Smooth muscle Flashcards
Describe single units
electronically couples
work as one unit
found in BV and hollow organs
spontaneously innervated
Describe multi units
relies on innervation
densely innervated
iris/ vas deferens
Describe the structure of a smooth muscle cell
- dense bodies
- cavolae
-gap junction
intermediate filament
dense bodies- act as Z disc to bind actin to sarcoelma
cavolae = increased surface area
Gap junctions: transfer electrical current
intermediate filament:
cytoskeleton
Describe Smooth muscles organisation and stretch
less organsied
has myosin and actin
has a large amount of stretch
can shorten
what is the important source of Ca for the smooth muscle
Ca channels within the cell membrane
Intiation contraction is dependent on what
influx of Ca from the Ca voltage gated channels
What triggers contraction
increase in intracellular CA
What are sources of Calcium
extracellular, SR, regulation of voltage, hormones, neurotransmitters and specific ions
describe the first step of initiation for Smooth muscle contraction
Ca enters via voltage dependent/independent channels in the ECF
OR
IPS binds to SR channel= SR to release calcium into the cytosol
what does calcium activated in the smooth muscle cell
It activated the camodulin
what does camodulin activate in smooth muscle
camodulin actiavtes the myosin light chain kinase (enzyme)
What enzyme activates the myosin head
Myosin light chain kinase
what enzyme deactivates the myosin head
myosin light chain phosphates
Smooth muscle contraction is regulated how?
enzyme related
what enzyme is reposible for the decrease in CA2+ in the cytosol
Ca ATPase reduces Ca levels within the cytosol
INcreased light chain kinases will cause?
relaxation
Increased myosin light chain kinases will cause
contraction
What occurs when their is a drop in Ca
Myosin light chain phosphatase will dominate
What is smooth muscle innervates by
Autonmic nerve fibres
What are the name of the autonomic nerve fibres
Varicosities
Describe Varicosities
Varicosities release neurotransmitters that diffuse across the matrix into the cell
what occurs in the response to stretch firstly
contraction and resistance to the stretch
-activated by the CA channels
what occurs in the response to stretch secondly
relaxation
adapt to change in the length
calcium dependent K channels hyperpolarise the membrane.
