Muscle 7 Flashcards
Long action potential duration prevents….
summation of contraction
How is e-c coupling achieved in cardiac muscles?
ca2+ induced ca2+ release
An increase in calcium conc. triggers contraction by..
removing the inhibition of cross bridge cycling
In cardiac muscle the SERCA pump is regulated by
phospholamban
phosphorylated phospholamban
Ca2+-pump inhibition is removed, enhancing relaxation rates and contractility
dephosphorylated phospholamban
inhibits SERCA
how to enhance contractile force in cardiac muscle
- an increase in intracellular Ca2+
- length tension relationship (greater force when stretched)
The heart is innervated by..
the autonomic nervous system
sympathetic and the heart
increases heart rate/conduction and contractility (autorythmic and contractile)
parasympathetic and the heart
decreases heart rate/conduction (autorythmic)
phosphorylation of Ca2+ channels
causes calcium channels to remain open longer during APs
phosphorylation of ryanodine receptors
increases release of Ca2+ from the sarcoplasmic reticulum
phosphorylation of SERCA
increase the speed of Ca2+ re-uptake which increases Ca2+ storage
a stretched sarcomere
- decreased diameter reduces distance that Ca2+ needs to diffuse, increasing probability of cross-bridge cycling
- increases Ca2+ induced Ca2+ release
heart rate is under…
tonic control
stimulation by parasympathetic nerves….
decreases heart rate (below 90 bpm)
stimulation by sympathetic nerves…
increases heart rate (above 90 bpm)
resting heart rate
70-72 bpm
Without autonomic stimulation, autorythmic cells have a firing rate of…
90 APs per minute
parasympathetic neurons containing ACh mainly innervates…
the SA and AV node
ACh acts on…
muscarinic cholinergic receptors, opening K+ channels and closing T-type Ca2+ and HCN channels
sympathetic neurons releases NE, which activates
Beta1 adrenergic receptors
Beta1 adrenergic receptors increase Na+ conductance through HCN channels and T-type Ca2+ causing….
cells to reach threshold more rapidly and a decreased level of repolarization
Smooth muscle is __________ than skeletal
more variable
smooth muscle is ……. in length
50 to 400 um
smooth muscle is …… shaped and __nucleated
spindle, uni
smooth muscle does not have…
troponin and t-tubules
thin filaments in smooth muscles are anchored to..
cell membrane or to cytoplasmic structures known as dense bodies (similar to z-lines)
in smooth muscle, what forms the cytoskeleton?
intermediate filaments
