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)
MLC phosphatase
de-phosphorylates myosin light chains for termination of smooth muscle contraction
caldesmon and calponin
inhibit interaction between actin and myosin (inhibit ATPase activity of myosin)
latch state
low rate of ATP hydrolysis in smooth muscle
skeletal mechanism of excitation
neuromuscular transmission
cardiac mechanism of excitation
pacemaker potentials
smooth muscle mechanism of excitation
synaptic transmission, hormone-activated receptors, electrical coupling, pacemaker potentials
skeletal muscle electrical activity of muscle cell
action potential spikes
cardiac muscle electrical activity of muscle cell
action potential plateaus
smooth muscle electrical activity of cell
action potential spikes and plateaus
skeletal muscle Ca++ sensor
troponin
cardiac muscle Ca++ sensor
troponin
skeletal muscle Ca++ sensor
calmodulin
skeletal excitation-contraction coupling
Ca++ channels in T-tubules coupling to Ca++ channels in SR
cardiac muscle excitation-contraction coupling
Ca++ entry through cell membrane triggers Ca++ channels in SR
smooth muscle excitation-contraction coupling
Ca++ through cell membrane
skeletal termination of contraction
breakdown of Ach by achetylcholinesterase
cardiac termination of contraction
action potential repolarization
smooth muscle termination of contraction
myosin light chain phosphatase
skeletal muscle regulation of force
frequency and multifiber stimulation
cardiac regulation of force
regulation of Ca++ chain
smooth muscle regulation of force
balance between MLC phosphorylation and dephosphorylation
