L13 - The Function of Sleep

Question 1

What did total sleep dep find in rats?

Answer 1

They died 10-20 days later, due to mixed causes such as infections, organ failure and hypothermia.

Sleep dep rates ate more than control rats, but still lost weight

Suggests that sleep has a role in maintaining body weight and resting energy expenditure.

Question 2

What’s different about monotremes and the way they sleep?

Answer 2

Their REM sleep is mixed with SWS.

they broke off from mammals early in the phylogenic tree.

Question 3

What’s diff about reptiles, fish, molluscs and insects in sleep?

Answer 3

They don’t have high voltage slow waves, or REM.

Question 4

What can we hypothesise about pre-evolved way of sleep?

Answer 4

From looking at monotremes and ostriches, we can see that SWS exists, but REM sleep is characterised by some eye movements and head dropping, but EGG eventually goes back to slow waves… MIXED ELEMENTS!!

Question 5

What is the relationship between sleep duration and body mass?

Answer 5

• HERBIVORES: strong relo b/w size and sleep duration. might be because they take longer to eat enough food to supply the body (eg. elephant)
  Small animals can also sleep in burrows which are safer.
• CARNIVORES: no relationship - high nutrient dense diet.

Question 6

What is the relationship between size of brain to and sleep?

Answer 6

animals with more REM sleep have bigger brains.

Animals with longer sleep cycles have bigger brains!!

doesn’t really tell us about the func of sleep though

Question 7

What is unique about dolphin sleep?

Answer 7

UNIHEMISPHERIC SLEEP SWS!

• 1/2 of the brain sleeps at a time.
• allows for body to keep swimming and swim up for air
• RHS has slow waves, then the other side does.
• Eye on side contralateral to sleeping hemisphere is closed.
• no evience of REM - this is the only mammal that doesn’t REM. makes sense bc atonia wouldn’t be good.
• weak rebound - mother’s don’t sleep during new born period

Question 8

How do cetaceans sleep postpartum?

Answer 8

• no sleep behaviour in both the neonate and mother
• absense of sleep in both dolphins and killer waves.e
• no sleep for 3 weeks
  unique

Question 9

How do fur seals sleep?

Answer 9

• Unihemispheric SWS only in WINTER!!

can alter sleep depending on the environment

• flipper contralateral to the sleeping hemisphere is immobile
• whiskers contralateral to the awake hemisphere used to monitor position
• severely reduced REM.

in the summer.. they have bilateral NREM AND REM. no REM rebound during immediate post-winter period.

therefore can survive w/o REM for a period of time?!

Question 10

How does the white crowned sparrow sleep?

Answer 10

• During migration period, they fly at night and are activie during the day, despite normally sleeping all night.
• no apparently sleep dep effects
• birds show this same seasonal effect when in a lab.
• can see cognitive impairments when task is done during night hours, during non-migration period, but no impairments during migratory period.

(pecking holes to get food, need to learn this task)

Question 11

What is unique in the sleep pattern of frigate birds?

Answer 11

They showed signs of uni, bi hemispheric sleep with SWS and REM sleep during flight .. overall only 7% of their normal duration of sleep

Question 12

What is evidence that sleep serves a func?

Answer 12

1. There are numerous brain pathways to maintain sleep - there is redundancy in the systems. means it’s important!
2. Serious physiological changes/death results from prolonged sleep dep of animals.
3. Sleep is seen in all mammals, birds and reptiles and probably exists in amphibians, fish and invertebrates.
4. Sleep has persisted in evolution even though it is apparently maladaptive with respect to other functions
5. Accomodations are made to permit sleep in different environemnts and lifestyles

Question 13

What is the relationship between sleep and predators?

Answer 13

Complicated relationship, but in general, the more predators an animal has, the less it sleeps.

But rabbits have a lot of predators but find a safe place to sleep.

Question 14

What is the immobility hypothesis?

Answer 14

• Suggests circadian rhythm causes rest-activity cycle.
• sleep evolved to ensure immobility during rest phase, and acts to support and reinforce the circadian organisation of behaviour.

–> leads to less exposure to danger.

also implies that sleep no longer serves a purpose in humans, as we have food readily available and can stay up at night without danger.

Question 15

What is evidence to support immobility hypothesis?

Answer 15

Sleep of species appears to fit with their ecologic niche.

but we’re can’t really test this.

Question 16

What is the energy conservation theory?

Answer 16

Weak form - immobility is associated with lower levels of energy expenditure than activity. Thus, immobility itself conserves energy.

Strong form - sleep actively lowers energy expenditure below that of immobile wakefulness.

Evidence does show that energy expenditure goes down during hours of sleep - but may also be associated with circadian rhythm.

• O2 consumption falls with sleep and time. slight reduction with time, as people lie in bed but not fall asleep, and dramatic reduction w sleep
• stage 4 sleep increases with reduced caloric. supports energy conservation theory bc more slow wave to save energy, for the energy deprived.

Question 17

What is metabolic rate?

Answer 17

how much energy you need at rest (when awake)