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Physical Education - Sliding filament theory
Sliding filament theory
For contraction [1] to occur, a nerve impulse must be sent from the brain.
Down at the motor end plate, calcium ions are released which effectively
act as a power switch. This power switch activates the crossbridges (which
connect thick and thin filaments).
ATP energises the crossbridges, which allows a pulling action to occur,
resulting in the thin filaments sliding over the thick filaments. This
occurs all down the length of the fibre (at each sarcomere [2]), and the
result is a contraction [3] of the muscle.
What happens to each of the following when a muscle contracts?
* Actin [4] - thin filaments: slide over the thick filaments; whether
they slide toward or away from one another depends on whether it is a
concentric or eccentric contraction [5]
* Myosin [6] - thick filaments; do not move under contraction [7]
* - oar-like structures that are attached to the thick (myosin [8])
filaments. These structures reach out and are attracted to the thin (actin
[9]) filaments. When contraction [10] occurs, these oar-like structures
drag the thin filaments in toward the centre of the sarcomere and the
muscle contracts (concentric contraction [11])
* - distance between the z-line [12] and the edge of the A band
* - the gap between the thin filaments before contraction. The H zone
disappears upon full contraction
* - the length of the thick filament
Make sure you have a good look at a diagram of the sliding filaments
(actin): one is on the previous page. It is quite possible that a question
with a diagram will be used in the exam.
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What is the sliding filament theory?
Sliding filament theory:- For contraction to occur, a nerve impulse must be sent from the brain. Down at the motor end plate, calcium ions are released which effectively act as a power switch. This power switch activates the crossbridges (which connect thick and thin filaments). ATP energises the crossbridges, which allows a pulling action to occur, resulting in the thin filaments sliding over the thick filaments. This occurs all down the length of the fibre (at each sarcomere), and the result is a contraction of the muscle. What happens to each of the following when a muscle contracts? Actin - thin filaments: slide over the thick filaments; whether they slide toward or away from one another depends on whether it is a concentric or eccentric contraction Myosin - thick filaments; do not move under contraction Crossbridges - oar-like structures that are attached to the thick (myosin) filaments. These structures reach out and are attracted to the thin (actin) filaments. When contraction occurs, these oar-like structures drag the thin filaments in toward the centre of the sarcomere and the muscle contracts (concentric contraction) I band - distance between the z-line and the edge of the A band H zone - the gap between the thin filaments before contraction. The H zone disappears upon full contraction A band - the length of the thick filament Make sure you have a good look at a diagram of the sliding filaments (actin): one is on the previous page. It is quite possible that a question with a diagram will be used in the exam.
What is the theory of sliding filament.