ________.

A

thin

“Acthin”

47
Q

Acetylcholine is degraded in the synapse by the enzyme known as ________________.

A

acetylcholinesterase

48
Q

Once acetylcholine is degraded, what happens?

A
  1. Signal terminates at neuromuscular junction
  2. Sarcolemma repolarizes
  3. Calcium release ceases
  4. SR takes up calcium from sarcoplasm
49
Q

The ________ period is the time between reaching threshold and the onset of contraction.

A

latent

when AP spreads along muscle and allows Ca2+ to be released from SR

50
Q

If a muscle fiber is exposed to frequent and prolonged stimulation, it will have insufficient time to relax. Contractions will combine and become stronger/prolonged. This is ____________ ____________.

A

frequency summation

51
Q

When contractions become so frequent that the muscle is unable to relax at all, this is known as ____________.

A

tetanus

52
Q

Slow-twitch muscle fibers have high levels of ____________.

A

mitochondria

53
Q

What process do muscles use to make ATP? Why?

A

oxidative phosphorylation, because they have lots of mitochondria

54
Q

There are two supplemental energy reserves in muscle. What are they?

A
  1. Creatine phosphateis
  2. Anaerobic glycolysis
55
Q

____________ ____________ is created by transferring a phosphate group from ATP to creatine during times of rest. How is ATP created from this when muscles are being used?

A

creatine phosphate; the reaction can be reversed to quickly generate ATP from ADP

creatine + ATP <–> creatine phosphate + ADP

56
Q

When muscles run out of oxygen during exercise, ____________ reserves are used to keep aerobic metabolism.

A

myoglobin

57
Q

________-________ muscle fibers have fewer mitochondria and must rely on glycolysis and fermentation to make ATP under most circumstances.

A

fast-twitch

58
Q

Sometimes, even ________-________ muscle fibers must switch to anaerobic metabolism and produce lactic acid, at which point the muscle begins to fatigue.

A

slow-twitch

(red fibers)

59
Q

The difference between the amount of oxygen needed by muscles and the actual amount present is called what?

A

oxygen debt

60
Q

After strenuous exercise, the body must metabolize all of the lactic acid it has produced. Most lactic acid is converted back into ____________, and enters what cycle?

A

pyruvate; citric acid cycle

61
Q

The axial skeleton consists of what 4 parts?

A
  1. Skull
  2. Vertebral column
  3. Rib cage
  4. Hyoid bone
62
Q

The appendicular skeleton consists of what?

A
  1. bones of limbs
  2. pectoral girdle
  3. pelvis
63
Q

Bone is derived from?

A

embryonic mesoderm

64
Q

Bone’s strength comes specifically from ____________ bone.

A

compact

65
Q

What are the other types of bone besides compact bone?

A
  1. spongy
  2. cancellous
66
Q

Spongy bone has bony spicules (points) known as ____________.

A

trabeculae

67
Q

The cavities between trabeculae are filled with bone ____________, which can be red or yellow.

A

marrow

68
Q

____ marrow is filled with hematopoietic stem cells.

A

red

69
Q

________ marrow is composed of fat and is relatively inactive

A

yellow

70
Q

Bones in the appendicular skeleton are typically ________ bones, and are characterized by cylindrical shafts called ____________ that swell at each end to form ____________, and terminate in ____________.

A

long; diaphyses, metaphyses, epiphyses

71
Q

The epiphyses use their ________ cores to disperse force and pressure at joints.

A

spongy

72
Q

At the internal edge of the epiphysis is an ____________ (growth) plate, which is a cartilaginous structure and the site of longitudinal growth.

A

epiphyseal

73
Q

What happens to the epiphyseal plate during puberty?

A

closes and stops vertical growth

74
Q

A fibrous sheath called the ____________ surrounds the long bone to protect it and serve as a site for muscle attachment.

A

periosteum

75
Q

________ attach muscle to bone, ____________ attach bone to bone.

A

tendon; ligament

76
Q

The strength of compact bone comes from the bone ________.

A

matrix

77
Q

The organic components of bone matrix are?

A
  1. collagen
  2. glycoproteins
  3. other peptides
78
Q

The inorganic components of bone matrix are?

A
  1. calclium
  2. phosphate
  3. hydroxide ions
79
Q

What happens to the hydroxide ions in matrix?

A

They harden together to form hydroxyapatite crystals.

80
Q

The bony matrix is ordered into structural units known as what?

A

osteons, or Haversian systems

81
Q

Each osteon contains concentric circles of bony matrix called ____________ surrounding a central microscopic channnel.

A

lamellae

82
Q

Longitudinal channels (axis parallel to bone) are known as ____________ ________

A

Haversian canals

83
Q

Transverse channels (perpendicular to bone) are known as ____________ ____________.

A

Volkmann’s canals

84
Q

Between lamellar rings are spaces called ____________, which house mature bone cells known as ____________.

A

lacunae; osteocytes

85
Q

Lacunae are interconnected by tiny channels called ________________ that allow exchange of nutrients/wastes between osteocytes and Haversian/ Volkmann’s canals.

A

canaliculi

86
Q

____________ build bone, and ____________ resorb it.

A

build; resorb

87
Q

____________ hormone (released by glands of a similar name in response to low blood calcium) promotes resorption of bone.

A

parathyroid

87
Q

____________ hormone (released by glands of a similar name in response to low blood calcium) promotes resorption of bone.

A

parathyroid

88
Q

________ ____, which is activated by parathyroid hormone, also promotes the resorption of bone.

A

Vitamin D

p434

89
Q

________________, released by the parafollicular cells of the thyroid in response to high blood calcium, promotes bone formation, lowering blood calcium levels.

A

calcitonin

90
Q

Cartilage consists of a firm but elastic matrix called ________ that is secreted by cells called ____________.

A

chondrin, chondrocytes

91
Q

Cartilage differs from bone how?

A
  1. avascular
  2. not innervated
92
Q

Most bones are created by the hardening of cartilage into bone. This is called what?

A

endochondral ossification

93
Q

Bones can also be formed through ____________ ____________, in which undifferentiated embryonic connective tissue (mesenchymal tissue) is transformed into, and replaced by, bone.

A

intramembranous ossification

94
Q

____________ joints consist of bones that are fused together to form sutures.

A

immovable

95
Q

Movable joints are strengthened by ligaments and consist of a ____________ ____________, which encloses the actual joint cavity.

A

synovial capsule

96
Q

A layer of soft tissue called the ____________ secretes synovial fluid, which does what?

A

synovium; lubricates movement of structures in joint space.

97
Q

The ____________ ____________ contributes to the joint by coating the articular surfaces of bones so that impact is restricted to the lubricated joint cartilage, rather than to the bones.

A

articular cartilage

98
Q

The end of the muscle with a larger attachment to bone is called the ________.

A

origin

99
Q

The end with the smaller attachment to bone is called the ____________

A

insertion

100
Q

A ________ muscle decreases the angle across a joint.

A

flexor

101
Q

An ____________ muscle increases or straightens this angle.

A

extensor

102
Q

An ____________ moves a part of the body away from the midline.

A

abductor

take away, kidnap

103
Q

An ____________ moves a part of the body toward the midline.

A

adductor

104
Q

A ________ rotator rotates the axis of a limb TOWARD the midline.

A

medial

105
Q

A ____________ rotator rotates the axis of a limb away from the midline.

A

lateral

105
Q

A ____________ rotator rotates the axis of a limb away from the midline.

A

lateral

MCAT Biology (12 decks)

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