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23 Cards in this Set

  • Front
  • Back
which is both phasic and tonic types contraction, smooth muscle or skeletal muscle?
Smooth muscle, skeletal muscle is only phasic
Which of the three muscle types is multinucleate and has somatic innervation?
skeletal muscle
Which type of muscle uses T-tubules to distribute the action potential, while the other uses Ca++ and second messengers?
skeletal muscle and smooth muscle respectively
How can skeletal muscle increase contraction force?
recruitment of motor neurons on the same fiber
What is the relationship between force and velocity?
Inversely proportionate: F=1/V
When do you get maximum force?
Isometric contraction
When do you get maximum velocity?
when there is zero load
When do you get maximum work or power?
at 1/3 maximum velocity of contraction
As contraction occurs, which two regions of the sarcomere get shorter or longer?
I-band gets shorter and the A-Band gets longer
Which receive individual neuronal innervation, multi-unit or unitary smooth muscle?
What type of innervation do arterioles have?
What type of smooth muscle is sphincter and blood vessel?
tonic… thus they constantly maintain tone
What type of smooth muscle is the small intestine?
what are the 3 phases of smooth muscle activation?
Phase I: CNS (ANS) to cellular actvation --> Phase II: cAMP or Ca/IP3 or cGMP to changes in activity of Ca and K channels --> Phase III: integration of cellular effects via Gap Junctions
what is a common target for Ca++ blockers in smooth muscle?
dihydropyridine Ca channel, which is a membrane channel
What effect does IP3 (which is itself produced as a consequence of a neurohormone sensitive receptor) have on the SR?
release of Ca
What do smooth muscle have as light filaments in lieu of troponin?
caldesmon and calponin
In smooth muscle, where do thin filaments attach?
Detail the steps of smooth muscle contaction.
1) Ca influx via voltage-operated Ca channels. 2) Release of Ca from SR stores. 3) Through G-protein coupled receptors, activation of phospholipase C stimulated by IP3. 4) Increased Ca activates calmodulin. 5) Calmodulin activates myosin light chain kinase and promotes phosphorylation of myosin light chain kinase and contraction. 6) Important regulation: RhoA and Rho kinase – regulate myosin phosphatase that can promote relaxation. Rho guanine nucleotide exchange factors – promote exchange of RhoA GTP to RhoA GDP in turn has effect on myosin phosphatase and promotes relaxation. Area of interest for pharmaceutical companies to promote relaxation. Therapy for hypertension and vagospasms related to angina have focused on this side of the equation (left), perhaps future will be more on this side (right).
What can cause abnormal contractile regulation?
1) faulty Ca leve control. 2) light chain phosphorylation. 3) Rho-A and Rho-Kinase. 4) changes in cAMP or cGMP
Detail normal erectile function.
1. Sexual arousal --> hypothalamus and parasympathetic nevers in sacrum --> inhibition of ß-adrenergic tone --> release of NO from non-adrenergic and non-cholinergic cells -> NO stimulate guanylate cyclase in erectile smooth muscle --> increase in cGMP --> increased arterial flow --> venous occlusion --> engorgement
What happens during the erection process at the second messenger level?
GTP is converted cGMP and activate PKG --> decrease in intracellular Ca --> reduced contraction.
How does Viagra work?
it inhibits phosphodiesterase-5 (PDE-5), which converts cGMP to GMP