Smooth Muscle Flashcards
What is the general shape of smooth muscle cells?
short and fusiform (spindle shaped) with one central nucleus
Are smooth muscle cells striated?
no
Do smooth muscle cells have actin and myosin?
Yes
What are dense bodies?
attachment molecules for actin; found in the cell and cell membrane
What is unique about membrane dense bodies?
some are bonded to the membrane dense bodies of adjacent cells
T/F Actin filaments of smooth muscle is the same as actin filaments of skeletal muscle
False. Smooth muscle actin filaments have calmodulun instead of troponin
Where would myosin be found in smooth muscle?
halfway between dense bodies (interspersed between actin filaments)
What are intermediate?
structural protein framework for the actin and myosin
What is meant by “sidepolar” cross bridges?
The myosin heads on one side of the filament are antiparallel to the heads on the opposite side.
What affect does the sidepolar cross bridge have on contraction?
contraction is spiral shaped, corkscrew-like
How does the sarcoplasmic reticulum of smooth muscle compare to the sarcoplasmic reticulum of skeletal muscle?
Smooth muscle SR is sparse with no transverse tubules
Where do smooth muscle cells source most of their calcium?
extracellular fluid, entering the cell via calcium channels in the sarcolemma. The SR stores very little Ca++
What type of channel is important for smooth muscle contraction?
Calcium channels
