ch 11 - The Musculoskeletal System Flashcards Preview

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Flashcards in ch 11 - The Musculoskeletal System Deck (58)
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Skeletal muscle

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


red fibers

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



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


white fibers

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


smooth muscle

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


Cardiac muscle

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


intercalated discs

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



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.



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


Division of sacromere

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


structure of myocytes

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


sarcoplasmic reticulum

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



modified cytoplasm just outside the sarcoplasmic reticulum


action of sarcolemma

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


neuromuscular junction

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


nerve terminal (synaptic button)

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


motor unit

nerve terminal and its myocytes together


Initiation of muscle contraction signal pathway

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


Shortening of Sarcomere

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.


sliding filament model

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



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


simple twitch

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


latent period of simple twitch

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


frequency summation

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



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


Creatine phosphate

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


oxygen debt

different bt oxygen needed by muscles and actual amount present


axial skeleton

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


appendicular skeleton

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


structure of a long bone

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