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Neurology and psychiatry > Cortical function, dysfunction and consciousness > Flashcards

Cortical function, dysfunction and consciousness Flashcards

1
Q

What are the inputs to the cortex? (3)

A

Monoamine neurones from reticular formation, thalamus and other parts of cortex

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2
Q

What are the output cells from the cortex called?

A

pyramidal cells - an example of a pyramidal cell is an upper motor neurone.

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3
Q

Give 6 functions of the frontal lobe

A
  • motor homunculus
  • expression of speech (brocas area)
  • behaviour regulation/ judgement
  • cognition and complex mental tasks
  • eye movements
  • continence- medial motor homunculus is responsible for pelvic floor and genitals.
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4
Q

In which hemisphere is wernickes and brocas dominant in 95% of people?

A

left

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5
Q

A lesion to which lobe may lead to compulsive gambling?

A

frontal

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6
Q

Give 6 functions of the parietal lobe

A
  • sensory homunculus
  • comprehension of speech (wernickes area)
  • body image (dominated by right hemisphere)
  • awareness of external environment
  • calculation and writing
  • superior optic radiations
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7
Q

What is hemispacial neglect and what causes it?

A
  • Inability to process and perceive stimuli to one side of the body or environment (usually left)
  • Will only shave half of face, draw half of clocks, may not recognise one arm as theirs etc
  • Causes by parietal lobe lesion eg due to stroke- in most cases it is the right hemisphere which is affected
  • Right sided are rare because the right side is processed by the left and right hemispheres whereas left side is only processed by right hemisphere.
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8
Q

Give 5 functions of the temporal lobes

A
  • hearing
  • olefaction
  • memory (hippocampus found here)
  • emotion
  • inferior optic radiations
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9
Q

What functions are dominated by which hemisphere?

A

Left: language, mathematics/logic, generally more dominant in most people-> linked to control of right hand?
Right: body image, visuospacial awareness, emotion, music

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10
Q

What is the corpus callosum?

A

A bundle of white matter connecting the two hemispheres.

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11
Q

What would be the result of cutting the corpus callosum?

A
  • split brain individuals
  • questions posed to left hemisphere (right visual field) would be answered differently to when they asked it to the right
  • They also struggle to name objects presented to the left visual field as info cant go to left wernickes area for processing. They do however recognise the object.
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12
Q

Describe the language pathway for repeating a heard word?

A
  • Auditory cortex sends impulses to wernickes area for interpretation of sound impulses, so you know what words were said
  • impulses sent to brocas area via the arcuate fasciculus
  • brocas area tells motor cortex how to make the words in response
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13
Q

What is wernickes aphasia/ dysphasia/ receptive aphasia?

A
  • lesions of wernickes area due to stroke etc (usually left sided)
  • pt cannot understand what other people say or write as interpretation center lost.
  • speech is fluent as brocas area still intact but wernickes area lost so its not being told what to say properly, leading to nonsense speech
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14
Q

What is brocas/ expressive aphasia?

A

lesion to borcas area (usually left) leading to non fluent speech, pt understands what is being asked but has trouble getting it out

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15
Q

What are the two types of memory?

A

declarative (factual, explicit) and non declarative (implicit, motor skills and emotions)

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16
Q

Where are declarative and non declarative memories stored?

A

declarative- spread diffusely throughout cerebral cortex

non declarative- memories stored in cerebellum

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17
Q

How is a muscle memory created?

A

you have to change the neural firing from a conscious thought to a cerebellar pathway

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18
Q

How are memories converted from short to long term?

A

Consilidation, this is carried out by the hippocampus repeating the memory over and over again which strengthens the synapses involved in the pathway so they fire more easily- neural plasticity

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19
Q

What 3 factors increase consolidation

A
  • rehersal/ repetition
  • emotional context
  • association
20
Q

In what 3 ways does neural plasticity work to increase strength of synapses

A
  • increase number of neuronal branches
  • increase number of post synaptic receptors
  • increase amount of neurotransmitter
21
Q

What is dysarthria?

A

slow mumbled speech due to motor cortex stroke also usually has muscle weakness

22
Q

What is arousal?

A

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

23
Q

What is consciousness?

A

difficult to define but something todo with awareness of both external world and internal state

24
Q

What are the inputs to the reticular formation?

A

sensory system and cortex both excite it

25
Q

What is the reticular activating system? where does it project to?

A

Projections from the reticular formation to the basal forebrain nuclei, hypothalamus and thalamus, which increases arousal. It stimulates these areas via Ach release.

26
Q

Describe the projections of the basal forebrain nuclei, hypothalamus and thalamus after they get stimulated by the reticular formation via the RAS.

A

BFN stimulated cortex via Ach release.
Hypothalamus stimulates cortex via histamine release
Thalamus stimulates cortex via glutamate release

27
Q

Why will Ach antagonists and anti histamines make you drowsy?

A

Ach antagonists inhibit RAS, so less arousal. Antihistamines inhibit stimulation of the cortex by the hypothalamus after reticular formation activation.

28
Q

What are the 3 aspects of the GCS?

A
  • eye opening (spontanous, to sound, to pain- this is a subcortical reflex, none)
  • motor response (commands, localised to stimuli, withdraw from pain, flexor response to pain= lesion above red nuclei, extensor response to pain= below red nuclei as unadaptive)
  • verbal response (appropriate, incorrect, inappropriate, incomprehensible, none)
29
Q

How is sleep bought about?

A

Complex, but basically deactivate reticular activating system and inhibiting the thalamus so you get less cortical activity.
This is assisted by behaviours to remove sensory inputs to reticular formation (eg turning off lights)

30
Q

What are beta waves seen on EEG?

A

Irregular, high frequency (50hz) and low amplitude waves seen when someone is awake with their eyes open. It represented complex processing in brain meaning few neurones can synchronise in their firing.

31
Q

What are alpha waves?

A

Waves seen when someone is awake but with their eyes closed, they are regular due to less sensory input meaning neurones activity is decreases leading to them synchronising. The frequency is around 10hz

32
Q

Describe the EEG seen in stage 1 sleep

A

There is a background of alpha waves with the odd theta wave thrown in- theta waves are wider and taller, with a frequency of 5Hz

33
Q

Describe the EEG seen in stage 2/3 sleep

A

Theta waves dominate with the odd sleep spindle- this is a burst of high frequency waves seen due to the thalamus trying to wake you up. You also start to see K complexes- very large waves with high amplitude due to loss of almost all inputs to the cortex, allowing the neurones to all synchronise.

34
Q

Describe the EEG seen in stage 4 sleep

A

Delta waves- high amplitude, low frequency (1Hz) waves- due to slow synchronous activity of all neurones in the cortex

35
Q

What is REM sleep and describe the EEG seen?

A

This is where the cortex stimulates the visual cortex (producing dreams) so brain activity is similar to being awake. Beta waves are seen.

36
Q

What part of the brain initiated REM sleep?

A

pons

37
Q

Why is someone in REM sleep difficult to rouse?

A

there is strong inhibition of the thalamus

38
Q

Why is muscle tone lost in REM sleep?

A

Due to descending inhibition of LMNs by glycinergic fibres arising from the reticular formation and running down the reticulospinal tracts

39
Q

Give 3 possible functions of sleep

A
  • energy conservation and bodily repair
  • memory consolidation
  • clearance of extracellular debris (fluid movement in brain at night and amyloid removal)
  • resetting of CNS
40
Q

What is insomnia and give 3 causes?

A

Inability to sleep.
Usually due to anxiety or depression, also caffine, menopause, BPH, thyroid disease, alzheimers, stress, alcohol, pain, rarer= fatal familial insomnia

41
Q

What is narcolepsy?

A

Irresistible urge to nap several times throughout the day. Cause unknown but they tend to have loss of neurones in lateral wall of their hypothalamus leading to impaired orexin production.
They also tend to get sleep paralysis, hypogonic hallucinations and cataplexy (muscle paralysis triggered by emotion) more often than most.

42
Q

What is sleep apnoea?

A

Air way obstruction in night (usually due to fat neck) leading to hypoxia which keeps waking them up. Manifests as irritability, tiredness etc.

43
Q

What is brain death?

A

Widespread cortical and brainstem damage leading to a flat EEG.

44
Q

What is a coma?

A

widespread brain stem and cortical damage but disordered EEG activity detectable. Theyre unrousable and unresponsive to psychologically meaningful stimuli, there is no sleep- wake cycle detected.

45
Q

What is a persistent vegetative state?

A

Widespread cortical damage with various disordered EEG patterns. They have spontaneous eye opening but cannot track objects. Some brain stem reflexes may be intact. They do have sleep awake cycles. They have no awareness of themselves- awake but unaware.

46
Q

What is locked in syndrome? What is cause

A

Basilar/ pontine artery occlusion, leading to eye movements being preserved by all other somatic motor functions being lost from the pons down, they are aware and aware as no cortical damage.

47
Q

What could cause RAS or reticular formation damage to cause daytime sleepiness?

A

MS, alzheimers, parkinsons and tumours

Neurology and psychiatry (8 decks)

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