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Muscle Tissue Cont.
Physiology
Chapter 10
Contraction of Skeletal Muscle =
The Sliding Filament Mechanism
• thin and thick
filaments slide past
each other to
shorten each
sarcomere and thus
each myofibril
• the cumulative
effect is to shorten
the muscle
http://www.lab.anhb.uwa.edu.au/mb140/Core
Pages/Muscle/Muscle.htm#SKELETAL
Skeletal Muscle Innervation
The Neuromuscular
Junction:
• where neurons
communicate with the
muscle fibers
• point of communication is
a small gap = synapse
• the chemical that travels
across the synapse =
neurotransmitter
(acetylcholine - ACh)
Steps of Skeletal Muscle Contraction
1. Neurotransmitter ACh is released from the neuron;
binds to its receptor on the sarcolemma, and causes
the sodium channels to open
Steps of Skeletal Muscle Contraction
2. As Na+ ions flow in, an
action potential begins
action potential = the
spread of depolarization
3. ACh removed by
enzyme
acetylcholinesterase
Steps of Skeletal Muscle Contraction
4. Action potential causes
release of Ca++ ions
5. Ca++ binds to troponin,
causing tropomyosin to
move out of its blocking
position
6. Contraction: myosin forms
cross bridges to actin,
muscle shortens, ATP is
used
Steps of Skeletal Muscle Contraction
7. Ca++ ions are reabsorbed
8. Myosin binds to new ATP
9. Troponin-tropomyosin
complex returns to normal
position
10. Contraction ends; muscle
returns to its resting length
STUDY FIG. 10.11 p. 317
Skeletal Muscle Contraction
= Sliding Filament Theory
The Contraction Cycle Animation
http://www.sci.sdsu.edu/movies/actin_myosin_gif.html
Rigor Mortis
• When death occurs, Ca++ ions leak and
cause some contraction of the muscles =
stiffness
• Without ATP, cross-bridges cannot detach
• Lasts ~24 hours, then lysosomal enzymes
break down myofilaments
To help you memorize muscles,
check out:
• http://msjensen.education.umn.edu/webanat
omy/
University of Minnesota, WebAnatomy
• With your laptop, check out:
www.gwc.maricopa.edu/class/bio201/muscl
e/mustut.htm