MI
Unit-8Basic components of Bio-Medical InstrumentsQ1) What is bio-electric potential?A1) Bioelectric potentials are generated at a cellular level and the source of these potentials is ionic in nature. A cell consists of an ionic conductor separated from the outside environment by a semipermeable membrane which acts as a selective ionic filter to the ions.The unequal charge distribution is a result of certain electrochemical reactions and processes occurring within the living cell and the potential measured is called the resting potential.A decrease in this resting membrane potential difference is called depolarization.
Figure 1. Potential WaveformRepolarization then takes place a short time later when the cell regains its normal state in which the inside of the membrane is again negative with respect to the outside. Repolarization is necessary in order to re-establish the resting potential.Q2) Explain the electrical activity associated with potential?A2) A typical cell potential waveform so recorded is shown in Figure.
Figure2 . Electrical activity associated with one contraction in a muscleThe wave of excitation while propagating in the muscle causes its contraction. The contraction wave always follows the excitation wave because of its lower velocity. This phenomenon is found with the skeletal muscles, the heart muscle and the smooth muscles.The cell action potential, therefore, shows a finite rise time and fall time. It may be noted that a cell may be caused to depolarize and then repolarize by subjecting the cell membrane to an ionic current. However, unless a stimulus above a certain minimum value is applied, the cell will not be depolarized and no action potential is generated. This value is known as the stimulus threshold. After a cell is stimulated, a finite period of time is required for the cell to return to its pre-stimulus state. This is because the energy associated with the action potential is developed from metabolic processes within the cell which take time for completion. This period is known as refractory period.Q3) What is the need for transducers?A3) A transducer is a device that converts a quantity from the measured object into an electrical signal. Biomedical transducers are transducers with specific uses in biomedical applications: physiological measurement, patient monitoring, health care. Measurement quantities: physical and chemical quantities that reflect the physiological functions in a living body. Examples: blood composition - determined from a sample extracted from the body real-time and continuous measurements - transducer is attached to the body.Q4) Explain recording and display devices?A4) In Bio Medical Instrumentation the transducer is a component which has a non- electrical variable as its input and an electrical signal as its output. To function properly one parameters of the electrical output signal in the form of voltages current frequency or pulse width must be non -ambiguous function of the non- electrical variables at the input. The relationship between input and output must be linear. A linear relationship is not possible always but the relationship between input and output should follow some rules like logarithmic function or square law. As long as the transduction function is nonambiguous it is possible to determine the magnitude of the input variable from the electrical output signal. There are two different principles used to convert nonelectrical variables into electrical signals. One of these is energy conversion transducer called active transducer. The other principle involves control of an excitation voltage or modulations of carrier signal. Transducers based on this principle are called passive transducers. Q5) Explain patient care and monitoring system?A5) Patient care Patient care is the focus of many clinical disciplines— medicine, nursing, pharmacy, nutrition, therapies such as respiratory, physical, and occupational, and others. Although the work of the various disciplines sometimes overlaps, each has its own primary focus, emphasis, and methods of care delivery. Each discipline’s work is complex, and collaboration among disciplines adds another level of complexity. In all disciplines, the quality of clinical decisions depends in part on the quality of information available to the decision-maker.The process of care begins with collecting data and assessing the patient’s current status in comparison to criteria or expectations of normality. Through cognitive processes specific to the discipline, diagnostic labels are applied, therapeutic goals are identified with timelines for evaluation, and therapeutic interventions are selected and implemented. At specified intervals, the patient is reassessed, the effectiveness of care is evaluated, and therapeutic goals and interventions are continued or adjusted as needed. If the reassessment shows that the patient no longer needs care, services are terminated.Q6) Write a short note on blood flow?A6) Some of the primary measurements are the concentration of O2 and other nutrients in the cells. Blood flow helps to understand basic physiological processes and example the dissolution of a medicine into the body. These are normally so difficult to measure therefore we force to use the second-class measurements of blood flow and changes in blood. If blood flow is difficult to measure the third-class measurement of blood pressure is used .If blood pressure cannot be measured, the physician may fall back on the fourth-class measurement of the ECG. Usually, the blood flow measurements are more invasive than blood pressure measurements. It also helps to understand many pathological conditions, since many diseases alter the blood flow. Also, the blood clots in the arterial system can be detected.
Figure 3. Blood FlowQ7) Write a short note on heart sounds?A7) Heart sounds are generated by blood flowing in and out of the heart’s chambers through the valves as they open and close. Listening to the heart sounds through a stethoscope (auscultation) is one of the first steps a physician takes in evaluating a patient’s medical condition.The heart is a muscular organ and has four chambers that receive and pump blood:The left atrium receives oxygenated blood from the lungs and pumps it into the left ventricle. The left ventricle pumps the oxygen-rich blood to the rest of the body through a network of arteries. The right atrium receives the oxygen-depleted blood from the body through veins and pumps it into the right ventricle. The right ventricle pumps the blood to the lungs for oxygenation. The left ventricle’s contractions while pumping out blood create the systolic blood pressure in the arteries. A web of nerve tissue runs through the heart to send electric signals to the heart muscle to initiate the heart’s contraction. These two phases constitute the heartbeat. In a healthy adult, the heart makes two sounds, commonly described as ‘lub’ and ‘dub.’ The third and fourth sounds may be heard in some healthy people, but can indicate impairment of the heart function. S1 and S2 are high-pitched and S3 and S4 are low-pitched sounds.First soundWhen the two ventricles contract and pump out blood into the aorta and pulmonary artery the mitral and tricuspid valves close to prevent the blood flowing back into the atria. The first sound S1 is generated by vibrations created by the closing of these two valves.Normally the mitral valve closes just before the tricuspid valve, and when the two different sounds are detectable, it is called a “split S1.” A split S1 may be indicative of certain conditions affecting the heart. Second soundAfter pumping the blood, the ventricles relax to receive blood from the atria, and the diastole phase starts. The aortic and pulmonic valves close and cause vibrations, giving rise to the second heart sound, S2. The increase in intensity of this sound may indicate certain conditions.When the aortic valve closes just before the pulmonic valve, it may generate a split S2. This may indicate impairment in the heart function.Third soundThe third heart sound is a low-pitched sound audible with the rapid rush of blood from the atrium into the ventricle as it starts relaxing. This may be a normal sound in some people but in people with heart conditions, S3 may indicate heart failure. Fourth soundThe fourth is a low-intensity sound heard just before S1 in the cardiac cycle. The sudden slowing of blood flow by the ventricle as the atrium contracts causes this sound, which may be a sign of heart disease.
Figure 4. Heart SoundsQ8) Explain nervous system?A8) The nervous system is one which is responsible for the task of controlling the various functions of the body & coordinating them into integrated living organisms. The basic unit of nervous system is the neuron. The neuron is the single cell with a cell body, sometimes called as soma, one or more input fibers called dendrites & a long transmitting fiber called as axon. The axon branches near its ending into two or more terminals
Figure 5. Nervous SystemThe portion of the axon immediately adjacent to the cell body is called axon hillock. This is the point at which the action potentials are usually generated. Branches that leave the main axon are often called collaterals. The axons & dendrites are coated with a fatty insulating substance called as myelin. The coating is called as myelin sheath. In some cases the myelin sheath is interrupted at rather intervals by the nodes of ranvier, which helps the speed of transmission of of information along the nerves. Outside of the central nervous system, the myelin sheath is surrounded by an insulating layer called as neurilemma. This layer is thinner than the myelin sheath & continuous over the nodes of ranvier, is made up of thin cells called Schwann cells. Both axons & dendrites are called as nerve fibers & a bundle of individual nerve fibber is called as nerve. Nerves that carry information from various parts of the body to the brain is called afferent nerves & that from brain to various parts of the body is called efferent nerves.Q9) Write a short note on ECG?A9)The recording of the electrical activity associated with the functioning of the heart is known as electrocardiogram. ECG is a quasi-periodical, rhythmically repeating signal synchronized by the function of the heart, which acts as a generator of bioelectric events. This generated signal is described by means of a simple electric dipole. The dipole generates a field vector, changing nearly periodically in time and space and its effects are measured on the surface.The waveforms recorded are standardized in terms of amplitude and phase relationships and any deviation from this would reflect the presence of an abnormality. Hence, it is important to understand the electrical activity and the associated mechanical sequences performed by the heart in providing the driving force for the circulation of blood. The heart has its own system for generating and conducting action potentials through a complex change of ionic concentration across the cell membrane. Located in the top right atrium near the entry of the vena cava, are a group of cells known as the sino-atrial node (SA node) that initiate the heart activity and act as the primary pace maker of the heart Figure. The SA node is 25 to 30 mm in length and 2 to 5 mm thick. It generates impulses at the normal rate of the heart.
Figure.6 The position of the sino-atrial node in the heart from where the impulse responsible for the electrical activity of the heart originatesQ10) Write a short note on action potential?A10) An action potential is a rapid rise and subsequent fall in voltage or membrane potential across a cellular membrane with a characteristic pattern. Sufficient current is required to initiate a voltage response in a cell membrane; if the current is insufficient to depolarize the membrane to the threshold level, an action potential will not fire. Examples of cells that signal via action potentials are neurons and muscle cells.
Figure 7. Action PotentialStimulus starts the rapid change in voltage or action potential. In patch-clamp mode, sufficient current must be administered to the cell in order to raise the voltage above the threshold voltage to start membrane depolarization. Depolarization is caused by a rapid rise in membrane potential opening of sodium channels in the cellular membrane, resulting in a large influx of sodium ions. Membrane Repolarization results from rapid sodium channel inactivation as well as a large efflux of potassium ions resulting from activated potassium channels. Hyperpolarization is a lowered membrane potential caused by the efflux of potassium ions and closing of the potassium channels. Resting state is when membrane potential returns to the resting voltage that occurred before the stimulus occurred.
|
|
|
|
| |
|
|
|
|
0 matching results found