Muscle contraction

A muscle contraction (also known as a muscle twitch or simply twitch) occurs when a muscle cell (called a muscle fiber) shortens. Locomotion is possible only through the repeated contraction of many muscles at the correct times.

Related Topics:
Muscle fiber - Muscles

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For most muscles, contraction occurs as a result of conscious effort originating in the brain. The brain sends signals, in the form of action potentials, through the nervous system to the motor neuron that innervates the muscle fiber. However, some muscles (such as the heart) do not contract as a result of conscious effort. These are said to be autonomic. Also, it is not always necessary for the signals to originate from the brain. Reflexes are fast, unconscious muscular reactions that occur due to unexpected physical stimuli. The action potentials for reflexes originate in the spinal cord instead of the brain.

Related Topics:
Brain - Action potential - Nervous system - Motor neuron - Heart - Autonomic - Reflexes - Spinal cord

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There are three general types of muscle contractions, skeletal muscle contractions, heart muscle contractions, and smooth muscle contractions.

Related Topics:
Skeletal muscle - Heart muscle - Smooth muscle

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