Chapter 9 Sleep
Biological Rhythms
1. Ultradian
a. Example: basic rest-activity cycle, REM
b. Length: less than 1 day
2. Circadian
a. Example: sleep-wake cycle
b. Length: approx. 1 day
3. Infradian
a. Example: menstrual cycle
b. Length: longer than 1 day
4. Circuannual
a. Example: annual breeding cycles, SAD (seasonal affective disorder)
b. Length: annual
Circadian Function
a. Definition: regular bodily rhythms that occur on a 24 hour cycle
b. Why might we have this internal biological clock?
a. Pacemaker cells
b. CLOCK and CYCLE proteins bind to a promoter and promote production of PER and TIM
until the max amount is produced. Then PER and TIM inactivate the CLOCK and CYCLE
protein. 1 cycle = 24 hours. We don’t know if this is in humans.
c. How do we measure the clock?
a. Rat studies
i. Measure the electrical activity of a rat; you see a pattern
ii. Lesion the master clock (suprachiasmatic nucleus).
1. No order to events but there is no affect to the total amount of sleep
d. Factors that help determine human clocks
a. Zeitgeber = external cues that help to set the clock
i. Examples: Light/dark, temperature, social interactions
1. Experiment: If you put someone in a room with lights always on
a. Timing of period increases to 24-25 hours.
i. Clock becomes a free-running clock
b. Fall asleep later and later
ii. How to disrupt your clock?
1. Travel, jetlag
e. Anatomical structures involved
a. Suprachiasmatic nucleus
i. Location: in the hypothalamus just above the optic chiasm
ii. Lesioning the fibers above the optic chiasm will disrupt cycles otherwise known as
the retinohypothalamic tract. This is because light is a primary zeitgeber for most
mammals’ activity cycles, we would expect that the SCN receives fibers from the
visual system.
iii. Pacemaker cells: cells that will fire in rhythm whether they get input or not. If you
transplant cells from one animal to another, the donor will impart their rhythm to the
host. Important because there is individual variability.
iv. Pineal gland: makes melatonin. Melatonin detects sunlight directly in birds. Circuit
that connects the SCN with pineal gland creates a feedback system, melatonin is also
very important for sleep.
Sleep
a. Definition:
a. Not the absence of waking
b. Not due to lack of sensory input
c. An active process
b. Stages of sleep (Kleitman)
Stage
Characteristics
Awake Small amplitude, high frequency waves
Drowsy Waves become more rhythmic, lower frequency
Stage 1 Slow rhythmic activity, will not see in people who are awake unless
they are meditating or very calm
Stage 2 See K-complex (sudden sharp waves) and Sleep spindles (short bursts
of waves 12-14 HZ)
Stage 3 Start seeing Delta activity
Stage 4 “Deep sleep” or “slow wave sleep”, see delta activity
REM
“Rapid eye movement”; EMG activity = 0 ;
Waveform
Beta waves
Alpha waves
Theta activity
Theta, sleep spindles, and
K-complexes
Delta activity (20%-50%)
Delta activity >50%
Theta + Beta activity
REM
a. Night terrors
a. Occur during deep sleep
b. Dreams based on reality, experiences during the day
b. Nightmares
a. Occur during REM
b. Dreams are crazy and outlandish
c. Sleepwalking
a. Possibly due to a dysfunction of muscle inhibition
How does the length of each sleep stage change with age? Between species?
Age
As infants:
Adult
- Sleep throughout the day
- Only 1 period of sleep needed
- Multiple periods of sleep
(possibly due to the development of the
needed
SCN)
- Half the time in REM and half
- Amount of time we spend in REM
the time in NREM
decreases to 20%
Elderly
- Wake up multiple
times during the night
after REM
Species - All animals sleep
- Smaller animals  more sleep? Maybe
- Spiny anteater
- huge brain compared to body. No REM. Theory = no REM so can’t consolidate memories and
delete unimportant memories, therefore need a big brain to hold all their memories
- Dolphin
- One hemisphere sleeps at a time. Why? They need to breathe!
Functions of sleep
Circadian Theory
- Conserve energy, forces us to be
quiet at certain times of the day
Recuperation Theory
- Our body needs time to recover to
overcome deficits you build up
during the day
Sleep promotes learning
- Sleep is needed to consolidate
memories and erase the memories
we don’t need
No single theory is correct!
Neural Mechanisms of Sleep
Reticular Formation
Raphe Nuclei
- Integrates sensory info; regulates - Where serotonin is generated
arousal, promotes wakefulness
- Promotes sleep
- Stimulation (in sleeping rat)
- Damage produces insomnia, REM
awakens them
inhibited
- Destruction results in drowsiness
Sleep is distributed between structures
Locus Coeruleus
- Where norepinephrine is
generated
- Promotes wakefulness
Disorders
Narcolepsy
a. Definition: neurological disorder characterized by sleep at inappropriate times
b. Primary symptom: sleep attack. Person falls asleep for 2-5 minutes and feels refreshed
i. See these too: cataplexy, hypnagogic hallucinations
c. Hypothesis: cholinergic hyperactivity, monoaminergic (neurons that secrete monoamines)
hypoactivity (less activity) in pons
d. Hypocretin: destruction of the system produces narcoleptic effects