EC2021-Medical Electronics Two Marks Questions With Answers

Anna University, Chennai

EC2021-Medical Electronics Year/semester:III/VI Department:ECE

Two Marks Q & A

1.Define cell.

A cell is the basic living unit of the body.

2.The entire body contains above 100 trillion cells.

3.) What is a tissue?

A group of cells of the same type is called tissue.

4. How energy is released for cell function?

In all cells, oxygen combines with carbohydrate, fat or protein to release the energy required for cell function.

5. Discuss briefly about cell.

Each cell consists of a centrally located nucleus (cell core) surrounded by the cytoplasm (cell body). The nucleus is separated from the cytoplasm by a nuclear membrane.

6. About 75 percent of cell is water.

7. The principle fluid medium of the cell is water.

8. What is protoplasm?

Different substances that make up the cell are collectively called protoplasm. It consists of water, electrolytes, proteins, lipids and carbohydrates.

9. The mitochondria organelles are called power houses of the cell.

10. What is DNA?

DNA is nothing but deoxyribonucleic acid (DNA) similar to that found in the nucleus. DNA is the basic substance of the nucleus that controls replication of the cell.

11. The structure which is present inside the nucleus is called nucleolus.

12. What is ECF?

Extra cellular fluid (ECF) is the fluid which lies outside the cell membrane.

13. What is ICF?

Intra cellular fluid (ICF) is the fluid which lies inside the cell membrane.

14What is active transport?

When a cell membrane moves molecules or ions uphill against a concentration gradient, then the process is known as active transport.

15. What is passive transport?

The transport of the substances through the cell membrane occurs by diffusion is called passive transport.

16. Define membrane potential.

The diffusion and drift processes give rise to membrane potential. The various ions seek a balance between the inside and outside of the cell by diffusion and drift.

17. Give the approximate value of the resting potential for living cell.

The approximate value of the resting potential for living cell is – 70mV.

18. What is the range of resting potential?

The resting potential ranges from -60 to -100nV.

19. List the characteristics of resting potential.

· The value of the resting potential is maintained as a constant until some kind of disturbance occurs.

· It is strongly depending on the temperature.

· Since the permabilities of the different cell types vary, the corresponding resting potentials vary.

20. When the cell is said to be polarized?

When the cell is in resting state, then it is said to be polarized.

21. Define depolarization.

The process of changing from the resting potential state to the action potential state is called depolarization.

22. State all-or nothing law.

Regardless of the method of excitation of cells or the intensity of the stimulus, which is assumed to greater than the threshold of stimulus. The action potential is always- the same for any given cell. This is known as all- or nothing law.

23. Define absolute refractory period.

Absolute refractory period is the time duration of the cell non response to further stimuli. It is about 1 millisecond in nerve cell.

24. Define relative refractory period.

Following the absolute refractory period there is a brief period of time during which another action potential can be triggered but a much stronger stimulation is required. This period is called relative refractory period.

25. Define conduction velocity.

The rate at which an action potential moves down a fiber of a nerve cell or is propagated from cell to cell is called the propagation rate or conduction velocity.

26.Give the range of nerve conduction speed.

The conduction velocity varies in nerves depending on the type and diameter of the fiber and is from 20 n/s to 140 m/s. But in heart muscle, it is very slower ranging from 0.2 to 0.4 m/s.

27. Define depolarization and repolarization.

When the cell fires however, the outside of the cell becomes momentarily negative with respect to the interior. A short time later, the cell regains the normal state in which the inside is again negative with respect to outside. The discharging and recharging of the cell is known as depolarization and repolarization.

28. A long is called axon.

29. The nerve cell with its dendrites and fiber is called neuron.

30. A connection between two excitable cells, in the form of a contact surface between two neurons is called synapse.

31. Discuss briefly about organ.

The organ of the body is composed of various tissues. The organ contains tissue that furnishes some mechanical strength and specialized tissue that gives a particular function. There are five sense organs of the body. They are eye, nose, ear, tongue and skin.

32. The skeleton consists of 206 bones.

33. The skeletal bone are completely enclosed by a membrane called periosteum.

34. At the top of the skeleton cranium skull is placed.

35. Define inspiration and expiration.

Breathing IN is called inspiration, and breathing OUT is called expiation.

36. The central nervous system is made up of brain and spinal cord.

37. The peripheral nervous system consists of all the nerves and group of neurons outside the brain and spinal cord.

38. Bio signal amplifier should be at least a differential amplifier.

39. List the conditions satisfied by a bio-signal amplifier.

· The gain and the frequency response should be more than 100 db. So as to amplify the bio-signal property to drive the recorder.

· It should have 10 W frequency response from d.c. to required frequency of the particular bio-signal.

· The gain and the frequency response should be uniform throughout the required bandwidth.

· The output impedance of the amplifier should be very small.

· The common mode rejection ratio(CNRR) should be at least a differential amplifier.

40. For what purpose isolation amplifier is used?

Isolation amplifier is used to increase the input impedance of the monitoring system in order to isolate the patient from the biomedical instrument.

41.Define noise figure.

The amount of degradation of the signal can be defined in terms of the noise figure. (nj) as defined as

Noise figure = signal to noise ratio at the input signal to the output signal.

42. For what purpose line driving amplifier is used?

Whenever a transducer has high impedance and its output voltage is so low and if want to couple this transducer output to a load having low impedance, we can use line driving amplifier.

43. Define CMRR.

The ability of the differential amplifier circuit to ignore common mode inputs like

50 HZ interference from mains is known as common mode rejection ratio. (CNRR).thus CMRR = amplification of the differential voltage amplification of the common mode voltage.

44. Define early receptor potential. (AU –June 06)

When light falls on the retina, the absorption of photons by photo pigments localized in the outer segment of the retina’s photoreceptors is taking place. This causes the change in the membrane potential. This in turn results in the development of action potential that is transmitted down the optic nerve. The first part “A”of the response to a brief flash light is due to early receptor potentials.

45. Define Later receptor potential (LRP).

The second component “B” with a delay of 1 to 5 milliseconds is due to the Later

receptor potential (LRP).

46. Define Electrooculogram.

A record of corneal- retinal potentials associated with eye movements is called electrooculogram.

47.Define Electroretinography(ERG).

The recording and interpreting the electrical activity of eye is called electrorectinography.

48. What is BRONCHOSPIROMETER?

A bronchospirometer is a dual Spirometer that measures the volumes and capacities of each lung individually. The air-input device is a double luman tube that divides for entry into the airway to each lung, and thus provides isolation for differential measurement. The main function of the bronchospirometer is preoperative evaluation of oxygen consumption of each lung.

49. Define pattern recognition.

Pattern recognition is the detection of specific waveforms by some means. Human beings are often more efficient at recognizing specific waveforms in the bio- signals than electronic analyzers designed for this purpose.

50. List the factors to be considered for designing medical instrument.

Accuracy, frequency response, hysteresis, isolation, linearity, sensitivity, signal- to- noise ratio, simplicity, stability and precision.

51. Define signal processor.

Signal processor is an important part of the instrument system which amplifies, modifies or changes the electrical output of the transducer in a suitable manner to run the recording or display ratio, simplicity, stability and precision.

52. What are electrodes?

Electrodes are devices which are employed to pick up the electrical signals of the body.

53. For what purpose electrode paste is used?

The dry outer skin of the body is highly non-conductive, and will not establish a good electrical contact with an electrode. The skin should therefore be washed thoroughly and rubbed briskly to remove some of the outer cells. This area should then be coated with an electrode paste. The purpose of the electrode paste is to make the skin electrically conductive.

54. List the types of electrodes.

There are three types of electrodes. They are

· Microelectrodes

· Depth electrodes

· Needle electrodes.

55. Discuss about microelectrodes.

Microelectrodes are used to measure the bioelectric potential near or within a single cell. These are also called as intracellular electrodes. They are divided into metallic and non-metallic electrodes.

56.For what purpose depth and needle electrodes are used?

Depth and needle electrodes are used to measure the bioelectric potential of the highly localized extra cellular regions in brain or bioelectrical potentials from a specific group of muscles.

.57. List the uses of surface electrodes.

Surface electrodes are used to measure the potentials available from the surface of the skin and are used to sense the potentials from heart, brain and nerves.

58. List the types of surface electrodes.

· Metal plate electrode

· Suction cup electrode

· Adhesive tape electrode

· Multipoint electrode

· Floating electrode.

59. Define electro pointing.

Electrically etching the tip of a fine tungsten or stainless steel wire to a fine point is known as electrpointing.

60. What is the major advantage of floating type skin surface electrodes?

Floating type skin surface electrodes eliminate movement artifact by avoiding any direct contact of the metal with skin.

61.Give the uses of silver-silver chloride electrode.

Silver-Silver chloride electrodes are used in bio-medical instrumentation.

62. Define half-cell potential.

Half cell potential is defined as the voltage developed at an electrode- electrolyte interface. It is also called as electrode potential.

63.Define electrocardiogram (ECG)

The electrocardiogram is a graphic recording or display of the time variant voltage display produced by myocardium during cardiac cycle.

64.Electrocardiography (ECG) deals with the study of electrical activity of heart muscles.

65.What is arrhythmia?

Arrhythmia is the disturbances in the heart rhythm.

66.What does the ECG reflect?

The ECG reflects the rhythmic electrical depolarization and repolarization of the myocardium (heart muscle) associated with contractions of the atria and ventricles.

67.Draw typical ECG waveform.

The EKG complex. P=P wave,

PR=PR interval, QRS=QRS complex, QT=QT interval, ST=ST segment,

T=T wave

68.List the types of electrodes systems for ECG lead configurations.

· Bipolar limb leads or standard leads

· Augmented unipolar limb leads

· Chest leads 9or) pericardial leads.

· Frank lead system (or) corrected orthogonal leads. Among these four systems, the first three are widely used.

69. How the leads taken in bipolar limb leads?

In standard leads, the potentials are tapped from 4 locations of our body. They are (i) right arm (ii) let arm (iii) right leg (iv)left leg. Usually the right leg electrode is acting as ground reference electrode.

70. List the colour codes used for identifying ECG potentials.

White –right arm Black – left arm Green – right leg Red – Left leg. Brown- chest.

71. the graphic record of the heart sounds is called Phonogram.

72. Define phonocardiograph.

Phonocardiogram is an instrument used to measure the heart sounds. The basic aim of phonocardiograph is to pick up the different heart sounds, filter out the heart sounds and to display them or record them.

73.Define heart sounds.

Heart sounds are acoustic phenomena resulting from the vibrations of cardiac structures.

74.List the classifications of heart sounds.

Heart sounds are classified into four group on the basis of their mechanism of origin. They are

· Valve closure sounds

· Ventricular filling sounds

· Valve opening sounds

· Extra cardiac sounds.

75. Acoustic events of the heart can be divided into two categories as heart sounds and murmurs.

76. How the heart sounds and murmurs characterized?

Heart sounds and murmurs are usually characterized by three physical properties. They are

· Frequency

· Amplitude

· Quality

77.List the three augmented lead connections.

The three augmented lead connections are

· Augmented voltage right arm (aVR)

· Augmented voltage left arm (VL)

· Augmented voltage foot (aVF).

78. Were we are using frank lead system?

The corrected orthogonal leads system (or) frank lead system is used in vector cardiography.

79. How many lead selections are required for electrocardiograms?

Twelve lead selections are required to record the electrocardiogram. i.e. 3 standard bipolar leads, 3 augmented leads and 6 chest leads.

80. List the practical considerations for ECG recording.

Artifacts, wandering of base line, solid base line, frequency response.

81.Define heart murmurs.

Heart murmurs are sounds related to non-laminar flow of blood in the heart and great vessels.

82.Give the origin of heart sounds.

There are four basic separate heart sounds that occur during the sequence of one complete cycle.

First heart sound: it is produced by the sudden closure of the mitral and tricuspid valves associated with myocardial contraction.

Second heart sound : it is due to the vibration set up by the closure of semilunar valves. i.e. the closure of arotic and pulmonary valves.

Third heart sound : It arises as the ventricles relax and the internal pressure drops below the pressure in the atrium.

Fourth heart sound : it is also called an atrial sound. It is caused by an accelerated flow

of blood into ventricles or due to atrial contraction.

83.List the conditions that causes turbulence in blood flow.

· Local obstructions to the blood flow

· Abrupt changes n the diameter of the blood stream.

· Pathologic communications in the cardio vascular system.

· Ruptured cardiac structures

· Valve insuffiency

84. For what purpose condenser microscope is used in ECG recording set up?

The condenser microscope is used for conversion of the heart sounds into electrical signals.

85.List the special applications of phonocardiogram.

· Fetal phonocardiogram

· Esophagear phonocardiogram.

· Tracheal phonocardiogram.

86.Define echocardiography.

Echocardiography is also a useful technique for diagnosis of heart diseases. Echocardiogram displays the time verses motion information about the intra cardiac structures on slow speeds.

87.What is vectrocardiography?

In the case of electrocardiography, only the voltage is generated by the electrical activity of the heart is recorded. But in vectrocardiography, the cardiac vector is displayed along with its magnitude and spatial orentaion.

88. What is EEG?

The abbreviation of electroencephalograph is called EEG. It deals with the recording and study of electrical activity of the brain.

89. How EEG is recorded?

By means of electrode attracted to the skull of a patient the brain waves can be picked up and recorded.

90. What are brain waves?

The brain waves are the summation of neural depolarization in the brain due to stimuli from the five senses as well as from the thought process.

91. What are graded potentials?

Graded potentials are variations around the average value of the resting potential. Thus the EEG potentials originate with in the dendrite.

92 Define inhibitory post synaptic potential (IPSP).

If the transmitter substance in inhibitory, the membrane potential of the receptor neuron increases in a negative direction. So that it is less likely to discharge, this induced potential change is called inhibitory post synaptic potential.

93. Define excitory post synaptic potential(EPSP).

If the transmitter substance is excitatory, the receptor membrane potential increases in a positive direction. So that the receptor neuron is more likely to discharge and produces a spike potential. This induced change is called excitory post synaptic potential(EPSP).

94.What are Evoked potentials?

Evoked potentials are the potentials developed in the brain as the responses to external stimuli like light, sound etc. the external stimuli is detected by the sense organs, which cause changes in the electrical activity of the brain. Nowadays the term event related potential has been used instead of evoked potential.

95. List the parts of the brain.

The brain consists of three parts, such as cerebrum, cerebellum and the brain stem..

96. Give the classifications of the brain waves.

Brain waves are classified into our types. They are

· Alpha wave

· Beta wave

· Theta wave

· Delta wave

97. How many electrodes are used in modern EEG unit?

12 electrodes are used in modern EEG unit.

98. How the EEG can be recorded?

EEG may be recorded by picking up voltage difference between an active electrode on the scalp with respect to a reference electrode on the ear lobe or other part of the body. This type o recording is called monopolar recording.

99.What are brain tumors?

The tumor displaces, the cortex, and if it is large enough, the electrical activity will be absent in that part of hemisphere, since no electric potentials originate in the tumor itself. Thus a extinguished or damped EEG over a certain part of cortex can thus be due to brain tumor.

100. Define Epilepsy.

Epilepsy is a system for brain damage. This may be due to defects in the birth delivery or head injury during accident or boxing. It may also be due to brain tumor.

101. In what way EEG helps physicians?

EEG helps physicians to diagnose the level of consciousness, sleep disorders brain death, brain tumors, epilepsy and multiple sclerosis.

102.What is EMG?

EMG- electromyography is the science of recording and interpreting the electrical

activity of muscle’s action potentials.

103.How EMG is recorded?

EMG is usually recorded by using surface electrodes or more often needle electrodes may be disposable adhesive types or the ones which can be used repeatedly.

104. List the diseases which affect the steady potential of the eye.

· The effects of certain drugs on the eye movement system can be determined.

· The state of semicircular canalizes analyzed by EOG.

· Diagnosis of the neurological disorders may be possible.

· The level of anesthesia can be indicated by characteristic eye movements.

105. Discuss about the electrodes for offline analysis.

The online recorders are directly connected with the input. Therefore one can get the live recording at the spot itself. In the case of off-line analysis, the input equipment system is used to prepare data for further analysis using computers which may be located at the same location of the input or remote.

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107. Define PH. How it is related with blood?

The PH is defined as the logarithm of the reciprocal of W ion concentration.

i.e. PH = log10 (1/W) = - log10 (W)

the chemical balance of the body is identified by the measurement of PH of blood and other body fluids.

108.The PH. value of venous blood is about 7.35. and for atrial blood it is about 7.40.

109.The glass electrode is normally used as PH. electrode.

110.For what purpose chemical electrodes are used?

Chemical electrodes are generally used to measure PH and PO2 of the blood. They are also used to determine the oxygen tension or carbon dioxide tension in the

blood.

111.The hydrogen electrode is also called a reference electrode.

112.For what purpose silver-silver chloride is used?

The silver – silver chloride is used as a reference electrode due to its smaller and stable half cell potential.

113.Define electrophoresis.

Electrophoresis is a method for separating and analyzing macromolecular substances such as plasma proteins. The method is based on the fact that, the molecules carry electric charges and therefore migrate in a electric field.

114.In the electrophoresis, macromolecular substances are analyzed by determining their

migration velocity.

115.Discuss about PCO2 electrode.

It consists of a standard glass pH electrode covered with the rubber membrane

permeable to CO2, between the glass surface and membrane; there is a thin film of

water. The solution under test which contains dissolved CO2 is presented to the outer surface of the rubber membrane. After equilibrium, pH of the aqueous film is measured by the glass electrode and interpreted log PCO2 and pH of the solution.

116.. For what purpose PO2 electrode is used?

PO2 electrode is used to determine the oxygen tension in the blood. It is a piece of platinum wire embedded in an insulating glass holder with the end of wire

exposed to the electrolyte into which the oxygen from the solution under measurement is allowed to diffuse through the membrane.

117. Discuss about blood cells.

The blood cells have important functions in our body. The red blood cell is used for the transport of oxygen and carbon dioxide. The white blood cells are part of the body’s defense against infections and foreign substances. The platelet are involved in the clotting of blood.

118. Give the changes in the hemoglobin content of red blood cells.

When the body produces too many red blood cells, the amount of hemoglobin in the blood increases, and a chronic disease called polycythemia or dehydration is produced. When the hemoglobin in the blood decreases, anemia is produced.

119. Define cardiac output.

Cardiac output is the amount of blood delivered by the heart to the arota per minute.

120. For what purpose colorimeters and photometers are used?

Colorimeters and photometers are used to measure he transmitted and absorbed light as it passes through a sample.

121. What is SEN?

The SEN is scanning microscope. The SEN is recently developed electron microscope. Here the image is built up by using an electron probe of very small diameter which scans the specimen surface in parallel straight lines as does a television camera.

122. In what way the composition of blood sample is determined?

The composition of blood serum is determined by specialized chemical techniques. The different components of biological substances can e determined by measuring how they either absorb or emit visible light.

123. Define transmittance and absorbance.

The transmittance is defined as the ratio of transmitted light intensity to the incident light intensity.

124. For what purpose flame photometer is used?

Flame photometer is used to analyze urine or blood in order to determine the concentration of potassium (K), sodium (Na), calcium (Ca), and lithium (Li).

125. What is flame photometer?

By measuring optical density or absorbance A, the concentration of given substance in the sample can be determined. Colorimeters can be in the filter photometer or spectrophotometer. When an interference filter is used to select a given wavelength, it is called filter photometer.

126. In what way cardiac output is used?

Using implanted electromagnetic fine probe on the arota, we can find the cardiac output per minute directly by multiplying the stroke volume with the heart beat rate per minute.

127. Define stroke volume.

Stroke volume is defined as the amount of blood that is ejected during each heart beat.

Stroke volume = Cardiac output / number of beats/ min.

128. Define total lung capacity.

Total lung capacity (TLC) is the amount of gas contained in the lungs at the end of maximal inspiration. It is the sum of vital capacity and residual volume.

129. Define vital capacity.

The vital capacity (VC) is the maximum volume of gas that can be expelled from the lungs after a maximal inspiration.

130. Define residual volume.

The residual volume is the volume of gas remaining in the lungs at the end of a maximal expiration.

131. Define inspiratory reserve volume (IRV).

It is the extra volume of gas that can be inspired with maximal effort after reaching the normal end of inspiratory level.

132. Define expiratory reserve volume(ERV).

It is the extra volume of gas that can be expired with maximum effort beyond reaching the normal end of expiratory level.

133. Define mean velocity of blood.

Mean velocity = blood flow through a vessel cross sectional area of the vessel.

134. Define mean circulation time.

Mean circulation time is defined as the total amount of blood in the circulation divided by the cardiac output.

135. For what purpose Spirometer is used?

Spirometer is mainly used to measure the respiratory volume measurement.

136. Define pneumotachograph.

Pneumotachograph is an instrument to measure the patient’s air flow rate during

respiration and vital air capacity of the lung.

137. Give the uses of gas analyzers.

Gas analyzers are used to determine the quantitative composition of inspired and expired gas to assess the lung function.

138. Define systole.

Systole is defined as the period of contraction of the heart muscles, specifically the ventricular muscle at which time blood is pumped into pulmonary artery and the aorta.

139. Define diastole.

Diastole is defined as the period of dilation of the heart cavities as they fill with blood.

140. Give the uses of blood flow meters.

Blood flow meters are used to monitor the blood flow in various blood vessels and to measure caridiac output.

141.Name three methods to obtain the direct measurement of blood pressure.

· Percutaneous insertion

· Catheterization

· Implantation of a transducer.

142. Normal diastolic pressure ranges from 60 to 90 mmHg.

143. What is the range of systolic blood pressure in the normal adult?

95 to 140 mmHg.

144. When does heart block occurs?

Heart block occurs when the internal electro conduction system of heart is interrupted.

145. What are tachycardia and bradycardia?

The human hear rate varies normally over a range of 60 to 110 BPM. Rate faster than 110 BPM is called tachycardia. Heart rate slower than 60 BPM is called bradycardia.

146. For what purpose pacemaker is used?

Pacemaker is an electrical pulse generator for starting and for maintaining the normal heart beat.

147. How the heart muscle can be stimulated?

Like all the muscle tissues, the heart muscle can be stimulated with an electric shock. The minimum energy required to excite the heart muscle is about 10 joules.

148. List the methods of stimulating the heart muscles.

There are two types of stimulation or pacing. External stimulation and internal stimulation.

149. For what purpose external stimulation and internal stimulation are employed?

External stimulation is employed to restart the normal rhythm of the heart in the case of cardiac standstill. Internal stimulation is employed in cases requiring long term pacing because of permanent damage that prevents normal self triggering of the heart.

150. List the modes of operation of pacemakers.

Based on the modes of operation of the pacemakers, they can be divided into five types. They are:

· Ventricular asynchronous pacemaker(fixed rate pacemaker)

· Ventricular synchronous pacemaker.

· Ventridefibrillator inhibited pacemaker (demand pacemaker)

· Atrial synchronous pacemaker.

· Atrial sequential ventricular inhibited pacemaker.

151. The other name for asynchronous pacing is competitive pacing.

152. Based on the placement of the pacemaker, how we are classifying it?

Based on the placement of the pacemaker, there are two types as external pacemaker and internal pacemaker.

153. Compare external pacemaker and internal pacemaker.

External pacemaker	Internal pacemaker
It does not necessitate open heart surgery	The pacemaker is surgically implanted beneath
The skin near the chest or abdomen with its output leads are connected directly to he heart muscle	It requires open chest minor surgery to place the circuit
These are used for temporary heart irregularities. There is no safety or pacemaker.	These are used for permanent heart damages. There is cent percent safety for circuit from external disturbances

154. What is fibrillation? What are the types of fibrillation?

The condition at which the necessary synchronizing action of the heart is lost is known as fibrillation.

types of fibrillation are : 1. Atrial fibrillation and ventricular fibrillation.

155.What are the various electrodes used for defibrillation?

Internal(spoon shaped) electrodes and external (paddle shaped) electrodes are used for defibrillation.

156. What is counter shock?

The phenomenon of application of an electrical shock to resynchronize the heart is known as counter shock.

157. What is IPP?

IPP means intermittent positive pressure.

Positive pressure ventilators are used to inflate the lungs with IPP.

158. What is meant by monophasic waveform?

Monophasic means most of the excursion of curve is above the base line.

159. What is the need for ventilator?

It is used to provide artificial respiration. Artificial respiration should be applied to the patient, whenever respiration is suspended due to reasons like gas poisoning, electric shock etc.

160. What is meant by defibrillation?

Ventricular fibrillation can be converted into a more efficient rhythm by applying a high energy shock to the heart. This sudden surge across the heart causes all muscle fibers to contract simultaneously. The fibres may then respond to normal physicological pace making pulses. the instrument administering the shock is known as defibrillator. This process is known as defibrillation.

161. What is the need for pre-amplifier?

Isolation amplifiers are used as pre-amplifiers. It is used to increase the input impedance of the monitoring system, so that the stray currents can be reduced. The isolation amplifiers are used in ECG measurement.

162. What is the need for earthing of medical instruments?

Grounding is needed in medical equipments to avoid the macro and micro shocks. The leakage current is also reduced by proper grounding.

163. What is diathermy? List its types.

Diathermy is the treatment process by which cutting, coagulation of tissues are obtained. Its various types are:

· Shortwave diathermy.

· Microwave diathermy

· Ultrasonic diathermy.

· Ultrasonic diathermy.

164. Distinguish between microshock and macroshock.

A physiological response to a current applied to the surface of the body that produces unwanted stimulation like tissue injury or muscle contractions is called as macro shock.

A physiological response to a current applied to the surface of the heart that results in unnecessary stimulation like muscle contractions or tissue injury is called as microshock.

165. What is a defibrillator? State its use.

The condition of heart at which the necessary synchronism is lost is known as fibrillation. Defibrillation is the application of an electric shock to the area of the heart. that is, it is an electronic device that creates a sustained myocardial depolarization of a patient’s heart in order to stop ventricular fibrillation and atrial fibrillation.

166. What is angiography?

Angiogram: It is a special- x-ray imaging technique through which high contrast can be obtained. The outlines of the blood vessels also visible in angiogram.

167. State the principle by which body organs could be visualized by radioisotope method.

The body organs could be visualized in X-ray by using the principle of energy absorption. Two types of radiations are used.

168. Name the principal ions involved in the phenomena of producing cell potentials.

Sodium and potassium ions.

169.Why glass electrode is very much preferred as active electrode in a pH meter?

The glass electrode provides a membrane interface for H+ ions. so that, it is preferred as an active electrode in pH measurement. The pH meter with hydroscopic glass observes the water readily and provides best pH value.

170. Name the four physical principles based on which blood flow meters are constructed.

The blood flow meter is constructed based on the following principles:

· Electromagnetic induction.

· Ultrasonic principle (Transmit type, Doppler type)

· Thermal convection

· Radiograpic principle

· Indicated dilution principle.

171. Distinguish radiographic and fluoroscopic techniques.

Radiography	Fluoroscopy
The patient dose is very low.	The patient dose is very high.
Wide range of contrast can be obtained.	Less contrast and it can be improved by introducing electromagnetic intensifier.
High resolution in images can be obtained.	Fair resolution in images can be obtained.
Permanent record is available.	Permanent record can be made by inserting video tape-recorder,
X- ray images developed by photographic or photosensitive film.	X-ray images developed by fluorescent principle and photoelectric effect on the fluorescent screen.
Patient is not exposed to X-rays during examination of the X-ray image.	Patient is exposed to x-ray during examination.
Efficient is more.	Efficient is less in direct fluoroscopy but it can be increased by using the modern television system.
The image can be obtained after developing the film and examination cannot be made before developing the film.	Immediately the image can be seen and examination can be finished within short time.
Movement of organs cannot be observed.	Movement of organs can be observed.

172. Define cardiac output.

Cardiac output is the amount of blood delivered by the heart to the aorta per minute. for normal adult, the cardiac output is 4-6 litres/min. The measurement of cardiac output is due to low blood pressure, reduced tissue oxygenationnnn, poor renal function, shock and acidosis.

173. What is the pH value of arterial blood and venous blood?

pH value of venous blood = 7.35 pH value of arterial blood = 7.40

174. What is the use of biphasic D.C. defibrillator?

It is used to correct the fibrillation effectively.

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