الرحمن الله بــسمالرحــيم

Anas saad alsaab

SLEEP

:Objectives

a)Describe the normal sleep pattern. Sleep-wake cycles and factors that control them.

b)Describe the mechanism of sleep generation

a)Describe the normal sleep pattern. Sleep-wake cycles and factors that control them

• Sleep is defined as unconsciousness from which the person can be aroused

by sensory or otherstimuli.

distinguished from coma, which is unconsciousness from which the person cannot be

aroused. There are multiple stages of sleep, from very light sleep to very deep sleep; sleep

researchers also divide sleep into two entirely different types of sleep that have different qualities,

Sleep-wake cycle refers to our 24 hour daily sleep pattern which consists of

approximately 16 hours of daytime wakefulness and 8 hours of night-time sleep.

The complex process of the sleep-wake cycle is controlled by the body’s circadian rhythm and sleep homeostasis (the amount of accumulated sleep need that builds during time spent awake) .

Two Types of Sleep-Slow-Wave Sleep and Rapid Eye

Movement (REM) Sleep:

During each night, a person goes through stages of two types of sleep that alternate with each other.

They are called (1) slow-wave sleep, and (2) rapid eye movement sleep (REM sleep)

• Slow-Wave Sleep:

• restful and is associated with decreases in both peripheral vascular tone and many other vegetative functions of the

body.

30 percent decreases in blood pressure, respiratory rate, and basal metabolic rate.

Although slow-wave sleep is frequently called "dreamless sleep," dreams

•Stage 1 is a time of drowsiness or transition from being awake to falling asleep. Brain waves and muscle activity

begin to slow down during this stage.

People in stage 1 sleep may experience sudden muscle jerks.

. •Stage 2 is a period of light sleep during which eye movements stop. Brain waves become slower, coupled with spontaneous periods of muscle tone mixed with

periods of muscle relaxation .

The heart rate slows and body temperature decreases, theta activity is observed

Stages 3 and 4 (called slow wave sleep), the presence of slow brain waves called delta waves interspersed with smaller, faster waves. , body becoming immobile. Sleep is deeper, with no eye movement and

decreased muscle activity, though muscles retain their ability to function

The amount of stage 4 slow-wave sleep declines with age and in many people is nearly absent by age 70 .

REM Sleep (Paradoxical Sleep, Desynchronized Sleep)

REM sleep is an active period of sleep marked by intense brain activity. Brain waves are fast and desynchronized, similar to those in the waking state.

Breathing becomes more rapid, irregular, and shallow; eyes move rapidly in various directions and limb muscles become temporarily paralyzed.

REM sleep lasting 5 to 30 minutes usually appear on the average every 90 minutes. When the person is extremely

sleepy.

Each bout of REM sleep is short and may even be absent. important for obtaining restful, restorative sleep and for promoting processes such as learning,

memory, mood, and ability to concentrate.

•

REM sleep has several important characteristics:

1. It is an active form of sleep usually associated with dreaming and active bodily musclemovements.

2. The person is even more difficult to arouse by sensory stimuli than during deep slow-wave sleep,

3. Muscle tone throughout the body is exceedingly depressed, indicating strong inhibition of the

spinal muscle control areas.

4. Heart rate and respiratory rate usually become irregular, which is characteristic of the dreamstate.

5. Despite the extreme inhibition of the peripheral muscles, irregular muscle movements do occur.

These are in addition to the rapid movements of the eyes.

6. The brain is highly active in REM sleep, and overall brain metabolism may be increased as much

as 20 percent.

•

:The electroencephalogram (EEG)

• shows a pattern of brain waves similar to those that occur during wakefulness.

This type of sleep is also called paradoxical sleep because it is a paradox that a person can still be asleep despite marked activity in the brain.

,REM sleep is a type of sleep in which the brain is quite active

•

• Alpha waves are rhythmical waves that occur at frequencies between 8 and 13

cycles per second.

• Beta waves occur at frequencies greater than 14 cycles per second and as high as

80 cycles per second.

• Theta waves have frequencies between 4 and 7 cycles per second.

• Delta waves have frequencies less than 3.5 cycles per second, and they often

have voltages two to four times greater than most other types of brain waves

• The complex process of the sleep-wake cycle :

• is controlled by the body’s circadian rhythm and sleep homeostasis .

 

• Circadian rhythms are regulated by the body’s internal master clock which is located in the brain.

• This master clock controls many biological functions over a 24 hour period, such as the release of hormones, body temperature changes, and sleep-wake cycles

• the biological clock consists of a group of neurons in the hypothalamus of the brain called the suprachiasmatic nucleus (SCN).

• Homeostasis is the process by which the body maintains a “steady state” of internal conditions such as blood pressure, body temperature, and

acid-base balance

b)Describe the mechanism of sleep generation

• 1- most conspicuous stimulation area for causing almost natural sleep is the raphe nuclei in the lower half of the pons and in the medulla..

Many nerve endings of fibers from these raphe neurons secrete serotonin. When a drug that blocks the formation of serotonin is administered to an animal, the animal often cannot sleep

for the next several days. Therefore, it has been assumed that serotonin is a transmitter substance associated with production of sleep.

Stimulation of several specific areas of the brain can produce sleep with characteristics near those of natural sleep. Some of these areas are the following::

2- Stimulation of some areas in the nucleus of the tractus solitarius can also cause sleep.

This nucleus is the termination in the medulla and pons for visceral sensory signals entering by way of

the vagus and glossopharyngeal nerves

3- Sleep can be promoted by stimulation of several regions in the diencephalon, including (1) the

rostral part of the hypothalamus, mainly in the suprachiasmal area, and (2) an occasional area in the

diffuse nuclei of the thalamus.

Summary

•

Sleep is defined as unconsciousness from which the person can be aroused by sensory or otherstimuli.

coma, is unconsciousness from which the person cannot bearoused.

Stimulation of several specific areas of the brain can produce sleep:

•the raphe nuclei in the lower half of the pons and in the medulla..

•the nucleus of the tractus solitarius • The rostral part of the

hypothalamus

Resources•

• 

• Guyton and Hall- Textbook of Medical Physiology 12thedition: Page: 721-725-

•http://sleepfoundation.org/sites/default/files/SleepWakeCycle.pdf

Questions

Done by: Anas saad alsaab.