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