Week 9 - Sleep

Question 1

What is the difference between an endogenous circannual rhythm and an endogenous circardian rhythm?

Answer 1

Endogenous circannual rhythm - an internal cycle that prepares birds for seasonal cycles

Endogenous circadian rhythm - lasting a day

Question 2

What happens to sailors on submarines trying to maintain 6 hours work, 6 play, 6 sleep?

Answer 2

Their bodies still generate rhythms of alterness and body chemistry that average about 24.3 to 24.4 hours.

Question 3

What functions do we have circadian rhythms for?

Answer 3

eating, drinking, urination, hormone secretion, metabolism, sensitivity to drugs, body temp, mood.

Question 4

What is the system that corrects the circadian rhythm?

Answer 4

Zeitgeber (time giver)

Question 5

What is the most dominant zeitgeber for land vs. sea animals?

Answer 5

Light and tide.

Question 6

What other zeitgebers are there?

Answer 6

Exercise, arousal of any kind, meals, temperature of the environment.

Question 7

Are social stimuli effective as zeitgebers?

Answer 7

No, unless they induce exercise or other vigorous activity.

Question 8

What does the Suprachiasmatic Nucleus?

Answer 8

It is the main driver of rhythms for sleep and body temperature.

Question 9

What happens if the Suprachiasmatic Nucleus is damaged?

Answer 9

The body’s rhythms become erratic.

Question 10

Where is the Suprechiasmstic Nucleus?

Answer 10

It is behind the Optic Chiasm, and is part of the hypothalamus.

Question 11

How does the SCN work?

Answer 11

It generates circadian rhythms in a genetically controlled manner.

Question 12

Which path alters the SCN’s settings?

Answer 12

the “retinohypothalamic path”. - retina to the hypothalamus.

Question 13

What is an EEG?

Answer 13

Electroencephalogram records an average of the electrical potentials of the cells and fibers in the brain areas nearest to each electrode on the scalp. The EEG rises or falls when most cells do the same things at the same time. It shows only slight fluctuates until some event gets everything yelling at once. it is an OBJECTIVE measure of sleep or wakefulness.

Question 14

What are alpha waves?

Answer 14

Consists of regular, high amplitude waves. Brain produces this activity when relaxed, not engaged in strenuous activity.

Question 15

What are beta waves?

Answer 15

Consists of low-amplitude irregular waves. Active when alert and attentive, or thinking actively.

Question 16

What is involved in Stage 1 of slow wave sleep?

Answer 16

Occurs when we first fall asleep.
Theta activity (4-7Hz)

• irregular, jagged, low-vltage waves.
• activity high but declining.

Question 17

What is involved in Stage 2 of slow wave sleep?

Answer 17

• Sleep spindles (burst of 12-14Hz waves lasting at least half a second)
• K-complex: sharp high-amplitude negative wave followed by a smaller, slower positive wave. Reduce the brain sensitivity to input.

Question 18

What is slow wave sleep?

Answer 18

It contains the 4 stages of sleep.

Question 19

What is involved in Stage 3 of slow wave sleep?

Answer 19

-High amplitude, low frequency waves (at least half a second) - delta waves (1-4hz) in spindle pattern

Question 20

What is involved in Stage 4 of slow wave sleep?

Answer 20

• More delta activity dominates half of recording.

- deepest stage of slow wave sleep, arousal is most difficult.

Question 21

What happens as sleep deepens?

Answer 21

Muscles lose tone, heart rate and temperature decrease. Sleeper is becoming perceptually less responsive to environment. Thalamus stops relaying sensory information to cortex.

Question 22

What are the physiological, psychological and electrical characteristics of REM?

Answer 22

Electrical - Irregular, low-voltage, fest EEG waves
Physiological - Dramatically decreased muscle tone, rapid eye movements, cardiac and respiratory acceleration and increase, increased vaginal blood flow and penile activity
Brain - Presence of PGO waves (Pons-Geniculate-Occipital) - sharp spikes from brainstem that drives eye movements

Question 23

What is paradoxical about paradoxical sleep?

Answer 23

During REM (paradoxical sleep), eye-movement is HIGHLY ACTIVE, while EEG activity is at LOW AMPLITUDE.

Question 24

What is the significance of PGO waves?

Answer 24

Activity in the PONS triggers REM sleep.

Question 25

What activity in the PONS regarding a particular neurotransmitter, signifies the onset of REM sleep?

Answer 25

Acetylcholine activity increases in the Pons. Some of these acetylcholine neurons control PGO waves, while others inhibit motor neurons in the spinal cord.

Question 26

What are the brain bits involved in arousal?

Answer 26

Reticular Formation - structure in midbrian
-sends axons into brain and into spinal chord. Pontomesencephalon maintains arousal in wide regions of cerebral cortex.

Locus coeruleus - small structure in the pons
-responds to meaningful events. Important for information storage, almost completely inactive during sleep (maybe why we forget dreams)

Basal forebrain axons go to thalamus and cerebreal cortex - increases arousal, learning and attention

Hypothalamus can release histamine, increasing arousal.

Question 27

What’s insomnia?

Answer 27

Difficulties going to or staying asleep. 20% of population affected at some stage in their lives.
Commonly reported by older, female, coffee or alcohol usage. Sometimes results from shift in phase of circadian rhythm for body temperature.

Question 28

What is sleep apnea?

Answer 28

A breathing difficulty. Narrow airway closes in sleep posture - relaxation of throat cavity. May be genetic, hormonal, old age - deterioration of brain mechanisms regulating breathing, obesity.

Question 29

What is narcolepsy?

Answer 29

Occurs in 1/1000. Abrupt sleep lasting 5 - 30 minutes. Occurs around every 90 minutes. Feel drowsy most of the time, can fall asleep within a few seconds.
4 symptoms: Gradual or sudden attack, occasional cataplexy (sudden loss of muscle tone)- cataplexic attack can involve loss of muscle tone while awake caused by sudden emotional stimulus, sleep paralysis (complete inability to move upon waking), hypnogogic hallucination often occurring during the onset of sleep.

Question 30

How is narcolepsy related to REM sleep?

Answer 30

Each stage can be interpreted as REM sleep intruding into consciousness. Narcolepsy associated associated with acetylcholine activity and neurotransmitter Orexin.

Question 31

What are night terrors?

Answer 31

Frequently occur during NON-REM sleep, more common in children than adults.

Question 32

What is sleep walking?

Answer 32

Walking while asleep. Causes not well understood, more common when sleep deprived or under stress. Runs in families, occurs in children.

Question 33

What is the evolutionary hypothesis for why we sleep?

Answer 33

Conservation of energy. Decreased heartate, lower blood pressure, reduced respiration. Reduced metabolic activity. Body temp decreases also, saving energy.

Question 34

What is the repair and restoration theory of sleep?

Answer 34

Enables brain and body to repair itself - restoring proteins and replenishes glycogen (energy store)

Question 35

What is the function of REM sleep?

Answer 35

1/5th of sleep is REM.

• REM helps discard useless connections formed during the day. Impaired REM prevents memory consolidation of learned motor skills.
• Assists in memory formation, especially motor skills
• Moving eyes increases supply of oxygen to cornera (it doesn’t get oxygen from blood).
• Symptoms of psychotic depression reduce when REM is REDUCED. Antidepressant treatments suppress REM.