Ch.28

Specialzied cells for the circadian rhythm show what kind of photopigment

melanopsin

Where do the axons of these melanopsin containing ganglion cells go to

superchiasmatic nucleus of anterior hypothalamus , also pineal gland

Pineal gland role in circadian rhythm

SCN cells project here too so that it can synthesize the sleep promoting neurohormone melatonin

Theory of sleep - glycogen

* we sleep to replenish glycogen in brain

Theory of sleep - memory

we need sleep to consolidate memories

Theory of sleep - waste

we need sleep to clear metabolic waste from our brain restorative

Stage I sleep

* drowsiness, theta waves
* decrease in muscle tone, BP, metabolic rate, HR, etc
* rolling eyes

Stage II sleep

sleep spindles, interactions between thalamic and cortical neurons, dont wake you

Stage III sleep

deep sleep, spindles decrease

Stage IV sleep

* delta waves, slow wave sleep
* lowest HR, breathing, metabolic, BP

Stages I-IV sleep are called

non-rem sleep

Most prominent feature of non-rem sleep

slow wave sleep

REM sleep

* almost like awake
* 10 minute periods
* about 4-5 stages of REM
* 2 hours at 20y, 45min at 75y
* increases in BP, HR, metabolism
* pupillary constriction
* ballistic eye movement
* peepee erection

REM sleep also has greater prevalence of

dreaming

Reticular activating system

* junction of pons and midbrain
* wakefullness and arousal

Why do we do saccade like movements in REM sleep

* abscence of visual stimuli

What waves characterize REM sleep

pontine-geniculo-occipital waves

Electtrically stimulating a group of neurons neat the junction of the pons and midbrain causes a state of

wakefullness

The group of neurons near the junction of pons and midbrain is called the

reticular activating system

Saccadic eye movements during REM sleep arise because

in absence of external visual stimuli, endogenously generated signals from the pontine reticular formation are transmitted ti the motor region of the superior colliculus

REM sleep is also characterized by EEG waves that originate where

pontine reticular formation and propagate through the LGN of the thalamus to the occipital cortex

Which system increases during REM sleep

limbic

What system decreases during REM sleep

frontal cortex areas

What does the simultaneous increase of limbic system and decrease of frontal lobe cause

heightened emotionality of dreams in REM sleep and their inappropriate social content

Cholinergic nuclei is a key component in what system and what does it do

reticular activating system, its a primary cause of wakefullness and REM sleep and its relative inactivity is important for causing non-REM sleep

The activation of the cholinergic and monoaminergic networks together causes …

awake state

TMN

tuberomammillary nucleus of the hypothalamus, where the histamine containing neurons are

The locus coeruleus

where the noradrenergic neurons are

The raphe nuclei

where the serotonergic neurons are

TMN neurons modulate

the locus coeruleus and the raphe nucleus

TMN is activated by ____ __that secrete the peptide__ ____

neurons in the lateral hypothalamus, orexin

Orexin promotes

waking

Antihistamines inhibit the _______. which is why…..

histamine containing TMN network, which is why they make people drowsy

What do VLPO neurons do

* inhibit the circuits responsible for wake state periodically
* contributes to the onset of sleep
* lesions cause insomnia

both ____nergic and__ ___nergic systems are active during the wake state, and their decreased activity leads to non-REM sleep

monoaminergic and cholinergic

____nergic and__ ____nergic are less active during rem sleep, while__ ___nergic neurons are similar to how they are when you’re awake

monoaminergic, serotonergic, cholinergic

Thalamocortical neurons receive input from where? and where do they project

locus coeruleus (noradrenergic), raphe nucli (serotonergic), and reticular activating system (cholinergic) , and TMN (histaminergic), project to cortical pyramidal cells

Thalamocortical neurons can be in one of two stable electrophysiological states:

1. intrinsic bursting state
2. tonically active

Intrinsic bursting state

* thalamus becomes synchronized with the cortex
* disconnect cortex from outside world
* maximal during slow wave sleep How

Tonically active state

* when thalamocortical neurons are depolarixsed
* when RAS generates wakefulness
* transmit info to cortex that is correlated with the spike trains encoding peripheral stimuli

How does intrinsic bursting get to tonically active

through the activity of cholinergic or monoaminergic projections from brainstem nuclei