Physio Ch 08 Flashcards
2 major types of smooth muscles
multi-unit smooth muscle and unitary (or single-unit) smooth muscle
discrete, separate smooth muscle fibers
multi-unit smooth muscle
major share of control is exerted by non-nervous stimuli
unitary smooth muscle
Where are some locations of multi-unit smooth muscle
ciliary muscle of the eye, iris muscle of the eye, piloerector muscles
mass of hundreds to thousands of smooth muscle fibers that contract together as a single unit
unitary smooth muscle
present in cell membrane of unitary smooth muscle wherein ions can flow freely from one muscle to the next
gap junctions
also known as syncytial smooth muscle because of its syncytial interconnections among fibers
unitary smooth muscle
visceral smooth muscle are found in these organs
GI tract, bile duct, ureter, uterus, blood vessels
It is mainly through these bonds that the force of contraction is transmitted from one cell to the next
dense bodies
serve the same role as the Z discs in skeletal muscle
dense bodies of smooth muscles
sidepolar of crossbridges in smooth muscles allows it to contract how many percent of their length
80 percent
major factor that determines the force of contraction in smooth muscles
fraction of time
these organs maintain muscle contraction indefinitely
intestines, urinary bladder, gallbladder
a typical smooth muscle reach full contraction in
0.5 seconds later
reaches full contraction about 0.5 second later, and then declines in contractile force in another
1 to 2 seconds
contraction time of typical smooth muscle
1-3 seconds
True or False. Contraction of some types
can be as short as 0.2 second or as long as 30 seconds
TRUE
maximum force of contraction of smooth muscle
4-6 kg per cm squared cross-sectional area
maximum force of contraction of skeletal muscles
3-4 kg
great force of smooth muscle contraction results from
prolonged period of attachment of the myosin cross bridges to the actin filaments
maintain prolonged tonic contraction in smooth muscle for hours with little use of energy
latch mechanism
Another important characteristic of smooth muscle, especially the visceral unitary type of smooth muscle of many hollow organs
stress relaxation of smooth muscle
allow a hollow organ to maintain about the same amount of pressure inside its lumen despite long-term, large changes in volume
stress relaxation or reverse stress relaxation
Factors that influence the increase of calcium ions in intracellular fluid
nerve stimulation, hormonal stimulation, stretch of the fiber, change in chemical environment of the fiber
In place of troponin, smooth muscle cells contain a large amount of another regulatory protein
calmodulin