smooth muscle

Question 1

Smooth Muscle

Answer 1

 in the walls of hollow organs and muscles of the eye
Non striated lacking sarcomere
Single nucleated
Arrang like a sheet

Question 2

structure of smooth muscle OVA

Answer 2

• no T-tubules
• have caveolae- invagination of surface membrane, act like T-tubules
• have action,myosin, and tropomysin
  -no troponin but have calmodulin
• no Z-line but have dense bodies
• actin achored to dense bodies
  -myosin form cross bridges with actin filaments

Question 3

What is the func of alpha actinin,vinculins?

Question 4

Types of smooth muscle

Answer 4

• single unit/ unitary
• multi-unit

Question 5

Unitary Smooth muscle

Answer 5

-a mass of hundreds to thousands of smooth muscle fibers that contract together as a single unit.
- fibers in bundle of sheet
- presence of gap junction- ion flow, syncytium
- has inherent rhythm
- walls of visceral organs-visceral smooth muscle

Question 6

which part is always activated by sympathetic nervous sytem? ova

Answer 6

blood vessel

Question 7

why skeletal has higher contraction but smooth muscle has longer contraction

Answer 7

skeletal- depolaristion through Na+ influx, reach +35
smooth - depolarisation through Ca++ influx,reach +8

latency
skeletal- moving through NMJ
smooth- moving through varicosity,slower depolarisation

Question 8

why in cold environment energy is less

Answer 8

• low temp-> Na+/H+ inhibited, sarcolemma less depolarised,Ca channels less open, less Ca++

Question 9

How is intercellular calcium is used

Answer 9

pg 13

Question 10

Describe the sequence of events of excitation contraction coupling in smooth muscle

Answer 10

go through entire process in l notes

Question 11

Describe the sequence of events of relaxation-coupling in smooth muscle.

Answer 11

For the mechanism of relaxation:

Once stimulus has been removed, Cytosolic Ca2+ will be removed by series of Ca2+-ATPases on sarcolaemma and on SR
➤ Lowers [Ca2+]; below the level necessary to form CaM complexes
> MLCK inactivated
> MLCP activated
➤ Myosin dephosphorylated and no longer have significant affinity to bind with actins
> Relaxation occurs

Question 12

Describe the latch state for smooth muscle

Answer 12

• As contraction lasts longer, [Ca2+]; begin to decline,
  Ca2+ leave calmodulin→ MLCK inactivated & myosin light-chain phophatase (MLCP) activated
  ► Myosin is dephosphorylated by MLCP
  > Dephosphorylated myosin have very low affinity for ATP and can still interact with actin→ latch-bridges
  > Latch-bridges do not detach, or detach slowly
  > Cannot generate active tension but can resist passive stretching
  > This produces a sustained (tonic) contraction with little consumption of ATP

Question 13

Explain the property of plasticity of smooth muscle

Answer 13

Plasticity of smooth muscle is referred to when smooth muscle behaves more like a viscous mass than a rigidly structured tissue

Plasticity arise from molecular rearrangements within the contractile protein array and may form the basis for both long and short term mechanical adaptation.

For example, initially tension increases little as volume is increased due to the plasticity of the bladder wall. However, a point is eventually reached at which the bladder contracts forcefully.

Question 14

electromechanical vs pharmacochemical

Answer 14

-