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Sleep

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by

Melanie Rosenthal

on 26 July 2013

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Transcript of Sleep

But before we get to that, let's look a little closer
at the neuroanatomy.
When the
sleep
portion of the switch is turned on, the brain systems undergo a process to inhibit the
arousal-wake system
.
SLEEP
stage 1
stage 2
stage 3
stage 4
Stage one is the transition between wake and sleep.
During stage one, our brains produce mostly alpha waves.


Stage 2 of sleep is a light sleep from which we can be easily awoken.
Stage 3 of sleep is a deep sleep, also called "slow-wave sleep."
These waves are called delta waves.
Stage 4 of sleep is the very deepest slumber; it is a completely dreamless state.
why is sleep so important?
a chance for neurons to recoup and
for neurotransmitters to replenish
There is an
ACTIVE
mechanism that is involved when someone is falling to sleep.
The "Sleep-Wake" switch
Neural structures involved with both sleeping and arousal (waking)
Sleeping
:
hypothalamus- specifically the
ventrolateral preoptic nucleus (VLPO)

Arousal (waking)
:
tuberomammillary nucleus
lateral hypothalamus
laterodorsal tegmental nucleus
pedunculopontine tegmental nucleus
locus coeruleus
dorsal raphe
How the "sleep switch" works...
The VLPO uses the neurotransmitters
GABA
and
galanin
to initiate sleep by inhibiting the arousal regions of the brain.
Thanks for watching!
- Jane, Melanie, & Trudi
We all need it...
but Why?
Sleeping replenishes our bodies
and our minds. While much is still unknown, here are the most widely accepted theories of sleep.
Also...

* neural connections strengthen and recharge
* memories are stored away or discarded
So what does an average
night of sleep look like?
Over 8 hours, we cycle
through 5 progressively
deeper
stages
of sleep.
There are four stages
of non-REM sleep.
REM sleep occurs at
the very top of every
sleep cycle.
The sleep-wake switch is the mechanism by which we fall asleep, and also wake up. The two are interdependent.
VLPO "the sleep switch"
We do not just "fall" asleep. The brain undergoes a process every 24 hours to initiate or "turn on" sleep.
Here's a reminder about inhibitory neurotransmitters...
Inhibitory neurotransmitters make a neuron
hyperpolarized
, which means it is less likely to fire an
action potential
.
This leads to a disconnect between the hypothalamus with the thalamus and cortex-
a necessary step in falling asleep
.
The Neurophysiology of Sleep
Neuropathology of Sleep
A pathology is the study and diagnosis of diseases; looking at symptoms to understand the cause.
REM stands for "rapid eye movement" and is a
period of sleep in which our brains are very active. Most dreams occur during this stage.


Each full
cycle
becomes slightly more shallow than the last, so by the end of the night we are only in the lighter sleep stages.
Insomnia
Narcolepsy
circadian
rhythms
sleep
cycles
sleep
stages
circadian rhythms
are our "biological clock"
that regulates our body's
sleep/wake patterns, among other
things, on a 24-hour cycle. This
brings us to...
These individual stages make up the sleep cycle, which in turn is part of our daily sleep-wake pattern called circadian rhythms.


3 circumstances can lead to Insomnia:

1. Suprachiasmitic (biological clock) nucleus fails induction of sleep

2. Thalamocortical system impairment

3. Damage to the Sleep-Wake Switch
Biological Clock failing to induce sleep


A disconnect between the pineal gland and the suprachiasmatic nucleus occurs in Alzheimer Disease.

Damage to the Thalamocortical Systems



Thalamic lesions are thought to reduce or completely impair REM and NREM.

These systems are ALWAYS involved in fatal insomnias.



Degenerative Diseases that are involved when
the Sleep Switch is damaged:

Lewy Body Disorders
Alzheimer's Disease
Parkinson's Disease
Progressive supranuclear Palsy, PSP
Narcolepsy is characterized by uncontrollable sleep "attacks", skeletal muscle paralysis, atonia induced by emotional stress or laughing.
Sleep is then maintained by an oscillating signal between the thalamus and the cortex-
the Delta wave
.
The process that inhibited the arousal systems for sleep is now flip-flopped to return the body to a
wakeful state
.
If either side of the
sleep-wake switch
is damaged there can be a disruption in the states of sleeping and wakefulness.
The ascending reticular activating system (ARAS) is now in charge of establishing a state of
wakefulness
.
Neurodegenerative diseases often include sleep disorders.

This is because important information relays, synapes, are gone.


Sleep repairs the brain
and allows it to build new synaptic
relays (learn and process new info).
A degenerated brain can't tell itself or the body what time of day it is or when to fall asleep or stay awake.
Lewy Body Disease, Alzheimer's Disease, Parkinson's Disease, PSP and other neurodegenerative diseases may also present narcolepsy symptoms.
REM bombards wakeful moments and lesions in the hypothalamus. Narcolepsy can be primary, idiopathic, or secondary to another ailment.
Insomnia is characterized by difficulties falling asleep and staying asleep.
Pathologies involving certain parts the brain will cause extreme fatigue, memory loss, and cognitive impairments, among other serious implications.


So always make time to catch some...
's

Boeree, C. G. (n.d.). Sleep. General Psychology.
Hall, R. (n.d.). Stages of Sleep. Psychology World.
Hauw, J.-J., Hausser-Hauw, C., De Girolami, U., Hasboun, D., & Seilhean, D. (2011).
Neuropathology of Seep Disorders: A Review. J Neuropathol Exp Neurol.
Schwartz, J.R., & Roth, T. (2008). Neurophysiology of
Sleep and Wakefulness.
Stafford, T. (2012). Why do we need sleep? BBC.

How the "wake" switch works...

VLPO
ARAS includes arousal groups that fire in a pattern to promote arousal. This is creates the turning "
on
" of the awake switch.
During REM sleep the brain is producing the higher-frequency theta and beta waves.
Bibliography
Which can lead to...
During stage 4 the brain continues to produce even more of the large, slow delta waves.
During sleep . . .

* adnisone, a by-product of cell activity, is cleared from the system
During stage 2, the brain produces theta waves with bursts of alpha waves, called "sleep spindles."
What is a pathology, and what can lack of sleep do to your brain and body?
Full transcript