COGS 17 - Midterm 3

What is the Reticular Formation?

A net-like structure from Medulla & Pons throughout Forebrain; receives from all sensory systems.

What does the Reticular Formation do?

Alerts brain, stimulating Thalamus and Basal Forebrain via ACh and Glutamate.

What is the Locus Coeruleus?

Part of Reticular Formation in Pons, especially active during new task & during vigilance.

What does the Locus Coeruleus release?

Bursts of Norepinepherine (NE).

What do Amphetamines do?

Increase alertness and activity by acting as NE-agonists.

What is the Basal Forebrain?

Just anterior and dorsal to Hypothalamus, releases ACh throughout cortex for arousal & GABA to inhibit cortex.

What is the implication of damage to Basal Forebrain?

It is implicated in Alzheimer's Disease; arousal is critical to memory activation.

What is Adenosine?

A by-product of cell metabolism, builds up throughout the day, released in the brain, inhibits Basal Forebrain's release of ACh.

What does Adenosine allow?

GABA connections to dominate, suppressing cortical activity, promoting sleep.

What is the effect of caffeine on Adenosine receptors?

It blocks Adenosine receptors, allowing Basal Forebrain to continue to arouse the brain.

What is Orexin?

An excitatory NT from Lateral Hypothalamus that helps maintain arousal in above systems.

What does Orexin take into consideration?

Homeostatic conditions (hunger, thirst, temperature, sleep needs etc.).

What is an Electro-Encephalogram (EEG)?

Used to characterize brain activity during different states of wakefulness/sleep

What does EEG record?

Frequency (\# changes in average potential/time) & Voltage (average amplitude)

What is Beta Activity?

18-24 Hz, very high frequency, very desynchronized, awake and active

What is Alpha Activity?

8-12 Hz, somewhat lower frequency, somewhat desynchronized, awake and relaxed

What is Theta Activity?

4-7 Hz, lower freq, still quite irregular, significantly more synchronized, Sleep 1

What are Spindles and K Complexes?

Intermittent bursts of high freq and/or voltage, as brain settles into deeper sleep. K Complex \= Brief period of Delta activity. Spindles \= Help gate external stimuli from reaching cortex

What is Delta Activity?

< 4 Hz observed in less than 50% of this stage, very low freq, higher voltage, very synchronized, Sleep 3 and 4

What is Slow Wave Sleep (SWS)?

Stages 3 and 4, Delta Activity in more than 50% of this stage, hardest to wake

What happens to frequency and voltage as we move into deeper sleep?

Frequency decreases and voltage increases as brain activity becomes synchronized

What happens to heart rate and breathing rate as we move into deeper sleep?

They decrease

What happens to brain responsiveness to external stimuli as we move into deeper sleep?

It decreases

What is REM sleep?

Rapid Eye Movement sleep, characterized by desynchronized EEG, atonia, and dreaming.

What is atonia?

Loss of muscle tone throughout most of the body during REM sleep.

What inhibits motor neurons during REM sleep?

The medulla, which is signaled by the pons.

What happens to external stimuli during REM sleep?

They are detected and may be incorporated into dreams.

What is the sleep cycle?

90 minutes from Stage 1 to REM: Stage 1, 2, 3, 4, 3, 2, REM, 2, 3, 4, 3, 2, REM, 2, 3, 2, REM, 2, REM...

What happens to Stage 4 and Stage 3 as the night goes on?

Stage 4 becomes shorter and drops out after 2-3 cycles, then Stage 3 drops out.

What happens to REM as the night goes on?

It becomes longer.

What are the effects of sleep deprivation?

Lethargy, poor concentration, irritability, increased temperature, metabolism, and appetite, decreased resistance to infection.

What is REM rebound?

When allowed to sleep after REM deprivation, there is an increase in the amount and duration of REM sleep.

What happens when someone is continuously deprived of REM sleep?

They may become irritable, have poor concentration, anxiety, psychosis, hallucinations, and even death.

What is the function of sleep and dreaming?

Controversial.

What is the EEG like during REM sleep?

Desynchronized, high frequency, low voltage.

What happens to heart rate, breathing rate, and blood pressure during REM sleep?

They become more variable than in other sleep stages.

What happens to postural muscles during REM sleep?

They become paralyzed.

What is the relationship between REM sleep and dreaming?

Highly correlated, but not 100%.

What is an example of dream imagery in another sleep stage?

Night terrors, which occur during Stage 4.

What areas of the cortex are often active during REM sleep?

Higher sensory areas.

What is the role of the tegmentum during REM sleep?

Activation of cranial nerves for rapid eye movement.

Why is sleep restorative?

Not clear

Why can some species sleep less than others?

Unclear, but prey sleep less than predators

What is the role of the Hypothalamus nuclei in sleep?

Initiating & regulating sleep

What is the function of VLPOA in sleep?

Inhibits Brainstem and Cortex via GABA

What does the Tubero-Mammillary Body of Hypothalamus release?

Excitatory Histamine 1 after periods of Slow Wave Sleep

What is PGO Wave?

Sequence of activation in Pons \=\> (Lateral) Geniculate \=\> Occipital Cortex - initiates REM

What is the role of ACh in sleep?

Initiates PGO Wave and arouses visual (& other sensory/motor) pathways

What is the function of Raphe Nuclei in sleep?

Decreasing Serotonin (5HT) output \> sleepiness, irritability if not sleep

What is the role of 5HT in sleep?

Produces sudden, strong burst of 5HT, shuts REM off

What is the function of Suprachiasmatic Nucleus (SCN) of Hypothalamus?

Circadian Clock

What is the free-running rhythm in humans?

Activity/rest of ~ 24 +/-1 hours

What is the interaction between SCN & Pineal Gland?

Regulates sleep and arousal systems

What is the effect of damage to Raphe Nuclei?

No sleep

What is the effect of Basal Forebrain arousal/de-arousal?

Enters thru anterior cortex

What is the effect of ACh during REM?

Arouses (desynchronizes) visual (& other sensory/motor) pathways

What is the effect of 5HT during sleep?

Very low during sleep, none during REM

What is the effect of 5HT after REM?

Gradually falls, shifting system back into Slow Wave sleep

What is the effect of ACh before and after REM?

Builds up just before REM, holds steady during, then drops off radically as REM ends

What is the effect of the Pre-Optic Hypothalamus's assessment of fall in brain temperature?

Possibly initiates PGO Wave

What is the effect of the interaction of different types & sources of neural activity?

Controls stages of sleep

What is the effect of SCN in humans?

Establishes free-running rhythm of activity/rest of ~ 24 +/-1 hours

What is the effect of replacing SCN in adult hamster with fetal SCN cells from 20-hour-cycle strain?

Hamster will adopt 20 hour cycle

What are the functions of the Hypothalamus?

Releases hormones into bloodstream & projects to other Hypothalamic Nuclei, Brainstem, Pituitary glands

How is the cycle regulated?

Through projections to and from Pineal Gland

Where is the Pineal Gland located?

Just superior to midbrain, posterior to Thalamus

What is the daily cycle of production of hormone Melatonin?

Shows daily cycle of production of hormone Melatonin which increases sleepiness

What is the role of Melatonin in regulating the cycle?

SCN has receptor sites for Melatonin, so when Pineal increases Melatonin output at end of day, helps regulate cycle

How can Melatonin be used as a sleep aid?

Melatonin can be taken as sleep aid a few hours before bed, helps reset clock (e.g. anti-Jet Lag)

What is Seasonal Affective Disorder (SAD)?

Less light in winter, some people over-produce Melatonin; Light therapy can help

What is the role of Retino-Hypothalmic Path in regulating the cycle?

First light of day to SCN via Retino-Hypothalmic Path produces inhibitory output to Pineal

What is Zeitgeber?

Together, above interaction becomes your Zeitgeber \= "Time Giver"

How can the clock be reset?

Possible to reset clock, via exposure to bright light, strenuous exercise, seasonal or travel-based changes etc.

What are the receptors in Retina that react to light?

Receptors in Retina (not Rods or Cones but specialized Ganglions!) w/photopigment Melanopsin react to light

Where do the axons of these receptors synapse?

These Receptor's axons synapse in SCN (not in retina or thalamus!) via collateral of Optic Nerve

What is Retino-Hypothalamic-Path?

Retino-Hypothalamic-Path

What is the function of the hypothalamus?

Controls endocrine systems via pituitary gland

What are releasing hormones?

Hormones that stimulate the anterior pituitary gland to release its own hormones

What are the other hormones produced by the hypothalamus?

Oxytocin and other hormones sent via axons to posterior pituitary

What are the organizing effects of reproductive hormones?

Effects on anatomy in fetal development and puberty

What are the activating effects of reproductive hormones?

Influence behavior

Do both sexes have female and male hormones?

Yes, in different proportions

Where are steroid hormones produced?

Mainly in ovaries/testes, also in hypothalamus and adrenal glands

What determines gender?

Hormone activity, not just sex chromosomes

What are the anatomical precursors for both sexes in every mammalian fetus?

Gonads

What is the earliest sex structure to develop?

Gonads

What are the same initial structures in all fetuses that develop into male or female anatomy?

Genitalia

What are Wolffian and Muellerian ducts?

Internal sex organs precursors

What determines the development of Wolffian and Muellerian ducts?

Androgens

What do Wolffian ducts and Muellerian ducts become?

Vas Defrens & Prostate or Fallopian Tubes & Uterus respectively

What happens to the other duct system that is not developed?

It degenerates

What genes control male/female body & brain development?

Present in both sexes

What is the 'switch' that determines male/female development?

Male's Y Chromosome

What is the enzyme produced by the Testis-Determining Factor (TDF) Enzyme?

TDF

When does TDF appear during fetal development?

6th-8th week

When are genitals developed?

By 4th month

What happens if TDF is not present?

Ovaries differentiate, Mullerian system develops, Wolffian regresses, female genitalia develop regardless of genotype

What happens if the fetus is XY but lacks the specific gene for TDF?

It will develop internally & externally as female

What happens if the fetus is XO (Turner's Syndrome, no Y Chromosome)?

It will develop internally & externally as female

What is the result of both non-XX fetuses?

Infertile