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brain and behaviour > blood supply to the brain > Flashcards

blood supply to the brain Flashcards

1
Q

how much of the body weight is the brain?

A

2%

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2
Q

how much of cardiac output, body O2 and total glucose does the brain use?

A

15% of cardiac output, uses 20% of body O2 and 25% of total body glucose

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3
Q

what is the average brain blood flow?

A

46mL/100g of brain/minute

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4
Q

how long does it take for anoxia to lead to unconsciousness?

A

20 seconds

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5
Q

how is blood flow to the brain regulated?

A

auto-regulation

the brain is more sensitive to high CO2 levels than low O2 levels through central chemoreceptors

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6
Q

how are arteries in the brain different to those in the body?

A

more thin walled, easily blocked/distorted/ruptured

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7
Q

how are veins in the brain different to those in the body?

A

no valves, thin walled, no muscles/elasticity to help return –> drainage relies on gravity

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8
Q

how much of the total cerebral blood flow do the internal carotids make up?

A

80%

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9
Q

how much of the total cerebral blood flow do the vertebral arteries make up?

A

20%

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10
Q

explain the path of the subclavian arteries to the vertebral arteries?

A

subclavian arteries –> transverse foramen of cervical vertebrae –> foramen magnum –> join to form basilar artery

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11
Q

what do the vertebral arteries supply?

A

most of brainstem and posterior 1/3 of cerebral hemispheres

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12
Q

why are the anterior and posterior communicating arteries normally closed?

A
  • Right and left internal carotid arteries supply their respective halves of the brain and keeps pressure the same
  • Communicating arteries only open when there’s a difference in pressure in pathologies
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13
Q

how much of the population is the normal circle of willis seen in?

A

34.5%

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14
Q

name some variations of the circle of willis

A
  • Missing posterior communicating artery – doesn’t affect blood flow. Only becomes problem if one artery is blocked.
  • Missing/small anterior communicating/cerebral artery
  • Abnormal origin of posterior cerebral arteries from ICA
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15
Q

how much of the brain does the anterior circulation supply?

A

anterior 2/3

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16
Q

what are the main branches of the internal carotid artery?

A

opthalmic
posterior communicating
middle cerebral artery
anterior cerebral artery

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17
Q

what does the opthalmic artery supply?

A

supplies the orbit, retina, optic nerve, choroid. Connects to the external carotid artery

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18
Q

what does the posterior communicating connect?

A

connects carotid and vertebral artery system.

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19
Q

what does the middle cerebral artery supply?

A

supplies the basal ganglia (needed in coordination of movement) and internal capsule (made of white matter tracts - striate arteries), lateral 2/3rds of cerebral cortex (frontal, parietal and occipital lobes)

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20
Q

what does the anterior cerebral artery supply?

A

Internal capsule, medial side of frontal and parietal lobes. Anastomose with MCA

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21
Q

what parts of the cerebral cortex does the MCA supply?

A

the frontal, parietal and the top half of the temporal lobe

o Primary motor, primary somatosensory, speech, language and understanding

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22
Q

what part of the cerebral cortex does the ACA supply?

A

supplies medial wall of the cerebral hemisphere

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23
Q

where does the MCA travel?

A

between the parietal and temporal lobe

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24
Q

what branches does the MCA give of and where do they go?

A

lenticulostriate branches (internal capsule, basal ganglia)

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25
Q

what does the primary motor cortex do?

A

upper motoneurons found here

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26
Q

what does the primary somatosensory cortex do?

A

integration centre for ascending tracts

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27
Q

what does Broca’s area do?

A

pre-motor cortex for speech (where speech is produced)

28
Q

what does Wernicke’s area do?

A

integrating and understanding what has been spoken to

29
Q

what does the primary auditory centre do?

A

where sound is processed (temporal lobe)

30
Q

how much of the brain does the posterior circulation supply?

A

posterior 1/3 of the brain

31
Q

what are the branches of the posterior circulation?

A

vertebral, basilar and posterior cerebral artery

32
Q

what are the branches of the vertebral artery and what do they supply?

A

meningeal - falx cerebri
anterior/posterior spinal arteries
postrior inferior cerebellar arteries - cerebellum and dorsal medulla of brainstem

33
Q

what are the branches of the basilar artery and what do they supply?

A

o Anterior inferior cerebellar artery: cerebellum, lateral medulla.
o Pontine arteries: supply the pons.
o Superior cerebellar arteries: supplies superior cerebellum

34
Q

what does the posterior cerebral artery supply?

A

o Inferior and medial aspects of temporal and occipital cortex
o Thalamus and posterior internal capsule
o Midbrain

35
Q

what does the posterior cerebral artery anastomose with?

A

MCA

36
Q

why is PICA most likely to be blocked by an embolus/blood clot?

A

one of the first branches of the posterior circulation

37
Q

what spinal tract does PICA not affect?

A

corticospinal tract

38
Q

what cranial nerves are found near the arteries in the brain?

A

VI passes underneath the AICA and III comes out at the joint of the basilar and posterior cerebral arteries and SCA

39
Q

where do the superficial cerebral veins cross?

A

the subarachnoid space

pierce the dura as they enter the intercranial venous sinuses

40
Q

what are arachnoid granulations and what are they for?

A

allow CSF to drain into venous blood of sinuses but prevent backflow of blood into sub-arachnoid space

41
Q

how are dural sinuses made?

A

between the periosteal and meningeal layers

42
Q

what blood vessels supply the dural sinuses?

A

superficial cerebral veins

43
Q

which sinus does the majority of blood in the brain drain into?

A

superior saggital sinus

44
Q

where is the inferior saggital sinus found?

A

runs across length of head. Drains into confluence of sinuses into right transverse sinus.

45
Q

describe the venous drainage system in the brain

A

inferior saggital –> straight –> transverse –> sigmoid

46
Q

what is the cavernous sinus?

A

large collection of thin walled veins

where the ICA comes in - makes an acute bend so its seen twice

47
Q

why is the ICA seen twice?

A

makes an acute bend

48
Q

where is the cavernous sinus found?

A

either side of the pituitary gland

49
Q

what effect can a pituitary adenoma have on the cavernous sinus?

A

pituitary adenoma can push into the cavernous sinus and compress CN 3

50
Q

which cranial nerves pass through the cavernous sinus?

A

3, 4 and 6

51
Q

why do spinal arteries need reinforcement and what do they receive reinforcement from?

A

small so they need reinforcement from lumbar and intercostal arteries to meet metabolic demands

radicular arteries from intercostal in the thoracic region
lumbar arteries in the lumbar region

52
Q

what is the biggest reinforcing artery?

A

Great segmental medullary artery (artery of Adamkiewicz)

53
Q

what level is Great segmental medullary artery (artery of Adamkiewicz) found? where is it found?

A

T9

• Found on left in 65% of population reinforces circulation to 2/3rds of spinal cord

54
Q

what complication can arise during surgery for aortic aneurysm?

A

may lose all sensation and voluntary movement inferior to level of occlusion bc of blockage of the reinforcing arteries bc the spinal arteries aren’t sufficient

55
Q

what are the types of cerebrovascular incidents/accidents?

A

• 2 types; extradural or subdural – depends whether the bleed is in or out of the dura

56
Q

what are the major causes of stroke?

A

atherosclerosis, hypertension, aneurysm, elderly, head injury, alcholics, arteriovenous malformation

57
Q

what are the 3 types of cerebral aneurysms?

A

saccular
fusiform
berry

58
Q

how many people develop a brain aneurysm? who is more at risk?

A
  • 1 in 15 people develop a brain aneurysm (not necessarily will rupture – then risk arises)
  • Women at higher risk 3:2
59
Q

why are cerebral arteries at risk of aneurysms?

A

• Arteries are so thin –> easy to distort, especially at junctions between arteries (e.g. posterior cerebral artery to basilar)

60
Q

what are symptoms of an MCA stroke?

A

 Global aphasia – inability to understand what’s being said and produce meaningful speech (not in grammatical order)
 Sensorimotor loss on contralateral face, upper limb and trunk – not the legs (anterior cerebral)

neglect syndrome

61
Q

what are symptoms of ACA stroke?

A

o Contralateral sensorimotor loss below waist (legs)
o Urinary incontinence
o Personality defects (frontal lobe is affected)
o Split-brain syndrome (corpus callosum is affected – right brain and left brain don’t communicate with each other)

62
Q

what are symptoms fo PCA stroke?

A

o Contralateral homonymous hemianopsia
o Reading and writing deficits
o Impaired memory

63
Q

what is a transient ischaemic attack?

A

• Temporary loss of brain function (<30 mins) -Sudden onset but resolves within 24 hrs

64
Q

what are TIAs a warning sign of?

A

heart attack or stroke

65
Q

what are TIA symptoms of the anterior circulation?

A

 Motor weakness
 Hemi-sensory loss
 Dysarthria
 Transient monocular blindness

66
Q

what are TIA symptoms of the posterior circulation?

A

Vertigo, Diplopia, Ataxia, Amnesia

brain and behaviour (24 decks)

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