Reticular Formation Flashcards
(46 cards)
What is arousal?
The emotional state associated with some kind of goal or avoidance of something noxious
What is consciousness?
Difficult to determine, something to do with ‘awareness’ of both external world and internal states
What parts of the brain are required for consciousness?
- Cerebral cortex
- Reticular formation
What is the reticular formation?
A population of specialised interneurones in the brainstem
What inputs to the reticular system regulate the level of arousal?
- Inputs from sensory system
- Inputs from cortex
What are the widespread outputs from the reticular formation?
- Thalamus
- Hypothalamus
- Basal forebrain
- Spinal cord
What is the part of the reticular formation that is devoted to arousal?
The reticular activating system
Where is the reticular formation found?
In the brainstem
What does the reticular formation consist of?
Diffuse population of interneurones
What are the major inputs to the reticular system?
- Sensory system
- Cerebral cortex
Describe the relationship between the reticular activating system and the cerebral cortex?
The cerebral cortex sends excitatory projections to the reticular formation, and the reticular formation activates the cortex - mutual excitation produces a positive feedback loop
What is the importance of the positive feedback loop produced between the cerebral cortex and the reticular activating formation?
It produces an all or nothing phenomenon which is required to maintain the awake state
Give two methods of assessing consciousness
- The glasgow coma scale
- EEG
What does the EEG measure?
Combined activity of thousands of neurones in a given part of the cortex
Describe the resolution of the EEG
- Very high temporal resolution
- Very poor spatial resolution
What do neurones in the brain tend to do when deprived of sensory input?
Fire synchonously
What happens to the EEG during sleep?
You typically pass through 6 stages of sleep, progressing from an awake state through to stage 4, and then periodically going from stage 4 rapidly up into REM sleep
What does the EEG show going down to the first 4 stages of sleep?
Decreasing frequency and increasing amplitude, as neuronal populations in the cortex become synchronous
Describe the brainwaves in an awake person
- ß-waves at about 50Hz
- Irregular
Why are the brainwaves in an awake person irregular?
Because you are processing sensory input
Describe the brain waves of a person with their eyes closed
- Alpha waves, at about 10Hz frequency
- More regular
What happens with increasing synchronicity amongst neurones?
Increased amplitude
Describe the brainwaves in stage 1 sleep
Background of alpha waves with occasional low frequency θ waves at about 5Hz
Describe the brainwaves in stage 2/3 sleep
Background of θ, but ocassional bursts of activity called sleep spindles. Occassionally get very big waves called K complexes
