1st step of skeletal muscle contraction
An action potential travels along a motor neuron toward a skeletal muscle. Their point of connection is called a neuromuscular junction.
2nd step of skeletal muscle contraction
At the junction, acetylcholine vesicles are released.
3rd step of skeletal muscle contraction
Acetylcholine binds to its receptor on the sarcolemme causing Na+ influx into the muscle fiber, generating an action potential within the muscle fiber.
4th step of skeletal muscle contraction
The action potential travels through the T-tubules, allowing calcium channels to open and release calcium into the cytoplasm.
5th step of skeletal muscle contraction
Calcium ions activate the actin-myosin binding sites and cross-bridges for between the actin and the myosin heads.
6th step of skeletal muscle contraction
An ATP is hydrolyzed to provide energy for flexing the myosin heads.
7th step of skeletal muscle contraction
Flexion brings the actin filaments closer to the middle of the sarcomere. The overall length of the sarcomere is shorter; contracted.
8th step of skeletal muscle contraction
In order for relaxation to occur, ATP must be used to pump calcium back into the sarcoplasmic reticulum.
one of the segments into which a myofibril is divided: smallest function unit in muscle tissue
contractile proteins which interact to cause contraction
makes a "z";
not a line, really a wall;
the border between sarcomeres
Antagonistic action of skeletal muscles?
Muscles can only contract: pull. They can't push. The movement produced by one can be reversed by another. The biceps flexes while the triceps extend.
The muscle that contracts to produce a particular action
The muscle that produces the opposite movement is the antagonist
the junction between a nerve fiber and the muscle it supplies
The system of vesicles in a muscle cell that surrounds the myofibrils and releases calcium in muscle contraction: modified endoplasmic reticulum
Sliding Filament Theory
When muscle contraction occurs. The actin and myosin filaments temporary form cross-bridge attachments and slide over each other, shortening the overall length of the sarcomeres.
transverse tubules : system of inward extensions of the muscle fiber plasma membrane.