S2W5Sleep

Question 1

hibernation

Answer 1

Temperature and heart rate decrease, and dendrites lose a quarter of their branches

Come out of hibernation every few days (but stay asleep) to raise their temperature

Slows down aging

conserving energy while food is scarce

Question 2

Nematodes

Answer 2

Sleep when they are shedding their old cuticle and forming another.

Sleeping nematodes adopt a hockey-stick-like posture

Question 3

Unihemispheric sleep

Answer 3

One hemisphere (and the contralateral eye) sleeps while the other remains awake.

Aquatic mammals, birds and reptiles.

Only slow-wave sleep (not REM) occurs unihemispherically

Question 4

Inactivity Theory

Answer 4

Inactivity at night helps animals survive, as they did not injure themselves in the dark and were not killed by predators.

This trait which was passed on through natural selection

HOWEVER always safest to remain conscious,

Question 5

Energy Conservation Theory

Answer 5

Food is not always easy so animal must conserve its energy (esp. night).

Support as energy metabolism is reduced in during sleep (10% in humans).

BUT animals in unihemispheric sleep are still using energy

Question 6

Restorative Theories

Answer 6

During sleep there is restoration of what has been lost from the body (muscle mass, tissue cells)

Many major restorative functions do occur mainly in sleep

Question 7

Brain Plasticity Theory

Answer 7

Sleep is a time in which the brain develops and changes.

Sleep does appear to be crucial for initial brain development in infants.

Extensive research to suggest improvement in cognitive function (especially memory) following sleep

Question 8

Brain Stem

Answer 8

Responsible for mediating levels of arousal – including cycles of Non-REM and REM sleep.

Electrical stimulation of anterior portions of the brain stem results in arousal of the forebrain.

During sleep, GABA-ergic neurons increase their own firing rate

Release of GABA to thalamus and cortex inhibits the brain – producing sleep

Question 9

Reticular formation

Answer 9

Within brain stem, extending from medulla to forebrain.

The part that deals with cortical arousal is pontomesencephalon

Question 10

Pontomesencephalon

Answer 10

Axons extend to forebrain releasing acetylcholine, serotonin and glutamate.

Excites cells in hypothalamus, thalamus and basal ganglia

Excitation is relayed to the cerebral cortex

Maintains arousal during wakefulness and increases it in response to tasks.

Stimulation wakes someone or increases alertness.

Question 11

Hypothalamus

Answer 11

Several pathways release a different neurotransmitter:

Acetylcholine
Histomine
Orexin

Orexin not for waking but for staying awake.

Optogenetic inhibition of orexin neurons causes mice to go quickly into slow-wave sleep.

Question 12

Polysomnograph

Answer 12

Records eye movements and EEG

Pyramidal neurons arranged in 6 layers of cerebral cortex.

All same way (dendrites up).

The voltage change produced by EPSP/IPSPs can be recorded on the scalp.

Some neurons reach peak just before/after majority.

Creates a wave.

Represents average activity of many interacting neurons in cortex.

Question 13

Neural Oscillations

Answer 13

Neural events characterised by series of repeating waves (oscillations).

Thought to be due to complex network of inhibitory interneuron networks.

Characterised by frequency and amplitude.

Different sleep stages characterised by distinctive patterns of activity

Question 14

Frequency

Answer 14

how fast they oscillate (measured in Hertz (Hz)

Question 15

Amplitude

Answer 15

how large the wave is, measured in mV

Question 16

Stage 1 Sleep

Answer 16

Transition period between sleeping and waking.

Irregular, jagged, low-amplitude waves of different frequencies.

Question 17

Stage 2 Sleep

Answer 17

Characterized by sleep spindles and K-complexes

Question 18

Sleep spindles

Answer 18

12-14Hz waves during a burst lasting 0.5+ secs

Results from interactions between thalamus and cortex

Question 19

K-complex

Answer 19

A sharp wave associated with temporary inhibition of neuronal firing.

Suggested to reflect either transient cortical arousal, or sleep-protective events

Question 20

Stage 3 and 4 Sleep:

Answer 20

Heart rate, breathing rate and brain activity decrease

Slow-frequency (delta, 1-3Hz), large-amplitude waves become more common

Stage 4 sleep has a greater prevalence of slow-waves.

Grouped together into single stage (slow-wave sleep)

Waves are synchronised over entire neocortex.

For 0.5 sec nearly all neurons silent simultaneously

Question 21

Stage 5 Sleep: REM

Answer 21

Irregular, low-amplitude, high-frequency oscillations.

Indicates increased activity suggesting lighter sleep.

Postural muscles of body more relaxed.

Higher variability of heart and breathing rate, erections and twitches

Includes features of light and deep sleep.

Question 22

REM and brain

Answer 22

GABAergic neurons from the medulla are responsible for initiating REM.

Ativity increased in the medulla and pons, limbic system, temporal and parietal cortices

Decreased in primary visual cortex, motor cortex, and dorsolateral prefrontal cortex

Question 23

NREM

Answer 23

Stages 1 > 4

Question 24

Cycles throughout the night

Answer 24

1 > 2 > 3 > 4 > 3 > 2 > REM >2 etc.

Each cycle lasts 90 mins.

Experience alterations in response to external stimuli

Four or five cycles a night