Chapter 10 Functions of Sleep and NREMS Notes

Unique Characteristics of Sleep:
- Found in all mammals, birds, reptiles, and possibly amphibians, fish, and invertebrates.
- Influenced by body size, age, diet, safety of sleeping site, and environment.
- Cannot be replaced by waking rest.
- Occurs at regular times each nychthemeron.
- Results in significant physiological and psychological changes.
- Characterized by quiescence, loss of consciousness, and reduced interaction with the environment.
- Actively produced by the brain.
- Rhythmic patterns: NREMS and REMS alternate.
- Young mammals exhibit similar sleep development.
- Unique brain waves (slow waves, K-complexes, spindles in NREMS; REMS waves resemble wakefulness).
- Differing brain metabolism levels: low during NREMS, high during REMS.
- Thermoregulation occurs during NREMS, absent in REMS.

Restoration and Energy Conservation:
- Sleep allows restoration of bodily processes depleted during wakefulness and conserves energy.
- Rest and Restoration Evidence:
- Sleep evolved from periods of rest.
- Wound healing hindered by sleep deprivation.
- Anabolic hormones (growth hormone, testosterone) peak during sleep.
- Short-term sleep deprivation does not lead to immediate breakdowns.
- Energy Conservation Evidence:
- Reduced body temperature and energy use during sleep.
- Greater metabolic costs in awake, active states.

Adaptive Non-Responding Hypothesis:
- Sleep may be safer during vulnerable times; reduced responsiveness aids survival.
- Certain animals sleep more during periods of danger or food scarcity.
- There is difficulty in scientifically testing predatory susceptibility during sleep.

Cognitive Benefits:
- Inadequate sleep leads to cognitive impairment.
- Sleep necessary for memory consolidation.
- Mechanisms of Memory Consolidation:
1. Deprivation Studies: Sleep loss impairs memory retention.
2. Brain Activity Changes: Alterations in sleep stages post-learning.
3. Stimulation During Sleep: Improvements observed in memory during sleep stimulation.
4. Replay of Activity: Specific brain activity patterns replayed during sleep strengthen memory connections.
- N3 sleep crucial for brain maintenance and synaptic stability.

Function of NREMS:
- Decreased body and brain activity, decreased body temperature, hormonal changes.
- Restoration, maintenance, and conservation hypotheses related to N3 sleep.
Function of N3:
- Restoration of body and brain during sleep.
- Hormonal changes that favor recovery.
- Need for N3 increases with wakefulness, showing homeostatic function.
Function of N2:
- May provide behavioral quiescence while maintaining selective vigilance.

The function of sleep may not be singular but serve multiple roles that differ among species.
Sleep is particularly beneficial for the brain, emphasizing its role in maintaining neuronal structures and brain chemistry.
Sleep requirements vary significantly across species and developmental stages.