Smooth muscle Flashcards
Features of smooth muscle
Non striated
Synsitial
Normally around hollow viscarea
Features in a transverse section
Much smaller cells
Many more of cells
Nuclei in centre of the cell
Features in a Longitudal section
Not stripy
Located nucleus in centre
Small single Nucleated cell
Short tapering fibres
What initiates synsitial function
Gap junctions
What is caveole
Small indentations present in the cell membrane
Function of the structural proteins
Act as anchoring points for our thick and thin filaments
What do thin filaments have
Actin
Tropomyosin
No troponin
Will tropomyosin be over binding site
No as no troponin so actin can immediately bind and immediately forms a cross bridge
Why is calmodulin present
It is a molecule with a calcium binding site
How does calmodulin becomes activated
Calcium binds to the calmodulin, then the calmodulin binds to myosin light chain kinase and this phosphorylates the myosin molecule
What is the enzyme associated with calmodulin
Myosin light chain kinase
What happens if we phosphorylation myosin
A cross bridge can be formed which forms a contraction
In smooth muscle, does myosin head have ATPase acitvity
No
Why do we need to use enzyme myosin phosphate
Cross bridging cant occur as no ATP so cant make or break the cross bridge so enzyme is needed. So this enzyme dephosphorylates the myosin bringing it back to its resting state
Increase calcium causes
A increase in drive of activity
Does calveoli contain calcium
Yes
Calveoli features
Extracellular calcium
No sacroplasmic reticulum
What happens if there is an increase in calcium
Voltage gated calcium channels open
Calcium flows into cells
Bind to calmodulin
Allow cross bridge cycling
How is the calcium pushed back out of the cell
ATP dependent pump
Specific features of smooth muscle contraction
Slower contractions
Low ATPase activity
Slow cross bridge cycling
What is tone
Continous activity at all times due to calcium coming into the cell
Stimulates calmodulin
Stimulates cross bridge cycling
What factors change the amount of calcium within the cell
Electrical activity
Protein coupled receptors (GPCR)
What do protein coupled receptors do
Linked to secondary messenger systems
These will change the response to calcium which can change force of contraction
What is pacemaker potiential
When a cell depolarises and fires an action potiential
