Smooth muscle

Question 1

unitary

Answer 1

• single-unit
  
  • respond in unison
  • have a lot of gap junctions
• ex: GI, uterus, bladder

Question 2

multi-unit smooth muscle cells

Answer 2

• cells respond independently
  
  • each has its own neuro-muscular junction
• allow for finer control
• Ex: large arteries, airways

Question 3

Dense body

Answer 3

where actin binds

Question 4

Contraction of smooth muscle

Answer 4

1. Ca enters from outside of cell and SR and binds with Calmodulin
2. Ca-Calmodulin comples activates myosin light chain kinase (MLCK)
3. MLCK phosphorylates the myosin ligh chain (MLC) leading to contraction of smooth muscle
4. When Ca concentration decreases, myosin phosphatase removes the phosphate from the MLC, causing relaxation

Question 5

latch state

Answer 5

smooth muscle can remain myosin bound (contracted) without using ATP to stay that way

Happens when myosin filament loses its phosphorus

ex. sphinctor

Question 6

things that activate smooth muscle

Answer 6

1. nerve innervation (ANS)
2. hormones and other chemicals signals (oxytocin causes uterine contraction)
3. stretch (blood vessels)
4. neighboring cells
   
   1. via gap junctions

Question 7

desmosomes

Answer 7

hold together cardiac cells, do not rip apart when contracted

Question 8

contraction cycle

Answer 8

1. Ca enters sarcoplasm from out of cell and SR
2. Ca binds with calmodulin
3. Ca and calmodulin activate myosin kinase which phosphoylates and ATP. ADP and P are put on a myosin head.
4. myosin binds to actin
5. ADP and P come off of myosin head causing flick action.
6. myosin head releases
7. ***myosin head releases as long as it has phosphorus. To be in Latch state, myosin does not have the P