EX1; Smooth Muscle

Question 1

True or False

Smooth muscles are very large

Answer 1

False; they are very small (2-10µm in diameter)

Question 2

Why are smooth muscle cells considered smooth

Answer 2

the striations are not present; have relatively little SR

Question 3

True or False

The thick and thin filaments are similar, but not identical to those in skeletal and cardiac muscle

Answer 3

True

Question 4

Smooth muscle cells have these; homologous to Z lines of started muscle

Answer 4

dense bodies

Question 5

What is attached to the dense bodies

Answer 5

thin filaments

Question 6

This is NOT expressed in smooth muscle

Answer 6

troponin

Question 7

All the neural innervation of the smooth muscle is from what

Answer 7

the autonomic nervous system; therefore control is involuntary

Question 8

Compared to cardiac and skeletal, there is a greater range of cell lengths over which what can occur

Answer 8

over which force can be generated; accommodates large changes in volume of organs that are designed to move fluids such as the bladder

Question 9

The rate of ATP splitting by myosin in activated smooth muscle fibers is how many times lower than in skeletal muscle

Answer 9

10-100 times

Question 10

Due to the extremely low rate of splitting of ATP, what is the virtually no of regarding smooth muscle

Answer 10

there is virtually no fatigue; the economy is much higher

Question 11

The economy of muscle contraction equals what

Answer 11

force/ATP consumed
in smooth muscle, the force/cross sectional area is about the same as in skeletal muscle, but the ATP splitting is so much lower

Question 12

In smooth muscle, a stimulus leads to what

Answer 12

increase in intracellular Ca concentration

Question 13

The Ca is coupled with what in smooth muscle

Answer 13

Ca + calmodulin ⃗ Ca-calmodulin

Question 14

The Ca-calmodulin is bound with what

Answer 14

myosin light chain kinase (MLCK) (inactive)

Question 15

When the Ca calmoduin is bound with MLCK, what occurs

Answer 15

it becomes an active form

Question 16

The Ca-calmodulin-MLCKacive then does what

Answer 16

it interacts with phosphatase and then either relaxes (Pi + myosin) or contracts (myosin + P)

Question 17

This is continuously active, of which activation results when the MLCK activity is greater than its activity

Answer 17

phosphatase

Question 18

This prevents the reattachment of myosin to actin

Answer 18

dephosphorylation

Question 19

ATP causes this of myosin from actin, as with striated muscle

Answer 19

dissociation

Question 20

Dephosphorylated myosin cannot bind actin, however, myosin bound to actin in smooth muscle can be dephosphorylated and what

Answer 20

remains attached in a rigor state with no movement of the cross bridges

Question 21

This course of Ca is relatively sparse; there are no T tubules in smooth muscle

Answer 21

sarcoplasmic reticulum

Question 22

There is some SR that is associated with what in the membrane can cause release of Ca from this DR

Answer 22

plasma membrane and SP

Question 23

Ca ions enter from this through channels in the plasma membrane

Answer 23

extracellular fluid/extracellular space

Question 24

APs in smooth muscle; the inward flow of positive charge is carried by what

Answer 24

Ca ions during the rising phase of AP

Question 25

True or False

Some cells in the smooth muscle spontaneously generate APs; the resting potential is never steady

Answer 25

True

Question 26

These cells cause membrane potential to reach threshold

Answer 26

pacemaker potential

Question 27

Endings of motor neurons of autonomic nervous system release what in the vicinity of smooth muscle cells

Answer 27

neurotransmitters; may be excitatory or inhibitory

Question 28

True or False

There are neuromuscular junctions in smooth muscle

Answer 28

False; there are not

Question 29

These act similarly to neurotransmitters in control smooth muscle activation

Answer 29

hormones

Question 30

What are three mechanisms that remove Ca from the smooth muscle

Answer 30

Ca pump in sarcolemma
Na/Ca exchanger
Sarcoplasmic reticulum

Question 31

What are the two type smooth muscle

Answer 31

single unit

multi unit

Question 32

Which one, single unit or multi unit contains gap junctions for electrical synapses

Answer 32

single unit

Question 33

Which one, single unit or multi unit is spontaneously activated

Answer 33

single unit

Question 34

Which one, single unit or multi unit is stretch activated

Answer 34

single unit

Question 35

Which one, single unit or multi unit has each cell activated independently

Answer 35

multi unit

Question 36

Which one, single unit or multi unit innervation is primarily restricted to pacemaker cells

Answer 36

single unit

Question 37

Which one, single unit or multi unit smooth muscle is found in large arteries and large airways

Answer 37

multi unit

Question 38

Which one, single unit or multi unit smooth muscle is found in the intestinal tract, uterus, and small diameter blood vessels

Answer 38

single unit