Muscle Types and Their Characteristics

These flashcards cover key concepts and terms related to smooth, skeletal, and cardiac muscle types, including their structures and functions.

Pharynx

A muscular tube that connects the mouth and nasal passages to the esophagus.

Smooth Muscle

Muscle type that surrounds hollow organs and is involuntary; it has a single nucleus and no striations.

Skeletal Muscle

Striated muscle that is under voluntary control and has multiple nuclei.

Cardiac Muscle

Striated muscle found only in the heart, characterized by branched cells and intercalated discs.

Contraction Control in Smooth Muscle

Involves phosphorylation of myosin regulated by the enzyme myosin light chain kinase (MLCK).

Sarcoplasmic Reticulum

An organelle that stores calcium ions in muscle cells; less developed in smooth muscle than in skeletal muscle.

Pacemaker Potential

The slow, spontaneous depolarization that occurs in some smooth muscle cells.

Multi-unit Smooth Muscle

Muscle type where cells respond independently to stimuli and have few gap junctions.

Single-unit Smooth Muscle

Muscle type where cells function as a single unit due to gap junction connectivity.

Absolute Refractory Period

The time during which a second action potential cannot be initiated, preventing tetany; crucial in cardiac muscle.

Ca2+-Troponin Interaction

In cardiac muscle, calcium binds to troponin to facilitate muscle contraction.

Cytosolic Ca2+ Sources

Calcium ions in smooth muscle come from both the sarcoplasmic reticulum and extracellular fluid.

Myosin Light Chain Phosphatase (MLCP)

Enzyme that dephosphorylates myosin, leading to relaxation of smooth muscle.

Cross-bridge Cycling

The process by which myosin heads bind to actin and pull to contract muscle fibers.

Graded Activation

A response in smooth muscle where contraction strength varies with the degree of depolarization.

Gap Junctions

Connections between neighboring cells that allow for electrical and metabolic coupling, important in both cardiac and single-unit smooth muscle.