Smooth Muscle

Question 1

Location of multiunit smooth muscle

Answer 1

ciliary muscle of eye, iris muscle of eye, piloerector muscles

Question 2

What is the primary stimulus of multiunit smooth muscle

Answer 2

neuronal innervation of each fiber, ANS

Question 3

Multiunit smooth muscle

Answer 3

discrete smooth muscle fibers that contract independently

Question 4

Is there gap junction connectivity in multiunit smooth muscle?

Answer 4

no

Question 5

Unitary smooth muscle

Answer 5

large number of fibers contract together as a single unit arranged in sheets or bundles

Question 6

Innervation of unitary smooth muscle

Answer 6

ANS innervates sheets of muscle

Question 7

What non-neuronal factors regulate contraction of unitary smooth muscle

Answer 7

oxygen concentration, histamine, endothelin, and distension

Question 8

Are there gap junctions in unitary smooth muscle

Answer 8

yes

Question 9

Where is unitary smooth muscle located

Answer 9

GI tract, bile ducts, ureters, uterus, blood vessels

Question 10

What are the contractile elements in skeletal muscle

Answer 10

actin
myosin
tropomyosin
troponin

Question 11

What are teh contractile elements in smooth muscle

Answer 11

actin
myosin
tropomyosin

Question 12

What is different about the myosin heads in smooth muscle

Answer 12

they are not all arranged in teh same direction, which allows for pulling of actin filament in multiple directions

Question 13

Smooth muscle structure

Answer 13

• diffuse branches of nerve fibers lie over sheets of smooth muscle
• nerve fiber has multiple varicosities along axis of a nerve fiber
• has diffuse and contact junctions

Question 14

Skeletal muscle structure

Answer 14

• structured neuromuscular junction

- end feet

Question 15

Where is the primary source of Ca++ in smooth muscle

Answer 15

extracellular fluid

Question 16

What are the 2 main roles of Ca++ in smooth muscle

Answer 16

Membrane depolarization

contraction

Question 17

Spike potential resting membrane potential

Answer 17

-50 to -60 mv

Question 18

Spike potential depolarization results from what

Answer 18

movement of Ca++ and Na+ into cell

Question 19

Spike potential repolarization results from what

Answer 19

movement of K+ out of cell

Question 20

What is the plateau due to

Answer 20

prolonged and slow opening of Ca++ channels

Question 21

how is multiunit smooth muscle regulated

Answer 21

ANS

Question 22

how is unitary smooth muscle regulated

Answer 22

ANS and non-neuronal factors

Question 23

what does smooth muscle have instead of a Z disc

Answer 23

dense bodies

Question 24

dense bodies function

Answer 24

allow for force of contraction to be transmitted from one cell to the next

Question 25

how is actin arranged in smooth muscle

Answer 25

attached to dense bodies

Question 26

how is myosin arranged in smooth muscle

Answer 26

interspersed between the actin filaments

Question 27

how are actin and mysoin arranged together in smooth muscle

Answer 27

in every plane, allowing for “shrink and bulge”