The Brainstem and Consciousness (Reticular Formation)

Question 1

Define arousal

Answer 1

the emotional state associated with some kind of goal or avoidance of something noxious

Question 2

Define consciousness

Answer 2

difficult to define but:

something to do with ‘awareness’ of both the external world and internal states

Question 3

What two areas of the brain are requried for consciousness?

Answer 3

Cerebral Cortex + Reticular Formation

Question 4

Where is the reticular formation located?

Answer 4

Located in the Brainstem

(diffuse structure/area)

Question 5

What is the nature of the feedback loop between the cerebral cortex and reticular formation?

Answer 5

Positive Feedback Loop

Question 6

Damage or lesions to which 3 areas of the brain can cause an altered level of consciousness?

Answer 6

Cerebral Cortex

Brainstem (reticular formation)

• *Conenctions Between Both**
• (e.g. in diffuse axonal injury)*

Question 7

Which neurotransmitter is used by the excitatory neurones originating from the reticular formation to stimulate the subcortical nuclei?

Answer 7

Acetylcholine

(cirlces left to right:
basal F/B nuclei, hypothalamus, thalamus)

Question 8

Which neurotransmitter is used from the neurones of the basal nuclei to excite the coertex?

Answer 8

Acetylcholine

Question 9

Which neurotransmitter is used by the hypothalamic neuronal projections to the cortex, which help maintain consciousiness?

Answer 9

Histamine

Question 10

What neurotransmitter is used by the thalamic projections to the cerebral cortex to help maintain consciousness?

Answer 10

Glutamate

Question 11

How can anticholinergic drugs and anti-histamines cause drowsiness?

Answer 11

inhbit the positive/excitatory inputs from the reticular formation to the cerebral cortex

Question 12

What scale is used to assess a patients level of consciousness?

Answer 12

Glasgow Coma Scale

(GCS)

Question 13

What is measured by an electroencephalogram (EEG)?

Answer 13

combined activity of thousands of neurones

located to different geographical regions of the brain

Question 14

What happens to the EEG waveform as you progress into deeper sleep?

Answer 14

decreasing frequency in firing

increasing amplitude as neuronal populations become synchronous

Question 15

Which types of waves are found on an EEG when a person is awake?

Answer 15

Beta Waves

Irregular - up to 50Hz

Question 16

When do alpha waves appear on an EEG?

Answer 16

Once eyes are closed and visual stimuli are removed

pattern becomes more synchronous

around 10Hz

Question 17

How many stages of sleep are there on an EEG?

Answer 17

5 Stages (including REM)

Question 18

What are sleep spindles seen during stage 2 of sleep cycles on an EEG?

Answer 18

rapid neuronal firing from the thalamus in an effort to maintain consciousness

Question 19

Which type of waves are predominant during stage 2/3 of the sleep cycle on an EEG?

Answer 19

Theta Waves

around 5Hz

Question 20

Why does REM sleep appear similar to the beta waves seen when patients are awake?

Answer 20

period when patients are dreaming

visual simulation from brain generated images > stimulated cortex

Question 21

What changes in the brain occur to allow you to sleep?

Answer 21

deactivation of the reticular activating system (and therefore thalamus), to allow decreased cortical activity

achieved by removal of sensory inputs
e.g. closing eyes

Question 22

Which area of the brain is responsible for initiating REM sleep?

Answer 22

neurones in the pons

Question 23

Why are patinets in the REM phase of sleep difficult to rouse?

Answer 23

strong inhibition of the thalamus

Question 24

Patients in the REM phase of sleep have very little muscle tone, outline the neruonal mechanism of this phenomenon

Answer 24

descending inhibition of LMNs by glycinergic fibres arising in the reticular formation

Question 25

What autonomic effects are seen during the REM phase of sleep?

Answer 25

Penile Erection

Loss of Thermoregulation

Question 26

What are 2 functions of sleep?

Answer 26

Energy Conservation & Bodily Repair

Memory Consolidation

Clearance of Extracellular Debris

Question 27

What are the two most common causes of insomnia?

Answer 27

Depression

Anxiety

Question 28

What causes narcolepsy?

Answer 28

issues with neurotransmitters

patients are unable to maintain the positive feedback between reticular activating system and cortex

patients are unable to stay awake

Question 29

How can sleep apnoea cause sleep disturbances?

Answer 29

soft tissues compress the neck during sleep and cause obstruction to airflow

common in obese patients

obstruction results in hypoxia and awakening to change position and remove obstructon

Question 30

Outline the EEG findings in a patient with brain death?

Answer 30

flat EEG

widespread cortical and brainstem damage

Question 31

Outline the features of a patient in coma (including EEG findings)

Answer 31

widespread brainstem & cortical damage

unarousable and unresponsible to psychologically meaningful stimuli

EEG - various disorganised patterns

no sleep-wake cycle detectable

Question 32

How do patients with permenant vegetative state differ from those in a coma?

Answer 32

some sponteanous eye opening is possible

some patients can localise to stimuli via brainstem reflexes

sleep-wake cycle detectable

Question 33

What is a cause of locked in syndrome and how do patients present?

Answer 33

caused by basilar/pontine artery occlusion

eye movements can be preserved but loss of ALL somatic motor functions from pons down