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MCAT Biology Review > The Musculoskeletal System > Flashcards

The Musculoskeletal System Flashcards

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
Sliding filament model
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
26
Rigor mortis
Condition where muscles do not relax and lengthen as myosin heads cannot detach from actin due to cease in ATP production after death
27
Single twitch
Response of a single muscle fiber to a brief stimulus at or above threshold, consisting of a latent period, contraction period, and relaxation period
28
Latent period
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
Frequency summation
Contractions will combine and become stronger and more prolonged if a muscle fiber is exposed to frequent and prolonged stimulation
30
Tetanus
When contractions become so frequent that the muscle is unable to relax at all, resulting in muscle fatigue
31
Creatine phosphate
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
Oxygen debt
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
Exoskeletons
Encase whole organisms and are usually found in arthropods, must be shed and regrown to accommodate growth
34
Endoskeletons
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
Axial skeleton
Consists of the skull, vertebral column, ribcage, and hyoid bone, providing basic central framework for the body
36
Appendicular skeleton
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
Bone
Connective tissue derived from embryonic mesoderm, much harder than cartilage, relatively lightweight, there are 206 in the adult human
38
Compact bone
Dense and strong bone structure that gives bone its characteristic strength
39
Spongy (cancellous) bone
Consists of bony spicules (points) known as trabeculae, and the cavities between these trabeculae is filled with bone marrow
40
Red marrow
Filled with hematopoietic stem cells, responsible for generation of all blood cells
41
Yellow marrow
Composed primarily of fat and is relatively inactive
42
Long bones
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
Epiphyseal (growth) plate
Cartilaginous structure that is the site of longitudinal growth, found at the internal edge of the epiphysis (vertical growth is halted during puberty)
44
Periosteum
Fibrous sheath surrounding the long bone to protect it and serve as a site for muscle attachment
45
Tendons
Connective tissue that attaches muscle to bone
46
Ligaments
Connective tissue that holds bones together at joints
47
Bone matrix
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
Osteons (Haversian systems)
Structural units of the bony matrix that contain concentric circles of bony matrix called lamellae surrounding a central microscopic channel
49
Haversian canals
Longitudinal channels with an axis parallel to the bone
50
Volkmann's canals
Transverse channels with an axis perpendicular to the bone
51
Lacunae
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
Osteoblasts
Cells that build bone from calcium and phosphate obtained from the blood
53
Osteoclasts
Polynucleated resident macrophages of bone that resorb bone by calcium and phosphate ions being released back into the bloostream
54
Osteoporosis
Result of increased osteoclast resorption and some concomitant slowing of bone formation, leading to loss of bone mass
55
Cartilage
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
Endochondral ossification
Hardening of cartilage into bone, responsible for the formation of most of the long bones of the body
57
Intramembranous ossification
Undifferentiated embryonic connective tissue (mesenchymal tissue) is transformed into, and replaced by, bone, occurring in bones of the skull
58
Immovable joints
Consist of bones that are fused together to form sutures or similar fibrous joints, found primarily in the head
59
Movable joints
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
Synovium
Layer of soft tissue that secretes synovial fluid to lubricate the movement of structures in the joint space
61
Articular cartilage
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
Osteoarthritis
Degradation of articular cartilage that becomes painful due to bones rubbing directly on one another
63
Origin
The end of the muscle with a larger attachment to bone (the proximal connection)
64
Insertion
The end of the muscle with the smaller attachment to bone (the distal connection)
65
Antagonistic muscle pairs
One muscle relaxes while the other muscle in the pair contracts
66
Synergistic muscle pairs
Both muscles in a pair work together to accomplish the same function
67
Flexor and extensor muscles
Decreases the angle across a joint and increases/straightens the angle across a joint, respectively
68
Abductor and adductor muscles
Moves a part of the body away from the midline and moves a part of the body toward the midline, respectively
69
Medial and lateral rotation
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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