What are the 2 parts of conciousness
Arousal and awareness
What are examples of arousal
Sleep and wakefulness
What is a minimally conscious state
Reproducible evidence of awareness exists but communication is limited
Sleep wake cycles can be seen on EEG
What is a persistent vegetative state
- pts eyes open and close
- they can track objects
- they can chew and swallow
- do not respond to auditory stimuli, pain, hunger
Good example of arousal but no awareness
What is a coma
Deeply unconscious and displays unresponsiveness to stimuli
May display reflexes
What marks irreversible brain death
No EEG activity recorded
What is required for arousal and awareness
Cortical function
Disruptions in consciousness arise from
Subcortical lesions
- brainstem
- midbrain
- hypothalamus
What are the excitatory amino acid arousal systems
- reticular activating system (RAS)
- parabracial nuclei (PBN)
What are the cholinergic arousal systems
Pedunculopontine tegmental and laterodorsal nuclei (PPT/LDT)
What are the noradrenergic arousal systems
Locus coeruleus (LC)
What are the serotonergic arousal systems
Raphe nuclei (RN)
What are the dopaminergic arousal systems
Ventral tegmental area (VTA)
What does the RAS project to
- hypothalamus
- thalamus
- cortex
What tract does the RAS descend to in spinal cord
Reticulospinal tract
What is the function of the RAS
- regulates arousal and consciousness
- all ascending (sensory) info goes through it
- modal specificity is lost because all pathways are converged
- USES GLUTAMINE
The ascending RAS has 2 outputs. Where do they go and what do they do
Ventral
-goes to cortex or through hypothalamus and then to cortex
Dorsal
-through thalamus and then diffuses to cortex
What is the parabrachial nuclei complex
Different neurons that play a role in promoting wakefulness through cortical activation \
What does the parabrachial nuclei do
Generates respiration patterns during waking state
- amygdala activation of PBN causes hyperventilation during anxiety
- USES GLUTAMINE
What are the PBN outputs
Ventral pathway (like RAS) -goes straight to cortex or through hypothalamus to cortex
How is the PBN and RAS similar
Both use EAA glutamate
-RAS has interneurons that release GABA and ACh
Excitable amino acids are crucial to
Baseline excitation of cortical activity
What are the outputs of the PPT and LDT
Dorsal (to thalamus then cortex) or Ventral (to cortex or hypothalamus and then cortex)
What is the major neurotransmitter over the PPT/LDT
ACh
What nuclei are the primary cause wakefulness and REM sleep
Cholinergic nuclei
Also involved in wakefulness and REM sleep (beside LDT/PPT)
- noradrenergic neurons of locus ceruleus
- serotonergic neurons of raphe nuclei
- histaminergic neurons of the tuberomammilary nuclei (of hypothalamus)
What does antihistamines inhibit in the brain
TMN network to make you drowsy
In addition to sleep, cholinergic neurons also
Provide baseline excitation that is crucial to cortical activity
What is the locus coeruleus
Noradrenergic neurons that function in the alerting response
Being startled is also associated with this system
What are the functions of the locus coeruleus
- startle and alerting responses
- sleep-wake cycles
- behavioral vigilance
What are the ascending outputs of the locus coerulus
Dorsal and ventral pathways used by RAS
Becomes the dorsal adrenergic bundle
What is the descending output of locus coeruleus
Sensory modulation
What are the outputs used by the RAS
Dorsal and ventral (same as RAS)
What does the raphe nuclei use
Serotonin (basis of SSRI anti-depressants)
What are the functions of the raphe nuclei
- quiet awareness
- mood and affect
- modulation of pain
The ventral tegmental nuclei uses what NT
Dopamine
The VTN provides input for
Cognitive functions
Motor activity
Emotions
Intracortical neurons relating to the RAS use GABA to create oscillations seen in the EEG as
Spindle-like discharges
Hyperpolarization of dorsal and ventral pathways occurs during
Low activity states like sleeping
During PVS (persistent vegetative state) cortical neurons are
Hyperpolarized
Levadopa has been shown in some to increase cognitive function
During sleep, the thalamocortical neurons are __________ and occasionally show
Hyperpolarized; spindle-like discharges
Hyperpolarization of the thalamic arousal system shuts of
Cortex from the excitatory influence during deepest levels of sleep
Alertness is primarily done by what NT
Dopamine
Awareness is done primarily by what NT
Norepinephrine and serotonin (5HT)
Arousal is primarily done by what NT
EAA (glutamate) and ACh
