The Reticular Formation

Question 1

Define consciousness

Answer 1

Something to do with awareness of both external world and internal states

Question 2

Define arousal

Answer 2

Emotional state associated with some kind of goal or avoidance of something noxious

Question 3

What do we need for consciousness?

Answer 3

Functioning cerebral cortex

Functioning reticular formation

Question 4

What is the reticular formation?

Answer 4

Population of specialised interneurones in the brainstem

Numerous inputs - regulate the levels of arousal = somatosensory system and cortex

Multiple outputs – thalamus, hypothalamus, basal forebrain nuclei, spinal cord

Question 5

Outline the maintenance of consciousness

Answer 5

RF inputs = descending excitatory cortex stimulation, sensory inputs

RF outputs = 1) ACh to thalamus – gutamate to cortex, 2) ACh to hypothalamus – histamine to cortex, 3) ACh to basal forebrain nuclei – Ach to cortex

Question 6

What is the role of the basal forebrain nuclei?

Answer 6

Receive cholinergic inputs from the reticular formation

Question 7

What is GCS?

Answer 7

Glasgow coma score

Assess eye opening, motor response, verbal response

Lower the score the more severe the damage

Question 8

What is an EEG – electroencephalogram?

Answer 8

Measures the combined activity of thousands of neurones in a given part of the cortex to a very high temporal resolution

Question 9

Sleep includes what stages?

Answer 9

REM – rapid eye movements

Stage 1

Stage 2

Stage 3

Stage 4

Question 10

Outline an EEG when awake with eyes open

Answer 10

Beta waves

50 Hz

Irregular = processing complex input

Question 11

Outline an EEG when awake with eyes closed

Answer 11

Alpha waves

10Hz

Synchronised = if you deprive the brain of input it will tend to go into synchrony

Question 12

Outline the features of Stage 1 sleep

Answer 12

Background of alpha waves with occasional theta waves

5 Hz

Question 13

What are the characteristics of stages 2/3 sleep?

Answer 13

Background of theta waves with occasional sleep spindles and K-complex

Question 14

What do sleep spindles represent?

Answer 14

Last attempt of the thalamus trying to wave you up

Question 15

What is a K-complex?

Answer 15

Taken away all the inputs to the cortex and we start to see its intrinsic rate

Question 16

Describe how stage 4 sleep appears on an EEG

Answer 16

Dominated by intrinsic rate of the cortex = delta waves

1 Hz

Synchronous

Question 17

Describe REM sleep and how it appears on EEG

Answer 17

Beta waves

Dream state

Its as if you are awake as the cortex is suppling visual info

Initiated by groups of neurones in the pons

Very diff to awake someone from REM sleep = strong inhibition of the thalamus

Paralysed due to LMN inhibition by glycine

Question 18

Outline the neural mechanism of sleep?

Answer 18

Removing as many inputs into the reticular formation as possible = deactivating

Question 19

What are the functions of sleep?

Answer 19

Enigmatic

Energy conservation and bodily repair

Memory consolidation

Clearance of extracellular debris

Question 20

What is narcolepsy?

Answer 20

Rare

Problems in neurotransmission = problem maintaining wakefulness

Question 21

Outline sleep apnoea

Answer 21

Compression of airway by soft tissue = constantly being woken by hypoxia

Question 22

Name some disorders of consciousness

Answer 22

Brain death = widespread cortical and brainstem damage

Coma = widespread brainstem and cortical damage, EEG patterns detectable, unarousable, unresponsive, no sleep-wake cycle

PVS = widespread cortical damage, EEG patterns detectable, spontaneous eye opening, sleep-wake cycle detectable

Locked in syndrome = basilar/pontine A occlusion, eye movements, somatic functions from pons down lost