טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentViner Netanel
SubjectMultiphysics Modeling of Smooth Muscle Contraction
DepartmentDepartment of Civil and Environmental Engineering
Supervisor Professor Mahmood Jabareen
Full Thesis textFull thesis text - English Version


Abstract

Smooth muscles play a major role in the proper function of hollow organs, particularly in blood vessels. Generally speaking, the process which leads to smooth muscle contraction is governed by an electro-chemo-mechanical chain of actions. A signal is sent from the nervous system to a specific muscle cell or group of cells, causes membrane depolarization and ion exchange of different materials, first and foremost calcium. Increase in intracellular calcium allow muscle fibres actin and myosin to slide over each other through myosin heads power strokes. In this manner the entire muscle cell contracts.

This research thesis is concerned with developing a unified finite element scheme to fully couple smooth muscle electro-chemo-mechanics. In the first phase, a spatio-temporal electro-chemical model was developed for smooth muscle activation. The second phase included development of a spatio-temporal chemo-mechanical model to describe smooth muscle contraction. The emphasis in the chemo-mechanical model was given on proper material description. The last stage included unification of the electro-chemical and chemo-mechanical models into a fully coupled model. The coupled model account for both electrical activation and agonist activation through norepinephrine (NE) and nitric oxide (NO). Calcium release from intracellular storage is considered through the inositol triphosphate receptor and the ryanodine receptor. Cytosolic chemical balance is considered for the following ions: calcium (Ca2) sodium (Na), potassium  (K), chloride (Cl-). Interaction between adjacent cells is obtained by applying the diffusion equation considering cell to cell conductance. Material description accounts for both passive and active tissues with specific description of the fibres' mean orientation and statistical dispersion. Due to the incompressible nature of biological tissues, the three field mixed formulation was applied in order to preserve the physical behavior while avoiding phenomena such as volumetric locking. The fully coupled model was implemented into the finite elements framework utilizing a fully implicit approach, which guarantees solution convergence. Each element node in the fully coupled model holds four degrees of freedom, three displacements and one for the electrical potential. The finite elements framework offers the possibility to perform a wide range of simulations for complex geometries. These types of simulations may shed light and yield insights regarding the factors controlling smooth muscle contraction. In addition, the model may be used to perform more complex simulations evolving smooth muscles such as analyzing plaque stability and blood flow regime through coupled fluid structure interaction (FSI).