Homeostatic system

• possible functions of sleep

  1) Energy conservation

  2) Niche adaptation

  3) Physical restoration (body and brain)

  4) Memory consolidation
• 3 types of rhythms

  Ultradian, Circadian, and Infradian
• ultradian rhythms


  biological rhythms that occur more than once each day
• circadian rhythm


  the biological clock; regular bodily rhythms that occur on a 24-hour cycle
• infradian rhythms


  biological rhythms that occur once a month or once a season
• circadian rhythms clock

  Melatonin secretes at 9pm, deepest sleep at 2am, melatonin stops at 7am, highest alertness at 10 am
• What is the function of the suprachiasmatic nucleus (SCN)?

  It is the master clock in the hypothalamus.
• What type of neurons are found in the Ventrolateral SCN?


  Neurons with light-induced gene expression.
• Where do neurons in the Ventrolateral SCN receive projections from?


  Retinal ganglion cells.
• What is the role of Ventrolateral SCN neurons after receiving projections from retinal ganglion cells?

  They relay the information throughout the SCN.
• Photoentrainment

  synchronization of the circadian clock by light

  Photosensitive retinal ganglion-->projects to SCN-->Pineal gland--> releases melatonin
• What is melatonin?

  A hormone manufactured by the pineal gland that produces sleepiness.
• What triggers the release of melatonin?

  SCN in darkness turns on the pineal gland to release melatonin.
• At what time does the release of melatonin typically start?


  The release of melatonin typically starts at 9pm.
• How long does the release of melatonin last?

  The release of melatonin typically lasts for 12 hours.
• sleep cycle


  stage 1 --> stage 2 --> stage 3 --> stage 4 --> REM
• Waves during awaken attentiveness


  Beta
• Waves during awaken non attentiveness


  alpha
• waves during drowsiness/stage 1 of non rem sleep


  theta
• Stage 2 (Non-REM sleep cycle)


  theta waves, sleep spindles, K complexes
• Stage 3 & 4 of NREM sleep


  characterized by delta waves (low frequency; DEEP SLEEP)
• REM sleep


  the stage of sleep marked by rapid eye movements, dreaming, and paralysis of motor systems
• How many times do the stages occur in our sleep?

  Average only 2 slow wave sleep per night and 5 REM sleep per night
• Dreams during non rem sleep?

  shorter, less visual, less emotional, related to everyday activities, more thought like

  Freud's "day's residue"
• Dreams during rem sleep?

  longer, more visual, emotional

  sometimes bizarre and emotional
• During REM sleep what part of our brain is active?

  Limbic system: amygdala, parahippocampus, pontine tegmentum, anterior cingulate
• During REM sleep what part of our brain is inactive/decreases?


  Prefrontal and posterior cingulate
• What is the role of the pedunculopontine nucleus in REM sleep?


  It suppresses activity of lower motor neurons in the spinal cord via projections to the pons.
• How does REM sleep affect motor output?

  It leads to decreased motor output due to the activity of the pedunculopontine nucleus.
• Reticular Activating System (RAS)


  Stimulation of cholinergic neurons in pons and midbrain awakes the animal.
• Neurons needed for reticular activity system?

  Serotonergic neurons, Noradrenergic neurons, Histamine neurons.
• serotonergic neurons

  Neurons that use serotonin as their transmitter.
• noadrenergic neuron

  Neurons that use noradrenaline as their transmitter
• Histamine neurons

  -Located in the tuberomammillary nucleus (TMN) of the hypothalamus.

  -Exhibit high activity during waking and low activity during sleep.

  -Their receptor blockers increase sleep.
• Orexin

  Modulates TMN and LC(Locus coeruleus), prominent in waking up.
• Hormones that are active when we are awake?


  Acetylcholine, serotonin, norepinephrine, histamine and orexin
• narcolepsy caused by?

  Deep, sporadic sleep that immediately takes you to REM sleep caused by destroyed orexin neurons.
• Adenosine

  Decreases orexin
• Structure of awake

  SCN/Limbic system-->orexin-->mononergic neurons-->thalamus cortex.

  
  

  SCN and limbic system excites orexin which then activates mononergic neurons such as serotonin to activate and then it sent to the thalamus
• Structure of asleep

  VLPO-->orexin

  VLPO-->mononergic neurons

  
  

  VLPO inhibits orexin and mononergic neurons