Muscle 13 Flashcards
What is the shape of smooth muscle?
They are spindle shaped
What is the relative size between smooth muscle and skeletal muscle?
Smooth muscle cells are a lot smaller than skeletal muscle cells
What do the myosin filaments look like in smooth muscle?
They are thick
Why are striations in smooth muscle not visible?
Because the actin and myosin filaments are not highly organized
What is the orientation of actin filaments in relation to the cell?
Actin filaments are mainly parallel or oblique to the long axis of the cell
Where do actin filaments of smooth muscle join?
At Dense Bodies
Where are Dense Bodies found?
Immediately beneath the smooth muscle cell membrane and in the interior of the smooth muscle cell
What are the thin filaments anchored to in smooth muscle?
To the plasma membrane or to cytoplasmic structures
What are Dense Bodies functionally similar to?
Z lines in skeletal muscle
What physically happens when smooth muscle contracts?
The regions of the plasma membrane between the points where actin is attached to the membrane, ballon out in the smooth muscle
What is strange about the thick and thin filaments of smooth muscle?
They are not organized into myofibrils and there is not regular alignment
What does smooth muscle contain?
- Actin
- Myosin
- Tropomyosin
- Calmodulin
- Myosin light kinase
- Myosin light chain phosphate
What is something the thin filaments of smooth muscle lack?
Troponin
What is Myosin Light Chain important for in smooth muscle?
Terminating contraction
What are the two types of Smooth Muscle?
- Multiunit
* Unitary
What are the characteristics of of Unitary smooth muscle?
- Large sheets
- Low resistance gap junctions
- Functions as one
What are the characteristics of Multiunit Smooth Muscle?
- Made of individual units
- No gap junctions
- Little electrical coupling
- Cell can contract independently of neighbor
What do Varicosities do on smooth muscle?
Release neurotransmitters
Does the Smooth muscle have end-plates or neuromuscular junctions?
No. there is no well defined post synaptic structure
Which type of smooth muscle has little electrical coupling and why?
Multiunit smooth muscle because they lack gap junctions
What allows multiunit smooth muscle to have finer control?
The lack of gap junctions between the smooth muscle that reduce electrical coupling
Where can Multiunit smooth muscle be found?
- Iris
- Ciliary body of the eye
- Piloerector muscles of the skin
What do the gap junctions allow for in Unitary smooth muscle?
They allow ions to flow from cell to cell to allow the cells to function as a single unit
Where is unitary smooth muscle found?
GI tract, uterus, bladder and some blood vessels
