64. Neurobiology Of Consciousness, Sleep..

Front 1

What is consciousness?

Back 1

-Awareness of self/environment
-Subjective experience
-Globally available information
-Integrated information

Front 2

What is consciousness not?

Back 2

Wakefulness

Front 3

What are the 2 dimensions of consciousness?

Back 3

-Awareness
-Wakefullness

Front 4

What is the highest level of consciousness? What is just below it?

Back 4

Conscious wakefullness
Drowsiness

Front 5

What dimension of consciousness is altered in sleepwalking and vegetative states?

Back 5

Awareness is low but wakefulness is high

Front 6

What is the lowest level of awareness and wakefulness?

Back 6

Coma

Front 7

What 4 structures of the brain are necessary for consciousness?

Back 7

1. Rostral pontine tegmentum
2. Midbrain tegmentum
3. Diencephalon (intralaminar thalamic nuclei)
4. Medial hemispheric wall (cortex and subcortex)

Front 8

What is not necessary for consciousness?

Back 8

-Spinal cord
-Medulla (if you maintain artificial resp and BP)
-Caudal half of pons
-Entire basis pontis
-CN motor nuclei
-Cerebellum/hippocampus
-Basal ganglia

Front 9

How much of the cerebral cortex is needed for consciousness?

Back 9

Only one hemisphere

Front 10

What is the ARAS?

Back 10

The ascending reticular activating system

Front 11

What does the ARAS do?

Back 11

Enables the conscious state

Front 12

What are the 4 levels/components of the ARAS?

Back 12

1. Medulla
2. Pons
3. Midbrain
4. Thalamus

Front 13

What happens if you transect the spinal cord at C1?

Back 13

The normal sleep-wake cycle is preserved

Front 14

What happens if you transect the brainstem between the diencephalon and mesencephalon?

Back 14

A permanent state of sleep results.

Front 15

Does the waking state require constant sensory input?

Back 15

No

Front 16

What happens when you electrically stimulate the reticular formation in a sleeping animal? if you lesion?

Back 16

Stimulation - It wakes it up
Lesion - It sleeps

Front 17

What do we know innervates the reticular core?

Back 17

Ascending sensory pathways

Front 18

What happens when we're awake and sensing things?

Back 18

Ascending sensory systems give input via collateral branches to the ARAS which produces nonspecific cortical activation

Front 19

What else gives input from the spinal cord to ARAS?

Back 19

Somatic activation

Front 20

What is the result of descending activation by the ARAS and somatic output from ARAS?

Back 20

Physiologic regulation

Front 21

What 2 types of input does the cortex give to the ARAS?

Back 21

1. Positive feedback - Arousal during daydreaming
2. Negative feedback - Inhibitory during boring lectures

Front 22

What pathway is the source of active sleep?

Back 22

Medularry Reticular Negative Feedback

Front 23

What will result from a lesion of the frontal forebrain projection from the ARAS to cortex?

Back 23

Akinetic mutism

Front 24

What will result from a lesion of the dorsal forebrain pathway from the ARAS?

Back 24

Hypersomnia

Front 25

What will happen if you lesion the ARAS at the level of the dorsal tegmentum?

Back 25

Coma

Front 26

What happens if you lesion the ventral tegmentum?

Back 26

Locked in syndrome

Front 27

What 4 important systems in the brain give input to the ARAS?
What are their nuclei?

Back 27

-Dopaminergic (Subst nigra pc)
-Serotonergic (Raphe)
-Cholinergic (septal / basalis)
-Noradrenergic (Locus ceruleus)

Front 28

What is Sleep?

Back 28

An altered state of consciousness - not unconsciousness.

Front 29

What are 2 hypothesized functions of sleep?

Back 29

-Cell regeneration
-Memory consolidation

Front 30

What causes the regionally specific changes in dreaming?

Back 30

Prefrontal deactivation

Front 31

What controls the switch between wakefulness and sleep?

Back 31

The thalamus

Front 32

What is the nature of thalamic neuron firing during wakefulness?

Back 32

Single spikes at a steady rate

Front 33

What is the nature of thalamic neuron firing during slow wave sleep?

Back 33

Bursts

Front 34

What is the level of Aminergic and Cholinergic tone during:
-Waking
-REM sleep
-NREM sleep
Why? What is Rem-on and -off?

Back 34

Waking: both high
REM: Aminergic low, Cholinergic high (latter are Rem-on!)
NREM: both low (Aminergic are REM-off)

Front 35

What nucleus in the thalamus regulates our state of awakeness or sleep? How?

Back 35

NRT - nucleus reticularis of the thalamus (intralaminar);
Interacts with Thalamocortical cells reciprocally.

Front 36

What type of cells are in the NRT? (what do they release)

When does slow-wave sleep occur?

Back 36

GABAergic

SWS = during Nonrem sleep

Front 37

What are the GABAergic cells of the NRT in reciprocal relationship with?

Back 37

Glutamatergic Thalamocortical TC Relay cells

Front 38

What does the NRT receive its input from?

Back 38

Cholinergic ascending collaterals from the brainstem and forebrain, and Cholinergic desc collaterals from cortex.

Front 39

What do the asc/desc collaterals release and how does it affect the NRT?

Back 39

They release acetylcholine during wakefulness and REM sleep, which inhibits the NTS

Front 40

What does the NRT do when it is NOT inhibited?

Back 40

NRT releases gaba on the TC cells, which hyperpolarizes them and opens low-threshold Ca channels.

Front 41

What happens when Ca channels open in the TC cells?

Back 41

Sodium activated Action Potentials occur in bursts

Front 42

When do we see bursts of APs in the thalamus?

Back 42

During slow wave sleep

Front 43

What causes the bursts to cease in the TC cells?

Back 43

Opening of Ca-activated K channels

Front 44

So the result of NRT inhibition of TC cells is:

Back 44

Slow wave sleep

Front 45

Can slow wave sleep occur during wakefulness? Why not?

Back 45

No; because cholinergic neurons from the cortex and brainstem inhibit the NRT from releasing GABA.

Front 46

How many stages of sleep do we have?

Back 46

4

Front 47

What happens to sleep as the night goes on?

Back 47

It gets less deep

Front 48

How is consciousness split up in the brain?

Back 48

Each hemisphere has awareness of its own but only the left is reportable.

Front 49

What happens when a person has a split brain?

Back 49

Confabulatory interpretation - the left brain tries to make sense of things.

Front 50

Couple things more about sleep

Back 50

k

Front 51

What are REM-on cells?

Back 51

Cholinergic

Front 52

What are REM-off cells?

Back 52

Aminergic

Front 53

Do TC cells have anything to do with REM-on and REM-off cells? Why/why not?

Back 53

No - TC cells are GLUTAmatergic

Front 54

So the 4 cell types and NTs we're talking about here are:

Back 54

1. Rem on - Cholinergic
2. Rem off - Aminergic (dopa)
3. TC cells - Glutamatergic
4. NRT cells - GABAergic

Front 55

What nuclei in the brain cortex and brainstem release Acetylcholine?

Back 55

-Nucleus basalis
-Nucleus parabrachialis

Front 56

What does Acetylcholine from the brain and brainstem do?

Back 56

Inhibits the NTS during wakefulness

Front 57

What are off-REM cells?
What do they release?
In what state are they during Wake, NREM, and REM states?

Back 57

-Aminergic
-Release dopamine
-On during wake
-Turning off during NREM
-Off during REM

Front 58

What are REM-on cells?
What do they release?
In what state are they during Wake, NREM, and REM states?

Back 58

-Cholinergic
-Release ACh
-Off during wake
-Off during NREM
-On during REM

Front 59

When are Beta waves seen on the EEG?

Back 59

During awake

Front 60

When are Alpha waves seen on the EEG?

Back 60

When eyes are closed and resting

Front 61

When are Theta waves seen on the EEG?

Back 61

During sleep

Front 62

When are Gamma waves seen?

Back 62

During deep sleep