Regulation of Sleep and Wakefulness

Question 1

About one third of your life is spent sleeping (what is sleep?)

Answer 1

• eyes are closed
• changes in breathing, heartbeat and muscle tone
• once believed that the brain shuts down during sleep
• sleep is associated with brain activity that differs from waking but not to a shutdown

Question 2

Polysomnography

Answer 2

• a set of physiological measures that includes electroencephalography, electrooculography and electromyography
• obtained through the use of (EOG and EMG)

Question 3

Electrooculography ( EOG)

Answer 3

recording of eye movement through changes in the electrical activity of eye muscles

Question 4

Electromyography (EMG)

Answer 4

recording movements of the body through measuring changes in the electrical activity of muscles

Question 5

Alfred Loomis (1930s)

Answer 5

• discovered that the brain’s pattern of electrical activity differed depending on whatever an individual was awake or asleep
• he did so by measuring the wavelengths emitted by the brain during waking and sleep using EEG , he noticed that pattern of activity changed during sleep
• Brain waves , differing in amplitude and frequency during sleep were identified, Alpha, Beta , Theta and Delta

Question 6

Brain Waves, what are they?

Answer 6

frequency and amplitude

Question 7

Alpha, Beta, Theta, Delta

Answer 7

• Brain waves that differ in amplitude and frequency
• Identified by EGG
• NREM sleep

Question 8

Non-rapid eye movement sleep

Answer 8

• sleep that is subdivided in to four stages of progressively deeper sleep

Question 9

REM SLEEP

Answer 9

• rapid eye movement sleep

- sleep stage mostly associated with dreaming; characterized by relative muscle paralysis and eye movements

Question 10

Stages of sleep in brief

Answer 10

Stage 1 : transitional sleep (theta)
Stage 2: sleep spindles and K-complexes. Sleep spindles (series of high frequency spokes of activity lasting anywhere from 0.5 to 10sec
k-complexes: slight negative deflections in brain waves ( wave movement exaggerated downward) followed by a positive deflection (exaggerated upward_
stages 3 and 4 : Slow- wave deep sleep (delta)

Question 11

Stage 1

Answer 11

stage 1 Sleep is the transmission between wakefulness and deeper stages of sleep
- it is characterized by theta waves, which are of slightly higher amplitude compared to that of beta and alpha waves but are of lower frequency

Question 12

stage 2 sleep

Answer 12

• marked by what are known as spindles and k-complexes
• sleep spindles are series of high-frequency spokes and activity lasting anywhere from 0.5 and 1,0 seconds
  k-complexes are slightly negative deflections in a wave followed by a positive deflection
• a light form of sleep which a person is easily awakened, if you wake someone up during this stage they may or may not know they were sleeping

Question 13

Stages 3 and 4 - sleep

Answer 13

the deep stages of sleep

• these stages are marked by high-amplitude and low-frequency wavelengths, ranging from 1 to 4 hz known as delta waves
• also known as slow-wave sleep

Question 14

REM SLEEP

Answer 14

• marked by brain activity that resembles wakefulness
• the rhythm observed here is similar to beta waves
• REM sleep is referred to as paradoxical sleep
• eyes moving back and forth under closed eyelids, significant loss of muscle tone resulting in the sleeper becoming relatively paralyzed as detected by an EMG.
• REM sleep is the sleep stage associated with dreams

Question 15

Sleep paralysis

Answer 15

you wake up but you are still in REM SLEEP

Question 16

Somnogens

Answer 16

substances in the body that produce sleep

Question 17

humoral theory of sleep regulation

Answer 17

• the idea that sleep - inducing chemicals accumulate in the body during wakefulness - until you fall asleep

Question 18

Circadian influences

Answer 18

“second wind” effect: periods of alertness interspersed with periods of sleepiness after being sleep deprived
circadian rhythm: psychological, behavioural, or physiological events that occur an approximate 24 hour cycle

Melatonin: a hormone, released by the pineal gland that induces sleepiness

Entrained rhythm : a rhythm regulated by external cues , such as light or heat

• free running rhythm
• a rhythm that is self-regulated , not requiring any external cues

Question 19

What controls circadian rhythms ?

Answer 19

• Suprachiasmatic nucleus (SCN) : the region of the hypothalamus is thought to control circadian rhythms ( sometimes called the master clock)
• melanopsin: a pigment in certain photoreceptor cells of the retina, which influences the light dark cycle through projections to the suprachiasmatic nucleus
• Retinohypothalamic projections: the projections of photoreceptors containing melanopsin from the retina to the hypothalamus

Zeitgebers : factors in the envi that influence circadian rhythms

Question 20

neurochemistery of wakefulness

Answer 20

neurotransmitters : norepinephrine, serotonin, histamine, glutamate and acetylcholine
neuropeptide : hypocretin (also known as orexin)

Question 21

Sleep neurochem

Answer 21

neurotransmitters : GABA, glutamate and adenosine

hormones: melatonin and melanin

Question 22

Drugs wakefulness

Answer 22

stimulants
inhibiting chemicals that promote sleepiness
(Ex: caffeine inhibits adenosine)

Question 23

Sleep drugs

Answer 23

Depressants
inhibiting chemicals that promote wakefulness
(ex: antihistamines make you drowsy (inhibit histamine))

Question 24

Melatonin and the retinohypothalamic tract

Answer 24

• the process by which waking and sleeping are regulated by the interactions between photoreceptors, the SCN, and the pineal gland. Not shown, is the ventrolateral preoptic area of the hypothalamus, which is the target of inhibition by the SCN

Question 25

Ascending arousal system (AAS)

Answer 25

a wakefulness promoting system that includes areas of the brainstem

Question 26

Executive system for wakefulness

Answer 26

A system that includes orexinergic neurons in the lateral hypothalamus

Question 27

The wake-sleep switch

Answer 27

GABA and glamin in the VLPO play the role of applying pressure to the switch to turn wakefulness on or off
- they are sleep promoting and they are both inhibitory

• wakefulness is promoted when the switch is in the “on” position. Orexin neurons in the LH excites neurons in the Locus Coeruleus, TMN and Rophe Nucleus (AAS), which in turn inhibits the firing in the Ventrolateral preoptic area
• sleep is promoted when the switch is in the “off: position. Gaba and glamin neurons in the Ventrolateral preoptic area inhibit the firing of orexin neurons in the Lateral hypothalamus in the ASS