Smooth Muscles and Disorders Flashcards
Phasic Contraction
Cycles of contraction and relaxation
-digestive system
Tonic Contraction
Constant state of contraction to some degree
-Sphincters
Single Unit (Visceral) communication
- Contraction of multiple cells as one
- Connected via gap junctions
- Most common type
Multiunit Contraction
Cells contract independently from one another
-occular and reproductive
Actin and myosin structure in smooth muscle
Bundle of actin and myosin
- 1 myosin surrounded by 12-15 actin molecules
- Actin bound to dense bodies to anchor plasma membrane
Where does Ca come from in smooth muscle?
SR and ECF
Determines if muscle is contracted or relaxed
Ratio of MLCK:MLCP
-more MLCP=relaxed
Rigor Mortis
No ATP production after death so myosin heads lock
-Ca leaks and continues to lock
Muscle Atrophy
Lack of use can cause muscles to shrink and lose strength
Muscular Dystrophy
Loss of function mutation in gene coding for dystrophin
-Mechanical stress fragments membrane and causes death of muscle cells
Muscle Cramps
Due to uncontrolled nerve impulses or uncontrolled contractions
True Cramps
-Usually caused by dehydration
-Imbalance of electrolytes (Na, Ca, Mg)
Leads to hyperexcitability of motor neurons and muscle cells
Dystonic Cramps
Contraction of uneeded muscle groups
-repetitive motion (writer’s cramp)
Contractures
Severe long lasting
- Depletion of ATP in muscles cells
- May be acquired or inherited disorder
Store-operated Ca channels
Open in response to low Ca in SR
