Smooth muscle Flashcards
what part of the nervous system is smooth muscle inverted by
automatic nervous system
features of smooth muscle
single, identifiable cells, myosin and actin filaments, filaments are arranged diagonally across cells and are anchored to membranes and cell structures by dense bodies, filaments slide together to contract but in different way to skeletal
X bridge activation
calcium binds to calmodulin, calcium calmodulin binds to myosin light chain kinase which phosphorylates myosin X bridges with ATP. these phosphorylated x bridges bind to actin filaments which causes contraction
how are the smooth muscles relaxed
myosin light chain phosphatase dephosphorylates X bridges
some smooth muscles that have to be slightly contracted at all times what happens there
phosphorylated X bridges may be dephospyrlated at the same time as it being bound to actin. decreases rate of ATP splitting which slows X bridge cycle which means you can maintain tension for long time with low ATP consumption. useful in blood vessel walls
sources of cytosolic calcium
sarcoplasmic reticulum, extracellular calcium
which type of muscle produces more ATP
skeletal
how does smooth muscle have tone
basal level of calcium in cells that causes constant level of tension
factors affecting contractile activity
autonomic neurotransmitters from varicosities(bulges), hormones eg oxytocin, local factors, stretch, spontaneous electrical activity in muscle membranes
types of smooth muscle
single or multiunit. usually a mix of both
single unit
many cells linked by gap junctions, signals travel between cells, contract synchronously, may contain pacemaker cells, stretch evokes contraction, GIT uterus small blood vessels
pacemaker cells
cells that create rhythmic impulses, setting the pace of blood pumping
multiunit
few or no gap junctions, richly innervated by ANS, don’t respond to stretch, airways large arteries hairs
