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2.03 Muscle Contraction
Transcript of 2.03 Muscle Contraction
Muscles are not a connective tissue, but it have connective tissues in it. a fascicle, or a bundle with a muscle, and around it is connective tissue. There are nerves, blood vesicles, and oxygen because it needs nutrients within the muscles for all the things it has to do.
Steps of the Sliding Filament Theory
Step 4: Nerves signal muscles around it and this signal then travels down the cell's membrane in folds, t-tubules. Once the signal reaches the SR, the calcium begins to pumps wide open and the calcium ions begin to flow. Now, at this point, the calcium ions stick to the troponin. After this happens, the troponin change it's shape and rotate around the actin. This moves the tropomyosin out of the way and leaves the binding sites exposed.
Step 5: Since the binding sites are open, myosin heads broaden and attach to the actin. This connection is called a cross-bridge. The contact causes the myosin heads to bend towards the core of the sarcomere, this will then shortening the length altogether. Finally, we call this a muscle contraction.
Step 6: For a contraction to stop, a nerve stimulus will stop, the calcium ions revert back inside the SR, an ATP molecule sticks to the head of the myosin, and the troponin and tropomyosin return to their settling positions. The ATP molecule release energy that is on the myosin head that replenish muscle relaxation.
Thin Filament: Actin
Actin is found within the thin filament. It is a complex of different proteins. Actin molecules and tropomyosin fibers are braided together. To make sure that the tropomysin fired are nice and secure, it is protected with troponin molecules. With larger muscles there are more actin than muscles that a smaller.
Tendons pull the muscle to the bone; it's a connective tissue. This tissue has nerves; so be very careful not to pull a break your tendon because it can really hurt. The tendon also has a supply of blood.
Sliding Filament Theory
The sliding filament theory was discovered in the 1950s, by several scientist. That was just the beginning and the only model that's most accepted. Over time more research has done of muscle contraction. So, the theory is a basically when muscles are moving there is a lot of contraction happening. Let's get this project moving to see into further detail what is the "sliding filament theory".
On every muscle cell, they are lined with multiple nuclei because they merge together to become like a grander cell. Inside of the muscle fiber there are many myofibril.
Thick Filament: Myosin
This single protein is long with a globular head. When the cell puts all the myosin together, then all of the head stick out away from the core busy working.
Myofibrils are made up of bundles of protein. The only was to really see this pattern is through a microscope. There are different sections within myofibrils called a sarcomere. The sarcomeres are made up of two kinds of filaments. One filament is a thin braided strand made up of three different proteins. The proteins for the thin filament are actin, tropomyosin, and troponin. Now the thick filaments are made up of myosin proteins. The thick filament can be found in between the thin filaments. Between each myofibril sections are z-lines. Since a German scientist was the first to really take a closer look at this the "z" stands for between. That is very well suiting!
Steps of the Sliding Filament Theory
Now we know all of the parts that is being studied for the theory, lets look at the steps that make it up.
Step 1: The muscle must be moving for the two stands to connect with one another.
Step 2: Muscles need actin, myosin, and ATP to provide enough energy to power movement. proteins change into ions when they come in contact, but when in a rested state tropomyosin and troponin that are wrapped around the actin. ADP molecules grab onto one of the myosin heads when the muscle, when relaxed. Tropomyosin, troponin, and ADP secure the myosin heads from extending and latching onto the protected actin strand.
Step 3: While muscles are resting, they build up a great amount of calcium ions so that when muscles contract, they will be used during that time. Sarcoplasmic reticulum are wrapped around sarcomere and when the cell allow these ions through, the calcium will be used to be pumped to the SR.