Consciousness and Brain Activity

Question 1

What is the neurological basis of consciousness?

Answer 1

Cerebral cortex involved but mainly the four group of neurons in the reticular activating system and anterior and posterior hypothalamus

Question 2

What is the reticular activating system?

Answer 2

A group of 4 neurons in the brainstem and forebrain which modulates the reticular formation to regulates arousal for attention and sleep-wake transition.

Question 3

What is the consequences of damage to the reticular activating system?

Answer 3

Loss of consciousness and coma.

Question 4

What are the nuclei of the reticular activating system?

Answer 4

These nuclei are the noradrenergic locus coeruleus, dopaminergic ventral tegmental, dorsal pontine nuclei and serotenergic raphe nuclei.

Question 5

What is the reticular formation?

Answer 5

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.

Question 6

What is the locus coeruleus?

Answer 6

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.

Question 7

What is the implication of locus coeruleus damage?

Answer 7

Damage or hypoactivity leads to depression and loss of REM sleep

Question 7

What is the Raphe nuclei?

Answer 7

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.

Question 8

What is the ventral tegmental area?

Answer 8

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

Question 9

What is the cholinergic nuclei of the RAS?

Answer 9

Basal forebrain nuclei and dorsal pontine nuclei.

Question 10

What is the basal forebrain nuclei?

Answer 10

Cholinergic nuclei which projects to the cortical areas for REM sleep and thermoregulation

Question 11

What is the dorsolateral pontine nuclei?

Answer 11

Cholinergic nuclei which uses acetylcholine to act on the cortical areas for wakefulness and synaptic plasticity for learning.

Question 12

What is the consequence of damage to the dorsolateral pontine nuclei?

Answer 12

It is implicated in dementia

Question 13

What does the ventral tegmentum modulate?

Answer 13

Wakefulness

Question 14

What does the basal forebrain modulate?

Answer 14

REM sleep

Question 15

Which areas of the brain are involved in consciousness and sleep?

Answer 15

Anterior hypothalamus and posterior hypothalamus

Question 16

What is the anterior hypothalamus?

Answer 16

Responsible for inducing sleep via GABA. Damage leads to insomnia.

Question 17

What is the posterior hypothalamus?

Answer 17

Responsible for inducing wakefulness via histamine. Damage leads to hypersomnia/excessive sleepiness.

Question 18

What is the thalamic reticular nuclei?

Answer 18

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.

Question 19

What happens when awake?

Answer 19

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.

Question 20

What happens when asleep?

Answer 20

Cholinergic nuclei are inactive. The sensory thalamus is inhibitedby the active reticular thalamus. There are slow rhythm, thalamocortical connections so the EEG is synchronous.

Question 21

How does wakefulness occur?

Answer 21

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.

Question 22

What does EEG measure?

Answer 22

Oscillations caused by the interactions between the thalamocortical, reticulo and corticothalamic neurons.

Question 23

What are the types of sleep?

Answer 23

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

Question 24

What waves are present when awake?

Answer 24

Beta waves

Question 25

What waves are present when drowsy?

Answer 25

Alpha waves

Question 26

What is Non-REM sleep?

Answer 26

4 stages which have slow and synchronised EEG waves that progress from Theta waves to delta waves

Question 27

What is REM sleep?

Answer 27

Stage where there is high frequency activity in the EEG with beta wave. It is deepest sleep associated with dreams.

Question 28

What are the stages of sleep?

Answer 28

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

Question 29

What is narcolepsy?

Answer 29

Sudden transition from awake to REM sleep caused by imbalance in the modulatory sleep-wake hormone orexin

Question 30

Which conditons can cause sleep disorders?

Answer 30

Obstructive sleep apnoea, enuresis and epilepsy

Question 31

What are the short term consequences of sleep deprivation?

Answer 31

Irritability, reduced reflexes, memory issues, aggression

Question 32

What is the chronic consequences of sleep deprivation?

Answer 32

Cardiovascular disease, obesity, diabetes, high blood pressure

Question 33

What is circadian rhythm?

Answer 33

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