Musculoskeletal system

Question 1

Skeletal muscle

Answer 1

voluntary movement, controlled by somatic nervous system; appears striped due to actin and myosin arrangement; contains red and white fibers; multiple nuclei

Question 2

Sarcomeres

Answer 2

repeating units of actin and myosin that make skeletal muscle appear striated

Question 3

Red fibers

Answer 3

slow-twitch fibers with high myoglobin content; derive most of energy aerobically- contain many mitochondria; muscles that slowly contract contain mostly red fibers

Question 4

Myoglobin

Answer 4

oxygen carrier that uses iron in a heme group to bind oxygen, resulting in the red color found in red fibers

Question 5

white fibers

Answer 5

fast twitch fibers, contain much less myoglobin and thus, less iron, resulting in a lighter color; muscles that quickly contract and are easily fatigued are mostly white fibers

Question 6

smooth muscle

Answer 6

involuntary action, controlled by autonomic nervous system; not striated- contains actin and myosin but not as well-organized; capable of more sustained contractions such as a constant state of low-level contractions; can exhibit myogenic activity; a single nucleus

Question 7

myogenic activity

Answer 7

contraction of muscle without nervous system input; can be accomplished by smooth or cardiac muscle

Question 8

cardiac muscle

Answer 8

involuntary movement, ANS; striated; cells are connected by intercalated discs, which contain gap junctions for communication; can maintain their rhythm via myogenic activity; 1-2 nuclei per cell

Question 9

Sarcomere

Answer 9

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

Question 10

Parts of the sarcomere

Answer 10

Z lines define ends of sarcomere (end of alpha)
M-middle of sarcomere
I band contains only thin filaments (thin letter)
H zone-only thick filaments (thick letter)
A band contains all the thick filament, including any overlap with thin filament

Question 11

Sarcomere during contraction

Answer 11

H, I, and distance between Z lines and between M lines becomes smaller while A band stays the same size

Question 12

sarcoplasmic reticulum

Answer 12

modified E.R. that contains a high concentration of calcium ions

Question 13

myocytes

Answer 13

a muscle consists of muscle fibers (myocytes) that contain may myofibrils in parallel

Question 14

sarcolemma

Answer 14

cell membrane of a myocyte that is capable of propagating an action potential to all sarcomeres in a muscle

Question 15

initiation of muscle contraction

Answer 15

motor neuron signals at neuromuscular junction–ACh release into synapse–ACh binds receptors on sarcolemma–depolarization–action potential down sarcolemma to T-tubules into sarcoplasmic reticulum–Ca2+ release–Ca binds troponin causing change in tropomyosin–exposes myosin binding sites

Question 16

shortening of sarcomere

Answer 16

heads of myosin bind with exposed sites on actin– shortens the sarcomere
Cycle: myosin carrying ADP+P binds myosin binding site; release of ADP and P provide energy for powerstroke and sliding of actin over the myosin filament- sarcomere contracts; ATP binds to myosin head, releasing it from actin; ATP hydrolyzed to ADP+P to start new cycle

Question 17

relaxation of muscle

Answer 17

ACh degraded in synapse; termination of signl, allows sarcolemma to repolarize; stops Ca release which means myosin-binding sites are not accessible; ATP binds myosin heads, freeing them from actin

Question 18

Simple twitch

Answer 18

single muscle fiber response; consists of latent period (time b/w reaching threshold and contraction during which Ca is released), contraction, and relaxation

Question 19

Frequency summation

Answer 19

prolonged muscle stimulation giving the muscle little time to relax; if unable to relax at all, known as tetanus

Question 20

Supplemental energy reserves in muscle

Answer 20

creatine phosphate produced during rest and can be hydrolyzed to form ATP; myoglobin keeps aerobic metabolism going due to it binding oxygen with high affinity

Question 21

Axial skeleton

Answer 21

skull, ribcage, vertebrae, hyoid bone; central framework for body

Question 22

Appendicular skeleton

Answer 22

bones of the limbs

Question 23

Red bone marrow

Answer 23

filled with hematopoietic stem cells

Question 24

tendons

Answer 24

attach muscle to bone

Question 25

ligaments

Answer 25

hold bones together at joints

Question 26

bone composition

Answer 26

organic components: collagen, glycoproteins, peptides; inorganic: calcium, phosphate, hydroxide ions which harden together to form hydroxyapatite crystals

Question 27

Parathyroid hormone

Answer 27

released by parathyroid glands in response to low blood Ca2+, promotes break down of bone

Question 28

calcitonin

Answer 28

hormone released by thyroid in response to high blood Ca2+, promotes bone formation

Question 29

cartilage

Answer 29

composed of a firm but elastic matrix called chondrin, secreted by the chondrocytes; provides flexibility or cushioning; bones can be formed by hardening of cartilage (endochondral ossification)

Question 30

immovable joints

Answer 30

bones fused together to form sutures or fibrous joints; found mostly in the skull

Question 31

movable joints

Answer 31

allow bones to shift relative to one another; strengthened by ligaments

Question 32

Origin

Answer 32

the end of the muscle with the larger attachment to bone

Question 33

insertion

Answer 33

end of the muscle with the smaller attachment to bone

Question 34

antagonistic pairs of muscles

Answer 34

one muscle relaxes while the other contracts