Smooth Muscle Flashcards
1
Q
Location
A
Vascular Gastrointestinal Urinary Respiratory Reproductive Ocular
2
Q
Contraction pattern
A
Phasic (relaxed)
Tonic (contracted)
3
Q
Communication with neighbouring cells
A
Single unit and multi unit
4
Q
What fibres come from the cytoskeleton
A
Intermediate filaments
Protein dense bodies
5
Q
Where does actin attach to
A
The dense bodies
6
Q
Single unit
A
Connected by gap junctions
Contract as a single unit
7
Q
Multi unit
A
Not electrically linked
Each cell must be stimulated independently
8
Q
Smooth muscle contraction
A
- Increase in Ca2+ concentration from SR and extracellular fluid
- Ca2+ binds to calmodulin (CaM)
- Ca2+-CaM activates myosin light chain kinase (MLCK)
- MLCK phosphorylates light chains in myosin heads and increases myosin ATPase activity
- Active myosin crossbridges slide along actin and creates tension
9
Q
Relaxation in smooth muscle
A
- Free Ca2+ in cytosol decreases when Ca2+ is pumped out of the cell or back I=into the SR
- Ca2+ unbinds from CaM. MLCK activity decreases.
- Myosin phosphate (MLCP) removes phosphate from myosin light chains, which decreases ATPase activity.
- Less myosin ATPase activity results in decreased muscle tension
10
Q
Pharmocomechanical coupling
A
Chemical signals change muscle tension through signal transduction pathways with little or no change in membrane potential
