20: Brain Arousal System Flashcards
What major factor decides different levels of consciousness?
Levels of cortical excitation
What arouses the cortex?
Brainstem regions
Two parts to consciousness
Arousal (being awake) + awareness (conscious processing of inputs)
What happens during the deepest levels of sleep?
Thalamocortical neurons are hyperpolarized, with only occasional APs
What does a comatose state typically result from?
Damage to brainstem, midbrain, or hypothalamus, not cortex which is a common misperception
Levodopa
Treatment for a limited number of pts in a persistent vegetative state have had dramatically increased cognitive function
The fundamental piece of consciousness in the arousal systems
EAA system
Two parts to the EAA system
- Reticular Activating System
2. Parabrachial nuclei
Interneurons in RAS
There are a substantial number of interneurons intrinsic to RAS that release GABA and Ach
What are PPT and LDT
Pedunculopontine tegmental and laterodorsal nuclei
Which arousal system is most hit in Alzheimers
Cholinergic csystem
Alerting response on EEG
Early indicator that cortex is “looking” for sensory input
Dorsal vs ventral pathway arousal systems
Dorsal: send axons to thalamus to synapse
Ventral: send axons straight to cortex, bypassing thalamus
Where does the dorsal pathway synapse?
Non-specific nulcei of the thalamus (ex: intralaminar Nucleus)
Thalamocortical nuclei of the dorsal pathway
Path to cortex that releases the Nts involved in the arousal systems
