(8) Smooth Muscle Physiology (Rogers)

Question 1

What is a major problem with skeletal muscle?

Answer 1

Once tension exceeds a certein length (stretch), the muscle looses tension (force)

Question 2

What are the two types of smooth muscle?

Answer 2

Multiunit Smooth Muscle

Unitary Smooth Muscle

Question 3

Describe multi unit smooth muscle

Answer 3

• Fibers operate individually
• Innervated by single nerve

Example: ciliary muscles of eye, iris, piloerector muscles

Question 4

Describe unitary smooth muscle

Answer 4

• Syncytial or visceral
• Works together as a unit
• Cell membranes adere and contain gap junctions

Example: GI tract, Bile ducts, uterus

Question 5

Skeletal vs. Smooth Muscle

Innervation?

Answer 5

Skeletal = alpha motor neurons

Smooth Muscle = Intrinsic (no direct innervation from CNS or PNS) , Extrinsic (ANS)

Question 6

Skeletal vs. Smooth Muscle

Neurotransmitters?

Answer 6

Skeletal = Acetylcholine

Smooth Muscle = ACh, NE, E, (NO-)

Question 7

Skeletal vs. Smooth Muscle

Transmission Specialization?

Answer 7

Skeletal = Neuromuscular junction (NMJ)

Smooth Muscle = No NMJ - varicosities

Question 8

Skeletal vs. Smooth Muscle

NT receptors?

Answer 8

Skeletal= nAChR

Smooth Muscle= mAChR, Adrenergic

Question 9

Skeletal vs. Smooth Muscle

Other forms of activation?

Answer 9

Skeletal= None!!!

Smooth Muscle= Blood-borne, paracrine, intrinsic

Question 10

[Contraction of smooth muscle]

State the 5 steps!!!

Answer 10

1. Ca2+ enters cytosol through PM Ca2+ channels
2. Ca2+ binds reversibly to CaM
3. CaM-Ca2+ complex activates myosin light chain kinase (MLCK)
4. Phosphorylated MLCK allows myosin and actin binding
5. Relaxation

Question 11

Function of myosin phosphatase?

Answer 11

Key regulator for relaxation of smooth muscle

Question 12

What is the latch mechanism with smooth muscle?

Answer 12

Myosin phosphatase removes the phosphate from myosin, however STILL LATCHED!!!!

Low affinity for ATP

Continues generating active tension

Question 13

Draw the length tension relationship graphs for skeletal muscle vs smooth muscle

(include active tension and passive tension)

Answer 13

Question 14

Answer 14

C. Elevation of intracellular [Ca2+] for excitation contraction coupling

Question 15

What are the two major types of smooth muscle?

Answer 15

Multi-unit

Unitary

Question 16

Multi-unit Smooth Muscle Type

Describe:

Innervated by how many nerves?

Examples:

Answer 16

Describe: Fibers operate individually

Innervated by how many nerves? Single nerve

Examples: Ciliary muscles of eye, iris, piloerector muscles

Question 17

Unitary Smooth Muscle Type

Describe:

How is it innervated?

Examples:

Answer 17

Describe: Works together as unit

How is it innervated?:One nerve–> Cell membranes adhere and contain gap junctions

Examples: GI tract, bile ducts, uterus

Question 18

Describe how contraction of smooth muscle occurs

Answer 18

*Different than skeletal muscle!!!

• No true sarcomere structures
• Actin attaches to dense bodies/adherens juhctions
• Myosin heads have bi-directional arrangement

Question 19

Cycling of myosin cross-bridges is ______ than skeletal muscle

Answer 19

Slower

Question 20

The time myosin and actin are attached in smooth muscle is ________

Answer 20

Greater

*makes for greater force

Question 21

The ATP demand in smooth muscle in comparison to skeletal muscle is…

Answer 21

LOWER

Question 22

Excitation slows in smooth muscle, contration remains…

This is known as:

Answer 22

Latch mechanism

Question 23

What major molecule does Ca2+ interact with in smooth muscle to induce a muscle contraction?

Answer 23

Calmodulin (CaM)

Question 24

How does Ca2+ enter cytosol?

Answer 24

Through plasma membrane Ca2+ channels

*release from SR is minor

Question 25

How does Ca2+ exit?

Answer 25

SERCA 3Na+/Ca2+ antiporter Sarcolemmal Ca2+ ATPase

Question 26

After Ca2+ is in the cytosol, what does Ca2+ do to continue the pathway to initiate a muscle contraction?

Answer 26

Ca2+ binds reversibly to **CaM**

Question 27

What activates the **myosin light chain kinase?**

Answer 27

Calmodulin-Ca2+ complex

Question 28

Contraction strength is generally proportaional to....

Answer 28

Ca2+ levels

Question 29

What needs to occur to cause muscle relaxation?

Answer 29

- Calcium pumps remove Ca2+ - **Myosin light chain phosphatase** removes phosphate group on myosin light chain

Question 30

Describe the summary of contraction in smooth muscle

Answer 30

Question 31

What is a **varicosity?**

Answer 31

**Varicosities** serve as neurotransmitter release sites

Question 32

NO is a

Answer 32

Vasodilator

Question 33

What are enviornmental ques that control smooth muscle?

Answer 33

1. Hypoxia 2. Excess CO2 3. Increased H+ 4. Adenosine \*EXERCISE!!!

Question 34

What are the major drawers of Ca2+ in this image?

Answer 34

VDCC GPCR

Question 35

What is the resting membrane potential of smooth muscle?

Answer 35

-50 to -60mv

Question 36

Describe the difference in skeletal vs smooth muscle activity

Answer 36

(Left) Skeletal (Right) Smooth

Question 37

Answer 37

Question 38

Answer 38