Deck 24: Smooth Muscle

Question 1

Sm oo th m us cle ce lls

A) Lack striations
B) Are sm aller than sk eletal musc le fibers
C) Have o ne nucleus instead of m any as in skeletal mu scle fibers
D) R es po nd to a va rie ty of sig na ls
E) All of the above

Answer 1

E

Question 2

The proteins that release Ca₂+ from the SR into the cytosol of sm ooth m uscle are

A) RyR
B) SERCa₂a
C) IP3R
D) NCX
E) Both A and C are correct

Answer 2

A

Question 3

The fun ction o f M LC K in s m ooth m usc le cells is to

A) Ph os ph or ylate ac tin
B) Ph os ph oryla te th e reg ulat ory lig ht c ha in o f m yos in
C) D ep ho sp ho ryla te tr op om yos in
D) Ph os ph or ylate tro po m yos in
E) Regulate the Ca₂+ sensitivity of TnC

Answer 3

B

Question 4

An example of electromechanical coupling in smooth m uscle is activation of contraction by

A) Release of Ca₂+ via G
B) Increased cytosolic [Ca₂+] through voltage-gated Ca₂+ cha nn els
C) Activation of protein phosphatase via G -protein coupled receptors
D) Ca₂+ release through RyR
E) Ca₂+ uptake into the SR m ediated by phospholamban phosphorylation

Question 5

Increased cytosolic [Ca₂+] in smooth muscle cells can be accomplished by release of Ca₂+ from internal stores. These internal stores are in the

A) Caveolae
B) M itoc ho nd ria
C) Golgi apparatus
D) Nucleus
E) SR, sarcoplasmic reticulum

Question 6

Addition of some chemicals can cause contraction of smooth muscle without changing the mem brane potential. The mechanism by which this happens is called

A) Electromechanical coupling
B) Excitation-contraction coupling
C) Pharamcomechanical coupling
D) Unitary smooth m uscle contraction
E) Multi unit smooth m uscle contraction

Question 7

Ac tiva tion of m yos in lig ht c ha in p ho sp ha tas e (M LC P) in s m oo th m us cle sh ou ld

A) Increase smooth muscle force
B) Re lax s m oo th m us cle
C) Increase the [Ca₂+] in smooth m uscle cells
D) D ep ola rize the sm oo th m us cle ce lls
E) Increase Ca₂+ release from the SR

Question 8

Ca₂+ exit from sm ooth muscle cells is accomplished through

A) SERCa₂a
B) R yR
C) NCX, sodium-calcium exchange
D) IP3R
E) Voltage-gated Ca₂+ ch an ne ls

Question 9

Ac tiva tion of m yos in lig ht c ha in k ina se (M LC K) in s m oo th m us cle sh ou ld

A) Increase smooth m uscle force
B) R ela x s m oo th m us cle
C) Increase the [Ca₂+] in smooth m uscle cells
D) D ep ola rize the sm oo th m us cle ce lls
E) Increase Ca₂+ release from the SR

Question 10

"Ca₂+ sen sitization" in s m ooth m usc le refe rs to

A) The ability of Ca₂+ to act ivate MLCK
B) Production of force at lower than normal levels of cytoplasmic [Ca₂+]
C) Ca₂+ activat ion of MLCP
D) Reduction in cytoplasmic [Ca₂+] by phosphorylation of phospholamban
E) None of the above

Question 11

Which of the following relaxes smooth muscle?

A) Stimulat ion of MLCK
B) Opening of voltage-gated Ca₂+ ch an ne ls
C) Inhibit ion of MLCP
D) NO (nitric oxide)
E) Release of Ca₂+ from the SR

Question 12

Pharmacom echanical coupling develops smooth muscle force by

A) Release of Ca₂+ via G
B) Voltage-gated Ca₂+ ch an ne ls a ctiv ate d b y ac tion po ten tials
C) Voltage-gated Ca₂+ channels activated by mem brane potential change without action po ten tials
D) Ca₂+ release through RyR
E) Ca₂+ uptake into the SR m ediated by phospholamban phosphorylation

Question 13

The sarcolemma of smooth muscles cells can let in Ca₂+ through

A) Voltage-gated Ca₂+ cha nn els
B) PMCA
C) SERCa₂a
D) R yR
E) IP3R

Question 14

Bulges in axons from which neurotransmitter can be diffusely secreted are called

A) N er ve ter m ina ls
B) Varicosities
C) Nuclei
D) G an glia
E) Plexus

Question 15

Be ta 2 receptors on smooth muscle cells work through a G s m ec ha nis m tha t ac tiva tes ad en ylyl cyclas e. T his pr odu ces 3',5'cyc lic AM P. T he c AM P ac tivates PK A tha t

A) Releases Ca₂+ from the S R th roug h IP
B) Releases Ca₂+ from the SR through RyR receptors and Increases force by activat ing MLCK
C) Depolarizes the membrane, leading to Ca₂+ entry by the voltage-gated Ca chan ne l, and Increases force by activat ing MLCK
D) Phosphorylates protein phosphatase and relaxes the smooth muscle by dephosphorylating the m yos in lig ht c ha in
E) Phosphorylates phospholamban, reducing [Ca₂+] and relaxing the smooth muscle by reduc ing M LCK activity

Question 16

Myosin light chain kinase is activated by

A) Ca₂+ bo un d to calm od ulin
B) PKA
C) cAMP
D) IP3
E) Diacylglycerol