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70 Cards in this Set

  • Front
  • Back
sheath that covers the muscle fiber
sheath that covers a fascicle, a group of muscle fibers
sheath that covers the entire muscle
Muscle Attachments:
Direct (fleshy)
epimysium of muscle is fused to periosteum of bone or perichondrium of cartilage
Muscle Attachments:
-muscle's connective tissue wrappings extend beyond the muscle either as a tendon or an aponeurosis
-much more common
-plasma membrane
-surrounds multiple muscle fibers & nuclei
-cytoplasm of muscle cell
-contains large amounts of glycosomes & myoglobin
A Band
-dark staining
1. H zone (M line)
2. Thick filament (myosin)
3. Thin filament (actin)
I Band
-light staining
1. Z disc (sarcomere)
2. thin filament (actin)
3. Elastic filaments (titin)
region of a myofibril between two successive Z discs
-rodlike tail, two globular heads
1.tail is 2 interwoven helical polypeptide chains
1. connection of myosin head to thin filament
-active sites for myosin heads to attach for contraction of muscle
1.helps stiffen actin chain
-troponin complex
1. binding polypeptide
Sarcoplasmic Reticulum (SR)
-similar to smooth ER
-contains terminal cisternae
1.channels created by the crossing of tubules at the junction of A&I bands
2.always occur in pairs
-major role to regulate levels of ionic calcium
T tubules
-a elongated, tublike section of the sarcolemma that penetrates into the cell interior
-zipper of integral proteins protruding into cell
(terminal cisternae/T tubule/terminal cisternae)
-act as voltage sensors
Neuromuscular Junction
a short curly section branched off of an axon
Synaptic Cleft
space separating the axon terminal and the muscle fiber
Synaptic vesicles
contain neurotransmitter acetylcholine (ACh)
Muscle stimulus by nerve junction
1.nerve impluse reaches end of axon, calcium channels release Ca^(2+) to flow into extracellular fluid
2.Calcium causes synaptic vesicles to fuse with axonal membrane & release ACh into synaptic cleft
3.ACh diffuses across cleft & attaches to receptors on sarcolemma
4. ACh is broken down to prevent continued muscle fiber contraction in abscence of additional stimulation
Action Potential
1.membranous areas adjacent to motor end plate are depolarized. Opens sodium channels so Na+ enters & initiates action potential
2.action potential moves along length of sarcolemma as depolarization spreads
3.Repolarization wave quickly follows depolarization wave to bring sarcolemma to polarized state
a transient change in membrane potential in which the interior of the sarcolemma becomes slightly less negative
-a consequence of Na+ channels closing & voltage-gated K+ channels opening
-refractory period
Excitation-Contraction Coupling
1.action potential propagates along sarcolemma & down T tubules
2.action potential in T tubule causes terminal cisternae to release Ca^(2+) into sarcoplasm
3.some calcium binds to troponin, which changes shape & removes blocking action of tropomyosin
4.myosin heads attach and pull actin toward center of sarcomere (active state)
5.Ca^(2+) signal ends, ATP-dependent calcium pump stored again
6.inactive state: Ca^(2+) levels drop too low for troponin, tropomyosin blockade reestablished
Muscle Fiber Contraction
1.Cross bridge formation
-myosin heads strongly attached to actin binding sites
2.Power stroke
-phosphate generated in previous contraction cycle released,initiating power stroke
3.Crossbridge detachment
-ATP molecule binds to myosin head, hold on actin loosens, and bridge detaches
4."cocking" of myosin head
-returning to start position
Muscle tension
force exerted by contracting muscle on an object
Force exerted on muscle by weight of an object
Muscle Twitch
1.Latent period
2.Period of contraction
3.Period of relaxation
Wave Summation
Occurs because second contraction occurs before muscle is completely relaxed
Unfused or Incomplete Tetanus
releaxation time between twitches shortens, concentration of Ca^(2+) in sarcoplasm is higher, degree of summation is greater creating a sustained but quivering contraction
Fused or Complete Tetanus
stimulation frequency continues to rise until all relaxation periods stop to create a muscle contraction plateau
Multiple motor unit summation
controls force of contraction
threshold stimulus
first observable contraction
maximal stimulus
strongest stimulus that produces increased contractile force
-the rising availability of Ca^(2+) to expose more active sites on thin filaments for cross bridges
-after long periods of rest initial muscle contraction is not as strong as those later in the contraction series (staircase effect)
Isotonic contractions
-muscle length changes (decrease angle at the joint) & moves load
-two kinds:
Concentric contractions
muscle shortens and does work
Eccentric contractions
muscle generates force as it lengthens
-ex: calf muscle walking up a steep hill
a muscle attempts to move load that is greater than the force the muscle is able to develop
Aerobic respiration
-happens during rest to moderate exercise
-happens in mitochondria, helps make ATP
-Glucose+oxygen=carbon dioxide+water+ATP
Anaerobic threshold
point at which muscle metabolism converts to anaerobic glycolysis
-results from lack of ATP for contraction
-states of continuous contraction; cross bridges can't detach
-ex: writer's cramp
Oxygen debt
-extra amount of oxygen that body must take in to "restore"
-difference between amount of oxygen needed for aerobic muscle activity & amount actually used
Force of Contraction
1.number of muscle fibers stimulated
2.size of muscle fibers stimulated
-greater the cross-sectional area of muscle, greater tension can develop, more force
3.Frequency of stimulation
-internal tension:force generated by cross bridges
-external tension:transfer of tension to the load
4.Degree of muscle stretch
-length-tension relationship
Oxidative fibers
cells that rely mostly on oxygen-using aerobic pathways for ATP generation
Glycolyic fibers
rely more on anaerobic glycolysis
contracting of the longitudal and circular layers of organs to mix object in lumen
-bulb-like swellings at ends of innervating nerve fibers
-release neurotransmitter into synaptic cleft in general area of smooth muscle
Smooth muscle myofilaments
1.thick to thin(1:13) actin-gripping heads on entired myosin length troponin
3.filaments arranged diagonally, contract in spiral motion
4.lattic-like arrangement of intermediate filaments, attach at dense bodies
Contraction of smooth muscle
1.actin and myosin interact by sliding filament mechanism trigger for contraction is the rise in intracellular level of calcium ions
3.sliding process energized by ATP
molecule that activates myosin to attach to actin
Myosin kinase
phosphorylates in myosin heads
-smooth muscle cells divide to increase their numbers
-ex: uterus contraction in response to estrogen (puberty)
Single-unit smooth muscle (visceral)
1.contract rhythmically as unit
2.electrically coupled, gap junction
3.spontaneous action potentials
Multi-unit smooth muscle
1.muscle fibers structurally independent
2.alot of nerve endings
3.responds to neural stimulation with graded contractions
embryonic mesoderm cells that produce muscle tissues
Muscular dystrophy
-a group of inherited muscle-destroying diseases
-affected muscles initially enlarge due to fat & connective tissue deposit, but muscle fibers atrophy and degenerate
Dudrenne muscular dystrophy (DMD)
-females are carries but symptoms only show in males
-diagnosed in young boys about 2-7, only live to 20s
Prime mover
muscle that provides main source of force
-muscles that oppose or reverse particular movement
-ex:tricep brachii->bicep brachii
-helps the prime mover by:
1.adding a little extra force
2.reducing undesirable movements
when a synergist immobalizes a bone or muscle's origin
Naming of Skeletal Muscles
-bone or body region of muscle
3.Relative Size -maximus,minimus,longus,brevis,etc.
4.Direction of fibers
5.Number of origins
-bi, tri, quad
6.Location of attachment
-origin & insertion
(origin is always first)
-ex:flexor, extensor,adductor, etc.
Arrangment of fascicles:
-surround external body openings
-arranged in concentric rings
-ex:orbicularis oris
Arrangement of fascicles:
-broad origin
-fascicles converge towards a single tendon of insertion
-triangular or fan shape
-ex:pectoralis major
Arrangement of fascicles:
-long axes of fascicles run parallel to long axis of muscle
Arrangement of fascicles:
Fusiform Muscles
-spindle shaped
-ex:bicep brachii
Arrangement of fascicles:
-fascicles short, run obliquely
1.fascicles insert into only 1 side of tendon
1.fascicles insert from opposite sides (like a feather)
2.ex:rectus femoris
First-class lever
-effort applied at 1 end of lever and load is at other with fulcrum inbetween
Second-class lever
-effort applied at end of lever and fulcrum located at other with load between
-ex:wheelbarrow, standing on toes
-uncommon in body
third-class lever
-effort applied between load and fulcrum
-most common in body