What type of actions use smooth muscles

As a result, contraction does not spread from one cell to the next, but is instead confined to the cell that was originally stimulated. Stimuli for multiunit smooth muscles come from autonomic nerves or hormones but not from stretching. This type of tissue is found around large blood vessels, in the respiratory airways, and in the eyes. Similar to skeletal and cardiac muscle cells, smooth muscle can undergo hypertrophy to increase in size.

Unlike other muscle, smooth muscle can also divide to produce more cells, a process called hyperplasia. This can most evidently be observed in the uterus at puberty, which responds to increased estrogen levels by producing more uterine smooth muscle fibers, and greatly increases the size of the myometrium.

Smooth muscle is found throughout the body around various organs and tracts. Smooth muscle cells have a single nucleus, and are spindle-shaped. Smooth muscle cells can undergo hyperplasia, mitotically dividing to produce new cells. Smooth muscle can be stimulated by pacesetter cells, by the autonomic nervous system, by hormones, spontaneously, or by stretching.

The fibers in some smooth muscle have latch-bridges, cross-bridges that cycle slowly without the need for ATP; these muscles can maintain low-level contractions for long periods. Single-unit smooth muscle tissue contains gap junctions to synchronize membrane depolarization and contractions so that the muscle contracts as a single unit. Single-unit smooth muscle in the walls of the viscera, called visceral muscle, has a stress-relaxation response that permits muscle to stretch, contract, and relax as the organ expands.

Multiunit smooth muscle cells do not possess gap junctions, and contraction does not spread from one cell to the next. Why can smooth muscles contract over a wider range of resting lengths than skeletal and cardiac muscle? Smooth muscles can contract over a wider range of resting lengths because the actin and myosin filaments in smooth muscle are not as rigidly organized as those in skeletal and cardiac muscle.

Describe the differences between single-unit smooth muscle and multiunit smooth muscle. Single-unit smooth muscle is found in the walls of hollow organs; multiunit smooth muscle is found in airways to the lungs and large arteries. Single-unit smooth muscle cells contract synchronously, they are coupled by gap junctions, and they exhibit spontaneous action potential.

Multiunit smooth cells lack gap junctions, and their contractions are not synchronous. Skip to content Muscle Tissue. Learning Objectives By the end of this section, you will be able to: Describe a dense body Explain how smooth muscle works with internal organs and passageways through the body Explain how smooth muscles differ from skeletal and cardiac muscles Explain the difference between single-unit and multi-unit smooth muscle.

Smooth muscle tissue is found around organs in the digestive, respiratory, reproductive tracts and the iris of the eye. Artery walls include smooth muscle that relaxes and contracts to move blood through the body. The heart wall is composed of three layers. Cardiac muscle, found only in the myocardium, contracts in response to signals from the cardiac conduction system to make the heart beat. Cardiac muscle is made from cells called cardiocytes.

Like skeletal muscle cells cardiocytes have a striated appearance, but their overall structure is shorter and thicker. Cardiocytes are branched, allowing them to connect with several other cardiocytes, forming a network that facilitates coordinated contraction. See more from our free eBook library. Newark: University of Delaware, Biological Sciences. How do muscles grow? Len Kravitz, Ph. Muscle Attachment and Actions.

Muscular System Pathologies. Digestive and Urinary Smooth Muscle Functions The digestive system is almost entirely made of smooth muscle. Functions of smooth muscle in the digestive and urinary systems include: Smooth muscles move food through the digestive tract. Folds in the stomach and small intestine, which are made of smooth muscle, help the body better absorb nutrients. Smooth muscle composes all sphincters in the digestive system.

In the bladder, smooth muscle helps to push out urine. When the bladder expands or contracts, folds of smooth muscle prevent refluxes of urine. Integumentary Smooth Muscle Functions Also known as the skin system, the integumentary system is the largest system in your body. Functions of smooth muscle in the integumentary system include: Skin stands on end when piloerector muscles contract also known as goosebumps.

Smooth muscles around blood vessels relax to allow more blood to flow into the skin. Smooth muscle lining around secretory cells allows sweat to be excreted from skin ducts. Nervous System Smooth Muscle Functions All smooth muscle and smooth muscle cells are controlled by the nervous system. The dilator muscle in the eye dilates the pupil.

Respiratory Smooth Muscle Functions Several parts of the respiratory system have smooth muscle that aids in breathing. The bronchi and bronchioles use smooth muscle to bring air from the trachea into the lungs. Smooth muscle in the lungs helps the airways to expand and contract as necessary. During exercise or exertion, smooth muscles in the bronchi relax and dilate. Reproductive Smooth Muscle Functions Both male and female reproductive systems include smooth muscles.

Their functions include: During menstruation, smooth muscle in the uterus contracts to expel the uterine lining. Smooth muscle helps sperm to move along the male reproductive tract. To prevent urination during ejaculation by men, the sphincter muscle constricts. The tunica dartos is a smooth muscle that contracts or expands to regulate temperature of the testicles. The smooth muscle in the uterus helps a woman to push out her baby.