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MCAT Biology Review > The Musculoskeletal System > Flashcards

The Musculoskeletal System Flashcards

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1
Q

Skeletal muscle

A

Responsible for voluntary movement and is innervated by the somatic nervous system, appearing striated (striped), multinucleated, made up of repeating units called sarcomeres (arrangements of actin and myosin)

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2
Q

Red fibers (slow-twitch fibers)

A

Skeletal muscle fibers that have high myoglobin content and primarily derive their energy aerobically, contain many mitochondria to carry out oxidative phosphorylation (found in muscles that contract slowly but can sustain activity)

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3
Q

Myoglobin

A

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

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4
Q

White fibers (fast-twitch fibers)

A

Skeletal muscle fibers that contain much less myoglobin and thus has a lighter color due to less iron (found in muscles that contract rapidly but fatigue quickly)

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5
Q

Smooth muscle

A

Responsible for involuntary action, controlled by the autonomic nervous system, contain actin and myosin but not in striations, have a single nucleus, capable of more sustained contractions

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6
Q

Tonus

A

A constant state of low-level contraction (such as in blood vessels) performed by smooth muscle

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7
Q

Myogenic activity

A

Smooth muscle contracting without nervous system input in direct response to stretch or other stimuli

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8
Q

Cardiac muscle

A

Primarily uninucleated, contraction is involuntary and innervated by autonomi nervous system (like smooth), appears striated (like skeletal), connected by intercalated discs

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9
Q

Intercalated discs

A

Contain many gap junctions that connect cytoplasm of adjacent cells to allow for flow of ions directly between cells allowing for progressive depolarizations

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10
Q

Sarcomere

A

Basic contractile unit of skeletal muscle made up of thick filaments (bundles of myosin) and thin filaments (made of actin, troponin, and tropomyosin)

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11
Q

Troponin and tropomyosin

A

Proteins in the thin filaments that help to regulate the interaction between the actin and myosin filaments

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12
Q

Titin

A

Protein that acts as a spring and anchors the actin and myosin filaments together, preventing excessive muscle stretching

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13
Q

Z-lines

A

Define the boundaries of each sarcomere (Z is end of alphabet and end of sarcomere)

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14
Q

M-line

A

Runs down the center of the sarcomere through the middle of the myosin filaments

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15
Q

I-band

A

Region containing exclusively thin filaments

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16
Q

H-zone

A

Region containing only thick filaments

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17
Q

A-band

A

Containing the thick filaments in their entirety, even those overlapping with thin filaments (size of it remains constant throughout contraction)

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18
Q

Myofibrils

A

Sarcomeres attached end-to-end, surrounded by sarcoplasmic reticulum (SR), a modified endoplasmic reticulum that contains high calcium ion concentration

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19
Q

Sarcoplasm

A

Modified cytoplasm located just outside the sarcoplasmic reticulum

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20
Q

Sarcolemma

A

Cell membrane of a myocyte, capable of propagating an action potential and can distribute it to all sarcomeres in a muscle using system of transverse tubules (T-tubules

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21
Q

Myocyte (muscle cell)

A

Contains many myofibrils arranged in parallel, also called a muscle fiber, many of which in parallel form a muscle

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22
Q

Neuromuscular junction

A

Where the nervous system communicates with muscles via motor (efferent) neurons, where contraction starts from binding of acetylcholine to receptors on the sarcolemma

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23
Q

Motor unit

A

The nerve terminal and its myocytes that it controls

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24
Q

Action potential in muscles

A

Spreads down sarcolemma to T-tubules, which then travels into sarcoplasmic reticulum, releasing calcium ions in sarcoplasm to bind to regulatory subunit in troponin, triggering a change in conformation in tropomyosin, exposing myosin-binding sites on actin thin filament

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25
Q

Sliding filament model

A

Myosin carrying hydrolyzed ATP is then able to bind with the myosin-binding site, and the release of ADP and inorganic phosphate in rapid succession provides energy needed for powerstroke (sliding of actin filament over myosin filament), then ATP binds to myosin head to release it from actin, where it can be hydrolyzed to recock the myosin head to start another cross-bridge cycle

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26
Q

Rigor mortis

A

Condition where muscles do not relax and lengthen as myosin heads cannot detach from actin due to cease in ATP production after death

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27
Q

Single twitch

A

Response of a single muscle fiber to a brief stimulus at or above threshold, consisting of a latent period, contraction period, and relaxation period

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28
Q

Latent period

A

Time between reaching threshold and onset of contraction, in which action potential spreads along the muscle and allows for calcium to be released from SR

29
Q

Frequency summation

A

Contractions will combine and become stronger and more prolonged if a muscle fiber is exposed to frequent and prolonged stimulation

30
Q

Tetanus

A

When contractions become so frequent that the muscle is unable to relax at all, resulting in muscle fatigue

31
Q

Creatine phosphate

A

Created by transferring phosphate group from ATP to creatine during times of rest, which can be reversed during muscle use to quickly generate ATP from ADP

32
Q

Oxygen debt

A

Difference between the amount of oxygen needed by the muscles and the actual amount present, this leads to anaerobic metabolism in muscles that produces lactic acid as a byproduct (leading to muscle fatigue)

33
Q

Exoskeletons

A

Encase whole organisms and are usually found in arthropods, must be shed and regrown to accommodate growth

34
Q

Endoskeletons

A

Internal but are not able to protect the soft tissue structures as well as exoskeletons, found in vertebrates, better able to accommodate growth of a larger organism

35
Q

Axial skeleton

A

Consists of the skull, vertebral column, ribcage, and hyoid bone, providing basic central framework for the body

36
Q

Appendicular skeleton

A

Consists of the bones of the limbs (humerus, radius and ulna, carpals, metacarpals, phalanges, femur, tibia and fibula, tarsals, metatarsals), the pectoral girdle (scapula and clavicle) and pelvis

37
Q

Bone

A

Connective tissue derived from embryonic mesoderm, much harder than cartilage, relatively lightweight, there are 206 in the adult human

38
Q

Compact bone

A

Dense and strong bone structure that gives bone its characteristic strength

39
Q

Spongy (cancellous) bone

A

Consists of bony spicules (points) known as trabeculae, and the cavities between these trabeculae is filled with bone marrow

40
Q

Red marrow

A

Filled with hematopoietic stem cells, responsible for generation of all blood cells

41
Q

Yellow marrow

A

Composed primarily of fat and is relatively inactive

42
Q

Long bones

A

Characterized by cylindrical shafts called diaphyses that swell at each end to form metaphyses, at that terminate in epiphyses, main type of bone in appendicular skeleton (outermost portion is compact while internal core is spongy)

43
Q

Epiphyseal (growth) plate

A

Cartilaginous structure that is the site of longitudinal growth, found at the internal edge of the epiphysis (vertical growth is halted during puberty)

44
Q

Periosteum

A

Fibrous sheath surrounding the long bone to protect it and serve as a site for muscle attachment

45
Q

Tendons

A

Connective tissue that attaches muscle to bone

46
Q

Ligaments

A

Connective tissue that holds bones together at joints

47
Q

Bone matrix

A

Its organic components include collagen, glycoproteins, and other peptides
Its inorganic components include calcium, phosphate, and hydroxide ions, which harden together to form hydroxyapatite crystals

48
Q

Osteons (Haversian systems)

A

Structural units of the bony matrix that contain concentric circles of bony matrix called lamellae surrounding a central microscopic channel

49
Q

Haversian canals

A

Longitudinal channels with an axis parallel to the bone

50
Q

Volkmann’s canals

A

Transverse channels with an axis perpendicular to the bone

51
Q

Lacunae

A

Small spaces between lamellar rings which house mature bone cells known as osteocytes, and they are interconnected by tiny channels called canaliculi that allow for exchange of nutrients and wastes between osteocytes and the Haversian and Volkmann’s canals

52
Q

Osteoblasts

A

Cells that build bone from calcium and phosphate obtained from the blood

53
Q

Osteoclasts

A

Polynucleated resident macrophages of bone that resorb bone by calcium and phosphate ions being released back into the bloostream

54
Q

Osteoporosis

A

Result of increased osteoclast resorption and some concomitant slowing of bone formation, leading to loss of bone mass

55
Q

Cartilage

A

Softer and more flexible than bone, consists of elastic matrix called chondrin that is secreted by chondrocytes, mostly makes up fetal skeletons (as fetuses must grow and develop in a confined environment and then traverse the birth canal), not innervated unlike bone

56
Q

Endochondral ossification

A

Hardening of cartilage into bone, responsible for the formation of most of the long bones of the body

57
Q

Intramembranous ossification

A

Undifferentiated embryonic connective tissue (mesenchymal tissue) is transformed into, and replaced by, bone, occurring in bones of the skull

58
Q

Immovable joints

A

Consist of bones that are fused together to form sutures or similar fibrous joints, found primarily in the head

59
Q

Movable joints

A

Permit bones to shift relative to one another, strengthened by ligaments and consist of a synovial capsule, which encloses the actual joint cavity (articular cavity)

60
Q

Synovium

A

Layer of soft tissue that secretes synovial fluid to lubricate the movement of structures in the joint space

61
Q

Articular cartilage

A

Contributes to the joint by coating the articular surfaces of the bone so that impact is restricted to lubricated joint cartilage rather than to bones

62
Q

Osteoarthritis

A

Degradation of articular cartilage that becomes painful due to bones rubbing directly on one another

63
Q

Origin

A

The end of the muscle with a larger attachment to bone (the proximal connection)

64
Q

Insertion

A

The end of the muscle with the smaller attachment to bone (the distal connection)

65
Q

Antagonistic muscle pairs

A

One muscle relaxes while the other muscle in the pair contracts

66
Q

Synergistic muscle pairs

A

Both muscles in a pair work together to accomplish the same function

67
Q

Flexor and extensor muscles

A

Decreases the angle across a joint and increases/straightens the angle across a joint, respectively

68
Q

Abductor and adductor muscles

A

Moves a part of the body away from the midline and moves a part of the body toward the midline, respectively

69
Q

Medial and lateral rotation

A

Rotates the axis of the limb toward the midline and rotates the axis of the limb away from the midline, respectively

MCAT Biology Review (10 decks)

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