role of physics in nerve condution; ….pdfvalue is called depolarization. followed by which the k+...

International Journal of Science and Research

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Role of Physics iElectrochemistry; Future Prospects

Raghottam Manoj Sattigeri

1TY BSc (Hons) Physics, Dept. Of Physics, Faculty of Science,

2Professor and Head, Dept. Of Pharmacology, Sumandeep Vidyapeeth’s, SBKS Medical Institute and Research Centre, Piparia, Vadodara, Gujarat

Abstract: The most important and vital structure of the human body is the nervous system which is complex and elaborate. A blur idea existed in the scientific community for more than 2000 years that, there exists a mode of communication between our brain andbody, but by the ground breaking work of Luig Galvani changed our perception about the nerve conduction. Contributions from the great Physicists like Hermann von Helmholtz, functioning of the nerve cell, the correlation between the transmission of an electrical impulse and nerve signal transmissioexperimental studies conducted by these Noble Laureates has today enabled us to understand the reasons behind neurologiand has also helped us advance in the management of the neurological disorders. Keywords: Biophysics, Nerve cell, Nerve signalling, Neurotransmitter, Neurological disorder, Neurophysics, Physics 1. Introduction The most important and vital structure of the human body is the nervous system which is complex and elaborate. The nervous system includes the Central Nervous System (CNS) and the Peripheral Nervous System (PNS), which coand function together to regulate different processes of the human body. The signal (stimuli such as pain, pressure, temperature) of various types are sensed and transmitted to the CNS, in turn the brain interprets the datand responds to the stimuli by conduction of an impulse through the PNS to the site of origin of impulse in the form of response. The entire process of response to stimuli by conduction of an impulse through the CNS happens in fractions of seconds [1], [2]. A blur idea existed in the scientific community for more than 2000 years that, there exists a mode of communication between our brain and our body, but by the ground breaking work of Luig Galvani (who conducted experiments on frogs with the help of galvanometer to understand the nerve function, in the late 18th century) successfully established that the electric currents are necessary for the conduction of impulse across neuron [3]. 2. The Structure of the Nerve Cell Neuron is the functional unit of the nervous system which consists of the cell body (which contains nucleus, mitochondria, and cell organelles), the dendrites (which function as a receiver/transducer) and the axon (similar to the electric cables) which functions as a transmittThese axons are surrounded by a membrane called myelin sheath which plays a major role in the rate of electric transmission. Those axons with myelin sheath are the myelinated fibres and those without myelin sheath are called as the unmyelinated fibres. However, in the myelinated fibres there are interruptions present which are called as the node of ranvier [4], [5].

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of Physics in Nerve Condution;Electrochemistry; Future Prospects

Raghottam Manoj Sattigeri1, Dr. Bhagya Manoj Sattigeri

TY BSc (Hons) Physics, Dept. Of Physics, Faculty of Science, The Maharaja Sayajirao University of Baroda, Vadodara, Gujarat

Professor and Head, Dept. Of Pharmacology, Sumandeep Vidyapeeth’s, SBKS Medical Institute and Research Centre, Piparia, Vadodara, Gujarat

The most important and vital structure of the human body is the nervous system which is complex and elaborate. A blur idea existed in the scientific community for more than 2000 years that, there exists a mode of communication between our brain and

y, but by the ground breaking work of Luig Galvani changed our perception about the nerve conduction. Contributions from the great Physicists like Hermann von Helmholtz, Erwin Neher , Bert Sakmann, Hodgkin and Huxley has helped us understand the basic functioning of the nerve cell, the correlation between the transmission of an electrical impulse and nerve signal transmissioexperimental studies conducted by these Noble Laureates has today enabled us to understand the reasons behind neurologiand has also helped us advance in the management of the neurological disorders.

Biophysics, Nerve cell, Nerve signalling, Neurotransmitter, Neurological disorder, Neurophysics, Physics

The most important and vital structure of the human body is the nervous system which is complex and elaborate. The nervous system includes the Central Nervous System (CNS)

s System (PNS), which co-ordinate and function together to regulate different processes of the human body. The signal (stimuli such as pain, pressure, temperature) of various types are sensed and transmitted to the CNS, in turn the brain interprets the data received by it and responds to the stimuli by conduction of an impulse through the PNS to the site of origin of impulse in the form of response. The entire process of response to stimuli by conduction of an impulse through the CNS happens in

A blur idea existed in the scientific community for more than 2000 years that, there exists a mode of communication between our brain and our body, but by the ground breaking work of Luig Galvani (who conducted experiments on frogs

the help of galvanometer to understand the nerve century) successfully established

that the electric currents are necessary for the conduction of

The Structure of the Nerve Cell

nal unit of the nervous system which consists of the cell body (which contains nucleus, mitochondria, and cell organelles), the dendrites (which function as a receiver/transducer) and the axon (similar to the electric cables) which functions as a transmitter (Fig-1). These axons are surrounded by a membrane called myelin sheath which plays a major role in the rate of electric transmission. Those axons with myelin sheath are the myelinated fibres and those without myelin sheath are called

fibres. However, in the myelinated fibres there are interruptions present which are called as the

Figure 1: Figure indicates the structure of Neuron 3. Conduction of an Impulse The neurons respond to the stimuli and conduct because of a membrane potential that is established across the cell membrane which can be explained by a voltmeter with one electrode placed inside the neuron and the other outside.

Figure 2: Difference in Membrane Potential Using Voltmeter

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n Nerve Condution; Electrochemistry; Future Prospects

Bhagya Manoj Sattigeri2

The Maharaja Sayajirao University of Baroda, Vadodara, Gujarat

Professor and Head, Dept. Of Pharmacology, Sumandeep Vidyapeeth’s, SBKS Medical Institute and Research Centre, Piparia, Vadodara, Gujarat

The most important and vital structure of the human body is the nervous system which is complex and elaborate. A blur idea existed in the scientific community for more than 2000 years that, there exists a mode of communication between our brain and our

y, but by the ground breaking work of Luig Galvani changed our perception about the nerve conduction. Contributions from the , Hodgkin and Huxley has helped us understand the basic

functioning of the nerve cell, the correlation between the transmission of an electrical impulse and nerve signal transmission. Various experimental studies conducted by these Noble Laureates has today enabled us to understand the reasons behind neurological disorders

Biophysics, Nerve cell, Nerve signalling, Neurotransmitter, Neurological disorder, Neurophysics, Physics

Figure indicates the structure of Neuron

Conduction of an Impulse

The neurons respond to the stimuli and conduct impulses because of a membrane potential that is established across the cell membrane which can be explained by a voltmeter with one electrode placed inside the neuron and the other

Difference in Membrane Potential Using

Voltmeter

Paper ID: OCT14418 1561



We find that as depicted in Fig-2 there exists negativity inside the neuron as compared to the outside of the neuron this difference is referred to as the resting membrane potential of a neuron. The resting membrane potential is expressed as -70 mV this is observed when the membrane is not stimulated or conducting impulses [2responsible for the membrane potential are sodium (Na+) and potassium (K+). Nernst and Planck in collaboration gave an equation that directly relates the membrane potenthe concentration of the ions at the either side of the membrane.

V�in mV� � RT [C']F [C″]

Where, V is the membrane potential (measured in mV),R is Rydberg constant, T is Absolute Temperature and C′ and C″ are the concentrations of the ions outside and inside the membrane respectively [6], [7], 4. Ion Gates/ Channels -Action Potential The nerve cell membranes contain special passage ways the two ions sodium (Na+) and potassiumcalled the ion gates or ion channels. These are the passages through which these ions diffuse, that occur on the arrival of stimulus, ultimately giving rise to the generation [10], [11].

Figure 3: Ion Channels An action potential is essential for neural communication which involves thefollowing steps[12]

Figure 4: Action Potential





2 there exists negativity inside the neuron as compared to the outside of the neuron this difference is referred to as the resting membrane potential of a neuron. The resting membrane potential is

observed when the membrane is not stimulated or conducting impulses [2], [3]. The ions responsible for the membrane potential are sodium (Na+)

Nernst and Planck in collaboration gave an equation that directly relates the membrane potential with the concentration of the ions at the either side of the

(1)

V is the membrane potential (measured in mV),

the concentrations of the ions outside and , [8],[9].

Action Potential

special passage ways for potassium (K+) which are

. These are the passages through which these ions diffuse, that occur on the arrival of stimulus, ultimately giving rise to the Action Potential

Ion Channels

potential is essential for neural communication

Action Potential

The dendrites receive stimuli which trigger the opening of the Na+ channels, this results into increase of the potential from -70mV to -55mV (Step the Na+ channel is wide enough then the process continues, else it dies out. Once the potential reaches action/gate threshold limit more and more Na+ channels open up and increase the potential to +33mV (potential is a peak value and the process to reach this peak value is called depolarization. Followed by which the K+ channels open (Step -3, Fig - 4) repolarization. Since the opening is slower in the case of K+ channels the Na+ channels do not close immediately and ensure that the process is one-channels close completely and the K+ influx decreases the potential from+33mV to -90mV, which thus overshoots the resting membrane potential (repolarization (Step – 4, Fig hyperpolarization state (when the potential is < 90mV) (Step - 5, Fig - 4). Again the continuous process of the K+ and Na+ pump brings the potential back to (resting membrane potential) (Action Potential is generated and the signal is transmitted. The equations relating impulse propagation to the ion permeability changes were presented by Huxley Theory (1952) by voltage clampwhich they received Nobel Prize in Medicine (1963)patch clamp technique allowed the study of single/ multiple ion channels in the cells, which was used to explain the flow (current) of ions and the fundamental cell processes such as action potential by Erwin Neher & Bert Sakmann in late 1970 who were awarded with Nobel Prize in Physiology and Medicine (1991) [3]. Hodgkin and Huxley used their results from the voltage clamp experiments to define sodium and potassium conductivities during action potential [13] For example the conductivity of the sodium ion is given by;

JNa

= (V –

Where, J

Na = Sodium Current Density;

gNa

= Sodium Conductivity;

V = Transmembrane Potential;V

Na = Sodium Nernst Potential.

(A similar equation can be obtained for potassium ion.) These definitions are nevertheless arbitrary.conducted by Hodgkin and Huxley membranes respond to smaller electric signals. This explains that propagation of an electric signal the propagation of a signal in a cable as shown in Figwas explained by the Resistancewhich is a landmark in medical science

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The dendrites receive stimuli which trigger the opening of the Na+ channels, this results into increase of the potential

Step - 1, Fig - 4). If the opening of the Na+ channel is wide enough then the process continues, else it dies out. Once the potential reaches action/gate threshold limit more and more Na+ channels open up and increase the potential to +33mV (Step -2, Fig- 4). This potential is a peak value and the process to reach this peak value is called depolarization. Followed by which the K+

4) which leads to the process of repolarization. Since the opening is slower in the case of K+

annels the Na+ channels do not close immediately and -way. As time elapses the Na+

channels close completely and the K+ influx decreases the 90mV, which thus overshoots the

resting membrane potential (-70mV). The process of 4, Fig - 4) is followed by a

hyperpolarization state (when the potential is < -70mV i.e., -). Again the continuous process of

the K+ and Na+ pump brings the potential back to -70mV ng membrane potential) (Step - 6, Fig - 4). Thus an

Action Potential is generated and the signal is transmitted.

The equations relating impulse propagation to the ion permeability changes were presented by Hodgkin and Huxley Theory (1952) by voltage clamp experiments for which they received Nobel Prize in Medicine (1963). The patch clamp technique allowed the study of single/ multiple ion channels in the cells, which was used to explain the flow (current) of ions and the fundamental cell processes such as action potential by Erwin Neher & Bert Sakmann in late 1970 who were awarded with Nobel Prize in Physiology and Medicine (1991) [3]. Hodgkin and Huxley used their results from the voltage clamp experiments to define sodium and

ing action potential [13] For example the conductivity of the sodium ion is given by;

– VNa

) gNa (2)

= Sodium Current Density;

V = Transmembrane Potential; = Sodium Nernst Potential.

(A similar equation can be obtained for potassium ion.)

These definitions are nevertheless arbitrary. Studies Hodgkin and Huxley explain that the

membranes respond to smaller electric signals. This explains propagation of an electric signal in an axon is similar to

the propagation of a signal in a cable as shown in Fig-5. This Resistance–Capacitance (RC) model,

landmark in medical science.




Figure 5: The Hodgkin Huxley Model Transmission

5. Impulse Conduction Movement of the action potential along a nerve cell is called as the impulse conduction. The impulses travel at a speed of anywhere from 1m/s to 120m/sand is influenced by the diameter of the fibre and the presence/absence of myelin sheath. Neurons with myelin (myelinated neurons) are fast in impulse conduction than those without myelin [6].

Figure 6 (a): Direction of Action Potential In a myelinated neuron, action potentials only occur along the nodes and therefore the impulses jump over the areas of myelin going from node to node and this is called as saltatory conduction of impulse (Latin saltate depicted in Fig 6 b.

Figure 6 (b): Saltatory Conduction of Nerve Impulse





The Hodgkin Huxley Model of Neural

Movement of the action potential along a nerve cell is called . The impulses travel at a speed of

and is influenced by the resence/absence of myelin

sheath. Neurons with myelin (myelinated neurons) are fast in impulse conduction than those without myelin [6].

Direction of Action Potential

action potentials only occur along the nodes and therefore the impulses jump over the areas of myelin going from node to node and this is called as

(Latin saltate – jump) as

Conduction of Nerve Impulse

Hermann von Helmholtz and Cremer in early 20developed cable theory for the neuronal fibres which was explained by modelling dendrites and axons as cylinders composed of segments with capacitances CRm combined in parallel with the resistance along the fibre Rdue to axoplasm as shown in Fig

Figure 7: Cable Theory of Neuronal Fibre Later in 1950 with improvement in technique, cable theory became important for analysing microelectrode recordings and for analysing the electrical properties of neuronal dendrites. 6. Synapse; Impulse Transmission at Synapse These are the junctions that occur between presynaptic neuron and dendrite or cell body of a postsynsynapse the end of the axon is referred to as synaptic knob, with a lot of synaptic vesicles in them that contain the neurotransmitters and mitochondria; hence the impulse is transmitted by the release of neurotransmitters. The neurotransmitters are of two types; eneurotransmitters which stimulate the postsynaptic membrane for example: neurotransmitters which inhibit transmission of an impulse for example: Gamma Amino Butyric Acid (GABA)[16], [17] The action potential travels down the presynaptic axon towards the synapse. This activates the voltage gated calcium (Ca) channels, leading to calcium influx that triggers of the neurotransmitter from the storage vesiclesreleased neurotransmitter diffuses across the synaptic cleft, binds to the postsynaptic receptors cause a physiological response inhibitory.

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Hermann von Helmholtz and Cremer in early 20th century developed cable theory for the neuronal fibres which was explained by modelling dendrites and axons as cylinders composed of segments with capacitances Cm and resistances

combined in parallel with the resistance along the fibre Rl Fig-7 [14].

Cable Theory of Neuronal Fibre

Later in 1950 with improvement in technique, cable theory became important for analysing data collected from microelectrode recordings and for analysing the electrical properties of neuronal dendrites.

Synapse; Impulse Transmission at Synapse

These are the junctions that occur between presynaptic neuron and dendrite or cell body of a postsynaptic neuron. At synapse the end of the axon is referred to as synaptic knob, with a lot of synaptic vesicles in them that contain the neurotransmitters and mitochondria; hence the impulse is transmitted by the release of neurotransmitters. The

itters are of two types; excitatory neurotransmitters which stimulate the postsynaptic membrane for example: Glutamate, and inhibitory neurotransmitters which inhibit transmission of an impulse

Gamma Amino Butyric Acid (GABA)[15],

travels down the presynaptic axon towards the synapse. This activates the voltage gated calcium (Ca) channels, leading to calcium influx that triggers release of the neurotransmitter from the storage vesicles. The

tter diffuses across the synaptic cleft, postsynaptic receptors and activates them, to

physiological response which may be excitatory or


International Journal of Science and Research (IJSR) ISSN (Online): 2319-7064




Figure 8: Impulse Transmission at Synapse

7. Conclusions Physics and Biology are intertwined, Erwin Schrödinger a quantum physicist, said that, “most of the biological phenomena's observe the thermodynamic laws of nature” [18]. We thus observe that the signal transmission in a nerve cell can also be explained by the laws of diffusion of ions. Knowledge of the molecular structure of the ion channels explain the occurrence of various genetic disorders affecting nerve conduction particularly the cardiac disorders [19]. Therefore, importance of the nerve conduction study is that it aids to diagnosis of many of the medical conditions such as Carpel Tunnel Syndrome, Cubital Tunnel Syndrome, Gullaine Barre Syndrome, Peripheral Neuropathy, Peroneal Neuropathy, Spinal Disc Herniation, Tarsal Tunnel Syndrome, and Ulnar neuropathy [20], [21]. Further, it has been proved that role of physics is important in the management of various neurological disorders. 8. Future Prospects This article is an effort to strengthen the understanding of relation between the principles of physics and neurobiology. Numerous efforts are being made in the field of Neurophysics. All these studies suggest that investigation and treatment of diseases such as; Alzheimer’s, Parkinsonism, Muscle atrophy, motor neuron disease etc… can be improved by further research in Neurophysics. The areas of further research can be as follows: • Application of external electrical stimuli in the paralysed

rats showed that the rats could walk and climb stairs. The same can be extended in the treatment of paralysed human beings [22].

• Wearable sensor network for health monitoring in Parkinsonism [24].

• Stem cell physics, multiple laser beam treatment of Parkinson disease [23].

• Use of complex realities of signal transduction in Alzheimer disease and in several nerve muscle conduction disorders [25].

• Understanding the organisation of brain matter in terms of sub-atomic particles (Quantum Mechanics) which may

help increase the capacity of the brain matter in memory and cognition [25].

• Laser regenerative medicine for the treatment of neurological diseases [23].

At this moment it seems long way to go before the

biophysics becomes a focused area of interdisciplinary research.

Figure 9: Paralysed rat walking and climbing the stairs

References

[1] Enger, Eldon D and Ross, Frederick. Concepts in

Biology, 10th Ed., McGraw-Hill, 2003 [2] http://people.eku.edu/ritchisong/301notes2.html

.Accessed on 25/09/2014 [3] Thomas Heimburg,” The Physics of Nerves”,

Biophysics, translation from: Physik Journal, 2009, 8 (3): 33-39

[4] Guyton and hall: Text book of Medical Physiology, 12th Ed, W. B. Saunders,p; 1016

[5] Ffrench-Constant, C., H.Colognato, and R.J.M. Franklin, Neuroscience: the mysteries of myelin unwrapped, 2004, Science, 304; 688-689

[6] Guyton and hall: Text book of Medical Physiology, 12th Ed, W. B. Saunders, P; 100-131

[7] http://www.kirbyresearch.com/index.cfm/wrap/textbook/microfluidicsnanofluidicsch 11.html.Accessed on 9/10/14

[8] ^Probstein R (1994)., Physicochemical Hydrodynamics [9] https://frank.itlab.us/datamodel/node95.html ,accessed

on 10/10/14 [10] T. C. Ruch and H. D. Patton, Physiology and

Biophysics, Saunders; Philadelphia, P. A. 1965; 19th Edition, Chapters 1, 43

[11] Kandel ER, Schwartz JH,Jessel TM: Principles of Neural Science, Ed 4, New York, 2000, Mc Graw Hill


International Journal of Science and Research (IJSR) ISSN (Online): 2319-7064




[12] http://hyperphysics.phy-astr.gsu.edu/hbase/biology/actpot.htmlKaXiongCharand., accessed on 25/09/2014

[13] Hodgkin, A. L., and A. F. Huxley. 1952. A quantitative description of membrane current and its application to conduction and excitation in nerve. J. Physiol. 117:500–544

[14] http://en.wikipedia.org/w/index.php?title=Cable_theory&oldid=620867466., accessed on 9/10/14

[15] Schikorski, T. And C.F.Stevens “Morphological correlates of functionally defined synaptic vesicle populations”, Nature Neuroscience, 2001, (4); 391-395

[16] Sigworth FJ, “Structural biology: life’s transistors”, Nature, 2003, (423); 21-22

[17] Guyton and hall: Text book of Medical Physiology, 12th Ed, W. B. Saunders, P; 1015-1042

[18] Schrödinger, E., 1944. What is life? Cambridge University Press

[19] Koch, Christof, and Klaus Hepp. "Quantum mechanics in the brain." Nature440.7084 (2006): 611-611

[20] Mark B.Bromberg and James W. Albers.”patterns of sensory nerve conduction abnormalities in demyelinating and axonal peripheral nerve disorders” Muscle & nerve, p,262-266

[21] Sandoval,AE.”Electrodiagnostics for low back pain”. Physical Medicine and rehabilitation clinics of North America 21 (4):767-776.doi:10.1016/j.pmr.2010.06.007

[22] Closed-loop neuromodulation of spinal sensorimotor circuits controls refined locomotion after complete spinal cord injury, SciTransl Med 24 September 2014: Vol. 6 no. 255 pp. 255ra133

[23] NEUROPHYSICS, STEM CELL PHYSICS, AND GENOMIC PHYSICS Beat-Wave-Driven-Free-Electron-Laser Beam Interactions with the Living Matter. By Alexander STEFAN - Google Books.

[24] M Pastorino, MT Arredondo, J Cancela and S Guillen; “Wearable sensor network for health monitoring: the case ofParkinson disease”, Journal of Physics: Conference Series, 2013;450, 012055.

[25] http://wavefunction.fieldofscience.com/2012/01/will-quantum-physics-help-us-cure.html., accessed on 9/10/14

Authors Profile

Raghottam M Sattigeri, a third year BSc (Hons) Physics student at The Maharaja Sayajirao University of Baroda, Vadodara, Gujarat. Who has been scoring 8.6 CGPA. He has received two Criterion Recognition Awards from NASA for his literary work in 2013. He is

interested in pursuing his research in the field of Solid State Physics and its applications to Biology, especially to Neuro-biology.


role of physics in nerve condution; ….pdfvalue is called depolarization. followed by which the k+...

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