smooth muscle physiology

Question 1

a smooth muscle that alternates between relaxation and contraction; the contraction force is at zero before being stimulated

Answer 1

phasic smooth muscle

Question 2

a smooth muscle that is always contracted, level of contraction can be lowered or raised

Answer 2

tonic smooth muscle

Question 3

which of this not true of a single unit (visceral) smooth muscle
a. outer layer of varicosities and once AP reaches threshold it can stimulate whole muscle to contract
b. have electrical synapses in the form of gap junctions
c. can have NT released for each cell
d. whole muscle contracts

Answer 3

c

Question 4

multi unit smooth muscles have what three things

Answer 4

1. individual chem. synapses with varicosities
2. no gap junctions
3. entire muscle can be stimulated by varicosities

Question 5

smooth muscle has what characteristics except
a. wider range for optimal length and force generation
b. bidirectional contractions (starts in middle of muscle)
c. fast myosin ATPase
d. less energy required for maintenance of tension and slower fatigue

Answer 5

c

Question 6

contractions of smooth muscle can have multiple stimuli but skeletal muscle can only be stimulated by

Answer 6

AP down alpha motor neuron

Question 7

smooth muscle have actin and myosin but not

Answer 7

troponin and tropomyosin

Question 8

what is true of the structure of smooth muscle
a. actin is anchored by dense bodies which are anchored to cell membrane
b. they contain no sarcomeres (have less developed sarcoplasmic reticulum)
c. have caveolae which are similar to t-tubules
d. all of the above

Answer 8

d

Question 9

depolarization in smooth muscle cell opens voltage gated Ca channels and extracellular Ca binds to _____ not troponin

Answer 9

calmodulin

Question 10

what is true of the activation pathway of smooth muscle
a. calmodulin activates myosin light chain kinase
b. myosin ATPase activity is inhibited
c. myosin light chains are dephosphorylated
d. all of the above

Answer 10

a

Question 11

myosin light chain phosphatase (MLCP) takes a phosphate off of myosin in _____

Answer 11

relaxation

Question 12

smooth muscle has a latch state, what is true of this process
a. dephosphorylated myosin heads don’t release from actin
b. maintains level of tension without crossbridge cycling
c. doesn’t require additional ATP
d. all of the above

Answer 12

d

Question 13

if there is more MLCK (adding phosphate) than MLCP (removing phosphate) the muscle

Answer 13

contracts

Question 14

what are the two sources for calcium for contraction

Answer 14

ECF and sarcoplasmic reticulum

Question 15

which of these is not true of extracellular Ca in smooth muscle?
a. mechanically gated Ca are stretch and pressure activated
b. ligand gated Ca receptors can be hormone and NT activated
c. ligand gated channels = electromechanical coupling
d. voltage gated Ca channels have graded potentials

Answer 15

c

Question 16

the sarcoplasmic reticulum has ____ gated Ca channels which results in G protein signaling and production of

Answer 16

IP3

Question 17

which of these are ways to modify/ inhibit smooth muscle contractions?
a. hyperpolarized membrane potential
b. slow wave potentials
c. chemical influences
d. pacemaker potentials
e. all of the above

Answer 17

e

Question 18

phospholipase C is a modifiable signal transduction pathway which elevates ____

Answer 18

IP3

Question 19

which of these are consequences of phospholipase C elevating IP3
a. low Ca release
b. relax
c. high MLCP activity
d. all of the above

Answer 19

c

Question 20

adenylyl cyclase ______ IP3

Answer 20

inhibits

Question 21

which of these are not consequences of adenylyl cyclase inhibiting IP3
a. low Ca release
b. Na channels open to hyperpolarize the cell
c. high MLCP activity
d. muscles relax

Answer 21

b (K+ channels open)

Question 22

cardiac muscle has what characteristics

Answer 22

single cells, branches, intercalated disks, gap junctions