L12 Smooth Muscle

Question 1

The walls of hollow organs have what kind of muscle/.

Answer 1

Smooth muscle

Question 2

How many nuclei does a smooth muscle cell have

Answer 2

ONE

Question 3

Does smooth muscle have t-tubules?

Answer 3

No

Question 4

What kind of muscle does these:

Produces motility

Maintains pressure

Regulates internal flow

Answer 4

Smooth msycle

Question 5

Does smooth muscle have sarcomeres?

Answer 5

No, it is NOT striated

Question 6

Where is the sarcoplasmic reticulum in smooth muscle?

Answer 6

In contact with the plasma membrane

Question 7

How does calcium flow from one cell to the next in smooth muscle units?

Answer 7

Through connexons

Question 8

Does smooth muscle have neuromuscular junctions?

Answer 8

NO!!!!!!!!!!

Smooth muscles are innervated by the autonomic nervous system

Question 9

If smooth muscles don’t have neuromuscular junctions, what do we call the part where neurotransmitters are released onto the muscle?

Answer 9

Varicosities

Question 10

Does smooth muscle have motor end plates?

Answer 10

NO!!

Question 11

Do you need a lot of neurons innervating single-unit (myogenic) smooth muscle?

Answer 11

NO, because they have gap junctions, so the signal will flow through all the cells from a few small spots

Question 12

What is another word for single-unit smooth muscle

Answer 12

Myogenic (because they have pacemakers and can originate their own signals sort of)

Question 13

What is another name for multi unit smooth muscle?

Answer 13

Neurogenic

because the signal is originating in the nervous system

Question 14

Why are multiunit muscles innervated so densely and so isolated

Answer 14

It allows for finer motor control

Question 15

What kind of smooth muscle (myogenic or neurogenic) is in the eye, skin hair follicles, large blood vessels, small airways and vas deferen?

Answer 15

Neurogenic (multiunit)

Question 16

What kind of smooth muscle (neurogenic or myogenic) is in thre GI tract, bladder, small blood vessels, uterus and ureter?

Answer 16

Myogenic (single unit)

Question 17

Which has longer myosin filaments: smooth or skeletal muscle

Answer 17

Smooth muscle

Question 18

Does smooth muscle contain troponin?

Answer 18

NO

Question 19

What do actin filaments attach to in smooth muscle (it’s not Z disks because there are no sarcomeres)

Answer 19

Dense bodies

Question 20

Instead of bands that contract, what is the arrangement of the dense bodies and filaments in smooth muslce?

Answer 20

Diamond shaped lattice

Question 21

Where is contraction of smooth muslce regulated?

Answer 21

At the thick (myosin) filament

Question 22

What increases the affinity of the myosin head for actin in smooth muscled?

Answer 22

A PHOSPHATE binding to the myosin

Question 23

What happens to the calcium in smooth muscle when it is released from the SR?

Answer 23

It binds to calmodulin

Question 24

What does calmodulin do?

Answer 24

Once calmodulin binds 4 calciums, it goes and turns on myosin light chain kinase (MLCK) and MLCK can then phosphorylate the myosins and promote muscle contraction

Question 25

What allows myosin to bind actin in smooth muscled?

Answer 25

A PHOSPHATE ON THE MYOSIN LIGHT CHAIN | It’s not the same phosphate that came out of ATP either

Question 26

If there is no calcium to allow MLCK to be active, which enzyme is active instead/

Answer 26

MLCP (myosin light chain phosphatase)

Question 27

What prevents the filaments from interacting in smooth muscle? Remember, there is no “chaperone”

Answer 27

DEPHOSPHORYLATION

Question 28

What are the two ways that smooth muscle can be stimulated via pharmaco-mechanical coupling?

Answer 28

Hormones/neurotransmitters can either: Open ligand gated Ca+ channels that bring in calcium from outside and then acts as a second messenger to induce calcium release from the SR Activate IP3 which causes calcium release from the SR (no outside calcium)

Question 29

What does electromechanical coupling do to stimulate smooth muscle?

Answer 29

DEPOLARIZATION opens VOLTAGE-gated Calcium channels and outside calcium comes in and acts as a second messenger to induce calcium release from the SR

Question 30

What is the only type of smooth muscle that does electromechanical coupling to elicit calcium release from SR?

Answer 30

Single-unit smooth muscle | It’s unique to the muscles that do their own pacemaker

Question 31

True or false: Both types of pharmacomechanical coupling can be used to elicit Ca release from SR in both single-unit and multiunit smooth muscle?

Answer 31

True

Question 32

A decrease in contractile force occurs when the concentration of intracellular calcium _______

Answer 32

Decreases

Question 33

What are the three mechanisms for decreasing intracellular Calcium in smooth muscle?

Answer 33

1. SERCA pumping it back into the SR 2. Sarcolemmal Na+/Ca+ exchanger (secondary active transport) 3. Sarcolemmal Ca+ ATPase (Primary active transport)

Question 34

How does the sarcolemmal Na+/Ca+ pump calcium out of the smooth muscle cell?

Answer 34

It uses secondary active transport using the energy from the sodium gradient that was established by the Na+/K+ ATPase pump. Exchanges calcium for Na

Question 35

What is the primary active transporter that provides the energy for the sarcolemmal Na+/Ca+ exchanger?

Answer 35

Na+/K+ ATPase

Question 36

What are the two primary active transporters that directly reduce intracellular calcium in the smooth muscle?

Answer 36

1. SERCA (sarcoplasmic reticulum Ca+ ATPase) | 2. Sarcolemmal Ca+ ATPase

Question 37

How is smooth muscle tone regulated by drugs?

Answer 37

1. Amount of intracellular Ca+ | 2. MLCK to MLCP ratio

Question 38

When calcium increases, what is the ratio of MLCK to MLCP?

Answer 38

MLCK will be more active than MLCP= more muscle contraction

Question 39

How do calcium antagonists lead to vasodilation?

Answer 39

They block the voltage gated calcium channels, so no calcium can get in and bind with calmodulin, so the whole muscle stays relaxed

Question 40

How do Potassium channel openers lead to vasodilation?

Answer 40

If you allow K+ to flow out, you will hyperpolarize the cell membrane, (bringing closer to -90mV) so it will be harder for the voltage gated Ca+ channels to open and let calcium in. Muscle stays relaxed

Question 41

How do B2 adrenergic receptor agonists work to make smooth muscle cells in the alveoli relax?

Answer 41

They stimulate adrenergic receptors that results in cAMP getting made. cAMP is a second messenger that blocks MLCK. No MLCK= no phosphates on myosin=no contraction

Question 42

How do nitrates (like nitroglycerin) promote smooth muscle relaxation?

Answer 42

They promote the formation of cGMP cGMP stimulates MLCP More MLCP=less phosphate on myosin=no contraction

Question 43

How do phoshopdiesterase inhibitors (like viagra) promote smooth muslce relaxation?

Answer 43

They inhibit the enzyme that degrades cGMP. cGMP stimulates MLCP. More MLCP=no phosphates on myosin=no muscle contraction