
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

Cardiac – forms the heart, cells fuse (intercalated
discs) into a branching pattern; striated; involuntary
control

Smooth – located mostly in the walls of hollow
organs; 1 nucleus/cell; not striated; involuntary
control

Move body parts as muscle contracts

Muscles usually attach to 2 different bones
 Insertion point – at moving bone
 Origin point – at stable bone

Move body parts as muscle contracts (con’t)

Muscles work in groups
 Prime mover – one muscle that is mainly responsible
for movement
 Synergists – other muscles that help movement
 Antagonists – produce movement in opposite direction

Posture and Stability

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

Heat production – only 25% of energy
produced by respiration is used for metabolic
processes, the rest is lost as heat




During rest or moderate exercise, O2 is supplied to
muscles in sufficient concentration to support
aerobic respiration
Strenuous exercise causes deficiency and lactic
acid accumulates as a result of anaerobic
respiration
C6H12O6  6CO2 + lactic acid + 2ATP = heat
Muscle fatigue – muscle loses ability to contract
because of strenuous exercise for prolonged
periods of time
Usually caused by lactic acid buildup
 May result from decreased blood supply
 Rarely from decreased acetylcholine from motor neuron



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.




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)


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

Sliding Filament Model



Muscle fiber contraction
Muscle fiber relaxation
Threshold stimulus



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





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




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






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






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


Flexion – makes
angle between two
bones smaller
Extenion – angle
between two bones
becomes larger;
straighten


Abduction – movement away from midline
Adduction – movement toward the midline

Rotation – movement around a longitudinal
axis


Supination –
hand position
with palm
turned to
anterior
position
(anatomical
position)
Pronation –
hand position
with palm
turned
posteriorly


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
