Cell Mechanobiology (9/3b) Flashcards
Connective tissue (CT)
made up of cells and extracellular matrix
Tendon
type of connective tissue
conveys the tension created by muscles onto the bones, and also provide support
Fibroblasts
cells in a tendon that separate the components of extracellular matrix
Extracellular Matrix (ECM)
made up of ground substance and fibers
Ground substance (ECM)
Proteins: Proteoglycans and glycosaminoglycans - strongly hydrophilic, attract water
Glycoproteins link ECM components
Fibers (ECM)
Collagen (primarily type 1), elastin
In tendon, collagen bundles arranged in parallel to resist tension
Fibroblast structure
Cytoskeleton provides structure and aids in mechanotransduction
Microtubules (MTs), Intermediate Filaments (IFs), Microfilaments (MFs)
Desmosomal cadherins and integrins
Continuous chain of communication (EX: gap junctions) from outside of the cell to nucleus
Gap junction
specialized intercellular connection between the cytoplasms of two cells, allowing messages to be relayed
Microtubules (MTs)
polymers of tubulin that form part of the cytoskeleton
provide structure and shape to the cytoplasm
Intermediate Filaments (IFs)
provide mechanical support for the plasma membrane where it comes into contact with other cells or with the extracellular matrix
do not participate in cell motility
Microfilaments (MFs)
mostly composed of actin, also called actin filaments
the smallest filaments of the cytoskeleton. aids in cell movement, muscle contraction, cell division
Cadherins
calcium-dependent cell adhesion molecules that play a role in cell-cell adhesion and maintaining integrity of multicellular structures
a main component of zonula adherens
Integrins
transmembrane receptors that facilitate cell-extracellular matrix adhesion
Mechanotransduction
transduction of mechanical stimuli into a cellular signal and a response
mechanical stimulus>tissue forces>cellular forces>molecular response
Types of Forces (Forces)
Tension Shear Vibration Compression Hydrostatic Pressure Fluid Shear
Tension (Forces)
force pulling away from point
Shear (Forces)
unaligned forces pushing one part of a body one way and another part of the body an opposite way
Vibration (Forces)
forces moving quickly and repeatedly around an equilibrium point
Compression (Forces)
force pushing down on point
Hydrostatic Pressure (Forces)
pressure exerted by a fluid at equilibrium at a given point within the fluid, due to gravity force
Fluid Shear (Forces)
shear stress developed due to particles in fluid moving relative to one another
How are mechanical stimuli sensed
Collagen fibers in ECM linked to cytoskeleton via integrin proteins
Stretch-activated ion channels
G-protein coupled receptors
Growth-factor receptors
Integrins
Signal Transduction
by direct structural links between cytoskeleton and nucleus, and intracellular signaling cascades
Physical Stress Theory (PST)
Changes in the relative level of physical stress cause a predictable response in all biological tissue
Physical stress (PST)
force applied to an area of tissue
Force = mass * acceleration
Stress = force/area of tissue
5 Characteristic Responses to Stress
Death Decreased tolerance Maintenance Increased tolerance Injury
Stress level is a composite of these 3 things
Magnitude
Time
Direction
Excessive stress can be
1) high magnitude brief duration
2) low magnitude long duration
3) moderate magnitude many times
What can increase thresholds for stress
Overload
Progression of exercise stimulus
What can decrease thresholds for stress
inflammation
prolonged low stress
RICE (Inflammation)
Rest, Ice, Compression, Elevation
PRICE (Inflammation)
Protection, Rest, Ice, Compression, Elevation
POLICE (Inflammation)
Protection, Optimum Loading, Ice, Compression, Elevation
