NS 10: Consciousness and its disturbances

Question 1

change in neurohormone levels associated with depression?

Answer 1

low levels of serotonin and noradrenaline

Question 2

change in neurohormone levels associated with Alzheimer’s Disease?

Answer 2

destruction of ACh secreting cells

Question 3

change in neurohormone levels associated with schizophrenia?

Answer 3

excessive dopamine

Question 4

waveforms of EEG characterising relaxed wakefulness?

Answer 4

alpha waves= 8-13 Hz

mainly occipital lobe as not receiving any visual stimuli, awake, quiet, eyes shut

Question 5

waveforms of EEG characterising mental activity, part. from front of brain?

Answer 5

beta waves= >14Hz, higher frequency

awake, eyes open, frontal and parietal lobes

Question 6

waveforms of EEG characterising 1st stages of sleep, drowsiness?

Answer 6

theta waves= 4-7Hz
parietal and temporal lobes
children, emotional adults

Question 7

waveforms of EEG characterising deep sleep?

Answer 7

delta waves= <4Hz
mainly cortical
also seen in serious brain conditions

Question 8

3 reasons as to why disturbance of consciousness may arise?

Answer 8

• metabolic e.g. hypoglycaemia, uraemia or anoxia (no O2)
• brain stem lesions or pressure on brain stem from any SOL causing raised ICP
• head trauma, which may bruise brain within skull

Question 9

3 sections to glasgow coma scale?

Answer 9

eye opening, 1-4
motor responses, 1-6
verbal responses, 1-5

Question 10

max and min scores for glasgow coma scale?

Answer 10

max=15

min=3

Question 11

what has control over the sleep-wake cycle?

Answer 11

reticular formation

hypothalamus- inhibits reticular formation to promote sleep

Question 12

why do we need sleep?

Answer 12

energy conservation
memory
CNS resetting/clearance

Question 13

neurohormones characterising waking?

Answer 13

5-HT and noradrenaline constantly active

ACh neurones active during a novel input

Question 14

neurohormones charactersing non-REM sleep?

Answer 14

5-HT and NA inactive

ACh inactive

Question 15

neurohormones charactersing REM sleep?

Answer 15

5-HT and NA inactive (memory, without emotion?)

ACh fully active

Question 16

neurohormones charactersing coming out of REM sleep?

Answer 16

increase NA activity

Question 17

what is AVPU?

Answer 17

system to assess level of consciousness:
A=alert
V= responds to verbal stimulus
P= responds to pain stimulus
U= unresponsive

Question 18

scores for eye opening with glasgow coma scale?

Answer 18

4= spontaneously
3= to speech
2= to pain
1= none

Question 19

scores for verbal resonse with glasgow coma scale?

Answer 19

5= orientated
4= confused
3= inappropriate words
2- incomprehensible
1= none

Question 20

scores for motor response with glasgow coma scale?

Answer 20

6= obeys commands
5= localises pain
4= flexion to pain
3= flexion/withdrawal
2= extension to pain
1= none

Question 21

what happens in a subfalcal hernia?

Answer 21

part of the cingulate gyrus is forced into space between falx cerebri (inward folding of meningeal layer of dura mater) and the corpus callosum- connects the 2 cerebral hemispheres.

Question 22

what happens in an uncal hernia?

Answer 22

the uncus- part of median temporal lobe, is pushed through the tentorial notch*

Question 23

what happens in pressure coning/tonsillar herniation?

Answer 23

the cerebellar tonsils and possibly the medulla are forced through the foramen magnum
this is induced when lumbar puncture performed in cases of raised IC pressure
usually sudden resp and CVS collapse
pupils may be pin point as PNS overdrive
pons compressed, and subsequently damaged, causing neurological difficulties

Question 24

what is the locked in state, and why does it occur?

Answer 24

as parts of reticular formation respons for consciousness lie above mid-pons, a lesion just below this e.g. pontine haemorrhage may disrupt descending activating pathways, so ptnt alert and awake, although mute and quadriplegic. Oculomotor pathways often remain intact so patient may only be able to communicate through blinking.

Question 25

why must a lumbar puncture NOT be done in cases of raised IC pressure?

Answer 25

will cause cerebello-tonsillar herniation, as pressure gradient created down SC as CSF would be give access to atmos pressure, so cerebellar tonsils forced through foramen magnum= coning.

Question 26

what system activates the cerebral cortex, as occurs in arousal and wakefulness?

Answer 26

ascending reticular activating system (ARAS)

Question 27

what does the body accumulate during the day which makes you want to go to sleep?

Answer 27

adenosine | *caffeine blocks adenosine receptors

Question 28

examples of discrete nuclei embedded in white matter which constitute the reticular formation diffuse modulating system?

Answer 28

raphe nucleus locus ceruleus ventral tegmental= all in brainstem and basal nucleus of Meynert= in basal forebrain

Question 29

neurotransmitter associated with locus ceruleus?

Answer 29

noradrenaline projections involved in regulation of attention, cortical arousal, and sleep-wake cycle, and learning, memory, anxiety and mood. NA increases brain responsiveness and speeds information processing.

Question 30

neurotransmitter associated with raphe nuclei?

Answer 30

5-HT (serotonin) those near pontomedullary junction are nucleus raphe magnus= projects to SC for modulation of slow pain. in rostral pons and midprain project to thalamus, limbic system, and cerebral cortex. Projections involved in sleep-wake cycle, and in control of mood, and certain types if emotional behaviour, especially aggression.

Question 31

characteristics of REM sleep?

Answer 31

rapid eye movements decreased tone in almost all muscles so that we don't act out our dreams, except external ocular muscles and diaphragm, descending inhibition of motor neurones muscle twitches HR fluctuations, irregular HR and resp rate, and BP, resp, body temp, miosis, penile erection, and clitoral engorgement BMR increased dreaming EEG patterns similar to that of wakefulness= paradoxical disturbed by alcohol

Question 32

charaacteristics of non-REM sleep?

Answer 32

``` absence of rapid eye movements reduced body movements decreased HR and BP, body temp and cerebral blood flor basal metabolic rate reduced active body, inactive brain sleep walking restorative neuroendocrine= 95% of pit hormones released ```

Question 33

why is ACh fully active in REM sleep?

Answer 33

allows information processing, can sort through memories

Question 34

what is the decorticate response?

Answer 34

cortex is effectively isolated from the lower brain and SC due to severe injury to head or a large infarct which destroys the connections between the thalamus and the cortex. Cerberal hemispheres, thalamus or internal capsule may be damaged. Lower limbs extend but arms flexed as brainstem reticular inhibiting centres are intact. Patient will be unconscious but able to respond to painful stimuli= decorticate responses. Hands are clenched into fists and feet turned inwards, also known as mummy baby. descending tracts e.g. rubrospinal (flexor muscle tone) and reticulospinal (automatic movements) from red nucleus in midbrain and reticular formation in brainstem respectively, intact, no inhibition on their function. May be seen in certain classes of people living with disability.

Question 35

what is the decerebrate response?

Answer 35

marked increase in muscle tone with involuntary tonic extension of upper and lower limbs. head arched back occurs if damage affects lower parts of brain/brainstem, so lose inhibition from reticular formation on descending motor tracts. Patients respond by reflexive extension to pain. Damage, in particular, at level of red nucleus at mid-collicular level. It is characteristic of pontine damage It is commonly seen in uncal or tonsilar herniation Decerebrate posturing is only seen in the acutely ill.

Question 36

when is decerebrate posturing commonly seen?

Answer 36

in uncal or tonsilar herniation | so only seen in the acutely ill

Question 37

why is uncal/transtentorial herniation a life-threatening development, and what signs may the patient have on examination?

Answer 37

pressure on brainstem breathing centres patient may have difficulty breathing, mid-point or dilated non-reactive pupils and ptosis due to oculomotor nerve damage. usually reduced consciousness and decerebrate rigidity= upper and lower limbs in involuntary tonic extension as loss of inhibition on descending motor tracts from reticular formation in brainstem.

Question 38

importance of cholinergic neurones in pons and midbrain, forming part of reticular system?

Answer 38

these project to thalamus and regulate excitability of thalamic nuclei. Those in the basal nucleus of Meynert project to areas of cerebral cortex and play major role in cortical excitability, memory and learning. Degeneration of these in Alzheimer's may be resonsible for their impaired cognitive functioning.

Question 39

which areas of reticular formation are associated with dopamine production?

Answer 39

substantia nigra= dopaminergic projections to caudate nucleus and putamen, degeneration results in Parkinson's disease. Ventral tegmental area= dopaminergic neurones to accumbens, amygdala, and prefrontal cortex. Increased dopaminergic activity in accumbens nucleus caused by psychostimulant drugs e.g. amphetamines and cocaine coincides with its reward and pleasure functions.

Question 40

where are the neurones located that chiefly regulate REM sleep?

Answer 40

at midbrain-pontine junction

Question 41

where are neurones located that chiefly regulate NREM sleep?

Answer 41

anterior hypothalamic nucleus in hypothalamus, preoptic area and medulla 95% of pituitary hormones are released in NREM sleep so not having enough sleep damages homeostasis. anterior hypothalamic sleep centre can facilitate sleep by inhibiting arousal centres in posterior hypothalamus, so bilateral lesions of anterior hypothalamic sleep centre results in insomnia.

Question 42

where do lesions occur that interrupt ascending reticular activating system causing a coma?

Answer 42

paramedian tegmental lesions in rostral midbrain

Question 43

various functions of reticular formation?

Answer 43

``` sleep regulation motor control cardio/resp control autonomic functions motivation and reward ```

Question 44

function of ascending reticular activating system?

Answer 44

=projections of reticular formation in brainstem which is responsible for keeping us awake, filters out unimportant sensory info, and is inhibited by hypothalamic sleep centres (anterior hypothalamic sleep centre?) *Taking LSD switches off filtering system so signals and clearer, more intense, get hallucinations, can't cope with vol of info.

Question 45

what inhibits the ascending reticular activating system?

Answer 45

hypothalsmic sleep centres alcohol sleeping tablets

Question 46

what is happening within the ascending reticular activating system when we are awake, and in REM sleep?

Answer 46

stimulation up to cortex from thalamus inhibitory pathway inactive, so no inhibition on thalamo-cortical projections ACh neurones sensitise thalamus to sensory signals brain active

Question 47

what is happening within ascending reticular activating system in non-REM (slow wave) sleep?

Answer 47

no excitation to thalamus and cortex, ACh neurones quiet, so they can't inhibit the inhibitory interneuone, this is therefore active, inhibiting thalamo-cortical projections. however, cerebral cortex is capable of overiding pathway e.g. in stress, which keeps you awake, =+ve feedback mechanism.

Question 48

what is EEG?

Answer 48

algebraic sum of electrical activity, both inhibitory and excitatory, of neurones from scalp.

Question 49

characteristics of EEG waveforms when awake with eyes open?

Answer 49

desynchronised high frequency, low amplitude electrical activity all over brain as responding to lots of different stimuli, in different directions so can cancel each other out so very low amplitude

Question 50

how doe EEG waveforms change between NREM and REM sleep?

Answer 50

NREM starts off with theta waves in stage 1, which have lower amplitude than alpha waves. As progress through stages of NREM sleep, amplitude becomes greater and frequency less, so stage 4= delta waves, but in REM sleep, looks like you're awake with eyes open= low amplitude high frequency waveform.

Question 51

what is obstructive sleep apnoea?

Answer 51

loss of tone of upper resp tract muscles in sleep e.g. palatal muscles, closure of airways, patient actually stops breathing- 1 min or more, waking them up in sleep repetitively, so end up tired during day. Snore. RFs= obesity, smoking.... can use continuous +ve airway pressure therapy to treat- keep airways open

Question 52

what is parasomnia?

Answer 52

sleep paralysis*

Question 53

what is hypersomnia?

Answer 53

daytime sleepiness e.g. with OSA, or narcolepsy= sudden and spontaneous episodes of sleep at any time during day, begins with REM phase of sleep.