Cigarette smoke contains over 4,000 chemicals, including 43 known cancer-causing (carcinogenic) compounds and 400 other toxins. These include nicotine, tar, and carbon monoxide, as well as formaldehyde, ammonia, hydrogen cyanide, arsenic, and DDT.
Involuntary muscles are muscles that are not controllable consciously, and instead contract due to unconscious impulses sent by the autonomic nervous system or certain specialized cells or hormones.Both smooth muscle and cardiac muscle can be classified as involuntary muscles.Smooth muscle is comprised of spindle-shaped cells that have no striations and is found in numerous locations throughout the human body. Cardiac muscle is striated rather than smooth, and is found only within the walls of the heart. beating heart is one of the best examples of an involuntary muscle. Contractions of cardiac muscles push blood through the four chambers of the human heart. The process of peristalsis, which pushes food through the esophagus and small intestine, is controlled by involuntary muscles.
Smooth muscle is called involuntary muscle because you can not control this type of muscle movement. These muscles line internal organs, blood vessels, and organs such found in the digestive and reproductive systems.keletal Muscle. Skeletal muscle is called voluntary because you can control this type of muscle. You can voluntarily choose to move them. These muscles attach to bones, move the skeleton, and are found in the arms, legs, neck, or anywhere you can voluntarily move a body part.