Sleep and arousalByAnanya DuttaMSc 3rd Sem.Roll number -3

Sleep is defined as unconsciousness

from which the person can be aroused by sensory or other stimuli.

Not the passive state many people once considered it to be, sleep is now known to be a highly active process during which the day’s events are processed and energy is restored.

What is sleep?

Why do we need to sleep? Some believe that -• sleep gives the body a chance to

recuperate from the day's activities but in reality, the amount of energy saved by sleeping for even eight hours is miniscule - about 100 kCal

• essential to maintain normal levels of cognitive skills such as speech, memory, innovative and flexible thinking.

Basic theories of sleep• Sleep Is Believed to Be Caused by an Active

Inhibitory Process.

There seems to be some center located below the mid pontile level of the brain stem that is required to cause sleep by inhibiting other parts of the brain. The ventrolateral preoptic nucleus (VLPO or VLPN) of the hypothalamus is one area of the brain that is particularly involved in the switch between wakefulness and sleep.

Contd..

• Neuronal Centers, Neurohumoral Substances,and Mechanisms That Can Cause Sleep—A Possible Specific Role for SerotoninSerotonin is a transmitter substance associated with productionof sleep.

Contd..

• Other Possible Transmitter Substances Related to Sleep.

The cerebrospinal fluid as well as the blood or urine of animals that have been kept awake for several days contains a substance or substances that will cause sleep when injected into thebrain ventricular system of another animal

STAGES of sleep• Stage 1 the eyes move slowly and muscle activity

slows. • In stage 2, eye movement stops and brain waves

become slower with only an occasional burst of rapid brain waves. 

• When a person enters stage 3, extremely slow brain waves called delta waves are interspersed with smaller, faster waves.

• In stage 4, the brain produces delta waves almost exclusively

• In Stage 5,increase of heart rate,body temperature

Sleep: Its types

• Rapid Eye Movement Sleep(REM)• Non Rapid Eye Movement(NREM)or

Slow wave sleep

Defining REM sleep A period of sleep characterised by

rapid periodic twitching movements of the eye muscles and other physiological changes,such as

accelerated respiration and heart rate,increased brain activity,and

muscle relaxation.

Defining non REM sleep NREM (non-rapid eye

movement) sleep is dreamless sleep. During NREM, the breathing and heart rate are slow and regular, the blood pressure is low, and the sleeper is relatively still. NREM sleep is divided into 4 stages of increasing depth leading to REM sleep.

Arousal or Wakefulness

Defining Wakefulness• Wakefulness is a state of arousal

in which there is a conscious monitoring of the environment and there is potential for efficient responsiveness to external stimuli or threats. It is in contrast to the state of sleep in which there is reduced responsiveness to environmental stimuli.

CYCLE BETWEEN SLEEP AND AROUSAL

• When the sleep centers are not activated: 1. the mesencephalic and upper pontile reticular

activatingnuclei are released from inhibition (which allows thereticular activating nuclei to become spontaneouslyactive).

• excites both the cerebral cortex and the peripheral nervous system, both of which send numerous positive feedback signals back to the same reticular activating nuclei to activate them still further.

• After the brain remains activated for manyhours:

1. the neurons themselves in the activatingsystem presumably become fatigued.,

2. the positive feedback cycle between the mesencephalic reticular nuclei and the cerebral cortex fades,

3. the sleep-promoting effects of the sleep centerstake over, leading to rapid transition from wakefulnessback to sleep.

Changes in the EEG at DifferentStages of Wakefulness and Sleep

Sleep disorders Sleep problems, including snoring,

sleep apnea, insomnia, sleep deprivation, narcolepsy and restless legs syndrome, are common. Good

sleep is necessary for optimal health and can affect hormone levels, mood

and weight.

Concluding remarksLifestyle, technology and health behaviors including sleep are all

intertwined and strongly embedded in the cultural and social

environment.

References

Books• Barret et al(2010).Ganong’s Review of Medical

Physiology,23rd Ed.McGraw Hill Companies Inc,United States.Pp 235-237

• Gyton C.A & Hall J.E (2006). Textbook of Medical Physiology,11th Ed. Elsevier’s Health Sciences Rights Department in Philadelphia, PA, USA.Pp 739-743

Contd..

Urls:• www.sleepdex.org/flipflop• www.ncbi.nlm.nih.gov/pubmed/20969999• http://www.webmd.com/sleep-disorders/• https://sleepfoundation.org/sleep-news/sleep-and-

lifestyle-managing-priorities-and-sleep• http://www.howsleepworks.com/how_neurological.

html• www.healthysleep.med.harvard.edu

Thank you