Sleep and Brain Waves Dr. Sumera Gul Associate Professor Department of Physiology
Sleep and Brain Waves
Dr. Sumera Gul
Associate Professor
Department of Physiology
Learning Objectives:
• At the end of the lecture the students should be able to:
• Describe sleep and explain the types and stages of sleep
• Explain the mechanism of slow and REM sleep
• Elaborate the basics of brain waves
• Discuss common sleep disorders
• Discuss the various types of seizures and epilepsy
Sleep
• Sleep is defined as unconsciousness from which the person can be aroused by sensory or other stimuli.
• How is it distinguished from coma ?
Types of Sleep
• There are multiple stages of sleep, from very light sleep to very deep sleep.
• (1) slow-wave sleep,
• (2) rapid eye movement sleep (REM sleep),
REM Sleep (Paradoxical Sleep, Desynchronized Sleep)• Rapid eye movement sleep.
• 25% of total sleep time
• Every 90 minutes
• 5 to 30 minutes usually appear on the average every
Slow Wave Sleep Slow Wave SleepREMSlow Wave SleepREM
60-90 mins 60-90 mins 60-90 mins5-30 mins 5-30 mins
REM Sleep
• active dreaming
• active bodily muscle movements.
• Muscle tone throughout the body is exceedingly depressed, indicating strong inhibition of the spinal muscle control areas.
• Heart rate and respiratory rate usually become irregular
REM Sleep
• Despite the extreme inhibition of the peripheral muscles, irregular muscle movements do occur.
• The brain is highly active and brain metabolism may be increased as much as 20 per cent.
• EEG shows a pattern of brain waves similar to those that occur during wakefulness.: Paradoxical Sleep
What causes REM
• Why slow-wave sleep is broken periodically by REM sleep is not understood.
• However, drugs that mimic the action of acetylcholine increase the occurrence of REM sleep.
• So we believe that large acetylcholine secreting neurons in the upper brain stem reticular formation might, through their extensive efferent fibers, activate many portions of the brain.
• What can happen to REM sleep if we are extremely sleepy and tired?
Slow Wave Sleep
• It is deep sleep.
• Initial one hour of sleep is the slow wave sleep.
• All the vegetative functions decrease: there are 10 to 30 per cent decreases in blood pressure, respiratory rate, and basal metabolic rate.
• Dreamless sleep
What Causes Sleep?
• Active Inhibitory Process
• Neuronal Centers, Neurohumoral Substances, and Mechanisms
• Sleep-Promoting Centers
• Other Possible Transmitter Substances
What Causes Sleep?
• Active Inhibitory Process: There is a center below the level of mid pons that will inhibit other centers of brain , probably the raphe nucleus.
• Neuronal Centers, Neurohumoral Substances, and Mechanisms: Serotonin is believed to be the neurotransmitter mainly involved in induction of sleep.
• Sleep-Promoting Centers : Raphe nucleus, tractus solitarius, suprachiasmatic nucleus, anterior hypothalamus
• Other Possible Transmitter Substances: muramyl peptide, nonapeptide, orexin
• Another sleep factor isolated from neurons
Why is sleep important?
Physiological Functions of Sleep
• Important for cognitive functions
• Physical performance
• Overall productivity and health
• Rats deprived from sleep for 2-3 weeks die
• Neural maturation
• Facilitation in learning and memory
• Memory consolidation
• Clearance of metabolic waste products generated by awake brain
• Conservation of energy
• Diurnal cycles
Disorders of Sleep
Abnormalities of Sleep
• Insomnia
• Narcolepsy
• Sleep Apnea
• Snoring
• Sleep walking
Brain waves
Brain Waves
• The recording of electrical activity of brain by placing electrodes on the scalp: EEG.
• The intensities of brain waves recorded from the surface of the scalp range from 0 to 200 microvolts.
• frequencies range from once every few seconds to 50 or more per second.
Alpha waves
• Rhythmical waves occurring at 8 and 13 cycles per second
• During awake and quiet, resting state of cerebration.
• Occur intensely in occipital , parietal and frontal regions of the scalp.
• Voltage: 50 microvolts.
• Sleep: the alpha waves disappear.
• If an awake person’s attention is directed to some specific type of mental activity, the alpha waves are replaced by beta waves.
Beta Waves
• If an awake person’s attention is directed to some specific type of mental activity, the alpha waves are replaced by beta waves.
• Beta waves occur at frequencies greater than 14 cycles per second and as high as 80 cycles per second.
• Recorded mainly from the parietal and frontal regions.
• Low amplitude and more frequent.
• Sleep: REM sleep
Theta Waves
• Theta waves have frequencies between 4 and 7 cycles per second.
• They occur normally in the parietal and temporal regions in children, but they also occur during emotional stress in some adults, particularly during disappointment and frustration.
• Theta waves also occur in many brain disorders, often in degenerative brain states.
• During sleep: stage 2 and 3
Delta waves
• include all the waves of the EEG with frequencies less than 3.5 cycles per second
• Voltage is usually two to four times greater than most other types of brain waves.
• They occur in very deep sleep, in infancy, and in serious organic brain disease.
• Cortex
• Sleep: Deep sleep
Seizures and Epilepsy
Seizures• Temporary disruption of brain function caused by uncontrolled
excessive neuronal activity.
• Electrolyte imbalance
• Hypoglycemia
• Drugs
• Kidney failure
• Encephalopathy
• Meningitis
Epilepsy
• Chronic condition of recurrent seizures of nearly no symptoms or vigorous shaking and convulsions.
• Organic disease• Injury• Tumors• Infections• Degenerative changes• Genetics
• Drugs and pathologies
Epileptic seizures
• Focal seizures (Partial seizures)
• Generalized seizures
Focal Seizures
• Involves localized reverberating signals.
• In localized organic lesion or functional abnormality like tumor, congenital circuit problem, scar, injured area.
• Jacksonian March
• Simple Partial
• Complex Partial
Generalized Seizures
• Grand Mal Seizures
• Tonic-Clonic Seizures
• Post-seizure depression, stupor.
• Mostly idiopathic
• Drugs
• Alkalosis
• Fever
• Certain aggravating factors
• What stops these seizures?
Petit Mal Seizure
• Absence seizure
• 15-20% epilepsy in children
Treatment
• Age
• Type
• History
• Other factors
Treatment
• Blockage of voltage gated sodium channels
• Calcium currents
• Increase GABA activity
• Inhibit Glutamate
• Surgery