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<p>As seen in the other parts of this wiki, we chose to use a nanoporous membrane in our device. The first goal of the membrane was to confine our biofilm, so it does not escape the prosthesis. Moreover, we also used our membrane as a conductive electrode. This solution was interesting since we didn’t have enough time to develop an entire electrical device which collects and treat the signal of the nerves. However, we know we still need to improve our interface if we want the patient to fully control his prosthesis. That is why we decided to look at what is already made in this field. So, first, we detailed how it is possible to model the electrical characteristics of a nerve. Then, we searched for information on electrodes and signal treatment. </p> | <p>As seen in the other parts of this wiki, we chose to use a nanoporous membrane in our device. The first goal of the membrane was to confine our biofilm, so it does not escape the prosthesis. Moreover, we also used our membrane as a conductive electrode. This solution was interesting since we didn’t have enough time to develop an entire electrical device which collects and treat the signal of the nerves. However, we know we still need to improve our interface if we want the patient to fully control his prosthesis. That is why we decided to look at what is already made in this field. So, first, we detailed how it is possible to model the electrical characteristics of a nerve. Then, we searched for information on electrodes and signal treatment. </p> | ||
− | <p><i>This section is | + | <p><i>This section is principally based on the thesis of Olivier Rossel: Dispositifs de measure et d’interprétation de l’activité d’un nerf. Electronique. Université Montpellier II - Sciences et Techniques du Languedoc, 2012. Français. </i></p> |
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<div class="block title"><h1>I. physiological characteristics of the human nervous system<sup>[1]</sup></h1></div> | <div class="block title"><h1>I. physiological characteristics of the human nervous system<sup>[1]</sup></h1></div> | ||
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− | <p>The nervous system is divided | + | <p>The nervous system is divided into two different parts: the central nervous system (CNS) and the peripheral nervous system (PNS). We will focus on the peripheral nervous system as it transports the information between the rest of the body and the central nervous system. Moreover, it includes the somatic nervous system which consists of afferent nerves, also called sensory nerves, and efferent nerves also called motor nerves. Afferent nerves are responsible for relaying sensation from the body to the central nervous system; efferent nerves are responsible for sending out commands from the CNS to the body, stimulating muscle contraction; they include all the non-sensory neurons connected with skeletal muscles and skin. Generally, the fibers of the somatic nervous system have an insulating sheath called a myelin sheath.</p> |
<img src="https://static.igem.org/mediawiki/2018/c/c2/T--Pasteur_Paris--InterfaceNerveFigure1.jpg" style="width:300px"> | <img src="https://static.igem.org/mediawiki/2018/c/c2/T--Pasteur_Paris--InterfaceNerveFigure1.jpg" style="width:300px"> | ||
<div class="legend"><b>Figure 1: </b>Structure of nerves<sup>[2]</sup></div> | <div class="legend"><b>Figure 1: </b>Structure of nerves<sup>[2]</sup></div> | ||
− | <p>Nerve fibers, consisting of axons and associated Schwann cells are grouped together in fascicles, sheathed by the perineurium (Cf. Figure 1). It is composed of layers of perineural cells. About half of the fascicular surface is occupied by the fibers, the rest is composed of the endoneurium which | + | <p>Nerve fibers, consisting of axons and associated Schwann cells are grouped together in fascicles, sheathed by the perineurium (Cf. Figure 1). It is composed of layers of perineural cells. About half of the fascicular surface is occupied by the fibers, the rest is composed of the endoneurium which segments the inside of the fascicle into several groups of nerve fibers which will then form new fascicles.</p> |
− | <p>The fascicles are contained in an isolated connective tissue called the epineurium that contains fibroblasts, collagen and fat in different proportions. This envelope allows the fixation of the nerve on the surrounding structures. It contains the lymphatic and vascular network which crosses the perineurium to communicate with the network of arterioles and venula of the endoneurium. The epineurium constitutes 30 to 70% of the total area of a nerve.</p> | + | <p>The fascicles are contained in an isolated connective tissue called the epineurium that contains fibroblasts, collagen, and fat in different proportions. This envelope allows the fixation of the nerve on the surrounding structures. It contains the lymphatic and vascular network which crosses the perineurium to communicate with the network of arterioles and venula of the endoneurium. The epineurium constitutes 30 to 70% of the total area of a nerve.</p> |
<p>The fascicular architecture is ordered only distally, close to the emergence of a nerve trunk. Going up to the proximal part, fascicles divide and some fibers change their fascicles, the size of the fascicles decreases and their number increases. An orderly organization relative to the target organ is found only in the final branches that innervate a muscle, a group of muscles or sensory receptors.</p> | <p>The fascicular architecture is ordered only distally, close to the emergence of a nerve trunk. Going up to the proximal part, fascicles divide and some fibers change their fascicles, the size of the fascicles decreases and their number increases. An orderly organization relative to the target organ is found only in the final branches that innervate a muscle, a group of muscles or sensory receptors.</p> | ||
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<div class="block title"><h3 style="text-align: left;">1. Introduction </h3></div> | <div class="block title"><h3 style="text-align: left;">1. Introduction </h3></div> | ||
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− | <p>The purpose of this part is to know the potential “seen” by an electrode wrapped around the nerve. For this we will study the extracellular potential at the surface of the nerve by considering an axon parallel to the longitudinal | + | <p>The purpose of this part is to know the potential “seen” by an electrode wrapped around the nerve. For this, we will study the extracellular potential at the surface of the nerve by considering an axon parallel to the longitudinal axis of the nerve. Each Ranvier node is considered as a point current source. To estimate the potential at a point M at the periphery of the nerve, it is necessary to determine a transfer function linking this potential to each of the transmembrane currents of the axon. The simulation of the membrane current of the axone we developed previously is used as the input of the nerve model.</p> |
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<div class="block title"><h3 style="text-align: left;">2. Medium transfer function </h3></div> | <div class="block title"><h3 style="text-align: left;">2. Medium transfer function </h3></div> | ||
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<p>The neural information is coded by the frequency of the impulses of the action potentials and the number of fibers recruited. The shape and amplitude of the action potentials collected do not convey any neural information but only information on the distance where the nerve fiber is located in the nerve.</p> | <p>The neural information is coded by the frequency of the impulses of the action potentials and the number of fibers recruited. The shape and amplitude of the action potentials collected do not convey any neural information but only information on the distance where the nerve fiber is located in the nerve.</p> | ||
− | <p>In the same nerve, several types of information transit. The nerve carries efferent neuronal signals, from the central nervous system to the peripheral nervous system, which | + | <p>In the same nerve, several types of information transit. The nerve carries efferent neuronal signals, from the central nervous system to the peripheral nervous system, which regulates and control the body's natural functions through muscle recruitment. But nerves also carry information from natural sensors (mechanoreceptors, proprioceptive, etc.) and transiting to the central nervous system by activation of the afferent nerve fibers. Generally, muscle recruitment and sensory fiber activation are not coded in the same way.</p> |
− | <p>In the case of motor or efferent fibers, the number of active motor units as well as their discharge frequencies vary at the same time as the force produced by the muscle<sup>[10]</sup>.</p> | + | <p>In the case of motor or efferent fibers, the number of active motor units, as well as their discharge frequencies, vary at the same time as the force produced by the muscle<sup>[10]</sup>.</p> |
</div> | </div> | ||
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Revision as of 13:33, 17 October 2018
Membrane
When manipulating genetically engineered organisms, it is crucial to guarantee the confinement of these organisms. In our case, we want genetically modified bacteria to stay at the interface between the prosthesis and the external organic medium. At the same time, one of the main issues our project wants to tackle is the conduction of the neuron influx to the prosthesis. The answer to these questions came as a double solution: confinement of the bacteria by conductive nanoporous membranes. The membrane’s nanoporosity allows substances produced by our modified biofilm to pass through the membrane, but the bacteria remain confined. We tested the conductivity and biocompatibility of two types of membranes.
Membrane
Nerve and electrodes
As seen in the other parts of this wiki, we chose to use a nanoporous membrane in our device. The first goal of the membrane was to confine our biofilm, so it does not escape the prosthesis. Moreover, we also used our membrane as a conductive electrode. This solution was interesting since we didn’t have enough time to develop an entire electrical device which collects and treat the signal of the nerves. However, we know we still need to improve our interface if we want the patient to fully control his prosthesis. That is why we decided to look at what is already made in this field. So, first, we detailed how it is possible to model the electrical characteristics of a nerve. Then, we searched for information on electrodes and signal treatment.
This section is principally based on the thesis of Olivier Rossel: Dispositifs de measure et d’interprétation de l’activité d’un nerf. Electronique. Université Montpellier II - Sciences et Techniques du Languedoc, 2012. Français.