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MCAT > Chapter 11: The Musculoskeletal System > Flashcards

Chapter 11: The Musculoskeletal System Flashcards

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MCAT flashcards
1
Q

Skeletal muscle

A

Responsible for voluntary movement and is therefore innervated by the somatic nervous system; sacromeres - repeating units of actin and myosin; striated

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2
Q

Red fibers

A

Slow-twitch fibers; high myoglobin content and primarily derive their energy aerobically

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3
Q

White fibers

A

Fast-twitch fibers; contain much less myoglobin; less iron and the color is lighter; both red and white fibers can be mixed in muscles

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4
Q

Smooth muscle

A

Involuntary action; controlled by the ANS; found in the respiratory tree, digestive tract, bladder, uterus, blood vessel walls, and many other locations; each muscle cell has a single nucleus; no striations; involved in tonus; can contract without nervous system input known as myogenic activity

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5
Q

Cardiac muscle

A

Characteristics of both smooth and skeletal muscle types; primarily uninucleated but cells may contain two nuclei; involuntary and innervated by the ANS; striated; connected by intercalated discs which contain many gap junctions

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6
Q

Z-lines

A

Define the boundaries of each sarcomere

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7
Q

M-line

A

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

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8
Q

I-band

A

Region containing exclusively thin filaments

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9
Q

H-zone

A

Contains only thick filaments

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10
Q

A-band

A

Contains the thick filaments in their entirety, including any overlap with thin filaments

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11
Q

Myofibrils

A

Sarcomeres are attached end-to-end to form myofibrils

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12
Q

Sarcolemma

A

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

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13
Q

Myocyte

A

Contains many myofibrils arranged in parallel and can also be called a muscle fiber; many myocytes in parallel form a muscle

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14
Q

Initiation of muscle contraction

A

Neuromuscular junction; nervous system communicates with muscles via the motor (efferent) neurons; signal travels down the neuron until it reaches the nerve terminal (synaptic bouton) where acetylcholine is released into the synapse; each nerve terminal controls a group of myocytes; depolarization triggers an AP which spreads via T-tubules; release of Ca2+ from SR; Ca2+ binds to troponin and triggers a conformational change in tropomyosin; exposes the myosin-binding sites on the actin thin filament

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15
Q

Actin-myosin cross-bridge cycle

A

1) ATP is hydrolyzed
2) Ca2+ binds to troponin; myosin binds to actin
3) Powerstroke occurs; the sarcomere contracts; ADP and Pi dissociate from myosin
4) New ATP binds to myosin, causing detachment of myosin from actin; hydrolysis of ATP to ADP and Pi causes recocking of the myosin head

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16
Q

Relaxation

A

Acetylcholinesterase degrades acetylcholine, resulting in termination of the signal

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17
Q

Simple twitch

A

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

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18
Q

Frequency summation

A

Contractions will combine, become stronger, and more prolonged

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19
Q

Tetanus

A

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

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20
Q

Creatine phosphate

A

Created by transferring a phosphate group from ATP to creatine during times of rest

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21
Q

Oxygen debt

A

After the cessation of strenuous exercise, the body must metabolize all of the lactic acid it has produced; most lactic acid is converted back to pyruvate which can enter the CAC; difference between the amount of oxygen needed by the muscles and the actual amount present

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22
Q

Axial skeleton

A

Consists of skull, vertebral column, ribcage, and hyoid bone (a small bone in the anterior neck used for swallowing)

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23
Q

Appendicular skeleton

A

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

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24
Q

Compact bone

A

Where bone’s characteristic strength comes from

25
Q

Spongy or cancellous bone

A

Consists of bony spicules (points) known as trabecular and bone marrow

26
Q

Red marrow

A

Filled with hematopoietic stem cells; responsible for generation of all the cells in our blood

27
Q

Yellow marrow

A

Composed primarily of fat and is relatively inactive

28
Q

Long bones

A

Characterized by cylindrical shafts called diaphyses that swell at each end to form metaphyses and that terminate in epiphyses

29
Q

Bone composition

A

The outermost part of bone is composed of compact bone while the internal core is made of spongy bone

30
Q

Epiphyseal plate

A

Catilaginous structure and the site of longitudinal growth; filled with mitotic cells prior to puberty

31
Q

Periosteum

A

Surrounds the long bone to protect it as well as serve for muscle attachment

32
Q

Tendons

A

Attach muscle to bone

33
Q

Ligaments

A

Hold bones together at joints

34
Q

Organic components of the bone matrix

A

Collagen, glycoproteins, and other peptides

35
Q

Inorganic components of the bone matrix

A

Calcium, phosphate, and hydroxide ions, which harden to form hydroxyapatite; minerals such as sodium, magnesium, and potassium are also stored in bone

36
Q

Osteons or Haversian systems

A

Structural units of the bony matrix

37
Q

Lamellae

A

Concentric circles of bony matrix surrounding a central microscopic channel

38
Q

Haversian canals

A

Longitudinal channels

39
Q

Volkmann’s canals

A

Transverse channels

40
Q

What do the canals contain?

A

Blood vessels, nerve fibers, and lymph vessels that maintain the health of the bone

41
Q

Lacunae

A

Between the lamellar rings; house mature bone cells known as osteocytes

42
Q

Canaliculi

A

Tiny channels that allow for the exchange of nutrients and wastes between osteocytes and the Haversian and Volkmann’s canals

43
Q

Osteoblasts

A

Build bone

44
Q

Osteoclasts

A

Polynucleated resident macrophages of bone, resorb it

45
Q

Cartilage

A

Softer and more flexible than bone; consists of a firm but elastic matrix called chondrin that is secreted by cells called chondrocytes; not innervated and relatively avascular

46
Q

Endochondral ossification

A

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

47
Q

Intramembranous ossification

A

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

48
Q

Immovable joints

A

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

49
Q

Movable joints

A

Structures include joints like the elbow and knee, ball-and-socket joints (like the shoulder or hip) and others; 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)

50
Q

Synovium

A

Secretes synovial fluid which lubricates the movement of structures in the joint space

51
Q

Articular cartilage

A

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

52
Q

Origin

A

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

53
Q

Insertion

A

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

54
Q

Flexor

A

Decreases the angle across a joint (biceps_

55
Q

Extensor

A

Increases or straightens this angle (triceps)

56
Q

Abductor

A

Move a part of the body away from the midline (deltoid)

57
Q

Adductor

A

moves a part of the body toward the midline (pectoralis major)

58
Q

Medial and lateral rotation

A

Describe motions that occur in limbs, rotating their axis toward or away from the midline, respectively

MCAT (12 decks)

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