6 Questions
What is the term for the fused cell membranes between cardiac muscle cells that allow ions to diffuse rapidly?
Gap junctions
What is the functional significance of intercalated discs in cardiac muscle?
They allow ions to move easily along the longitudinal axes of the fibers
What is the term for the network of interconnected cardiac muscle cells?
Syncytium
How many syncytia make up the heart?
Two
What occurs when one cardiac muscle cell becomes excited?
The action potential rapidly spreads to all connected cells
What is the significance of the atrial and ventricular syncytia?
They enable the separation of atrial and ventricular functions
Study Notes
Cardiac Muscle Structure
- Cardiac muscle fibers are composed of many individual cells connected in series and in parallel with one another
- Dark areas crossing the fibers are intercalated discs, which are actually cell membranes separating individual cardiac muscle cells
- Intercalated discs fuse to form permeable communicating junctions (gap junctions) allowing rapid diffusion of ions
Function of Intercalated Discs
- Gap junctions enable ions to move easily in the intracellular fluid along the longitudinal axes of the cardiac muscle fibers
- Action potentials travel easily from one cardiac muscle cell to the next, past the intercalated discs
Syncytium of Cardiac Muscle Cells
- Cardiac muscle is a syncytium of many heart muscle cells, interconnected to allow rapid spread of action potentials
- When one cardiac muscle cell becomes excited, the action potential rapidly spreads to all others
Heart Composition
- The heart is composed of two syncytia: the atrial syncytium and the ventricular syncytium
- The atrial syncytium constitutes the walls of the two atria
This quiz explores the structure and function of cardiac muscle, including the intercalated discs and gap junctions that allow rapid diffusion of ions.
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