Consciousness and Brain Activity Flashcards
What is the neurological basis of consciousness?
Cerebral cortex involved but mainly the four group of neurons in the reticular activating system and anterior and posterior hypothalamus
What is the reticular activating system?
A group of 4 neurons in the brainstem and forebrain which modulates the reticular formation to regulates arousal for attention and sleep-wake transition.
What is the consequences of damage to the reticular activating system?
Loss of consciousness and coma.
What are the nuclei of the reticular activating system?
These nuclei are the noradrenergic locus coeruleus, dopaminergic ventral tegmental, dorsal pontine nuclei and serotenergic raphe nuclei.
What is the reticular formation?
Group of nuclei in the midbrain which extends into the hindbrain to induce and maintain wakefullness via output tracts. It is modulated by the reticular activating system.
What is the locus coeruleus?
Noaradrenergic nuclei in the brainstem with outputs to the CNS such as the forebrain and spinal cord to modulate wakefulness and attention via sympathetic activation. It is activated by novel stimuli and during arousal.
What is the implication of locus coeruleus damage?
Damage or hypoactivity leads to depression and loss of REM sleep
What is the Raphe nuclei?
Serotenergic Nuclei in the midline of the midbrain which projects to the CNS via 5-HT receptors. It promotes wakefulness and attention and inhibits REM sleep via serotonin release.
What is the ventral tegmental area?
Dopaminergic Nuclei in the ventral area of the midbrain which projects to the frontal lobe and limbic system for pleasurable sensation and is implicated in drug addiction
What is the cholinergic nuclei of the RAS?
Basal forebrain nuclei and dorsal pontine nuclei.
What is the basal forebrain nuclei?
Cholinergic nuclei which projects to the cortical areas for REM sleep and thermoregulation
What is the dorsolateral pontine nuclei?
Cholinergic nuclei which uses acetylcholine to act on the cortical areas for wakefulness and synaptic plasticity for learning.
What is the consequence of damage to the dorsolateral pontine nuclei?
It is implicated in dementia
What does the ventral tegmentum modulate?
Wakefulness
What does the basal forebrain modulate?
REM sleep
Which areas of the brain are involved in consciousness and sleep?
Anterior hypothalamus and posterior hypothalamus
What is the anterior hypothalamus?
Responsible for inducing sleep via GABA. Damage leads to insomnia.
What is the posterior hypothalamus?
Responsible for inducing wakefulness via histamine. Damage leads to hypersomnia/excessive sleepiness.
What is the thalamic reticular nuclei?
GABA-nergic Nuclei located between the cortex and the thalamus. It modulates the excitatory glutamergic cortical connections for the sleep-wake cycle. It regulates the dorsal thalamus for arousal, cognitoin and senspry processing.
What happens when awake?
During wakefulness, cholinergic neurons are fired from the dorsal pontine nuclei and the basal forebrain nuclei to induce transition from sleep t waking. This decreases when asleep.
What happens when asleep?
Cholinergic nuclei are inactive. The sensory thalamus is inhibitedby the active reticular thalamus. There are slow rhythm, thalamocortical connections so the EEG is synchronous.
How does wakefulness occur?
Cholinergic neurons are active and fired from the basal forebrain. Reticular nuclei is inhibited and the sensory thalamus is active and forms thalamocortical connections. EEG is desynchronised.
What does EEG measure?
Oscillations caused by the interactions between the thalamocortical, reticulo and corticothalamic neurons.
What are the types of sleep?
Non-REM sleep which progresses from theta waves to alpha waves
REM Sleep which has both alpha and beta waves. There is abolition of muscle tone and it is associated with sleep
What waves are present when awake?
Beta waves
What waves are present when drowsy?
Alpha waves
What is Non-REM sleep?
4 stages which have slow and synchronised EEG waves that progress from Theta waves to delta waves
What is REM sleep?
Stage where there is high frequency activity in the EEG with beta wave. It is deepest sleep associated with dreams.
What are the stages of sleep?
Sleep cycle lasts for 90 minutes each, from awake -> drowsy -> Stage 1 sleep w/theta waves -> Stage 2 sleep Theta + Delta waves -> Stage 3/4 sleep with more delta waves -> Stage 4 REM sleep
What is narcolepsy?
Sudden transition from awake to REM sleep caused by imbalance in the modulatory sleep-wake hormone orexin
Which conditons can cause sleep disorders?
Obstructive sleep apnoea, enuresis and epilepsy
What are the short term consequences of sleep deprivation?
Irritability, reduced reflexes, memory issues, aggression
What is the chronic consequences of sleep deprivation?
Cardiovascular disease, obesity, diabetes, high blood pressure
What is circadian rhythm?
Biological internal clock- suprachiasmatic nuclei of the hypothalamus secretes vasopressin to act on local brain areas including the pineal gland indirectly to secrete melatonin for sleep
