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Skeletal – attached to skeleton by tendons; during development individual cells fuse to form protein fibers and nuclei are pushed to the side; striated; under voluntary control

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Cardiac – forms the heart, cells fuse (intercalated discs) into a branching pattern; striated; involuntary control

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Smooth – located mostly in the walls of hollow organs; 1 nucleus/cell; not striated; involuntary control

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Move body parts as muscle contracts
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Muscles usually attach to 2 different bones
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Insertion point – at moving bone
Origin point – at stable bone

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Move body parts as muscle contracts (con’t)
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Muscles work in groups
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Prime mover – one muscle that is mainly responsible for movement
Synergists – other muscles that help movement
Antagonists – produce movement in opposite direction

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Posture and Stability
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Tonic contraction – only a few muscle fibers contract, therefore muscle as a whole doesn’t shorten
- creates muscle tone
- favors best function of other body parts

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Heat production – only 25% of energy produced by respiration is used for metabolic processes, the rest is lost as heat

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During rest or moderate exercise, O aerobic respiration
2 is supplied to muscles in sufficient concentration to support
Strenuous exercise causes deficiency and lactic acid accumulates as a result of anaerobic respiration
C
6
H
12
O
6
 6CO
2
+ lactic acid + 2ATP = heat
Muscle fatigue – muscle loses ability to contract because of strenuous exercise for prolonged periods of time
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Usually caused by lactic acid buildup
May result from decreased blood supply
Rarely from decreased acetylcholine from motor neuron

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Oxygen Debt. This term describes how the body pays back its debt incurred after the exercise is over. You will notice that even after you are done racing you will continue to breath hard. At this point your body is still trying to repay the oxygen debt that was created when you were working hard. Technically, it is excessive post-exercise oxygen consumption. That's it.
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Each muscle is composed of many muscle fibers
Each muscle fiber is composed of many myofibrils
Each myofibril is composed of actin (thin) & myosin (thick) filaments
Sarcomere – functional contractile unit (Z line to Z line)

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Connection point of motor neuron to muscle fiber;
Synaptic vesicles that release neurotransmitters
(usually acetylcholine) stimulate muscle to contract

 http://www.youtube.com/watch?v=ZscXOvD gCmQ

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Sliding Filament Model

Muscle fiber contraction
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Muscle fiber relaxation
Threshold stimulus

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Actylcholine is released from the distal end of a motor neuron
Acetylcholine diffuses across the gap at the neuromuscular junction
The sarcolemma is stimulated, and a muscle impulse travels over the surface of the muscle fiber and deep into the fiber through the transverse tubules and reaches the sarcoplasmic reticulum

Fig. 50-29
ACh
Synaptic terminal
T tubule
Sarcoplasmic reticulum (SR)
Myofibril
Plasma membrane of muscle fiber
Sarcomere
Synaptic terminal of motor neuron
Synaptic cleft
Motor neuron axon
Mitochondrion
Ca 2+ released from SR
T Tubule Plasma membrane
SR
Ca 2+
ATPase pump
Ca 2+
ATP
CYTOSOL
Ca 2+
ADP
P i

Fig. 50-28
Tropomyosin
Actin
Troponin complex
Ca 2+ -binding sites
(a) Myosin-binding sites blocked
Ca 2+
Myosinbinding site
(b) Myosin-binding sites exposed

Fig. 50-27-1
Thin filaments
Thick filament
ATP
Thin filament
Myosin head (lowenergy configuration
Thick filament

Fig. 50-27-2
Thin filaments
Thick filament
ATP
Thin filament
Myosin head (lowenergy configuration
Thick filament
Actin
Myosin binding sites
ADP
P i
Myosin head (highenergy configuration

Fig. 50-27-3
Thin filaments
Thick filament
ATP
Thin filament
Myosin head (lowenergy configuration
Thick filament
Actin
Myosin binding sites
ADP
P i
Myosin head (highenergy configuration
ADP
P i
Cross-bridge

Fig. 50-27-4
Thin filaments
Thick filament
ATP
Thin filament moves toward center of sarcomere.
Myosin head (lowenergy configuration
ATP
Thin filament
Myosin head (lowenergy configuration
Thick filament
Actin
Myosin binding sites
ADP
P i
Myosin head (highenergy configuration
ADP + P i
ADP
P i
Cross-bridge

Fig. 50-28
Tropomyosin
Actin
Troponin complex
Ca 2+ -binding sites
(a) Myosin-binding sites blocked
Ca 2+
Myosinbinding site
(b) Myosin-binding sites exposed

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Calcium ions diffuse from the sarcoplasmic reticulum into the sarcoplasm and bind to troponin molecules
Tropomyosin molecules move and expose specific sites on actin filaments
Linkages form between actin and myosin filaments
Actin filaments slide inward along the myosin filaments
Muscle fiber shortens as a contraction occurs

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 http://www.youtube.com/watch?v=EdHzKY
DxrKc http://www.youtube.com/watch?v=WRxsO
MenNQM http://www.youtube.com/watch?v=0kFmbrR
Jq4w http://www.youtube.com/watch?v=70DyJww
FnkU&NR=1 http://bcs.whfreeman.com/thelifewire/conte nt/chp47/4702001.html

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Cholinesterase causes acetylcholine to decompose and the muscle fiber membrane is no longer stimulated
Calcium ions are actively transported into the sarcoplasmic reticulum
Linkages between actin and myosin filaments are broken
Troponin and tropomyosin molecules inhibit the interaction between myosin and actin filaments
Actin and myosin filaments slide apart
Muscle fiber lengthens as it relaxes and its resting state is reestablished


Threshold stimulus is an all or none response – the minimal level of stimulation required to cause a fiber to contract; therefore not necessarily all muscle fibers in muscle contract

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Tonic contraction – only a few fibers at a time contract – maintain muscle tone
Twitch contraction – single contraction that only lasts a fraction of a second; muscle fiber is able to relax between stimuli
Tetanic contraction – a rapid series of stimuli produce a sustained contraction (summation of twitches); muscle does not relax before next contraction
Isotonic contraction – Fig. 7-5A – produce movement of joint; tension remains fairly constant and muscle shortens
Isometric contraction – Fig. 7-5B – tension increases with no shortening of the muscle

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Flexion – makes angle between two bones smaller
Extenion – angle between two bones becomes larger; straighten

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Abduction – movement away from midline
Adduction – movement toward the midline

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Rotation – movement around a longitudinal axis

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Supination – hand position with palm turned to anterior position
(anatomical position)
Pronation – hand position with palm turned posteriorly

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Dorisflexion – dorsum (top) of foot is elevated with toes pointing upward
Plantar flexion
– bottom of the foot is directed downward
(stranding on toes)


Facial Muscle Video http://www.gustrength.com/forum/t-283781 http://www.mhhe.com/biosci/genbio/virtual_l abs_2K8/labs/BL_13/index.html
(Virtual Lab
– Muscle Stimulation)