Human Phys 2.9

Question 1

What do smooth muscles lack?

Answer 1

Striations

Question 2

Do smooth muscles have actin and myosin?

Answer 2

Yes, but they are not arranged in sarcomeres

Question 3

Motility

Answer 3

To propel chyme down the GI tract (Phasic)

Question 4

Tension

Answer 4

To maintain appropriate vascular diameter in blood vessels (tonic)

Question 5

What are the types of smooth muscles?

Answer 5

Unitary/visceral/single unit

Multi unit

Combination

Question 6

What are single unit smooth muscles linked by?

Answer 6

Gap junctions

Question 7

What are single unit smooth muscles present in?

Answer 7

GI tract

Bladder

Uterus

Ureter

Question 8

What are single unit smooth muscles characterized by?

Answer 8

Spontaneous pacemaker activity (slow waves) (Phasic contractions)

Question 9

Are multi unit smooth muscles linked by gap junctions?

Answer 9

No

Question 10

What are multiunit smooth muscles present in?

Answer 10

Iris

Ciliary muscles of the lens

Vas deferens

Question 11

What are characteristics in multiunit smooth muscles?

Answer 11

Each muscle fiber behaves as a separate motor unit

Little or no coupling between cells

Densely innervated by the ANS

Question 12

What type of contractions do multiunit smooth muscles do?

Answer 12

Tonic

Question 13

What is a combination of both types of smooth muscles present in?

Answer 13

Vascular smooth muscle

Question 14

What do smooth muscles not contain?

Answer 14

Troponin complex

Question 15

What are dense bodies in smooth muscles?

Answer 15

Behave like Z disc in the skeletal muscles

Question 16

Have much of there length can smooth muscles contract?

Answer 16

80% (skeletal can do 30%)

Question 17

What is the myosin ATPase activity in the smooth muscles compared to the skeletal muscles?

Answer 17

1/10 compared to 1/300 is required ti maintain the same tension

Question 18

Why is myosin cross bridge much slower in smooth muscles compared to skeletal muscles?

Answer 18

Because less energy is used

Question 19

What does smooth muscle require more time for?

Answer 19

To contract and relax (slow onset of contraction)

Question 20

What is the maximum force of contraction in smooth muscle compared to skeletal muscle?

Answer 20

Much higher (4-6 kg/cm2)

Question 21

How can smooth muscles maintain prolonged tonic contractions, for hours using minimal energy?

Answer 21

Via the latch mechanism

Question 22

Stress relaxation and reverse stress relaxation

Answer 22

Allows hollow organs to maintain constant luminal pressure despite large changes in volume

Question 23

What is poorly developed in the smooth muscle?

Answer 23

Sarcoplasmic reticulum

Question 24

What is used in smooth muscles instead of troponin?

Answer 24

Calmodulin

Question 25

What is smooth muscle cell contraction initiated by?

Answer 25

Extracellular calcium

Question 26

What is the correct temporal order of events for the smooth muscle?

Answer 26

MLC phosphorylation

Contraction

MLC dephosphorylation

Relaxation

Question 27

Actin and myosin filaments in smooth muscles are structured how?

Answer 27

Overlap, with the actin filaments anchored at dense bodies