Body Rhythms&

Sleep

Biological Rhythms• Natural variations we experience daily in our psychological and physiological

functioning• Fall into three main categories

• Circadian Rhythms• Ultradian Rhythms• Infradian Rhythms

Circadian Rhythms• Any rhythmic change that occurs approximately once in a 24-hour

cycle

• Responsible for our arousal levels throughout the day.

• Many of your processes like blood pressure, hormones, pain sensitivity along with sleep and wake cycles vary over the day

• If time, watch the Cave Experiment from The Brain: Module 13 (6 min)• In the absence of time

cues, the cycle period will become somewhat longer than 24 hours

The Body’s Clock• Suprachiasmatic

nucleus (SCN) — cluster of neurons in the hypothalamus that governs the timing of circadian rhythms

• Melatonin —hormone of the pineal gland that produces sleepiness

The Body’s Clock: How it works• Special photoreceptors in the retina regulate the

effects of light on the body’s circadian rhythms • In response to morning light, signals from these

special photoreceptors are relayed via the optic nerve to the suprachiasmatic nucleus.

• In turn, the suprachiasmatic nucleus causes the pineal gland to reduce the production of melatonin, a hormone that causes sleepiness.

• As blood levels of melatonin decrease, mental alertness increases.

• Daily exposure to bright light, especially sunlight, helps keep the body’s circadian rhythms synchronized and operating on a 24-hour schedule.

How Melatonin works:• More melatonin = sleepy and reduce activity levels

– highest levels between 1-3 AM

• Less Melatonin = more alert and active – Body stops produced melatonin shortly before sunrise and

sunlight suppresses melatonin levels throughout the day

• Jet Lag – Since your body is still operating on the time you left from, your melatonin levels will be off causing a disruption in your circadian rhythms and making you mentally fatigued, depressed, irritable and have problems sleeping.

• Night workers will always have some problems due to sunlight resetting their biological clock.

Biological Rhythms

• Play “Can You Beat Jet Lag?” (6:44) - (Start at 16:00).

• Segment #15 from Scientific American Frontiers: Video Collection for Introductory Psychology (2nd edition)

• How light is used by the body to “reset” your biological clock.

Not a Morning Person?

• Sleep Inertia - feeling of grogginess or impaired mental ability immediately following an abrupt awakening

• Staying in bed until the last possible moment will only intensify disorientation as you hustle to work.

• Staying in bed until the last possible moment will only intensify disorientation as you hustle to work.

• Best way to treat it is to allow for more passage of time. – Set your alarm 15 minutes earlier and make it so you have to get

up to turn it off.

• Drink something with caffeine and sit near sunlight.

• Read something or do meditation to get your brain engaged.

Ultradian Rhythms• Biological rhythms that occur more than once

each day

• Example: Cycling through the stages of sleep throughout the night, appetite

Infradian Rhythms• Biological rhythms that occur once a month or once a

season

• These rhythms are infrequent

• Example: – Women’s menstrual cycle

– bear’s winter hibernation

The Stages of Sleep

Why do We Sleep?• Restoration theory—body wears out during the day

and sleep is necessary to put it back in shape– NREM sleep sees increases in the release of growth hormone,

testosterone, prolactin.– REM sleep plays a role in rate of brain development that occurs in the

early stages of the lifespan. – Allows neurons to repair themselves while pruning unused connections– Sleep consolidates memories – strengthening neural connections– Allows us to be better problem solvers the next day

• Adaptive theory—sleep emerged in evolution to preserve energy and protect during the time of day when there is little value and considerable danger– Animals with few natural predators sleep the most while animals with

many sleep less. – Hibernation occurs during the time of year most hazardous to the animal.

Electroencephalograph (EEG)• A machine that amplifies and records waves of

electrical activity that sweep across the brain’s surface

• Electrodes are placed on the person’s scalp to measure the waves

• Used as a means to measure the stages of sleep

Electroencephalogram (EEG)

• Electrodes placed on the scalp provide a record of the electrical activity of the brain• EEG recordings are a rough index of psychological states

EEG Waves of Wakefulness

Alpha Waves:Awake but non-attentive

Larger amplitude

Beta Waves: Awake & attentive

low amplitude fast, irregular

Onset of Sleep• Awake & alert, your brain produces small, fast brain

waves called beta waves.• As you lay down and close your eyes, your brain's

electrical activity gradually gears down generating slightly larger and slower alpha brain waves.

• During drowsy, presleep stage you may experience vivid sensory phenomena called hypnagogic hallucinations.

• Most common hallucination is that of falling which can produce a myoclonic jerk or sleep starts – involuntary muscle spasm of the whole body that jolts the person completely awake.

Stage 1 Sleep• Breathing is slowed.• Brain waves become irregular.• It is easy to wake the person, who will

insist they are not asleep.• Lasts only a few minutes. • Familiar sounds fade away but your can

regain alertness if something interrupts you.

• Some imagery is common although no very strange or vivid.

Stages of Sleep

Stage 1

Stage 1

Stage 2 Sleep

• Brain activity slows considerably and breathing becomes rhythmic.

• Slight muscle twitches occur.

• Brain waves begin to slowly switch from Theta waves to slower and larger delta waves.

• Brain wave cycle slows.• Appearance of sleep spindles or brief

bursts of brain activity and K complexes or large high-voltage spikes of brain activity that periodically occur.

Stage 2

K Complex

Stages 3 and 4 Sleep“Slow Wave Sleep”

• Increase in delta waves (large & slow waves per second) – 20% = Stage 3. More than 50% = Stage 4.

• First time through stage 4 is about 30 minutes and is where one gets rejuvenated

• During the first stage 4 of sleep, heart rate, blood pressure and breathing drop to their lowest levels and it is very hard to wake up.

• Sleepwalking occurs here. • People can "wake up" during stage 4 and do a simple task and not

remember it.

Stage 4

Stages of Sleep1-4Quick Review

• Sleep stage 1: brief transition stage when first falling asleep

• Stages 2 through 4 (slow-wave sleep): successively deeper stages of sleep

• Slow Wave 3 & 4: Characterized by an increasing percentage of slow, irregular, high-amplitude delta waves

Delta waves

Sleep stage 11 second

Sleep stage 4

Sleep stage 2

Spindlers (bursts of activity)

REM Sleep

• N-REM (non-REM sleep) = Stages 1 - 4 • REM Sleep - Rapid eye movement as eyes

move quickly back and forth• Most dreaming occurs in REM

– muscle activity is suppressed to keep you acting them out.

• REM Rebound - If denied REM sleep and then allowed a person will “Catch Up” on REM sleep and will increase their time in REM by 50%.

REM Sleep

REM: Paradoxical Sleep• One’s physiology is close to that of being awake but the brainstem

blocks all muscle movement• Brain wave patterns are similar to when a person is awake• Visual and motor neurons in the brain fire like they do when you are

awake.• Eyes dart back and forth and heart rate, blood pressure and respirations

fluctuate up and down.• The first REM cycle lasts for 5 to 15 minutes. Each one gets longer as

night goes on.

Stages of Sleep• Upon reaching stage 4 and after about 80 to 100 minutes of

total sleep time, sleep lightens, returns through stages 3 and 2

• REM sleep emerges, characterized by EEG patterns that resemble beta waves of alert wakefulness– muscles most relaxed– rapid eye movements occur– dreams occur

• Four or five sleep cycles occur in a typical night’s sleep; less time is spent in slow-wave, more is spent in REM

Typical Night’s Sleep

Sleep Changes through Life

Sleep Review• Play “Sleep: Brain Functions” (11:12)

– Module #14 from The Brain: Teaching Modules (2nd edition).

• Review of the stages of sleep.• What happens to animals that are not

allowed to sleep?• What defines normal & abnormal sleep?• Categories of Sleep Disorders