Sleep and Circadian rhythms

Question 1

What are the features of sleep?

Answer 1

• 1) Unconscious. We never know we are sleeping while we are asleep.
• 2) We switch from awake to sleep instantaneously, it is not a gradual process
• 3) Parts of the brain can be very active during sleep

Question 2

What is an EEG?

Answer 2

Records the fluctuations of the electrical activity of large ensembles of neurons in the brain, mostly in the cortex.

Question 3

What are the different classes of sleep?

Answer 3

• Short wave sleep

- Rapid-eye movement

Question 4

Describe short wave sleep

Answer 4

can be divided into four stages and is characterized by slow-wave EEG activity

Question 5

Describe rapid-eye movement sleep

Answer 5

characterized by small amplitude, fast-EEG waves, no postural tension, and rapid eye movements

Question 6

What happens in Stage 1 SWS?

Answer 6

• Shows events of irregular frequency and smaller amplitude, as well as vertex spikes, or sharp waves
• Heart rate slows, muscle tension reduces, eyes move about
• Lasts several minutes

Question 7

What happens in Stage 2 SWS?

Answer 7

• Waves of 12 to 14 Hz that occur in bursts, called sleep spindles
• K-complexes appear–sharp negative EEG potentials

Question 8

What happens in Stage 3 SWS?

Answer 8

•Early stage 3 sleep
–Continued sleep spindles as in stage 2
–Defined by the appearance of large-amplitude, very slow waves called delta waves
–Delta waves occur about once per second
•Late stage 3 (stage 4) sleep
–Delta waves are present about half the time

Question 9

What happens in REM sleep?

Answer 9

•REM sleep follows SWS
–Active EEG with small-amplitude, high-frequency waves, like an awake person
–Muscles are relaxed—called paradoxical sleep

Question 10

How do sleep patterns and needs change with age?

Answer 10

• Infants spend about 8 hrs in non-REM sleep and about 6 hours in REM sleep
• Children spend about 10-12 hrs a night sleeping (2-4 hrs of REM)
• Adolescents through adults sleep about 7-8 hrs (1-2 hrs in REM)
• Starting at about 50 REM sleep= 30-1hr and they only sleep about 6 hours

Question 11

What parts of the brain are involved in neural control of sleep?

Answer 11

• Recticular formation
• Hypothalamus
• Forebrain
• Pontine system

Question 12

What are some of the chemical controls of arousal?

Answer 12

•Histamine
–Cell bodies in tuberomammillary nucleus of the hypothalamus
–Increases cortical activation and arousal
•Hypocretin
–Cell bodies in lateral hypothalamus
–Has an excitatory, wakefulness-promoting effect
•Acetylcholine (Ach)
–Basal forebrain Ach neurons that activate cortex
•Norepinephrine (NE)
•Serotonin (5-HT)

Question 13

What is the locus coeruleus involved in?

Answer 13

Norepinephrine
Arousal
-firing rate significantly decreases during SWS and REM sleep compared to waking

Question 14

Describe the activity of the 5-HT neurons in the raphe nuclei

Answer 14

-firing rate decreases as we progress from active waking to quiet waking, to drowsiness, through stage 1, 2, and 3 sleep. It reaches its lowest during REM sleep and then the first second after REM sleep the firing rate significantly increases (past active waking level)

Question 15

What area of the brain are involved in sleep promotion?

Answer 15

•Ventrolateral preoptic area (VLPA) of hypothalamus
–lesions produce total insomnia, leading to death
–electrical stimulation induces drowsiness

Question 16

What part of the brain generates SWS?

Answer 16

•Basal forebrain
–Subset of GABA releasing neurons
-Need to have a connection between your basal forebrain and pontine system to have cycles between wakefulness and sleep

Question 17

Why do we sleep?

Answer 17

• Energy conservation
• Adaptive value
• Body restoration
• Memory consolidation

Question 18

What are some of the features of REM sleep?

Answer 18

–Dreaming
–Paralysis with some twitching: subceorelor nucleus sends out signals to motor neurons in the spinal cord
–Breathing heart rate irregular
–Rapid eye movements: pons sends signals to the tectum which causes this

Question 19

What are dreams?

Answer 19

activation of the cortex which activates some memories and the cortex tries to tie bits of information together and they seem to make sense in the dream

Question 20

What can sleep deprivation do to us?

Answer 20

•Cognitive function
•Alterations in mood
–Aggressive oppositional kids
•Death (rats)
–Immune function
•Beauty sleep
–Rated less attractive

Question 21

What is insomnia?

Answer 21

•Insomnia: Difficulty falling asleep or waking early
–Transient- lasting one to several days
–Chronic- lasting weeks, months or years
•Causes:
–Hyperarousal due to stress, anxiety or excitement
–Time zone changes
–Sleep environment, e.g. noises

Question 22

What is snoring?

Answer 22

•Snoring:
–Narrowing of airway
–Vibration of soft tissue

Question 23

What is Apnea?

Answer 23

–Airway closes shut during snoring for a few seconds up to 1 minute.
–Obesity increases risk of apnea
-treated with continuous positive airway pressure

Question 24

What do pontine lesions result in?

Answer 24

•REM sleep
–Atonia/paralysis
–Inhibition of spinal motor neurons
•REM sleep behavior disorder
–Act out dreams

Question 25

What is narcolepsy?

Answer 25

•Nacolepsy
–Uncontrollable sleep
–Fall into REM sleep instantaneously
•Cataplexy is a type of narcolepsy where the episodes of REM sleep occur in response to emotional stimulation (e.g. laughing, crying, excitement)

Question 26

What causes narcolepsy in humans?

Answer 26

–Loss of hypocretin cells in hypothalamus

–Autoimmune disease