Biophysics Lecture 1 PDF

BIOPHYSICS FOR PHYSICAL THERAPY STUDENTS PROF. DR. IBRAHIM HAGER  Contents Chapter 1: Electric and magnetic fields effect and therapy for muscles, joints and bones Chapter 2: Laser Therapy for Joints and Muscles Chapter 3: Ultrasound Therapy for J...

BIOPHYSICS FOR PHYSICAL THERAPY STUDENTS PROF. DR. IBRAHIM HAGER  Contents Chapter 1: Electric and magnetic fields effect and therapy for muscles, joints and bones Chapter 2: Laser Therapy for Joints and Muscles Chapter 3: Ultrasound Therapy for Joints and Muscles  Chapter 1 Electric and Magnetic Fields Effect and Therapy for Muscles, Joints and Bones Electricity Within The Body  Electricity plays an important role in medicine.  There are two aspects of electricity and magnetism in medicine:  1. Electrical and magnetic effects generated inside the body.  2. Applications of electricity and magnetism to the surface of the body.  The electricity generated inside the body serves for the control and operation of nerves, muscles, and organs.  Electric fields are an integral part of our daily lives, even though we may not always be aware of their presence.  These fields are generated by various sources, such as power lines, electrical appliances, and electronic devices.  One of the most common sources of electric fields in our environment is power lines.  These high voltage lines carry electricity from power plants to our homes and businesses.  As electricity flows through these lines, it creates an electric field around them.  Although the electric fields generated by power lines are relatively weak, they can still have an impact on our bodies. Electric Fields from Electrical Appliances  Electrical appliances, such as refrigerators, televisions, and computers, also generate electric fields.  These fields are produced by the flow of electricity within the appliances and can extend a short distance beyond them.  When we use these appliances, we are exposed to their electric fields However, the strength of these fields is generally much lower than that of power lines. Electric Fields from Electronic Devices  In today's digital age, electronic devices have become an integral part of our lives.  Devices such as smartphones, tablets, and laptops emit electric fields due to the electrical currents flowing through their circuits.  These fields are relatively weak compared to power lines and electrical appliances but can still have an impact on our bodies, especially when we use these devices for extended periods. - - Minimizing Exposure to Electric Fields  While the effects of electric fields on the human body are still being studied, it is advisable to take certain precautions to minimize exposure. Here are some safety guidelines to consider 1. Maintain Distance  When possible, maintain a safe distance from high voltage power lines and electrical substations.  The strength of electric fields decreases rapidly with distance, so keeping a reasonable distance can reduce your exposure. 2. Limit Device Usage  Limit the durtion of your exposure to electronic devices, especially when using them close to your body.  Take breaks and give your body time to rest from the electric fields emitted by these devices 3. Use Shielding  Consider using shielding materials, such as metal screens or special fabrics, to reduce your exposure to electric fields.  These materials can help block or redirect the electric fields away from your body. Effects of Electric Fields on the Human Body Electric Fields and Health  Electric fields can have both positive and negative effects on the human body, depending on various factors such as: 1. field strength 2. duration of exposure 3. human sensitivity Figure An external electric field causes an electrical charging of the body surface in humans and (in the case of an alternating field) very low internal body currents. The effects of the electric field are therefore generally limited to the body surface. Figure An external extremely low frequency magnetic field causes eddy currents in the human body. The field penetrates the body. The simplified figure shows the eddy currents of an alternating magnetic field perpendicular to the body axis. In healthy conditions the effects of induced fields and currents are not perceptible below the limit values of induced fields and currents in our everyday lives. 1. Direct Effects (rare) A) At low levels, electric fields have minimal direct effects on the human body. They do not cause any immediate harm or noticeable physiological changes. B) At extremely high levels, such as those experienced during electrical accidents or lightning strikes, electric fields can cause severe injuries, including burns, tissue damage, and even death. 2. Indirect Effects (more common)  While direct effects are rare, indirect effects of electric fields on the human body are more common.  These effects primarily occur through the interaction of electric fields with other environmental factors or the body's own electrical systems. Effects of Electric Fields on Cell Behavior  Electric fields have been found to affect different cell types involved in wound healing, including: 1. fibroblasts 2. keratinocytes 3. endothelial cells 1. Fibroblasts: play a crucial role in wound healing by :  producing extracellular matrix components  promoting tissue remodeling.  Electrical stimulation can: A) enhance fibroblast migration and proliferation. B) leading to accelerated wound closure. 2. Keratinocytes: are the primary cells responsible for (re-epithelialization): the process of forming a new epithelial layer over the wound  Electric fields can: A) stimulate keratinocyte migration and proliferation B) facilitating the re epithelialization process C) reducing the healing time 3. Endothelial cells are essential for (Angiogenesis): the formation of new blood vessels  Electric fields can: A) promote endothelial cell migration and tube formation B) facilitating the development of a functional vascular network in the wound bed. This enhanced angiogenesis, improves oxygen, and nutrient supply to the healing tissue, further promoting wound healing. - Electric Fields and the Nervous System  The nervous system is one of the most electrically sensitive systems in the human body.  Electric fields can influence the functioning of nerve cells and have various effects on the nervous system. 1) Sensory Perception Electric fields can affect sensory perception, altering the way we perceive touch, taste, and smell. Studies have shown that exposure to certain electric fields can enhance or diminish sensory perception, leading to: A) changes in sensitivity , B) the perception of phantom sensations. Figure Effect of alternating magnetic fields on people: they generate more or less pronounced eddy currents. Figure Magnetic Field around human body. Figure Proposed axial and longitudinal current flow generation within a neuron. Different from Current models which approximated the electric current flow through the neuron as a continual flow of ions through sodium, potassium and leak channels which is constant in time during an action potential, we propose an additional term of applied current to be added to each consecutive axonal segment. This axial current is a product of the continuous ion flow through the cell’s membrane and its transversal components and, with that, aids action potential propagation and attenuation. 2) Nerve Cell Excitation  Electric fields can also influence the excitation of nerve cells.  When exposed to an electric field, nerve cells may become more excitable, leading to increased firing rates and altered neural activity.  This effect has been utilized in medical applications such as deep brain stimulation for the treatment of neurological disorders like Parkinson's disease. Electric Fields and the Cardiovascular System  The cardiovascular system, which includes the heart and blood vessels, relies on electrical signals for proper functioning.  Electric fields can affect the cardiovascular system in various ways. 1) Heart Rhythm  Electric fields can influence the rhythm of the heart,  Exposure to certain electric fields can disrupt the normal electrical signals in the heart, leading to irregular heartbeats or arrhythmias  This effect is particularly significant in individuals with pre-existing heart conditions. 2) Cardiac Health  On the other hand, electric fields can also be used for therapeutic purposes in the cardiovascular system.  Electric stimulation techniques, such as cardiac pacing, can help regulate the heart's electrical activity and restore normal heart rhythm.  These techniques are commonly used in the treatment of cardiac arrhythmias and other heart related conditions. - - Electric Fields and Muscles  Muscles are another vital component of the human body that can be influenced by electric fields.  Electric fields can affect muscle contraction and have implications for muscle health and rehabilitation. 1) Muscle Contraction  Electric fields can stimulate muscle contractions.  This principle is utilized in various therapeutic techniques such as: A) transcutaneous electrical nerve stimulation (TENS) B) neuromuscular electrical stimulation (NMES)  These techniques involve the application of electric currents to specific muscles or nerve pathways to promote muscle activation, improve blood circulation, and aid in muscle recovery. 2) Muscle Rehabilitation  Electric stimulation techniques have proven to be effective in muscle Rehabilitation.  They can help prevent muscle atrophy, improve muscle strength and coordination, and facilitate the recovery process after injuries or surgeries.  These techniques are commonly used in physical therapy settings to enhance muscle function and promote overall rehabilitation. Electrical Stimulation of The Nervous System Figure: Electrodes touch a frog, and the legs twitch into the upward position. - Electric Fields and the Brain  The brain is a complex organ that depends on intricate electrical signaling for its functioning  Electric fields can influence brain activity and have implications for brain function and cognitive enhancement. Brain Stimulation  Electric fields can be used to stimulate specific regions of the brain: A. Transcranial electrical stimulation (TES) techniques B. transcranial direct current stimulation (TDCS) C. transcranial magnetic stimulation (TMS)  involve the application of electric currents or magnetic fields to the scalp to modulate brain activity  These techniques have shown promise in various applications, including the treatment of depression, pain management, and cognitive enhancement. - - - - Electric Signals in Neurons  Neurons communicate with each other through electrical signals called action potentials.  These action potentials are generated by the movement of ions across the neuron's cell membrane.  At rest, the inside of the neuron is negatively charged compared to the outside.  This difference in charge is maintained by the selective permeability of the cell membrane and the action of ion channels.  When a neuron receives a signal from another neuron, the permeability of its cell membrane changes, allowing positive ions, such as sodium (Na) and potassium (K) to flow in and out of the cell.  This movement of ions creates a temporary reversal of the charge across the cell membrane, known as depolarization.  If the depolarization reaches a certain threshold, an action potential is generated.  Once an action potential is initiated, it travels along the axon of the neuron, propagating the electrical signal.  At the end of the axon, the electrical signal is converted into a chemical signal, allowing the neuron to communicate with the next neuron or target cell through synapses. - - - - - - - Potential Effects of Electric Fields  However, some studies have suggested that exposure to high levels of electric fields may lead to certain health concerns include: 1. Skin Sensations  Some individuals may experience tingling or prickling sensations on their skin when exposed to strong electric fields.  This phenomenon, known as electro sensitivity is not well understood and is still a topic of debate among scientists. 2. Thermal Effects  Electric fields can generate heat when they interact with the body's tissues.  Prolonged exposure to high levels of electric fields may lead to localized heating, which can potentially cause burns or tissue damage.  However, it is important to note that the electric fields encountered in everyday life are typically too weak to cause significant thermal effects. - - Interference with Medical Devices  Strong electric fields can interfere with the proper functioning of certain medical devices, such as pacemakers and implantable cardioverter defibrillators (ICDS).  These devices rely on electrical signals to regulate the heart's rhythm (Pulses) and external electric fields can disrupt their operation  It is crucial for individuals with such medical devices to be cautious and avoid close proximity to strong electric fields. Electric Stimulation for Medical Purposes  Electric stimulation, also known as electrotherapy, is a medical technique that utilizes electric fields to stimulate various parts of the human body for therapeutic purposes  This non invasive procedure has been used for decades to treat a wide range of medical conditions and promote healing.  By applying controlled electrical currents to specific areas of the body, electric stimulation can have profound effects on the nervous system, muscles, and other bodily functions. How Electrical Stimulation Works  Electric stimulation works by delivering low level electrical currents to targeted areas of the body.  These currents are typically generated by a device called an electrical stimulator, which is designed to produce specific waveforms and frequencies.  The electrical stimulator is connected to electrodes, which are placed on the skin over the area to be treated.  When the electrical currents are applied, they interact with the body's own electrical signals, influencing the behavior of cells, tissues, and organs.  The electrical currents can modulate nerve activity, promote muscle contractions, increase blood flow, and stimulate the release of natural pain relieving materials. - - Applications of Electric Stimulation  Electric stimulation has a wide range of applications in the field of medicine.  It is commonly used in physical therapy, rehabilitation, and pain management.  Some of the specific medical purposes for which electric stimulation is utilized include: 1.Pain treatment  Electric stimulation can be an effective method for managing pain, particularly chronic pain Conditions.  By stimulating the nerves and altering pain signals, electric stimulation can: - provide relief from various types of pain, including musculoskeletal pain, neuropathic pain, - and postoperative pain It can also help reduce the need for pain medications, which can have unwanted side effects 2.Muscle Rehabilitation  Electric stimulation is frequently used in muscle rehabilitation programs to help restore muscle strength and function.  By stimulating the muscles, electric currents can promote muscle contractions and prevent muscle atrophy.  This is particularly beneficial for individuals who have experienced muscle weakness or loss of function due to injury, surgery, or neurological conditions. 3.Wound Healing  Electric stimulation has been shown to enhanace the healing process of wounds.  By increasing blood flow and promoting the production of growth factors, electric currents can accelerate tissue repair and regeneration  This can be especially beneficial for chronic wounds, such as diabetic ulcers, that are difficult to heal using conventional treatments. 4.Nerve Stimulation  Electric stimulation can be used to stimulate nerves and improve their function.  It is often employed in the treatment of conditions such as peripheral neuropathy, where the nerves in the extremities are damaged or dysfunctional.  By stimulating the affected nerves, electric currents can help alleviate symptoms such as numbness, tingling, and pain. Basic principle of electricity and electrical stimulation current