Muscular contraction and Action potential.

... Muscular contraction and Action potential Muscle can contract only when a nerve ending is stimulated by outgoing impulses from the Central Nervous System (CNS), which consists of the brain and spinal cord. There are Three types of muscle: smooth, cardiac and skeletal: - Smooth: smooth muscle is involuntary and found within hollow internal organs. It is slow to contract, although can sustain a contraction for a long period. There is a single nucleus and no striations (bands); smooth muscle is arranged in parallel lines. Cardiac: cardiac muscle is involuntary and only found in the heart. It contracts rhythmically. Its intercalated disks permit quick spreading of the impulse, so contractions are also quick. There I complete relaxation between contractions and no fatigue. Skeletal: Skeletal muscle is attached to bones under voluntary control; the contraction of these muscles causes bone movement. The fibres are cylindrical, striated and multinucleated. Skeletal muscle

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