Smooth Muscle Anatomy and Function

The property exhibited by certain smooth muscle fibers where their membrane potential gradually drifts towards threshold, triggering action potentials and causing rhythmic contractions. This is often observed in the GI tract.

A type of smooth muscle where fibers are independently innervated and not connected by gap junctions. Contraction occurs only in the stimulated fiber, not in the entire bundle.

A type of smooth muscle where fibers are connected by gap junctions, allowing synchronous depolarization and contraction throughout the bundle. Stretching of one fiber triggers a coordinated response in the entire unit.

A specialized junction in skeletal muscle where a motor neuron releases neurotransmitters to stimulate muscle fiber contraction. Smooth muscle does not have these.

Small swellings on autonomic nerve branches that release neurotransmitters in smooth muscle, allowing for communication without a specialized junction.

The process in which muscle fibers shorten due to the sliding of actin and myosin filaments, driven by ATP.

A protein found in muscle fibers, responsible for forming cross-bridges with actin during contraction.

A protein found in muscle fibers, forming thin filaments, which interact with myosin during contraction.

A molecule that provides energy for cellular processes, including muscle contraction.

A chemical messenger that transmits signals between nerve cells and muscle cells, triggering contraction or relaxation.

A type of muscle tissue found in the walls of internal organs like the stomach, bladder, and blood vessels. It contracts slowly and involuntarily, helping to move substances through the body.

The thick filaments in smooth muscle contain myosin with two subunits. The heavy chain has the myosin ATPase activity, crucial for muscle contraction, while the light chain regulates this activity, controlling the formation of cross-bridges between myosin and actin.

The process of activating smooth muscle contraction by increasing intracellular calcium levels. Calcium influx occurs through voltage-gated, ligand-gated, and mechano-gated channels in the plasma membrane.

A type of smooth muscle contraction triggered by changes in membrane potential, either through graded depolarization, hyperpolarization, or action potentials. These changes cause a rise or fall in intracellular calcium levels, initiating or inhibiting contraction.

The ability of some smooth muscle to exhibit spontaneous contractile activity in the absence of nerve or hormonal stimuli. This rhythmic contraction occurs due to intrinsic pacemakers within the muscle tissue.

A primary mechanism for regulating the activity of myosin light chain kinase, a key enzyme controlling smooth muscle contraction. Calcium binding to calmodulin activates the kinase, initiating the phosphorylation of myosin light chains, which in turn triggers muscle contraction.

Characterized by slow, sustained contractions, drawing only a small fraction of the energy required by skeletal muscle for the same work. This efficiency allows smooth muscle to function effectively in long-term tasks like maintaining blood vessel tone or moving food through the digestive system.

The ability of smooth muscle to adjust its tension widely, allowing it to adapt to varying needs and functions. For example, smooth muscle in the blood vessels regulates blood pressure through changes in tension.