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Lecture 37

BIOL 1082 Lecture Notes - Lecture 37: Sliding Filament Theory, Human Musculoskeletal System, Endoplasmic ReticulumPremium

2 pages84 viewsSpring 2018

Department
Biological Sciences
Course Code
BIOL 1082
Professor
Mosley
Lecture
37

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Ch. 46 LO
Musculoskeletal system Textbook Reading: Sections: 46.1 & 46.4
1. Explain the sliding filament mechanism of skeletal muscle contraction.
The length of muscle determines the relationship between the thick and thin filaments.
The amount of overlap determines the number of potential cross bridges that may be
formed
A short L, there is overlap of thin filament into the region of the thick filament with no
myosin head or cross bridges.
As the length is increased towards Lo more and more possible cross bridges may be
formed, when Lo is exceed then there will be myosin heads in the center of the sarcomere
that can't bind to actin sites and the number of potential cross bridges are reduced.
2. Describe the origin and role of calcium in muscle contraction.
Calcium binds to troponin that is around actin
In turn this triggers the sarcoplasmic reticulum to release calcium ions into the
muscle interior where they bind to troponin, thus causing tropomyosin to shift from the
face of the actin filament to which myosin heads need to bind to produce contraction.
1. Explain how motor units produce precise coordinated movement.
In vertebrates, each branched neuron can motor neuron may synapse with many muscle
fibers, although each fiber is controlled by only one motor neuron.
A motor unit: a single motor neuron and all of the muscle fibers it controls
When a motor neuron produces an action potential, all the muscle fibers in it motor unit
contract as a group.
As more and more of the more and more of the neurons controlling the muscles are
activated a process called recruitment, the force (tension) developed by a muscle
progressively increases depending on the number of motor neurons your brain recruits and
the size of their motor units.
The nervous system regulates muscle contraction not only by controlling which motor units
are activated but also by varying the rate of muscle fiber stimulation.
A single action potential produces a twitch lasting about 100 milliseconds. If a second action
potential arrives before the muscle fiber has completely relaxed, the two twitches add
together resulting in a greater tension.
Further summation occurs as the rate of stimulation increases.
When the rate is so high that the muscle fiber cannot relax at all between the stimuli, the
twitches fuse into one smooth sustained contraction cell tetanus.
2. Differentiate between tetanus and twitches, and between slow-twitch and fast-twitch muscle
fibers.
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