ch 11 - The Musculoskeletal System

Question 1

Skeletal muscle

Answer 1

innervated by somatic nervous system; voluntary; arrangement of actin and myosin into repeating units called sarcomeres causes it to appear striated; multinucleated

Question 2

red fibers

Answer 2

fibers in skeletal muscle; also known as slow-twitch fibers - high myoglobin content and primarily derive their energy aerobically; contain many mitochondria for oxidative phosphorylation. Muscles that contract slowly but sustain activity

Question 3

myoglobin

Answer 3

oxygen carrier that uses iron in a heme group to bind oxygen

Question 4

white fibers

Answer 4

skeletal muscle fiber; also called fast-twitch fibers - contain less myoglobin than red fibers and because of this color is much lighter. Muscles that contract rapidly but fatigue quickly

Question 5

smooth muscle

Answer 5

no striation; found in respiratory tree, digestive tract, bladder, uterus, blood vessel walls and elsewhere. contains actin and myosin but not well organized. Mononucleated cells; involuntary, innervated by autonomic NS. Myogenic activity is seen (not requiring input from nervous system to contract); some areas exhibit tonus - a constant state of low-level contraction

Question 6

Cardiac muscle

Answer 6

characteristics of both smooth and skeletal muscle types; primarily uninucleated but some have two nuclei; involuntary, innervated by autonomic NS. Striated. Exhibits myogenic activity

Question 7

intercalated discs

Answer 7

connect cardiac cells; these contain many gap junctions which are connections between the cytoplasm of adjacent cells

Question 8

Sarcomere

Answer 8

basic contractile unit of skeletal muscle made of thick and thin filaments; thick are organized into bundles of myosin; thin are made of actin along with the proteins troponin and tropomyosin which help regulated interaction bt actin and myosin filaments.

Question 9

Titin

Answer 9

acts as a spring in sarcomeres, anchoring the actin and myosin filaments together, preventing excessive stretching of the muscle

Question 10

Division of sacromere

Answer 10

Z-lines define boundaries of each sarcomere; M-line runs down center of sarcomere; I-band is region containing exclusively thin filaments; H-zone contains only thick filaments; A-band contains thick filaments in their entirety including any overlap with thin filaments; contraction results in smaller H-zone, I-band, distance bt Z-lines and distance bt M-lines. A-band’s size remains constant

Question 11

structure of myocytes

Answer 11

sarcomeres attached end to end form myofibrils which are surrounded by a covering known as the sarcoplasmic reticulum (SR); cell membrane of myocyte is sarcolemma which is capable of propagating an action potential; each myocyte contains many myofibrils arranged in parallel and can also be called muscle fiber

Question 12

sarcoplasmic reticulum

Answer 12

(SR) a modified endoplasmic reticulum which contains high conc of Ca2+ ions that covers myofibrils

Question 13

sarcoplasm

Answer 13

modified cytoplasm just outside the sarcoplasmic reticulum

Question 14

action of sarcolemma

Answer 14

propagates an action potential and distributes it to all sarcomeres in a muscle using transverse tubules (T-tubules) oriented perpendicularly to the myofibrils

Question 15

neuromuscular junction

Answer 15

site where muscle contraction starts where nervous system communicates with muscles via motor (efferent) neurons

Question 16

nerve terminal (synaptic button)

Answer 16

site where acetylcholine is released into the synapse; in case of neuromuscular junction this can also be called motor end plate

Question 17

motor unit

Answer 17

nerve terminal and its myocytes together

Question 18

Initiation of muscle contraction signal pathway

Answer 18

neuromuscular junction - down neuron - nerve terminal where acetylcholine is released into synapse - acetylcholine binds to receptors on sarcolemma (depolarization) - depolarization triggers action potential which spreads down sarcolemma - T-tubules - T-tubules travel into muscle tissues to sarcoplasmic reticulum where Ca2+ is released which bind to subunit in troponin changing tropomyosin (attached to troponin) which exposes myosin-binding sites on actin filament

Question 19

Shortening of Sarcomere

Answer 19

Next step in muscle contraction pathway following initiation: free globular heads of myosin bind with exposed sites on actin; these actin-myosin cross bridges cause myosin to pull on actin drawing thin filament toward M-line.

Question 20

sliding filament model

Answer 20

repetitive binding and releasing of myosin heads on actin filaments allowing thin filament to slide along the thick filament, causing sequential shortening of sarcomere during muscle contraction

Question 21

relaxation

Answer 21

final phase of muscle contraction: acetylcholine degraded in synapse by enzyme acetylcholinesterase which results in termination of the signal at neuromuscular junction allowing sarcolemma to repolarize; signal decay causes calcium release to cease and SR takes calcium from sarcoplasm

Question 22

simple twitch

Answer 22

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

Question 23

latent period of simple twitch

Answer 23

time between reaching threshold and onset of contraction. action potential spreads along muscle and allows calcium release form sarcoplasmic reticulum during this period

Question 24

frequency summation

Answer 24

muscle fiber exposed to frequent and prolonged stimulation will exhibit continued contractions that combine, become stronger and more prolonged

Question 25

tetanus

Answer 25

physiological phenomenon in which muscle contractions have become so frequent that muscle is not able to relax at all

Question 26

Creatine phosphate

Answer 26

one of two supplemental energy reserves in muscle; created by transferring a phosphate group from ATP to creatine during times of rest which can be reversed

Question 27

oxygen debt

Answer 27

different bt oxygen needed by muscles and actual amount present

Question 28

axial skeleton

Answer 28

consists of skull, vertebral column, ribcage, and hyoid bone (small bone in the anterior neck used for swallowing) and provides basic framework for body

Question 29

appendicular skeleton

Answer 29

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

Question 30

structure of a long bone

Answer 30

ends are called epiphysis as a whole including spongy bone, epiphyseal plate which is a division within the spongy bone, periosteum which is the outer layer. small section just below epiphysis is called metaphysis. Long part of bone is diaphysis with periosteum as outer layer, compact bone as layer beneath that and marrow cavity inside

Question 31

Red bone marrow

Answer 31

filled with hematopoietic stem cells which are responsible for generating cells in our blood

Question 32

Yellow bone marrow

Answer 32

composed primarily of fat and is relatively inactive

Question 33

Tendons

Answer 33

attach muscle to bone

Question 34

ligament

Answer 34

hold bones together at joints

Question 35

organic components of bone matrix

Answer 35

bone matrix gives compact bone its strength; collagen, glycoproteins, other peptides

Question 36

inorganic components of bone matrix

Answer 36

calcium, phosphate, hydroxide ions which harden to form hydroxyapatite crystals (Ca10(PO4)6(OH)2)

Question 37

osteons

Answer 37

also called Haversian systems; bony matrix of strong bones are ordered into these structural units

Question 38

lamellae

Answer 38

concentric circles of bony matrix within osteons, surrounding a central microscopic channel

Question 39

Haversian canals

Answer 39

canals with axis parallel to the bone (vertical)

Question 40

Volkmann's canals

Answer 40

canals with axis perpendicular to bone

Question 41

lacunae

Answer 41

small spaces between lamellar rings which house mature bone cells known as osteocytes

Question 42

canaliculi

Answer 42

tiny channels that interconnect lacunae, which allow for exchange of nutrients and wastes between osteocytes and Haversian and Volkmann's canals

Question 43

osteoclasts

Answer 43

cell type that is polynucleated resident macrophages of bone that resorb it; release enzymes that dissolve bone, releasing calcium into the bloodstream

Question 44

osteoblasts

Answer 44

cell type that builds bone using inorganic and organic materials

Question 45

Effect of vitamin D on bone

Answer 45

activated by parathyroid hormone; promotes resorption of bone which encourages growth of new, stronger bone overcompensating for effect of resorbing bone

Question 46

calcitonin

Answer 46

peptide hormone released by parafollicular cells of thyroid in response to high blood calcium that promotes bone formation, lowering blood calcium levels

Question 47

chondrin

Answer 47

firm but elastic matrix that makes up cartilage; secreted by cells called chondrocytes

Question 48

endochondral ossification

Answer 48

process by which most bones are created by hardening of cartilage; responsible for formation of most long bones in body

Question 49

intramembranous ossification

Answer 49

another process through which bones may be formed; undifferentiated embryonic connective tissue (mesenchymal tissue) is transformed into and replaced by bone; this process occurs in the skull

Question 50

Immovable joints

Answer 50

bones that are fused together to form sutures or similar fibrous joints found primarily in skull where they anchor bones of the skull together

Question 51

movable joints

Answer 51

include hinge joints (like elbow or knee), ball-and-socket joints (like shoulder and hip), and others; and promote bones to shift relative to each other; strengthened by ligaments

Question 52

synovial capsule

Answer 52

make up ligaments and encloses joint cavity (articular cavity); layer of soft tissue called synovium secretes synovial fluid which lubricates the movements of structures in the joint space

Question 53

articular cartilage

Answer 53

coats articular surfaces so that impact is restricted to lubricated joint cartilage rather than bones; on the sides of bone ends which face each other

Question 54

origin (referring to muscles)

Answer 54

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

Question 55

insertion (referring to muscles)

Answer 55

end with smaller attachment to bone (usually distal connection)

Question 56

antagonistic pairs (referring to muscles)

Answer 56

one muscle contracts while the other relaxes to create a certain movement

Question 57

synergistic (referring to muscles)

Answer 57

muscles work together to perform same function

Question 58

types of muscles according to movements they coordinate

Answer 58

flexor - decreases angle across the joint; extensor - increases or straightens angle across the joint; abductor - moves part of the body away from the midline; adductor - moves part of the body toward the midline; medial rotator - rotates the axis of the limb toward the midline; lateral rotator - rotates axis of limb away from the midline