91.____ not required for contraction of smooth muscle fibers.
92.Calcium tha : 1417089
91.____ is not required for contraction of smooth muscle fibers.
92.Calcium that enters the cell during smooth muscle excitation binds with
b.inactive myosin kinase
93.Which of the following muscle types are myogenic?
b.single-unit smooth muscle
c.multi-unit smooth muscle
d.Both a and b
e.Both b and c
94.Multi-unit smooth muscle is
b.under ANS control
c.found in the iris of the eye
d.all of the above
e.none of the above
95.Single-unit smooth muscle
a.contains an abundance of gap junctions
c.is found in the walls of the digestive, reproductive, and urinary tracts and small blood vessels
d.forms functional syncytia
e.has all of the above characteristics
96.A functional syncytium
a.is a pair of antagonistic muscles causing a joint to move in opposite directions
b.is able to contract as a unit because action potentials move between adjacent cells through gap junctions
c.is a functional junction between a smooth muscle fiber and an autonomic nerve ending
d.is all of the above
e.is none of the above
97.What is responsible for initiating contraction of smooth muscle?
a.Stimulation by motor neurons
b.Inhibition of acetylcholinesterase
c.Membrane potential drifting to threshold as a result of automatic changes in ion movement across the membrane
d.Excitation of the gap junctions by a transmitter substance
e.Stimulation by the autonomic nervous system
98.Repaying the oxygen deficit after strenuous exercise involves
a.formation of lactate in the muscle cells
b.replenishing stores of creatine phosphate and glycogen
c.unloading oxygen from myoglobin
d.all of the above
e.both b and c
99.Pacemaker activity refers to spontaneous depolarizations resulting from
a.shifts in passive ionic fluxes accompanying
b.cyclical changes in Na+-K+ pump activity
c.automatic changes in channel permeability
d.both a and b
e.both a and c
100.Which statement is incorrect about smooth muscle?
a.It develops less tension per unit cross-sectional area compared to skeletal muscle.
b.It can maintain tension with comparatively less ATP consumption than skeletal muscle.
c.It lacks troponin.
d.The range of lengths over which it can develop near maximal tension is greater than for skeletal muscle.
e.In the walls of a hollow organ it can accommodate variable volumes with little change in the pressure exerted on the organ’s contents.
101.A functional syncytium of cardiac muscles cells means that they
b.exhibit muscle tone
c.have a short refractory period
d.lack the stimulation of a pacemaker
e.work as a unit mechanically and electrically
102.Which one of the following statements about cardiac muscle is incorrect?
a.It contains gap junctions.
b.It is found only in the heart
c.It is self-excitable.
d.It is striated with intercalated disks.
e.It lacks tropomyosin.
103.Dihydropyridine receptors are most closely associated with
104.Which of the following is most closely associated with a skeletal muscle fiber’s latent period?
c.diffusion of calcium out of the SR’s lateral sacs
d.development of tension
e.shortening of the muscle fiber
105.Considering muscles, bones, and joints as lever systems, a calculated “moment” for the load would be
a.force times load arm
b.force times power arm
c.load arm divided by force
d.either a and b
e.either b and c