EEG & ECG: Human Health & Diseases | Additional Study Material for NEET PDF Download

DISEASES

NORMAL ELECTROCARDIOGRAM (E.C.G.)

1st recorded by Waller. Father of ECG = Einthoven. An electrocardiogram records electrical activity of the heart. The impulse travelling in the neuro muscular pathway of the heart is conducted to the wall of heart musculature where it gets amplified and part of it leaks via the pericardium to the skin surface . This leaked current is picked up with help of electrode and amplified. A time voltage graph of this current is then plotted which is called the E.C.G. It is taken with help of 12 leads, placed at different positions on body

Electrocardiogram (ECG)

Electrocardiogram (ECG)

Components of a normal ECG

Waves 

“P” wave– it represents auricular depolarization which is followed by auricular contraction.  Its first half represents Rt. Auricle and second half  represents Lt.auricle.

“QRS” complex – it represents ventricular depolarization which is followed by ventricular contraction

“T” wave  - it represents ventricular repolarization during which the ventricles relax Intervals

P-Q  interval –time period between start of auricular depolarization and ventricular depolarization ( also called P-R interval, it lasts normally for 0.16 seconds)

S-T interval  -time period between ventricular depolarization and ventricular repolarization P-P ,

R-R  interval : The interval between any two successive similar wave denotes time taken for one heart beat.

EEG (ELECTRO-ENCEPHALOGRAPH) OR BERGER WAVES :

Hens Berger (1929) obtained electrical activity when a galvanometer was connected to human scalp.It gave birth to electroencephalography. Electro-encephalo graph is an electricity operated instrument having 16-30 electrodes which when attached to scalp gives information about the electric waves originating from different parts of the brain. It is a noninvasive technique.

There are four types of waves-alpha, beta, theta and delta.

(1) α - waves : An awake but resting person produces rhythmic alpha waves with a range of 8– 13 Hz Alpha waves originate from occipital region.

(2) β-waves : An alert wide awake person shows unsynchronised high frequency ECG. During intense mental activity, beta waves originate from frontal and parietal regions. Frequency is 14–30 Hz 

(3) θ waves : Theta waves occur in children as well as adults under stress and drowsy Frequency is 4–7 Hz 

(4) δ-waves : Higher amplitude and slower frequency waves called delta waves, originate when a person is in deep sleep. Frequency is below 1-3 Hz.

Deviations indicate brain disorders and changes in physiological state of brain. Electro-encephalogram is the recording of electrical potentials, originating from different parts of the brain in the form of waves. EEG can diagnose epilepsy, brain tumour, subdural haematoma, brain injury, sleep disorders, metabolic and drug effects on brain.

MET (Magneto encephalography) – It is magnetoencephalorgaphic technique which empolyees SQID for picking up weak magnetic waves emanating from brain. The technique gives information about the health of various parts of the brain.

SQID (Super Conducting Quantum Interference Device) – It is super–conducting quantum interference device, e.g., magnetoencephalograph. The device has a super– conducting ring where a change the magnetic flux into the voltage in amplified form.

Biochemical investigation : 

Haemoglobin Estimation:

Methods of Haemoglobin Estimation Haemoglobin is a chromoprotein consisting of the colourless globin molecule attached to four red coloured haem molecules. The globin molecules consist of two alpha-polypeptide chains and two beta-polypeptide chains.

Haem is a metal complex containing an iron atom in the centre of porphyrin structure. haemoglobin is formed in developing erythrocytes (normoblasts) in the narrow.

The biosynthesis of haemoglobin involves the triad of manufacture of haem, manufacture of globin and iron metabolism. Methods of estimation of haemoglobin are as follows :

Sahli's acid haematin method :-

Principle :- Hb is converted into acid haematin by hydrochloric acid. The brown colour of the compound is matched against a brown glass standard in a comparator.

Normal range of Hb :-

Adult 15.5 ± 2.5 g/dl

(c) One of the common method employed to determine Hb is Sahli method using as Haemoglobinometer (Brown complex – acid Haematin is formed).

(d) Some indicators of disorders are :

Low Hb – Anemia and leukemia

High Hb – Dehydration and polycythemia or erythrocytosis .

Erythrocyte Sedimentation Rate (ESR)

It is the rate at which the erythrocytes or RBC sediment. When they are allowed to settle out from plasma. ESR is measured in terms of millimeter per hour. It is useful in diagnosis of many diseases, though it is not specific for any particular disease.
Normal value of ESR in various methods are as follows :

ESR :
Increases during Rheumatoid arthritis, TB, Syphilis etc.
Decreases during Anemia, Polycythemia etc.

Estimation of blood groups:-

Blood groups detection is termed as typing of blood and is generally carried out by "Slide Technique" using antisera A and B. Climbing of cells due to serum indicate the blood groups as given below :

Lipid Profile : Blood Cholesterol Tests measure the levels of lipids (fatty acids), cholesterol and triglycerides in the blood. Elevated lipid levels indicate heart disease or stroke overweight or diabetes mellitus.

Two important cholesterol types are HDL (high-density lipoprotein) and LDL (low-density lipoprotein) HDL have a protective effect against atherosclerosis where as high blood level of LDL is a risk factor.

Normal cholesterol level in blood =  150 mg - 240 mg/dl, high risk levels > 240 mg/dl 

ELISA TEST (Enzyme linked Immunosorbent Assay Test or Diagnostic kit)

It is a technique which can detect and even quantitative extremely small amount of a protein, antibody or antigen with the help of enzyme. The reaction is allowed to proceed in specialised ELISA plate or tray. The commonly used enzymes are peroxidase and alkaline phosphatase.

ELISA for HIV antibody in serum :

1. Microsassay plate coated with HIV antigen. The sample suspected to contain the Ag immobilised on the surface of an ELISA plate.

2. Test serum is added and incubated. HIV antibody if present in the serum will attach to HIV antigen.

3. After washing, add goat anti-human immunoglobulin antibody conjugated with  horse serum peroxidase enzyme . The conjugate will attach to HIV antibody in a positive test.

4 After washing, add substrate OPD (orthophenyl diamine HCl/ paranitropheny phosphate). or (H₂ O₂ ⁺ 4-chloronapthol)

5. A colour develops in the positive test, while there will be no colour in a negative test. ELISA is very quick diagnostic technique for detection of a wide variety of pathogens, disorders, allergens and hormones, Like -

(i) Pregnancy test through presence of human chorionic gonadotropin (HCG) in urine or blood.

(ii) AIDS or HIV infection.

(iii) Hepatitis.

(iv) STD or sexually transmitted disease.

(v) Rubella virus.

(vi) Thyroid disorder.
 

Auto analyser It is a automatic, computerised instrument which can analyse qualitatively and quantitatively various biochemicals present in body fluids like urea, uric acid, ketones, cholesterol, glucose, proteins, enzymes, etc.
In batch type auto analyser (more common) only one type of analysis is carried out at a time while in multichannel auto analyser a number of biochemicals are tested from the same sample.

Polygraphy : It is popularly but quite incorrectly called "The lie detector". Polygraph is a simple, compact and portable machine that records qualitative changes in physiological parameters rather than measuring them accurately. These parameters include vital traces such as cardiac variables (ECG), Heart pulse rate (HR) relative blood pressure(BP), the rate and depth of breathing and the resistance of skin to the conduction of electricity.

A modern computerised version of this multi channel device is used to record neuro physiological parameters such as E.E.G, EMG (Electromyograph). and EOG (Electrooculograph).

Uses of polygraphy : (1) Lie detecting (2) Monitoring of stages of sleep (3) Electrophysiological behaviour of brain and its functions.

Laser (Light knife) :

Laser (LASER) or light amplified by stimulated emission of radiation is a beam of very high energy particles. Depending upon the source of generation, it is called argon laser, carbon dioxide laser or neon laser.
Medical lasers used for therapeutic purposes. They can be targeted on any tissue or organ inside the body.

(i) Breaking of kidney stones and gall bladder stones into fine powder for removal through natural excretory processes instead of surgery.

(ii) Treatment of cancerous and other tumours by selective burning of cells.

(iii) Treatment of opacity of eye lens. 

Laser Microsurgery :

In microsurgery type, use and effect of laser on tissue depends on its wavelength.

Type of laser used in microsurgery –

(1) Carbondioxide laser : This laser has a short wavelength (10.6 mm) It is absorbed by water in target cells and its energy is quickly converted into heat. As a result the effect of laser is highly localised. Used in Neurosurgery to remove the unoperable brain tumours.

(2) Visible Argon-ion laser : It is used in eye surgery has an intermediate effect on tissue.

(3) Lasik laser : It is used in treatment of myopia.

Cryosurgery : Cryosurgery, as the name implies, uses freezing temperatures to destroy. Liquid nitrogen, which has a temperature of –196°C, is sprayed onto the tissue either directly, as in the treatment of warts, or via a hollow probe that is inserted into the tissue. Cancerous tumours can also be destroyed in this way.