Skeletal Muscle Structure & Function Vs. Smooth Muscle Structure & Function

Front 1

which is both phasic and tonic types contraction, smooth muscle or skeletal muscle?

Back 1

Smooth muscle, skeletal muscle is only phasic

Front 2

Which of the three muscle types is multinucleate and has somatic innervation?

Back 2

skeletal muscle

Front 3

Which type of muscle uses T-tubules to distribute the action potential, while the other uses Ca++ and second messengers?

Back 3

skeletal muscle and smooth muscle respectively

Front 4

How can skeletal muscle increase contraction force?

Back 4

recruitment of motor neurons on the same fiber

Front 5

What is the relationship between force and velocity?

Back 5

Inversely proportionate: F=1/V

Front 6

When do you get maximum force?

Back 6

Isometric contraction

Front 7

When do you get maximum velocity?

Back 7

when there is zero load

Front 8

When do you get maximum work or power?

Back 8

at 1/3 maximum velocity of contraction

Front 9

As contraction occurs, which two regions of the sarcomere get shorter or longer?

Back 9

I-band gets shorter and the A-Band gets longer

Front 10

Which receive individual neuronal innervation, multi-unit or unitary smooth muscle?

Back 10

Multi-unit

Front 11

What type of innervation do arterioles have?

Back 11

unitary

Front 12

What type of smooth muscle is sphincter and blood vessel?

Back 12

tonic… thus they constantly maintain tone

Front 13

What type of smooth muscle is the small intestine?

Back 13

phasic

Front 14

what are the 3 phases of smooth muscle activation?

Back 14

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

Front 15

what is a common target for Ca++ blockers in smooth muscle?

Back 15

dihydropyridine Ca channel, which is a membrane channel

Front 16

What effect does IP3 (which is itself produced as a consequence of a neurohormone sensitive receptor) have on the SR?

Back 16

release of Ca

Front 17

What do smooth muscle have as light filaments in lieu of troponin?

Back 17

caldesmon and calponin

Front 18

In smooth muscle, where do thin filaments attach?

Back 18

sarcolemma

Front 19

Detail the steps of smooth muscle contaction.

Back 19

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).

Front 20

What can cause abnormal contractile regulation?

Back 20

1) faulty Ca leve control. 2) light chain phosphorylation. 3) Rho-A and Rho-Kinase. 4) changes in cAMP or cGMP

Front 21

Detail normal erectile function.

Back 21

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

Front 22

What happens during the erection process at the second messenger level?

Back 22

GTP is converted cGMP and activate PKG --> decrease in intracellular Ca --> reduced contraction.

Front 23

How does Viagra work?

Back 23

it inhibits phosphodiesterase-5 (PDE-5), which converts cGMP to GMP