Physiology week 16 Flashcards
Name the types of smooth muscle
- Multi Unit smooth muscle
- Single- Unit smooth muscle
Where is multi-unit smooth muscle found
- Ciliary muscle, iris muscle
Where is Single-Unit smooth muscle found
- Visceral organs
Explain the strcutrue of single unit smooth muscle
- Large mass of fibers that contract together as a unit
Explain the structure of the Multi-Unit smooth muscle
- Independent fibers, inervated separately
What is Multi-Unit smooth muscle controlled mainly by
- Nerve signals
What is Single-Unit smooth muscle connected by
Gap junctions
Explain the key differnces of smooth muscle from skeletal muscle
- Different excitation-contraction coupling
-Different calcium ion control mechanism
-Lower contraction duration
-Lower energy requirement
Explain the physical basis for smooth muscle contraction ( 4 characteristics)
- No striations , actin filaments attach to dense bodies
-Dense bodies are connected via intercellular protein bridges
-Have more actin than mysoin
-Myosin filaments have ‘side polar’ cross bridges
Explain the difference in contraction between skeletal muscles and smooth muscles
Skeletal muscle contracts and relaxes rapidly while the smooth muscle contraction lasts for hours or days
Explain the slow cycling of the myosin cross bridge in smooth muscle( attach and detaching)
- Cross bridges attach and detach slower and they remain attched for longer
What is the low energy requirement in smooth muscles imortant for
Energy efficiency in organs like intestines, bladder and gall bladder
What do smooth muscles lack
Troponin
What is the function of calmodulin
Activates contraction by binding to calcium.
- Then activates the myosin light chain kinase( MLCK) , which phospjorylates myosin heads
What does phosphorylation of the myosin heads allow
- Myosin to bind to actin
What does smooth muscle rely on
Extracellular calcium
Is skeletal muscle function affected by extracellular calcium level
- No
What does the calcium pump remove
- Calcium from the cytoplasm
What is the function of myosin phosphate
- Dephorylates myosin, stopping contraction
When myosin kinase and phosphate activity decreases what happens to the myosin heads
Myosin heads remain attched longer
What does smooth muscle contract due to , which is different in skeletal
- Nervous signals,hormone,stretch
Can skeletal muscles initiate their own contractions
- No
Can smooth muscle initiate their own contractions
- Yes
Describe the difference in neuromuscular junctions structure in smooth and skeletal muscles
- Smooth muscles have np structured neuromuscualr junctions but skeletal do
Name the 2 main receptos
- Acetylcholine
- norepinephrine
If acteycholine is excited, what is inhibted
- norepinephrine
Name the 2 types of Action Potential
- Spike potentials
-Plateau potentials
What are spike potentials triggered by
- Electrical, hormonal or neural stimuli
Where is plateau potentials seen in
- Uterus, blood vessels and heart muscle
In smooth muscle contraction what is more important calcium or sodium channels
Ca
What types of waves does slow muscle produce
- Slow wave potentials
Give 3 examples that show the way hormones work
-Opening sodium/calcium channels
-Closing sodium/calcium channels or opening potassium channels
-Activating second messengers (cAMP, cGMP)
