1. EEG: Electro Encephalo Graphy:
Recording & the study of electrical activity of brain
By electrodes : summation of neural depolarization in the brain due to stimuli from five senses and thought process
Surface of skull : 10 mV
Propagation through skull bone : 1 to 100 µV
Frequency : 0.5 to 3000 Hz

2. EEG

3. Origin of EEG:
Originate within the dendrite potential (acetylcholine)

4. The Cell Membrane: Na+ Cl- K+ A- Outside of Cell Inside of Cell
Cell Membrane at rest
Na+
Cl- K+ A-
Outside of Cell
Inside of Cell
Potassium (K+) can pass through to equalize its concentration
Sodium and Chlorine cannot pass through
Result - inside is negative relative to outside
- 70 mv
Key words: Cell membrane; semi-permeable; K+; Na+; Cl-
The cell membrane is semi-permeable. That is, when the neuron is at rest, the cell membrane allows some ions (K+) to pass freely through the cell membrane, whereas other ions (such as Na+ and Cl-) cannot.
Hit enter once and K+ ions will slowly pass through the cell membrane.
After K+ animation is finished, hit enter again and animation showing that Na+ and l- ions cannot pass through the membrane will occur.

5. Brain spatially represented:

6. Two ways
Tremendous numbers of nerve fibres can discharge in synchronous with each other
Large number of neurons can partially discharge, though not emit action potential

7. Action potential:
Disturbances in resting potential along the nerve fibre: transfers the message
When the action potential reaches the cell, it fires and spike is produced
IPSP (Inhibitory Post Synaptic Potential)
Transmitter: Inhibitory
Receptor : membrane potential increases in negative direction
EPSP (Excitatory Post Synaptic Potential)
Transmitter: Excitatory
Receptor : membrane potential increases in positive direction

8. Evoked potential:
Potentials developed in the brain as the responses to external stimuli like light, sound etc.
Event related potential

9. Types of Electrode Placement
10-20 System Of Electrode Placement
10-10 System Of Electrode Placement

10. Normal Recorded Sample EEG

11. EEG Waves alpha (8 – 13Hz): awake, closed eyes Occupital region
beta (13 – 30Hz): awake, alert
Parietal & frontal regions
gamma (> 30Hz): memory, active thought
delta (0.5 – 4 Hz): deep sleep
cortex region
theta (4 – 8Hz): infants, sleeping adults (frustration, disappointment)
parietal & temporal regions

12. Normal EEG Recorded in Man
Eyes opened condition.
Examples of different waves.

14. Placement of electrodes:
Disc like surface electrodes
Bipolar electrode (difference between 2 adjacent electrodes)
Monopolar electrode (potential of each electrode with respect to reference electrode)
Wilson technique (one of the electrode potential with respect to the central terminal)

15. Recording setup:

16. Modern EEG unit:

17. Contd..
The electrodes are attached to the channel selector in a group of eight : Mortage
50 Hz a.c. interference is reduced by
employing differential amplifiers as preamplifiers with more than 80 db CMRR
50 Hz notch filter
Room is covered with ferrous metal screen, avoids

18. Analysis of EEG: Level of consciousness: Brain tumors: Epilepsy:
REM : rapid eye movement
Anaesthesia: frequency decreases & amplitude ↑
Brain tumors:
In cortex, electrical activity will be absent
Epilepsy:
Symptom of brain damage
Synchronous discharge of large group of neurons
Grandmal & Peritmal

19. EMG – ElectroMyoGraphy:
is a science of recording & interpreting the electrical activity of muscle’s action potentials
Recording peripheral nerve’s action potentials
Action potentials: both positive & negative polarities of the electrode
Contraction of the muscles

20. Recording set up:

21. Amplitude depends on: the type of electrode Placement of electrodes
Degree of muscular exertions
0.1 mV to 0.5 mV
20 Hz to 10 kHz
Reflex responses and muscular diseases

22. Determination of conduction velocities in motor nerves:
Brain to sensory organs
By stimulating the nerves with brief electric shock
0.2 ms to 0.5 ms
Latency : elapsed time
Conduction velocity, v = (l1-l2) / (t1-t2) = 50 m/s
If v<40 m/s, disorder in nerve conduction

23. Determination of conduction velocities in motor nerves:

24. Electro Retino Graphy (ERG):
Recording and interpreting the electrical activity of eye
Retina is the extension of the cerebral cortex
The cornea is about 20 mV positive relative to the fundus of the eye
Change in illumination changes the potential
Ag-Agcl electrode on a contact lens
Reference electrode on cheek

25. Electro Ooculo Graphy (EOG):
Recording the corneal – retina potential associated with eye movements
More simpler than ERG

26. Electro Ooculo Graphy (EOG):

27. Electro Ooculo Graphy (EOG):
The source of electrical energy in eye is the corneo-retinal potential or electrostatic field which rotated with respect to eye
Applications:
Effects of drugs
State of semicircular canals
Neurological disorders
Level of anaesthesia

28. ERG Electrodes

29. ERG Electrodes

30. PHONOCARDIOGRAPHY
Phonogram – graphic record of heart sounds – vibrations of cardiac structure
Phonocatheter – catheter with microphone at the tip
Heart sounds – short duration – transient – opening and closing of valves
Murmur – longer duration – noisy – turbulent flow of blood in the heart – 1000 Hz

31. Heart sounds Valve closure sounds Ventricular filling sounds
Valve opening sounds
Extra cardiac sounds

32. Valve closure sounds
First heart sound : beginning of systole – closure of mitral and tricuspid valves
0.1 to 0.2 s
Second heart sound : beginning of diastole - closure of aortic and pulmonary valves
0.08 to 0.14 s

33. Ventricular filling sounds:
Third heart sound : rapid filling of the ventricles
0.12 to 0.18 s
Valve opening sounds:
Opening of Atrio - Ventricular valves and semilunar valves
Extra cardiac sounds:
Mid or late systole or early diastole – thickened pericardium

34. Characteristics of sound
Frequency – 10 to 1000 Hz
Low range – 10 to 60 Hz – 3rd and 4th heart sound
Medium range – 60 to 150 Hz – 1st and 2nd heart sounds
High range – 150 to 1000 Hz – diastolic murmurs & pulmonary insufficiency
Amplitude
quality

35. Block diagram

36. Placement of microphone

37. Microphone
Air coupled microphone
Contact microphone

38. Amplifier

39. Filter

40. BP, Heart sounds and ECG

41. Analysis of heart sounds