According to Biology-Online, involuntary muscles are muscles which contract without conscious control, and typically found inside internal organs, excluding the heart. The heart, as noted by TeachPE.com, contains cardiac muscle. Cardiac muscle is excluded from the definition of involuntary muscle because it is highly specialized and resembles skeletal muscles, the voluntary muscles which attach to bone, more than it does the involuntary muscles found within other major organs.Continue Reading
TeachPE.com adds that involuntary muscle found in other organs is sometimes called "smooth muscle." Involuntary muscles are found in the stomach, esophagus and lungs, as well as in the walls of blood vessels. While both cardiac and skeletal muscle contain pronounced stripes, involuntary muscle does not. Uic.edu states that involuntary muscle contracts much more slowly than does skeletal muscle. University of Illinois at Chicago says smooth muscle is classified based on the make-up and alignment of the fibers within the muscle; in single-unit smooth muscle, fibers run parallel to each other and contain connections between one other, while in multi-unit smooth muscle, there are no connections.
Smooth muscle is controlled by the autonomic nervous system in contrast to skeletal muscles, which receive signals from the somatic nervous system. As Medline Plus explains, the autonomic nervous system is specialized to handle involuntary actions, including breathing, swallowing, blood pressure and heartbeat.Learn more about Muscles
Some of the movements animals make are under conscious control, and are called voluntary movements. By contrast, other movements occur without the animal's conscious decision to do so. These types of movements are called involuntary movements or reflexes.Full Answer >
The stringy pectinate muscles are inside the heart chambers and help the heart walls expand and contract when the heart beats. This muscle group is located in the left and right auricles (atrial appendages) of the heart, as well as extending into the atria walls.Full Answer >
The primary function of smooth muscle cells is to help hollow organs contract. These organs include the bladder and uterus as well as organs in the gastrointestinal tract. Smooth muscle cells also help the eyes maintain normal focus.Full Answer >
Muscles contract through a series of steps that begin with an action potential. The action potential in a neuron travels down the axon of the neuron and reaches the synapse. At the synapse, the action potential releases a neurotransmitter that stimulates a motor neuron of a muscle cell to contract.Full Answer >