BIOL 319: EXAM 2
47 Cards in this Set
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functions of muscle (4)
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heat generation
posture
movement
stabilizing joints
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characteristics of muscle cells (4)
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excitability
contractibility
extensibility
elasticity
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connective tissue of skeletal muscle (3)
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1. epimysium - dense irregular CT
2. perimysium - fibrous CT
3. endomysium - reticular CT
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direct attachment (skeletal muscle)
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epimysium fused with periosteum (bone)
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indirect attachment (skeletal muscle)
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epimysium connected to bone by tendon or aponeurosis (dense CT)
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specialized components of sarcoplasm (2)
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glycosomes - store glycogen
myoglobin - oxygen storing pigment (red)
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H-zone
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central light zone of dark A band (thick filaments only)
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M-line
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biseects H-zone of dark A band
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Z-disc
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bisects light I-bands; connects sarcomeres together
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thick filaments
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bundles of myosin
tails=2 interwoven heavy meromysin chains
heads=2 connected light meromysins
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thin filaments (of skeletal muscle)
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backbone of actin molecules
tropomyosin - spirals around backbone
tropinin - acts as hinge (ITC)
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tropomyosin
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spirals around actin core of thin filaments
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tropinin
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"hinge" of thin filaments
TnI - binds to actin (inhibitory)
TnT - binds to tropomyosin
TnC - binds to calcium
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terminal cisternae
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ends of SR; release Ca when stimulated by impulses from T-tubules
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T-tubules
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form triads with terminal cisternae; conduct impulses that signal release of Ca from TC
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sliding filament hypothesis
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contraction due to filaments sliding past each other
dark a band widens, h-zone disappears
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Phase 1 - muscle fiber stimulation by motor neuron (5)
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1. AP arrives at axon terminal of neuromuscular junction
2. ACh released
3. Ion permeability of sarcolemma changes
4. local change in membrane voltage (depolarization)
5. AP ignited in sarcolemma
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Phase 2 - E-C coupling (4)
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1. AP travels across sarcolemma
2. AP travels along T-tubules down into sarcomere
3. Ca binds to troponin, active sites of actin exposed
4. myosin heads bind to actin; contractions begin
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cross bridge cycle (4)
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1. cross bridge formation
2. power stroke (ADP released)
3. cross bridge detachment
4. cocking of myosin head (ATP hydrolyzed)
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Requirements to maintain muscle contraction (2)
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1. high sarcoplasmic [Ca]
2. constant supply of ATP
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phases of muscle twitch (3)
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latent period
period of contraction
period of relaxation
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wave summation
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graded muscle responses to changes in stimulus FREQUENCY
muscle still partially contracted when next stimulus arrives
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tetanus
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sustained contraction of summated twitches
unfused and fused
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Recruitment (or multiple motor unit summation)
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higher intensity = more unitis activated
helps prevent fatigue
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asychronous activation
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recruitment; some motor units rest while others contract
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isotonic contraction
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tension>load
tension constant, length decreases
thin filaments sliding
1. concentric (shortening)
2. eccentric (lengthening)
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concentric isotonic contraction
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muscle shortens as it produces tension
ex-picking up heavy object
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eccentric isotonic contraction
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muscle lengthens as it produces tension
ex-setting down heavy object
more force than conceaerntric
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isometric contraction
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tension<load
tension increases, length constant
cross bridges generating force but not moving thin filaments
ex-muscle tone
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atp generation-aerobic metabolism
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low intensity, long (unlimited) duration
32 ATP/glucose
dependent on O2 from blood
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factors affecting muscle fatigue (3)
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depletion of fuels/CP
ionic imbalances
lactic acid build up (if anaerobic)
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cotractures
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state of continuous contraction
result of complete ATP depletion
crossbridges unable to detach
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brain regulation of metabolism 34)
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1. monitors chemical changes in blood
2. monitors degree of muscle stretch
3. monitors body temp
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steps to restoring cellular metabolic environment (5)
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1. decrease temp
2. restore glycogen stores
3. restore CP (via ox)
4. restore Oxygen stores
5. detoxify lactic acid in liver (Cori Cycle)
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ability of muscle to do work depends on... (3)
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force
velocity
duration
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factors affecting force (4)
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# muscle fibers
size of muscle fibers
frequency of stimulation
degree of muscle stretch
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hypertrophy
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increases sacromere size, adds myofilaments
from hormones, androgens, or exercise
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internal tension
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generated by sarcomeres (contractile units); force generated by cross bridges
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external tension
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CT (noncontractile units) stretch and exert tension from sarcomeres to load
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length-tension relationship
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amt of force depends on length of resting muscle
produce max force when stimulated at 100% resting length
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fascicle arrangements of muscle (5)
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circular sphincters (eye)
parallel (sartorius)
convergent
fusiformpenate (feather)
uni-, bi-, and multipennate
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smooth muscle contraction
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1. Ca enters cytosol from ECF
2. Ca binds to calmodulin
3. act calmodulin activates MLCKE
4. MLCKE phosphorylates myosin (ATP-->ADP)
5. activated myosin forms cross bridges with actin
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regulation of smooth muscle contraction (3)
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spontaneous depolarization
mechanical stimulation
hormonal factors
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stress-release response
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smooth muscle; allows hollow organ to expand and fill (mech. stimulation)
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diffuse junctions
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junctions where neurotransmitters from viscosities diffuse to smooth muscle
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single unit smooth muscle
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linked by electrical gap junctions; entire sheet contracts together
contraction initiated by stretch/hormonal factors (intestine/uterus)
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multiunit smooth muscle
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not electrically linked; independent contraction; initiated by stretch/hormonal factors (BVs, airway, eye muscles)
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Anatomy - Flashcards