Sleep and Biological Rhythms

Question 1

What is sleep?

Answer 1

A behavior
Mostly unconscious state
We spend about 1/3 of our lives asleep

Question 2

How do we measure sleep?

Answer 2

Electroencephalogram
Electrooculogram
Muscle tension

Question 3

Stages of sleep

Answer 3

Waking
Non-rapid eye movement (NREM) sleep (1, 2, 3)
Rapid eye movement (REM) sleep

Question 4

Waking

Answer 4

Alpha waves
Beta waves

Question 5

Alpha waves

Answer 5

8-12 Hz
Usually when eyes are closed
Resting, little mental activity
Just before skilled actions

Question 6

Beta waves

Answer 6

High frequency (13-30 Hz)
Irregular, desynchronous
Mostly frontal lobe
Alertness, attentiveness, active thinking
Dreaming

Question 7

NREM 1

Answer 7

First fall asleep
Very light sleep

Question 8

NREM 2

Answer 8

Light sleep where you can be easily aroused

Question 9

NREM 3 (slow wave sleep)

Answer 9

Deeper stage of sleep
More difficult to rouse
May feel disoriented if woken from this stage

Question 10

Rapid eye movement sleep

Answer 10

Rapid eye movement
On EEG looks similar to wakefulness

Question 11

Stage 1 sleep

Answer 11

Theta waves

Question 12

Theta waves

Answer 12

Low frequency (3.5-7.5 Hz)
Transition between waking and sleeping
Drowsiness, boredom
Hypnic jerks

Question 13

Stage 2 sleep

Answer 13

Sleep spindles
K complexes

Question 14

Sleep spindles

Answer 14

Short bursts of waves of 12-14 Hz
2-5 times a minute
Consolidation of memories, correlated with intelligence

Question 15

K complexes

Answer 15

Sudden, sharp waveforms
Only found during this stage
Unsure of what they do
Once a minute

Question 16

Stage 3 sleep

Answer 16

Delta waves

Question 17

Delta waves

Answer 17

Very low frequency (less than 3.5 Hz)
High amplitude
“Slow wave sleep”
If woken up at this stage, will feel groggy
Brain activity increases in visual and auditory cortexes, decreases in thalamus and cerebellum

Question 18

REM sleep

Answer 18

EEG becomes desynchronized, appears similar to waking state
Brain is very active with high oxygen consumption and blood flow
Increased limbic activity, but prefrontal is deactivated
Body mostly paralyzed, rapid eye movements, dreaming
If woken up, will remember dreams, alert and attentive
Easily aroused by relevant stimuli

Question 19

Sleep across the lifespan

Answer 19

Early in life, sleep a lot (about half the time is REM sleep)
By adulthood, average 8 hours a night, 20% is REM sleep
REM sleep decreases with age

Question 20

Functions of slow-wave sleep

Answer 20

Essential for survival
Allows brain to rest (decreased cerebral metabolic rate/blood flow)
Greater mental, but not physical, activity during the day increases slow wave sleep at night

Question 21

Functions of REM sleep (several hypotheses)

Answer 21

Need to survive
Maybe helps with early brain development
Maybe for learning and memory consolidation

Question 22

Neural control of sleep

Answer 22

Adenosine (a neuromodulator) may play a role in control of sleep
If awake too long, accumulation of adenosine –> cognitive/emotional effects of sleep deprivation
Caffeine is an adenosine antagonist

Question 23

5 neurotransmitters that play a role in arousal

Answer 23

Acetylcholine
Norepinephrine
Serotonin
Histamine
Orexin

Question 24

Acetylcholine

Answer 24

Involved in arousal of the cerebral cortex
2 groups: dorsal pons and basal forebrain
Agonists increase signs of cortical arousal
Most ach neurons elevated in REM sleep and when awake but decreased during slow-wave sleep

Question 25

Norepinephrine

Answer 25

Catecholamine agonists –> arousal/sleeplessness
Mediated by the noradrenergic system of the locus coreuleus, in dorsal pons
Locus coeruleus –> diffuse releasing norepinephrine in the cortex
Fluctuates throughout sleep/waking cycle (highest in morning and decreases throughout the day)

Question 26

Serotonin

Answer 26

Most serotonergic neurons are in the raphe nuclei
Axons project diffusely
Stimulation of raphe nuclei –> locomotion and cortical arousal
Serotonergic neurons are active during waking

Question 27

Histamine

Answer 27

Antihistamines cause drowsiness by blocking histamine receptors
Cell bodies of histamine neurons are in the tuberomammillary nucleus (TMN) of the hypothalamus
Activity of histaminergic neurons is high during waking but low during slow-wave and REM sleep

Question 28

Orexin

Answer 28

Neurons are in the hypothalamus and project to nearly every part of the brain
Rat study found orexinergic neurons fire at a high rate during active waking and low rate during quiet waking, slow-wave sleep, and REM sleep

Question 29

Neural control of sleep/wake transitions

Answer 29

Circadian rhythms
Lights serves as a zeitgeber

Question 30

Zeitgeber

Answer 30

Stimulus that resets biological clock
Melanopsin in the ganglion cells of the eye transmit light info to the suprachiasmatic nucleus (SCN) in hypothalamus
In humans artificial light delays bedtime and window coverings texted sleep

Question 31

Melatonin

Answer 31

Hormone secreted by the pineal gland
Melatonin is released during the night in response to input from SCN
Highest levels early in the night
Melatonin before bed reduces negative effects of shift work and jet lag