The muscular system consists of skeletal, smooth, and cardiac muscle and associated connective tissues. Skeletal, or voluntary, muscle has a connective tissue sheathing that becomes narrowed as a tendon to attach the muscle to a bony prominence. Smooth muscle is involuntary and generally has less associated connective tissue than skeletal muscle.
Cardiac muscle is involuntary and is found exclusively in the heart.
The three muscle subtypes have quite different histological appearances and very different functions, even though the general function of muscle is movement of body parts. Applications Toxins produced by certain bacteria can affect muscle cells, and hence bodily activity. The botulism exotoxin secreted by the bacterium Clostridium botulinum blocks the muscle cell membrane receptor for neurotransmitter, causing a flaccid paralysis. Clostridium tetani produces a tetanus toxin that inhibits normal breakdown and recycling of the neurotransmitter that stimulates muscle cells. Some parasitic worm life cycle stages encyst in muscle tissue, causing destructive or painful muscle disease.