that is greater than skeletal muscleCan develop considerable tension even when stretched up to 2.5 times its resting length (urinary bladder, small intestine); connective tissue within restricts how much stress can occur
oResting length is less than that for skeletal muscleoThin filaments in smooth muscle overlap the thick filaments even when stretched out Stress relaxation response: smooth muscle is stretched and increases in tension, but quickly adjusts to this new length and relaxes to the initial tension level – thus enabling smooth muscle to exist at a variety of lengths with little change in tensionSR is poorly developed on smooth muscle- contract the Ca2+by pumping it out of the cellnot sequestering itLength that gives you the most tension- Ioresting length is ready to exert the most power it can Stretched and maintain then revert back as if they weren’t stretched°°Comparisons of Muscle Types: Memorize the table and predict it Hormones don’t effect alpha motor neurons Autonomic is modified by hormones
°°°Figure 8.30:Comparison of the role of calcium in bringing about contraction insmooth muscle and skeletal muscle.°Smooth is biochemical event
Skeletal is physical event °Figure 8.6:Role of calcium in turning on cross bridges.°°Calcium activation of myosin cross-bridge in smooth muscleDepolarization of smooth muscle cells activates membrane Ca2+channels and releases Ca2+from underdeveloped sarcoplasmic reticulumMyosin light chains require phosphorylation to allow for actin-myosin interaction àBIG difference between skeletal and smooth muscleRise in Ca2+induces chemical change in myosin whereas in skeletal muscle Ca2+causes a physical change (movement of tropomyosin away from the actin bindingsite on the myosin head)
°°Figure 8.29:Calcium activation of myosin cross bridge in smooth muscle.Light chain- gets phosphorylated °°°
Cardiac PhysiologyChapter 9°Cardiac MuscleOnly found in the heartStriatedUnder involuntary controlActed on by the ANS°°Cardiac Muscle StriatedoThin filaments contain troponin and tropomyosinoClear length-tension relationship oT-tubules and moderately well-developed sarcoplasmic reticulum.Like oxidative skeletal muscle: possess lots of mitochondria and myoglobin As in smooth muscle, Ca2+enters extracellular and through voltage-gated DHP receptors(in T-tubule membrane).As in single-unit smooth muscle, cardiac muscle displays pacemaker (but not slow-wave) activity interconnected by gap junctions.Cardiac fibers exist in a branching network and action potentials last a relatively long time.99% contractile cells; 1% pacemaker (autorhythmic) cells that do not contractoSee Fig. 9-7 Pacemaker activity of cardiac autorhythmic cells.oSingle Unit: Both will contract when heart beatsright atrial activate those atrial fibers that are interconnected through gap junctions with the fibers on the left side
°°Blood flow through the heart:1.Superior and Inferior Vena Cava 2.Right Atrium 3.