unit 3

• For each type of rhythm, indicate if it is circadian, ultradian, infradian or circannual:

  • sleep/wake cycle: circadian
  • body temp in endotherms: circadian
  • migration: circannual
  • hibernation: circannual
  • menstrual cycle: infradian
  • melatonin secretion: circadian
  • eating and drinking: circadian and ultradian
  • testosterone secretion: ultradian
• endogenous: derived from within
• free-running: a cycle without cues for time of day
• zeitberger: something that sets the clock -- time giver
• entrain: to set the clock
• The sleep-wake cycle is generated from within and will continue even without knowledge of the time of day, and even without changes in lighting conditions. Therefore, the sleep-wake cycle is endogenous. A sleep-wake cycle that is occurring without changes in lighting conditions is free-running. Our sleep-wake cycle can be synchronized with lighting conditions, because light can set, or entrain the clock. Comparing temperature, exercise, and light, which can all entrain the clock, light is the strongest zeitberger
• retinohypothalamic tract: retina (specialized retinal ganglion cells) -> SCN (glutamate)
• The SCN sends information (indirectly) to the pineal gland, which secretes the hormone melatonin. The hormone feeds back to the SCN making it more sensitive to zeitgebers
• clock, cycle, per, and cry are in a family called clocked genes. these genes are turned on, make their protein products, turn off, and the proteins degrades over a period of approximately 24 hours
• the proteins that turn on the per and cry genes are: clock and cycle
• the proteins that turn off the per and cry genes: per and cry (negative feedback)
• the mechanisms by which per and cry turn off their own proteins are:

  1. block clock and cycle from activating per and cry
  2. block the region on per and cry where clock and cycle would bind/activate them
• The retinohypothalamic pathway reaches cells of the SCN, allowing glutamate to act at metabotropic glutamate receptors. The 2nd messenger created by activity at this receptor enters the cell nucleus and activates certain clock genes (per, in particular). This is the mechanism by which light entrains the clock.
• indicate which stage(s) of sleep is being described:

  1. when you first fall asleep: 1
  2. K-complexes and sleep spindles: 2
  3. Slow-wave sleep: 3
  4. Synchronous activity of neurons: 3
  5. High brain activity; low muscle tone: REM
  6. Vivid story-like dreams are most likely: REM
  7. Delta activity: REM
  8. Alpha activity: 1
• beta activity is high frequency and low amplitude
• delta activity is low frequency and high amplitude
• k-complexes are thought to be involved in protection from waking
• sleep spindle are thought to be involved in memory formation
• Based on brain activity during REM sleep, indicate the brain regions whose activity (or lack thereof) are associated with the following dream content

  1. emotional content: amygdala
  2. drives and motivations: hypothalamus
  3. lack of logic, memory, and judgement: PFC
• When do we have the most SWS?

  1st half of night
• when do we have the most REM sleep?

  2nd half of the night
• how does the amount of time sleeping and the percentage of REM sleep change over the lifespan?

  amount of time sleeping and percent time in REM both decreases throughout life
• Evidence that sleep is important for brain development is that human babies and infants of species that are equally underdevelopment at birth sleep a lot while infants of species that are born with a more developed brain sleep less
• sleep is important for memory formation. REM sleep seems to be important for implicit (nondeclarative) memories and SWS seems to be important for explicit (declarative) memories
• sleep deprivation interferes with the immune system, attention and working memory. does not affect most physical abilities, exception being reaction time.
• When we have to make up for lost sleep, what stage(s) do we preferentially make up?

  what we were deprived of, if there was a certain stage that we missed OR SWS, then REM
• How does the glymphatic system change during sleep?

  Space between astrocyte end plates and walls of vasculature. CSF washes through the brain within this space. Water channels in astrocytes control CSF entry to interstitial space. During sleep, this space expands so there is better washing of tissue. Cleans out waste, including beta-amyloid
• possible functions of sleep

  brain development, memory formation, niche adaptation, restoration, energy conservation
• List 4 brain regions involved in sleep, and their specific functions with regard to sleep

  1. Basal forebrain and ventrolateral POA -GABA-> tuberomammillary nucleus (TMN): slow wave sleep
  2. Reticular activating system (brainstem): widespread monoaminergic projections to cortex for wakefulness
  3. subcoeruleus (pons): activate REMs and Cortex and indirect inhibition of spinal neurons during REM sleep
  4. LH - produces orezin (aka hypocretin) - coordinates above brain regions
• Ach from the basal forebrain promotes wakefulness (along w/ reticular act system) and is involved in cortical activation during REM sleep.
• REM sleep is coordinated by orexin neurons in the lateral hypothalamus
• the 3 main components of REM sleep are

  1. rapid eye movements
  2. activation of (some of) cortex
  3. inhibition of spinal motor neurons
• Of the following factors that are involved in sleep, indicate if each is circadian, homeostatic or neural:

  1. melatonin: circadian
  2. accumulation of adenosine: homeostatic
  3. hypothalamic control: neural
  4. clock genes/proteins: circadian
• adenosine is breakdown product of ATP, so the more active neurons are, the more adenosine is created. Consider a very active synapse. Adenosine is produced by the post synaptic cell, and binds to receptors on the pre synaptic cell. this decreases further neurotransmitter release. caffeine is an adenosine receptor antagonist
• the 2 systems in the 2-system model of stress are the:

  1. HPA axis
  2. sympathetic nervous system

  what part of the brain controls both systems? hypothalamus
• what adrenal hormone(s) are secreted from each system, and what part of the adrenal gland do they come from?

  cortisol from the adrenal cortex, stimulated by HPA axis. NE and epi from adrenal medulla, stimulated by SNS
• examples of affects being felt during a stress response in the sympathetic nervous system are increased heart rate, dry mouth, sweaty, upset stomach/nausea
• what can affect the expression of glucocorticoid receptors?

  early life experience: increases with nurture, decreases with abuse or neglect
• with many glucocorticoid receptors (GR), cortisol can exert robust negative feedback, so the HPA axis turns off quickly. With fewer GRs there is less for cortisol to bind to in the hypothalamus and anterior pituitary so less negative feedback and the HPA axis stays on longer
• Associations between early life experience and adult mental health outcomes in humans: being bullied as a child increases anxiety, depression, and suicidality