biopotentials rrin medical applicat.pptx

The creation of bionic eyes, as a result of recent advances in science and technology, are restoring hope to many who are unable to see or are partially sighted due to injury, illness or genetics.

With nearly 40 million people suffering from blindness worldwide and another 135 million affected by low vision, according to the World Health Organization (WHO), the need for new solutions is pressing. Could bionic eye technology lead the way?

A healthy eye takes in light through the pupil and a lens focuses that light onto the back of the eye, where there is a thick layer of light sensitive tissue called the retina. Cells called photoreceptors turn the light into electrical signals which travel down the optic nerve to the brain, which then interprets the images. In 2009 surgeons at Manchester and Moorfields hospital, in the U.K. delivered the world's first trial of the Argus II bionic eye to patients with Retinitis Pigmentosa, according to the University of Manchester. They implanted the devices into ten patients with sight loss. The Argus II helped patients recognize shapes and patterns, and in 2013, the U.S. Food and Drug Administration legally approved the device for use.Bionic eye technology has continued to develop and in 2021 researchers at Keck School of Medicine of USC created an advanced computer model to mimic the human retina, according to the Association for Computing Machinery (ACM). This replicates the shapes and positions of millions of nerve cells and could help bring color vision and improved clarity to the technology.

Scientists at the University of Sydney and UNSW recently carried out successful trials of the Phoenix99 bionic eye in sheep, to determine how the body heals when it is implanted with the device . Researchers said there were no unexpected reactions and expect it could safely remain in place for "many years". The work will now pave the way for human trials. One of the problems with the tech though is that it can be relatively bulky, so the race is on to find new ways to power bionic eyes.

Scientists at the Harbin Institute of Technology in China and Northumbria University recently developed a low-power system to control the synaptic devices in the bionic eyes, with lead professor Professor PingAn Hu describing it as a ‘significant breakthrough’

1. Source of Bioelectric Potentials By: Somesh Kumar Malhotra Assistant Professor, ECE Deptt.,UIET,CSJM University

2. Introduction In carrying out their various function, certain system of the body generates their own monitoring signals, which convey useful information about the function they represent. These signals are bioelectric potentials associated with nerve conduction , brain activity, heart beat, muscle activity and so on. Bioelectric potentials are actually ionic voltages produced as a result of the electrochemical activity of certain special type of cells.

3. Introduction Through the use of transducer capable of converting ionic potential into electrical voltages, these natural monitoring signals can be measured and results can be displayed in a meaningful way to aid the physician in his diagnosis and treatment of various diseases.

4. Resting and Action Potential We know that some of the types of cells of the body are encased in a semipermeable membrane which allow some substances to pass-through the membrane whereas others are not allowed to pass through. we also know that these cells of the body are surrounded by body fluids which are conductive solutions containing charge atoms, i.e., ions. The prominent ions are sodium (Na+), potassium ( K+), and chloride ( Cl -)

5. Resting and Action Potential The membrane of the cells allow entry of potassium and chloride ions whereas blocks the entry of sodium ions. Various ions seek a balance between the inside of the cell and the outside. The sodium is unable to penetrate the membrane . This results in unbalance of ions concentration and electric charge.

6. Resting and Action Potential The concentration of sodium ions inside the cell becomes much lower than in the intercellular fluid outside. The sodium ions are positive, therefore, this makes the outside of the cell more positive than the inside. In an attempt to balance the electric charge, the additional potassium ions which are positive, enter the cell causing higher concentration of potassium on the inside than on the outside (see fig.

7. Resting and Action Potential

8. Resting and Action Potential Thus charge balance cannot be achieved. Hence, equilibrium is achieved with a potential difference across the membranes. The inside of the cell is negative and outside is positive. This membrane potentials called the Resting Potential.

9. Resting and Action Potential This potential is maintained until some kind of disturbance is caused to upset the equilibrium. The resting potentials range from - 60 mV to - 1OO mV. The figure (b ) illustrates the resting potential. A cell in the resting state is said to be polarized.

10. Resting and Action Potential

11. Resting and Action Potential The excitation of a section of cell can be by using the flow of ionic current or any externally applied energy. This excitation of a section of cell causes change in the characteristics of the membrane which allows some of the sodium ions to enter. The movement of sodium ions into the cell further accelerates entry of sodium ions. This leads to rush of sodium ions inside the cell whereas potassium ions try to go outside but are unable to out that fast . The net result is slightly higher potential inside the cell. This potential is known as the action potential which can be about + 20 mV.

12. Resting and Action Potential When the rush of sodium ions through the cell membrane stops a new state of equilibrium is reached ,the m embrane behaves in its normal condition i.e., sodium ions are not allowed to enter inside from outside. At this stage of the process, sodium ions are quickly transported from inside of cell to outside of cell and this active process is known as sodium pump. Once all sodium ions are pumped outside the cell , the cell reaches its Resting Potential. The process of change from Action Potential to Resting Potential is known as Repolarization .

13. Typical waveform of action potential

14. Typical waveform of action potential The waveform of the action potential is shown in fig. The time scale depends on the type of cell producing the potential Nerve and muscle have 1 m sec duration, w hereas heart muscle duration may be as high as 3OO m sec. Please note that after repolarization completion, resting potential is named "after potentials", which reaches restinl ' potential slowlY

15. Propagation of action potential Once a cell is excited and generated action potential, ionic currents begin to flow. This process excites neighbouring cells or areas of the same cell. A nerve cell with a long fiber may have potential over a small segment of the fiber, but it is propagated in both directions from the origin point of excitation.

16. Propagation of action potential The rate at which an action potential moves down a fiber is known propagation rate. In nerve cells the 140 meters per second. The propogation of heart muscles cells slower in the range of 0.2 to 0.4 m per second. Artria and venticles of the heart have special cells which have propagation rate of as low as 0.05 meter Per second.