Muscle Contraction
Tendon – cord of dense
fibrous tissue attaching the
muscle to a bone.
Epimysium – the sheath
of fibrous connective tissues
surrounding a muscle.
Perimysium– the
connective tissue enveloping
bundles of muscle fibers.
Endomysium – the thin
connective tissue surrounding
each muscle cells.
Fascicle – a bundle of
nerve or muscle fibers bound
together by connective tissues.
http://fitnessratchet.com/images/musclefiber.jpeg
Myofibril – contractile
organelles found in the
cytoplasm of the muscle cell.
Myofiber – is
an actual muscle
fiber.
Alexis Fitzpatrick
February 10th, 2010
Human Physiology
Mrs. Caldeira
3rd Quarter
Anatomy of Myofiber & Myofibril
•Myofilaments – are two myofibrils, is
what actin and myosin are.
•Actin – are a contractile protein of muscle.
•Myosin – one of the principal contractile
proteins found in muscle.
•Z Line – the line that divides the sarcomere in
a myofibril.
•I band – are light bands or thin filaments of
actin.
•A Band – are dark bands or thick filaments of
myosin.
•Sarcomere – are thick filaments composed
of protein myosin and has ATPase emzymes
located in the distance between two z lines.
•Sarcolemma – is a specialized plasma
membrane.
http://legacy.owensboro.kctcs.edu/gcaplan/anat/images/Image286.gif
Anatomy of the Neuromuscular
Junction
http://demo.classontheweb.com/CBSE/ClassX/images/NeuromuscularJunction.jpg
Steps Of Muscle Contraction
1.
2.
3.
4.
5.
Nerve impulse (electrical impulse)
moves down the axon of a motor
neuron towards the motor end plate
of a neuromuscular junction.
The axon terminal (end of axon)
releases the neurotransmitter –
acetylcholine (ACh).
Acetylcholine binds to receptors on
the sarcolemma at the
neuromuscular junction.
This causes the generation of a
new action potential (electrical
impulse) that spreads over the
sarcolemma (muscle fiber).
This impulse goes down the
transverse tubules (T tubules) into
the myofiber.
http://www.bmb.leeds.ac.uk/illingworth/bioc1020/image36.gif
Steps Of Muscle Contraction
(Continue)
6.
This impulse causes the
sarcoplasmic reticulum to release
calcium.
7. Calcium binds to troponin on actin
moving tropo,ysin and exposing the
binding sites (on actin) for the
crossbridges of myosin.
8. Myosin interacts with actin.
9. Crossbridges on myosin with
Energy supplied by ATP
(ATP=ADP+P+Energy) binds to
actin and actin slides in between
myosin (sliding filament theory).
10. Sarcomere shortens – myofiber
shorten – entire muscle shortens.
http://static.howstuffworks.com/gif/rigor-mortis-muscle.gif
Steps Of Muscle Contraction
(Continue)
11. Calcium returns (activily) to
sarcoplasmic reticulum.
12. Troponin returns to its original
position
13. Binging sites are covered by
tropomyosin.
14. Actin slides back to a relaxed position
15. Muscle relaxes.
http://www.biog1105-1106.org/demos/105/unit10/media/muscle-contraction.fig.jpg