Lecture 6: Brain Arousal Systems Flashcards
Eye/head motions
Sleep/wake cycle
Awareness
Verbal responses
Which are active in Coma patients
None but eye/head motions due to spinal or cortical reflexes may be seen
Eye/head motions
Sleep/wake cycle
Awareness
Verbal responses
Which are active in patient who is in a persistent vegetative state
Eye/ head motions
Sleep/wake cycles
Eye/head motions
Sleep/wake cycle
Awareness
Verbal responses
Which are active in patient who has minimal consciousness
Eye/head motions
Sleep/wake cycle
Awareness - inconsistent or intermittent
Verbal responses - inconsistent or itermittent
Eye/head motions
Sleep/wake cycle
Awareness
Verbal responses
Which are active in patient who is aware/alert
All of them
What are the levels of cosciousness
- Alertness
- Awareness (minimal consciousness)
- Arousal/Wakefulness (Persistent vegetative)
- Coma
What are the two parts of consciousness?
Arousal (being awake) Awareness (conscious processing of inputs)
What parts of of consciousness is missing in a coma?
Arousal and Wakefulness (EEG shows nothing)
Awareness
What parts of of consciousness is missing in a persistent vegetative state?
Awareness (Arousal is present on EEG)
What has to be damaged in cerebral cortex to cause comatose state?
Bilateral and massive damage
Injuries to what areas often cause disruptions to consciousness leading to a persistent vegative state?
Brainstem, Midbrain & Hypothalamus
What is the status of cortical neurons in a persistent vegetative state?
Hyperpolarized (30 mv below threshold)
State the Arousal System Heirachy
What NTs take one from a coma to Arousal/Wakefulness?
EAA
What supplies EAA
Reticular Activating System (RAS) - mid-ventral portion of medulla & midbrain
Parabrachial Nuclei - pons
What supplies the Cholinergeric system
Pedunculopontine Tegmental (PPT) Laterodorsal Nuclei (LDT)
Where supplies the Noradregenic (Norepinephrine) System
Locus Ceruleus
Where are Dopaminergic inputs received from
Ventral Tegmental Area & Substantia Nigra
What is the soruce of Seratonergic system?
Raphe Nucleus
Why is Reticular Activating System not specific?
All sensory pathways converge at RAS and there is too much input - basically RAS is just an event detector
How does RAS tell the cortex that something happened?
- Dorsal pathway
- Ventral pathway
Where do the dorsal pathways go?
Arousal systems send axons to thalamus and synapse. Axons from thalamus then go to cortex to synapse.
What are the axons from the thalamus to the cortex called in the dorsal pathway?
Thalamocortical neurons
Ventral Pathway
Skips thalamus via basal forebrain and hypothalamus and send axons straight to cortex to synapse directly onto cortical neurons
Difference between ventral and dorsal pathway
Ventral pathway
Release NTs produced by specific system
Dorsal pathway
- first synapse in thalamus - releases the NTs produced by the specific pathway.
- Second synapse in cortex - release NTs produced by specific system
Differentiate between RAS & Parabrachial Nuclei
RAS located in midventral portion of medulla & midbrain / Parabrachial Nuclei located in pons
RAS outputs utilizes dorsal & ventral pathways / Parabrachial Nuclei only uses ventral pathway
Both are involved in general sensation
Both release EAA
Differentiate between RAS & PPT/LDT
- Both RAS & PPT/LDT are involved general sensation and send their axons via the doral & ventral pathways.
- RAS releases EAA (EAA system)
- PPT/LDT releases Acethylcholine (Cholingeric system)
What happens if there is damage to PPT/LDT?
Severe Cognitive Defects & Slowing of Cortical processes as seen in Alzheimer’s
What NTs take one from Arousal/Wakefulness (PVS) to Awareness (minimal consciousness)?
Norepinephrine & Serotonin
What pathways are used to produce awareness
Both dorsal and ventral
What does it mean for sensory inputs to the Locus Coereuleus to be processed?
What does it release?
Sensory is no longer general as seen in RAS, PPT/LDT or parabrachial nuclei. Sensory receved in specific
Norepinephrine
What is the role of norepinephrine?
Startle and Alert (EEG Manifestation)
Sleep - wake
behavioral vigilance
Where is serotonin released and what is the role of serotonin?
- Raphe Nuclei
- Quiet Awareness (general awareness)
Mood & affect
Modulation of pain
What NT takes one from Awareness to Alertness and where is it produced?
Dopamine
Ventral Tegmental Area (VTA)
What does dopamine do?
Cognitive Function
Motor Activity
Emotion (pleasure)
How are oscillations created on EEG?
Thalamocortical NTs release EAA (excitatory) and also bind to intracortical neurons to release GABA (inhibitory)
What is affected in patients with Alzheimer’s?
Cholinergic systems: slow mental processes and impaired memory formation
What can treat some people in a persistent vegetative state
L - dopa (Levodopa)
