Lecture 29 – Muscle Types and Movement November 6, 2013
• Muscle is still composed of cells, but they are highly specialized cell
• There are two types of muscle, Striated and Smooth Muscle
• Reacts quickly
• It is highly structured, arranged in sarcomeres
• It has an Elaborate Membrane System
• Electrical Signals are quickly transferred to the muscle fibers.
• Wrapped around intestines, blood vessels, and uterus. Responsible for peristalsis.
• Reacts Slowly
• Disorganized Structure,
• No visible Structure of Membranes, though the organelles are present.
In the two muscle types, there is a difference in how the myosin/actin interact
• In striated muscle, myosin binding to actin is regulated by the position of α Tropomyosin.
• In smooth muscle, myosin binding to actin is in only possible if the Myosin Light Chain (MLC)
• This phosphorylation is achieved by MLC Kinase (a kinase is an enzyme that phosphorylates a
protein) this is abbreviated MLCK
• In turn, MLCK is activated via its interaction with Calmodulin.
• Just like Troponin C must be bound to Ca to facilitate the shifting of Tropomyocin in striated
muscle, Calmodulin must be bound to Ca in order to interact with MLCK.
• In smooth muscle, Ca is stored in the smooth ER, as there is not a significant SR. It is also
stored in the mitochondria, and can additionally be obtained from outside the cell, entering via
Putting it 2+l together
1. Ca binds to Calmodulin
2. Calmodulin activates MLCK
3. MLCK phosphorylates the MLC
4. With the MLC phosphorylated, contrac