Module 1 of BioMedical Engineering, MG University Kerala

1. MODULE 1-TOPICS
 BIOMETRICS
 CHARACTERISTICS OF BIOMEDICAL INSTRUMENTS
 PHYSIOLOGICAL SYSTEMS OF HUMAN BODY
 BIOCHEMICAL SYSTEM
 CARDIOVASCULAR SYSTEM- The Heart
 RESPIRATORY SYSTEM
 NERVOUS SYSTEM
 THE KIDNEY
 BIOELECTRIC POTENTIALS
 BIO-POTENTIAL ELECTRODES
 TRANSDUCERS- ECG, EEG, EMG

2. INTRODUCTION
 Concept of biomedical engineering
 Biometrics:- Science deals with the study of
measurements of physiological systems of the body
 Physiology:- Study of the normal functionality of the
human body organ
 Biomedical Instrumentation:- Provides the set of
equipments or tools required for the measurement
of physiological variables.

3. CHARACTERISTICS OF BIOMEDICAL
INSTRUMENTATION SYSTEM
 Range:- Should have minimum to maximum range
 Sensitivity:- Ability of instrument to measure small variations
accurately. Should not be too high or too low.
 Linearity:- Output should be steady or linear with respect to input.
 Hysteresis:- Should be minimum
 Frequency Response
 Accuracy:- True reading-Actual reading. Should be high

4. CHARACTERISTICS OF BIOMEDICAL
INSTRUMENTATION SYSTEM
 Signal-to-Noise Ratio:- Noise content should be low.
S/N ratio should be very high.
 Stability
 Isolation
 Simplicity

5. PHYSIOLOGICAL SYSTEMS OF
HUMAN BODY
 BIOCHEMICAL SYSTEM
 CARDIOVASCULAR SYSTEM
 RESPIRATORY SYSTEM
 NERVOUS SYSTEM

6. CARDIOVASCULAR SYSTEM
 Closed complex hydraulic system with a four-
chambered pump connected to flexible tubular
structures(blood vessels).
 Main functions:
 Transportation
 Blood purification
 Structural details:
 Two parts( right & left)
 Each part has two chambers
• Atrium(Auricle)
• Ventricle

7. CARDIOVASCULAR SYSTEM
 Heart wall has three layers:
 Pericardium:-
• Moist
 Myocardium:-
• Main muscle
• Short cylindrical fibers
• Automatic in action
 Endocardium:-
• Smooth lining

8. CARDIOVASCULAR SYSTEM- THE HEART

9. CARDIOVASCULAR SYSTEM
 It has four valves:-
 Tricuspid valve or right atrio-ventricular valve
 Bicuspid mitral valve or left atrio-ventricular valve
 Pulmonary valve or semilunar valve
 Aortic valve
o All these valves are unidirectional
o Provides synchronous operation

10. CARDIOVASCULAR SYSTEM
 2 types of blood circulation
 Pulmonary circulation
 Right ventricle Pulmonary artery Lungs
 Lungs Pulmonary veins Left atrium
 Systemic circulation
 Left atrium Left ventricle Aorta Arteries
(Exchange of gases)
 Veins Superior/Inferior venacavae Right atrium
Right ventricle

11. CARDIOVASCULAR SYSTEM - CIRCULATORY SYTEM

12. RESPIRATORY SYSTEM

13. RESPIRATORY SYSTEM
 The respiratory system is the structure in the
human body which allows us to breathe. It brings
oxygen into our body and removes carbon dioxide
out of our body.
 The respiratory system is made up of 5 main parts:
 1. Nose
 2. Mouth
 3. Trachea (windpipe)
 4. Lungs
 5. Diaphragm

14. RESPIRATORY SYSTEM

15. RESPIRATORY SYSTEM
 Includes
 Nostrils- opening of nasal cavity
 Mouth- alternate vent
 Pharynx- muscular tube
 Larynx- vocal cords
 Trachea- wind pipe through which air passes
 Bronchus- tube like structure at the end of trachea
 Lungs- main organ, bag like structure
 Diaphragm- controls the inspiration and expiration by
relaxation and contraction

16. RESPIRATORY SYSTEM
o The lungs are made up of 3 main parts:
• Bronchus (right & left)
• Bronchioles
• Alveoli

17. TERMS RELATED TO RESPIRATORY SYSTEM
 Tidal volume- volume of air inspired and expired during each
normal breathe
 Inspiratory reserve volume- additional volume that can be
inspired after a normal inspiration
 Expiratory reserve volume- additional volume that can be
expired after a normal expiration
 Residual volume-amount of air remaining in the lungs after all
possible air has been forced out.
 Vital capacity- sum of TV,IRV and ERV

18. KIDNEY
 Main function- remove the residue from blood
plasma. It also maintains acid-base balance
 It involves 2 processes
 Removal of waste products from blood plasma
 Regulation of the composition of blood plasma
 Situated at the back of the abdominal cavity and
just below the diaphragm

20. KIDNEY

21. KIDNEY
 Filtration system
 Main organs involved kidney(two bean-shaped
organs), ureter, bladder, urethra.
 Small individual units- nephrons
 Main parts- glomerulus and tubule
 Three main operations
• Filtration- glomerulus
• Secretion
• Reabsorption tubule

22. STRUCTURE OF NEPHRON

23. NERVOUS SYSTEM

24. NERVOUS SYSTEM
 Controls and co-ordinates all the functions of
human body
Nervous system
Central Peripheral Autonomous
• Brain (all the nerves) (part of PNS)
• Spinal cord
o Brain-cerebrum, cerebellum, brain stem

25. NERVOUS SYSTEM
 cerebrum
• Frontal
• Temporal
• Occipital
• Parietal
o cerebellum:- muscular activities
 Brain stem:- thalamus, hypothalamus, medulla
oblangata

26. NERVOUS SYSTEM
 Spinal Cord
• Runs through vertebral column
• Nerve cells connected to it.
• Decision without thinking
 Peripheral Nervous System
• Sensory nerves-brings sensory info into the CNS
• Motor nerves-control the motor functions of muscles
 Autonomous Nervous System
• Part of PNS
• Involved in emotional responses and controls smooth
muscles in various parts of the body
• controls heart rate, respiration rate, salivation,
perspiration…

27. BIOELECTRIC POTENTIAL
 Bioelectric potential?
 Resting Potential?
 Polarized state of a cell?
 Action Potential?
 Depolarized state of a cell?
 Depolarization & Repolarization?
 Terms related to ionic potential of a cell?
• Net height of the action potential
• Absolute refractory period
• Relative refractive period

28. BIOELECTRIC POTENTIAL
 Bioelectric potential
 Certain systems of the body generate their on monitoring
signals which convey useful information about the functions
they represent.
 These signals are bioelectric potentials associated with
nerve conduction, brain activity, heartbeat, muscle activity and
so on.
 So, bioelectric potentials are actually ionic voltages produced
as a result of the electrochemical activity of certain special
types of cells.
 Through the use of transducers capable of converting
ionic potentials into electric voltages, these natural monitoring
signals can be measured and results displayed in a
meaningful way to aid the physician in his diagnosis and
treatment of various diseases.

29. RESTING POTENTIAL

30. ACTION POTENTIAL

31. ACTION POTENTIAL

32. BIOELECTRIC POTENTIAL

33. EQUIVALENT CIRCUIT OF BIOPOTENTIAL
ELECTRODE INTERFACE

34. EQUIVALENT CIRCUIT OF BIOPOTENTIAL
ELECTRODE INTERFACE

35. CLASSIFICATION OF ELECTRODES
 Micro electrodes- to measure potential within a cell
or near the cell.
 Metal Microelectrodes- are formed by electrolytically
etching the tip of a fine tungsten or stainless steel wire
to the desired size.
 Micropipette Electrodes- here, a glass micropipette with
the tip drawn out to the desired size (usually 1 micron)
contains an electrolyte compatible with the cellular
fluids.

36. CLASSIFICATION OF ELECTRODES
 Skin surface or body surface electrodes- mainly for
ECG, EEG and EMG
 Immersion electrodes
 Floating type electrodes-with conductive path between
metal and skin being electrolyte paste or jelly
 Various Spray-on-electrodes and disposable electrodes
are available
 Ear clip electrode for EEG
 Scalp surface electrode for EEG

37. CLASSIFICATION OF ELECTRODES
 Needle electrodes:-
 Used to penetrate the skin to record the EEG potentials
or EMG potentials of a group of muscles.
 They reduce interface impedance
 A single wire inside the needle serves as a unipolar
electrode which measures the potential at the point of
contact with respect to some reference.
 Some of the needle electrodes are
• Concentric needle electrodes
• Bipolar needle electrodes
• Monopolar needle electrodes

38. TRANSDUCERS FOR BIO MEDICAL
APPLICATIONS
PHYSICAL VARIABLE TYPE OF TRANSDUCER
 Force (or Pressure) Piezoelectric
Unbonded strain gauge
 Displacement Variable resistance, ind, cap
Variable inductance
Variable capacitance
LVDT
Mercury strain gauge
 Surface strain Strain gauge
 Velocity Magnetic induction
 Temperature Thermocouple, Thermistor
 Light Photovoltaic, Photoresistive
 Magnetic field Hall effect

39. TRANSDUCERS FOR BIO MEDICAL
APPLICATIONS
 In medical applications, the basic
physiological variables are first
transformed into one of the physical
variables listed before. Examples
would be measurement of blood
pressure using strain gauges and
blood flow by magnetic induction.

40. ECG TRANSDUCER(RECORDING SET UP)

41. BLOCK DIAGRAM OF AN ECG MACHINE

42. ECG TRANSDUCER(RECORDING SET UP)
 Defibrillation and protection circuit:-
 Patient is connected to this circuit through different
connecting cables.
 Contains buffer amplifier and over voltage protection
circuit.
 Over voltage occur when ECG is used in conjunction
with the radiofrequency diathermy units.
 Over voltage protection circuit includes resistors and
neon lamps so as to avoid the entrance of excess of
voltage.
 Lead Selector Switch:-
 Used to feed the input voltage from the appropriate
electrode to the preamplifier.

43. ECG TRANSDUCER(RECORDING SET UP)
 Calibrator:-
 Push button closed, standardization of 1mV is
introduced to pre amplifier.
 BioAmplifier:-
 Consists of a pre amplifier, power amplifier
 Auxiliary Amplifier(CM Reduction Amplifier):-
 To reduce interference
 Isolated Power supply:-
 To power the bio amplifier
 Output unit:-
 Cathode Ray Oscilloscope or a paper chart recorder

44. ECG WAVEFORM

45. ECG WAVEFORM
 Electrocardiography
 Electrocardiogram-waveform
 Electrocardiograph- instrument
 Waveform Details:-
 P wave
 R wave(QRS complex)
 T wave
 S-T interval
 U wave

46. PHYSIOLOGICAL NATURE OF ECG WAVEFORM
Wave Origin Amplitue in Duration
mv sec
P wave contraction of right and left 0.25 0.12 to 0.22
atrium(depolarization of atrial (P-R interval)
musculature)
R Repolarization of the atria & 1.60 0.07 to0.1
wave(QRS the depolarzn. of the ventricles
complex) which occur almost
simultaneously
T wave ventricular 0.1 to 0.5 0.05 to 0.15
repolarization(relaxation of (S-T interval)
myocardium)
S-T interval Ventricular contraction < 0.1 0.2
U wave Slow repolarisation of < 0.1 0.1(T-U
intraventricular system. interval)

47. ANALYSIS OF ECG SIGNALS
 Normal ECG curve
 First degree AV block, due to prolonged conduction
time.
 Bundle block, due to the improper conduction of the
stimulus to the ventricle.

48. ANALYSIS OF ECG SIGNALS
 Myocardial infarction, due to obstruction of the
tissue’s blood supply
 Coronary insufficiency, ST segment depressed &
negative T wave is present.
 Ventricular fibrillation

49. SCHEMATIC DIAGRAM OF AN EEG MACHINE

50. EEG TRANSDUCER(RECORDING SET UP)

51. EEG TRANSDUCER(RECORDING SET UP)
 Electro encephalography - study of electrical
activities of the brain.
 Electrodes attached to different parts of the skull of
a patient.
 8 channel EEG recorder:-
 Patient cable consists of 21 electrodes
 Electrodes connected to selector in groups of 8-
Montage of electrodes
 Right ear electrode  reference electrode right brain
electrodes
 Left ear electrode  reference electrode left brain
electrodes

52. EEG TRANSDUCER(RECORDING SET UP)
 Interference problem is reduced by differential
amplifier(preamplifiers)
 Filter bank:- consists of appropriate filters to select
different types of brain waves.
 Output can be given to 8-channel pen recorder,
display unit, computer storage memory for further
processing.
 Evoked Potential:- Measure of the “disturbance” in
the EEG pattern that results from external stimuli.
 Time delay between stimulus and response can be
measured in signal processing unit.

53. EEG FREQUENCY BANDS
 Below 31/2 Hz -Delta waves
 From 31/2 Hz to about 8 Hz - Theta waves
 From 8 Hz to about 13 Hz - Alpha waves
 Above 13 Hz - Beta waves

54. BRAIN WAVES
 Alpha waves-normally
persons Awake and alert
,occipital region.
 Beta waves- recorded
from parietal and
temporal regions.
 Theta waves- recorded
from parietal and
temporal regions of
Children, adults-
emotional stress
 Delta waves-deep sleep,
premature babies, every
serious organic brain
diseases.

55. BLOCK DIAGRAM FOR EMG RECORDING SET UP

56. BLOCK DIAGRAM FOR EMG RECORDING SET UP
 Electro myography :- study and interpreting of muscle
action potential.
 potentials measured by placing surface electrodes on
the skin.
 Individual cell potential measured by means of needle
electrode
 EMG appears like random noise waveform.
 Contraction of muscle fibers produce action potentials

57. BLOCK DIAGRAM FOR EMG RECORDING SET UP
 Amplitude of EMG signals depends
• Type & placement
• Degree of muscular exertions
 Normal frequency of EMG signals is 60 Hz
 EMG signal amplitude ranges from 0.1 to 0.5 mV.
 Amplifier with high CMRR and input impedance
 Output can be given to oscilloscope, tape recorder or AF
amplifier.

58. ELECTROMYOGRAM-EMG

59. UNIVERSITY QUESTIONS- 4 MARKS
 Explain resting potential and how it is produced?
 Explain the respiratory system and bring out its
analogy with pneumatic system?
 Describe man-measurement system with diagram
and explain each.
 Define biometrics and the characteristics of
instruments used in BMI
 Explain bioelectric potentials, resting and action
potential with waveform.
 Differentiate Tidal Volume, Inspiratory Reserve
Volume, Expiratory Reserve Volume, Residual
Volume, Vital Capacity.

60. UNIVERSITY QUESTIONS-4 MARKS
 Define the important lung capacities and explain
them.
 How blood gets purified?
 Briefly explain pulmonary and systemic blood
circulation?
 What are the functions of kidney
 Explain different electrodes used in BMI
 Explain in brief about the transducers used for
ECG, EEG and EMG.
 Explain the cardiovascular system and bring out its
analogy with hydraulic system?

61. UNIVERSITY QUESTIONS- 12 MARKS
 (i) What are bioelectric potential? Discuss the
frequency and voltage range of ECG, EEG and
EMG signals- 8 marks.
(ii) How does the blood circulate throughout the
body?- 4 marks
o What is meant by central nervous system? With
diagrams, explain the different parts of it and their
activities.- 12 marks
o Draw the structure of a living cell of a human body
and explain its constituents. Discuss the different
methods of transport of ions through the cell
membrane.

62. UNIVERSITY QUESTIONS- 12 MARKS
 With neat diagrams explain the anatomy and the
function of the heart.
 Describe in detail about the function of kidney with
relevant diagram.
 With diagram explain in detail about the respiratory
system and lung capacities.
 Explain the recording and analyzing of ECG with
typical waveform.
 Explain the recording and analyzing of EEG with
typical waveform.
 Describe in detail about EMG recorder with typical
waveform.