Electrical activity of the brain

Electrical activity of the brain as studied with the help of Electroencephalogram. Sleep wake cycle and circardian rythym.
learn more about different brain waves.

1. Electrical activity of the brain.. By : Shlok Mathur

2. Introduction.. Electrical activity of the brain is complicated when compared to that of a single nerve fiber or neuron. It is due to the involvement of large number of neurons and synapses. Electroencephalography is the study of electrical activities of brain. Electroencephalogram (EEG) is the graphical recording of electrical activities of brain. EEG measures voltage fluctuations resulting from ionic current within the neurons of the  brain .  Neurons use  electrical  signaling to receive and send information. When a neuron is stimulated, an action potential is fired, which enables the message signals to travel rapidly down the axon terminal.

3. EEG… Electroencephalogram… Electroencephalograph is the instrument used to record EEG. The electrodes called scalp electrodes from the instrument are placed over unopened skull or over the brain after opening the skull or by piercing into brain.

4. Waves of EEG.. Electrical activity recorded by EEG may have synchronized or desynchronized waves. Synchronized waves are the regular and invariant waves, whereas desynchronized waves are irregular and variant. In normal persons, EEG has three frequency bands : Alpha waves Beta waves Delta waves In addition to these the EEG in children show Theta waves.

5. Alpha Waves.. Alpha Block.. Alpha block is the replacement of synchronized alpha waves in EEG by desynchronized and low voltage waves when the eyes are opened. Desynchronization is the common term used for replacement of regular alpha waves with irregular low voltage waves. Alpha waves are neural oscillations in the frequency range of 8–12 Hz arising from the synchronous and coherent electrical activity of thalamic pacemaker cells in humans. They are also called Berger's waves after the founder of EEG. Alpha rhythm is obtained in inattentive brain or mind as in drowsiness, light sleep or narcosis with closed eyes.

6. Beta Waves.. Beta wave, or beta rhythm, is a neural oscillation in the brain with a frequency range of between 12.5 and 30 Hz. Beta waves can be split into three sections: Low Beta Waves; Beta Waves; and High Beta Waves. Beta states are the states associated with normal waking consciousness.

7. Delta Waves.. A delta wave is a high amplitude brain wave with a frequency of oscillation between 0.5 and 4 hertz. Delta waves are usually associated with the deep stage 3 of NREM sleep, also known as slow-wave sleep, and aid in characterizing the depth of sleep.

8. Theta wave.. Theta brainwaves occur most often in sleep but are also dominant in deep meditation. Its frequency is 3 to 8 hz . Theta is our gateway to learning, memory, and intuition. In theta, our senses are withdrawn from the external world and focused on signals originating from within.

9. Sleep.. Sleep is the natural periodic state of rest for mind and body with closed eyes characterized by partial or complete loss of consciousness. Sleep requirement is not constant. However different age groups have different sleep requirements. Physiological changes during sleep : Plasma volume Cardiovascular changes Respiratory system Gastrointestinal system Excretory system Sweat secretion Lacrimal secretion Muscle tone Reflexes Brain

10. Types of sleep… Rapid Eye Movement sleep.. Rapid eye movement sleep (REM sleep or REMS) is a unique phase of sleep in mammals and birds, distinguishable by random/rapid movement of the eyes, accompanied with low muscle tone throughout the body, and the propensity of the sleeper to dream vividly. Non Rapid Eye Movement Sleep.. NREM sleep: NREM (non-rapid eye movement) sleep is dreamless sleep. During NREM, the brain waves on the electroencephalographic (EEG) recording are typically slow and of high voltage, the breathing and heart rate are slow and regular, the blood pressure is low, and the sleeper is relatively still.

11. Stages of Sleep.. Rapid Eye movement sleep. Non rapid Eye movement sleep : Stage of Drowsiness Stage of light sleep Stage of medium sleep Stage of deep sleep

12. Mechanism of sleep.. Sleep occurs due to the activity of some sleep-inducing centers in brain. Stimulation of these centers induces sleep. Sleep Centers : Raphe Nucleus Locus Cereleus of pons

13. Applied Physiology.. Sleep Disorders : Insomnia Hypersomnia Narcolepsy and cataplexy Sleep apnea syndrome Nightmare Night terror Somnambulism Nocturnal enuresis Movement disorder during sleep.

14. Thank you.. Doubt .. ?