Chapter 11: The Musculoskeletal System

Question 1

Skeletal muscle

Answer 1

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

Question 2

Red fibers

Answer 2

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

Question 3

White fibers

Answer 3

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

Question 4

Smooth muscle

Answer 4

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

Question 5

Cardiac muscle

Answer 5

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

Question 6

Z-lines

Answer 6

Define the boundaries of each sarcomere

Question 7

M-line

Answer 7

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

Question 8

I-band

Answer 8

Region containing exclusively thin filaments

Question 9

H-zone

Answer 9

Contains only thick filaments

Question 10

A-band

Answer 10

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

Question 11

Myofibrils

Answer 11

Sarcomeres are attached end-to-end to form myofibrils

Question 12

Sarcolemma

Answer 12

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)

Question 13

Myocyte

Answer 13

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

Question 14

Initiation of muscle contraction

Answer 14

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

Question 15

Actin-myosin cross-bridge cycle

Answer 15

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

Question 16

Relaxation

Answer 16

Acetylcholinesterase degrades acetylcholine, resulting in termination of the signal

Question 17

Simple twitch

Answer 17

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

Question 18

Frequency summation

Answer 18

Contractions will combine, become stronger, and more prolonged

Question 19

Tetanus

Answer 19

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

Question 20

Creatine phosphate

Answer 20

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

Question 21

Oxygen debt

Answer 21

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

Question 22

Axial skeleton

Answer 22

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

Question 23

Appendicular skeleton

Answer 23

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

Question 24

Compact bone

Answer 24

Where bone’s characteristic strength comes from

Question 25

Spongy or cancellous bone

Answer 25

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

Question 26

Red marrow

Answer 26

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

Question 27

Yellow marrow

Answer 27

Composed primarily of fat and is relatively inactive

Question 28

Long bones

Answer 28

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

Question 29

Bone composition

Answer 29

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

Question 30

Epiphyseal plate

Answer 30

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

Question 31

Periosteum

Answer 31

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

Question 32

Tendons

Answer 32

Attach muscle to bone

Question 33

Ligaments

Answer 33

Hold bones together at joints

Question 34

Organic components of the bone matrix

Answer 34

Collagen, glycoproteins, and other peptides

Question 35

Inorganic components of the bone matrix

Answer 35

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

Question 36

Osteons or Haversian systems

Answer 36

Structural units of the bony matrix

Question 37

Lamellae

Answer 37

Concentric circles of bony matrix surrounding a central microscopic channel

Question 38

Haversian canals

Answer 38

Longitudinal channels

Question 39

Volkmann's canals

Answer 39

Transverse channels

Question 40

What do the canals contain?

Answer 40

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

Question 41

Lacunae

Answer 41

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

Question 42

Canaliculi

Answer 42

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

Question 43

Osteoblasts

Answer 43

Build bone

Question 44

Osteoclasts

Answer 44

Polynucleated resident macrophages of bone, resorb it

Question 45

Cartilage

Answer 45

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

Question 46

Endochondral ossification

Answer 46

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

Question 47

Intramembranous ossification

Answer 47

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

Question 48

Immovable joints

Answer 48

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

Question 49

Movable joints

Answer 49

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)

Question 50

Synovium

Answer 50

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

Question 51

Articular cartilage

Answer 51

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

Question 52

Origin

Answer 52

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

Question 53

Insertion

Answer 53

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

Question 54

Flexor

Answer 54

Decreases the angle across a joint (biceps_

Question 55

Extensor

Answer 55

Increases or straightens this angle (triceps)

Question 56

Abductor

Answer 56

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

Question 57

Adductor

Answer 57

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

Question 58

Medial and lateral rotation

Answer 58

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