Cardiac & Smooth Muscle Flashcards
cardiac muscle cell differences from skeletal muscle
shorter, branched, interconnected at intercalated disks, desmosomes (mechanical), and gap junctions (chemical)
both cardiac and skeletal muscle have _
actin/myosin striations
cardiac muscle innervation
not initiated by neurons but from electrical excitation from the SA node within the heart
the SA node generates _
spontaneous action potentials
neurons in cardiac myocytes
modulate cardiac muscle contraction (do not initiate)
Ringer’s contains _
calcium
cardiac contraction requires _
Ca++ release from T tubules (skeletal does not, just needs SR)
phospholamban
inhibits the SR Ca++ pump in cardiac muscle
calreticulun
binds Ca++ in smooth muscle for storage
calsequestrin
binds Ca++ in skeletal muscle for storage
skeletal muscle force depends on _
frequency summation and multiple fiber summation
cardiac muscle force depends on _
increased entry of Ca++
smooth muscle can be _
multiunit or unitary (or both)
unitary smooth muscle
extensive intercellular communication via gap junctions; coordinated contraction
unitary smooth muscle is found in _
GI tract, uterus, bladder, most blood vessels
multiunit smooth muscle
no electrical coupling, each cell can contract independently (allows finer motor control)
multiunit smooth muscle is found in _
iris and ciliary body of eye, piloerector muscles of skin, some blood vessels
neurons in smooth muscle
can make multiple contacts with smooth muscle (only one contact in skeletal muscle) and more than one neuron can stimulate that same smooth muscle
smooth muscle does not have to be initiated by _
action potentials (mostly multiunit SM)
How can multiunit SM be stimulated without an action potential?
change in membrane potential allows Ca++ entry or generation of IP3 can open intracellular Ca++ stores
dense bodies
the Z disks of smooth muscle
cross bridge cycle in smooth muscle is controlled by _
myosin light chain phosphorylation
calmodulin
what smooth muscle binds to instead of troponin
smooth muscle contraction can occur independently of Ca++ if _
there is an increase in MLC phosphorylation or a decrease in MLC de-phosphorylation (PKC)
