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Muscle Contraction Project

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Priscilla Dong

on 10 April 2013

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Transcript of Muscle Contraction Project

Priscilla and Peter What is muscle contraction? How Muscles Work: Contraction Interaction between myosin and actin Motor Neurons Myosin-Actin ATPase Cycle THE ENDDDD. Muscle contraction is when a group of fibers or a muscle fiber is triggered by a nerve to change the tension within the muscle. In muscle contraction, there are thick and thin filaments that does the actual work of the muscle. The thick filaments made of proteins are known as myosin.
And the thin filaments made of another proteins are known as actin, these thin filaments looks like a two strands of of pearls twisting around each other.
When a contraction occurs, the myosin thick filaments attaches to the actin thin fliaments by forming crossbridges.
Crossbridges is a distinctive structure consisting of two head of a myosin molecule and reacts to calcium ions located on specific sites on a actin filament. The thick filaments pull the thin filaments past them, therefore making the sarcomere shorter.
Sacromere are segments of skeletal muscle fiber. They are divided into parts of filaments that are either myosin and actin. There are two structures in the grooves in each thin filament that allows the thin filaments to slide past the thick filaments.
One of them is a long rod-like protein known as tropomyosin.
And the other one is troponin, a shorter bead-like protein structure.
Both tropomyosin and troponin work as moleculer switches that controls the interaction of actin and mysoin during a contraction. Motor neurons stimulate muscle contraction and are branched and can stimulate more than one muscle fiber. The strength of the muscular contraction is regulated by the number of motor units. THANK YOU FOR LISTENING. Muscle Contraction Project Three types of muscle contraction There are three ways a muscle fiber can be activated. Two allows movement in the muscle and one just creates tension without joint movement.

Three types include:
- Concentric Muscle Contraction (shortening)
- Eccentric Muscle Contraction (lengthening)
- Isometric Muscle Contraction (static) The three following types of muscle contraction concentric: A type of muscle activation that increases tension on a muscle as it shortens. Most common concentric muscle contraction would be a in a gym, lifting weights, doing a squat, or pull up. Eccentric: A type of muscle activation that increases tension on a muscle as it lengthens. It usually happens when a muscle fights a stronger force and causes the muscle to lengthens as it contracts. Common exercises would be running down the stairs, lowering weights and push ups. Isometric: Also known as static exercise, it is when the muscle fires, but there is no movement in the joint and no change in the length of the muscle. An example of isometric exercise would be pushing against the wall. Benefits from isometric exercise is that its great for rehabilitation and general strengthen without putting stress on the joints. Some sports that includes static strengths are gymnastics and yoga. RELAXED Anatomy 1B CONTRACTED In Rigor stage, myosin is stuck due to lack of ATP, afterwards
ATP connects to the head of a myosin, which is released from an actin filament. After the binding, it is split into ADP and Phosphate and is in the relaxation stage.The energy derived from this process is used to cock the crossbridges in preperation for the power stroke. The power stroke starts when the myosin crossbridge binds with actin with the help of calcium and thats how you a get a contraction.

ATPase - enzymes that catalyze the decomposition of adenosine triphosphate (ATP), which releases energy.
ATP - Adenosine triphosphate is a chemical compound that a cell uses to store energy or to release energy, it is the basic source of energy.
ADP - Adenosine diphosphate an ester of adenosine that is converted to ATP for energy storage.
Phosphate can be quickly transferred to ADP to regenerate the ATP necessary for muscle contraction
What is calcium's role in muscle contraction?
Muscle contraction is regulated by calcium ions that changes the actin filament into an activated state by binding to troponin. The binding of calcium to troponin changes it's structure so the myosin binding sites on the actin are exposed. Neuromuscular Junctions Neuromuscular Junction is section of the body where axons of motor nerves meet the muscles, and sends signals from the brain to them so they can contract and relax. More motor units = stronger contractions Mechanism of stimulation: - An action potential releases acetylcholine into the neuromuscular junction.
- Acetylcholine then depolarizes the muscle cell channels inside on the sacroplasmic reticulum then release calcium so it can reach the contractile apparatus (skeletal muscle). Mechanism of relaxation: - Motor neurons stop firing - Calcium is pumped back into the sacroplasmic
reticulum. The expanded Muscle - Myofibril Acetylcholine - A compound that occurs throughout the nervous system, in which it functions as a neurotransmitter.
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