Conciousness Flashcards
What makes up the reticular formation?
Collection of cells in brainstem, pons and medulla
What are the functions of the reticular formation?
Sleep regulation Motor control Cardiac and resp control Autonomic functions Motivation and reward
What are the main projection of the reticular formation?
From the hypothalamus
To the entire cerebral cortex
What is the ascendign reticular formation and what does it do?
Formed by projections of the RF
Raises consciousness
What affects the ascending reticular activating system?
LSD - inhibits ARAS. REport more vibrant colours. Leads to sensory overload and hallucinations. Hypothalamic sleep centres
Alcohol
Sleeping pills
What are the neurotransmitters involved in the ARAS?
Noradrenaline
Dopamine
Acetylcholine
Serotonin
What are the actions of the ARAS when awake?
Takes sensory information and raises arousal levels- stimulates the cerebral cortex directly and via the thalamus- inhibits inhibitory interneurones of the thalamus which sensitises thalamus to sensory inputs
What are the actions of the ARAS during slow wave sleep?
Lack of sensory input
- removal of inhibition of the inhibitory interneurones which means the thalamus is no longer sensitised
- less sensory information is sent to the thalamus
- thalamocortical projections are now quiet
How are EEG waves stimulated?
The electricaly activity is generated by the feedback of the cortex to the thalamus which creates oscillating waves.
What can stimulate the cortex to stimulate the ARAS?
Stress
Anxiety
When it is not appropriate to fall asleep
Define EEG
The algebraic sum of the electrical activity of neurones measured from the scalp by electrodes.
Describe desynchronised pattern on EEG
Pt is awake with open eyes- High electrical activity occuring in all directions which goes on to cancel each other out- Cancelling out causes a small amplitude- High frequency due to high activity
Describe synchronised pattern on an EEG
Pt is awake, eyes shut- Large amplitude waves in the occipital cortex- No sensory info is being projected from the thalamus to the primary visual cortex- PVC is projecting down to the thalamus, due to lack of information- Frontal lobe is quite active due to Pt being awake
Why is sleep needed?
Energy conservation
CNS resetting
Memory (consolidate short term to long term)
Homeostasis
What is in control of the sleep-wake cycle?
Reticular formation
Hypothalamus sleep centres
What is non-REM sleep?
Slow wave sleep
“active body, inactive brain”
Restorative neurological rest
What are some physiological things that happen during non-REM sleep?
95% of hormones released in htis stage Decreased: - cerebral blood flow - O2 consumption - body temp - BP - Resp rate - BMR
Describe REM sleep
Active brain, inactive body EEG appears as when awake EEG waves spread from pons to thalamus then to the occipital lobe Dreams happen in this phase Difficult to disturb
What are some physiological things that happen during REM sleep?
Irregular HR and resp rate Increased BMR Descending inhibition of motor neurones Penile erection Reduced after drinking alcohol All ACh fibres are firing, stimulating the brain.
Why are ACh fibres active during REM sleep?
Thought to do with memory and information processing
What happens to neurones when we wake up?
The hypothalamus stops the inhibition of the thalamus and allows NA firbres to fire. This means that the thalamus is able to stimulate the cerebral cortex.
Define insomia
Inability to sleep
- Stress
- depression
insomnia
Define parasomnia
Abnormal things happen during sleep- sleep talking- sleep walking- sleep paralysis (wake up and are unable to move)
Define hypersomnia
Daytime sleepiness
