Blood Supply to the Central Nervous System Flashcards

1
Q

What percentage of cardiac output goes to the brain? What percentage of oxygen consumption?

A

10-20%

20%

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2
Q

What percentage of liver glucose does the brain use?

A

66%

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3
Q

State the two main sources of blood supply to the brain?

A

Vertebral arteries (posteriorly)

Internal carotid arteries (anteriorly)

  • Circle of willis and cerebral arteries
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4
Q

State the major artery that the vertebral arteries branch off and describe the path of the vertebral arteries to the brain.

A

Subclavian artery

The vertebral arteries pass through the transverse foramina of the cervical vertebrae and through the foramen magnum into the brain

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5
Q

Draw the circle of Willis.

A

DO NOT FORGET the superior cerebellar artery and the anterior inferior cerebellar arteries

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6
Q

State the names of the venous sinuses that are at the top and bottom of the falx cerebri.

A
  • Superior sagittal sinus
  • Inferior sagittal sinus
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7
Q

What is the name given to the place where all the sinuses meet?

A

Confluence of sinuses

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8
Q

What are the four main features of venous drainage in the brain?

A
  • Cerebral veins
  • Venous sinuses
  • Dura mater
  • Internal jugular vein
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9
Q

What connects the inferior sagittal sinus to the confluence of sinuses?

A

Straight sinus

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10
Q

What vessel does the inferior sagittal sinus join with to form the straight sinus?

A

Great cerebral vein

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11
Q

Which sinus ascends to join the confluence of sinuses?

A

Occipital sinus

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12
Q

Which two sinuses run along the temporal bone?

A

Superior petrosal sinus

Inferior petrosal sinus

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13
Q

Which main sinus drains into the internal jugular vein through the jugular foramen?

A

Sigmoid sinus

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14
Q

Which sinus connects the confluence of sinuses to the sigmoid and superior petrosal sinuses?

A

Transverse sinus

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15
Q

Which sinus runs along the sphenoid and parietal bones?

A

Sphenoparietal sinus

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16
Q

Which sinuses run on either side of the pituitary stalk?

A

Anterior and posterior intercavernous sinuses

17
Q

Which extension of dura mater separates the cerebellum from the inferior portion of the occipital lobe?

A

Tentorium cerebelli

18
Q

Define Stroke.

A

=CVA - cerebrovascular accident

A rapidly developing focal disturbance of brain function of presumed vascular origin that lasts more than 24 hours

19
Q

Define Transient Ischaemic Attack (TIA).

A

A rapidly developing focal disturbance of brain function of presumed vascular origin that resolves completely within 24 hours

20
Q

What percentage of strokes are caused by infarction and what percentage are caused by haemorrhage?

A

85% infarction

15% haemorrhage

21
Q

State two causes of occlusions.

A

Thrombus - blood clots

Embolus - plugging of small vessels by material from larger vessel e.g. atherosclerotic debris

22
Q

Describe the perfusion fields of the different cerebral arteries to the brain.

A
  • The ANTERIOR cerebral artery supplies the medial part of both hemispheres
  • The MIDDLE cerebral artery extends laterally and emerges through the lateral fissure between the frontal and temporal lobes – it supplies the front 2/3 of the lateral part of the hemisphere
  • The POSTERIOR cerebral artery supplies the medial and lateral parts of the posterior part of the hemisphere
23
Q

Describe the location of the leg in the motor and sensory homunculus compared to the arm.

A

Leg is more MEDIAL

24
Q

Describe the features of a disturbance in the anterior cerebral artery.

A
  • Contralateral hemiplegia in the LEG more than the arm
  • Disturbance of intellect and executive function and judgement (abulia)
  • Loss of appropriate social behaviour
25
Q

Describe the features of a disturbance in the middle cerebral artery.

A

This is a CLASSIC STROKE:

  • Contralateral hemiplegia in the ARM more than the leg
  • Contralateral hemisensory deficits
  • Hemianopia
  • Aphasia (can’t speak) – left-sided lesion of the middle cerebral artery will result in aphasia because the language centres are more on the left side than the right
26
Q

Describe the features of a disturbance in the posterior cerebral artery.

A

Supplies the occipital lobe, which is where the primary visual cortex is located so:

Visual defects such as -

    • homonymous hemianopia
    • visual agnosia (unable to recognise what you are seeing)
27
Q

Which parts of the brain are involved in speech and understanding language?

A

Broca’s area – speech

Wernicke’s area – understanding language

28
Q

What are lacunar infarcts?

A
  • Small spaces (lacunae) that appear in the brain due to small vessel occlusion
  • The clinical deficit is dependent on the location of the small vessel occlusion
  • Hypertension can cause lacunar infarcts
29
Q

State the four types of haemorrhagic stroke and their likely causes.

A
  1. Extradural – rapid onset – caused by trauma
  2. Subdural – slow onset – caused by trauma
  3. Subarachnoid – usually caused by ruptures aneurysms
  4. Intracerebral – usually due to spontaneous hypertensive rupture of small vessels
30
Q

What is the difference between the dura in the vertebral column compared to the brain?

A

The dura in the vertebral column has ONE layer whereas the dura in the skull has TWO layers

31
Q

What are the two layers of dura in the skull called?

A

Periosteal and Meningeal

32
Q

What is the name given to the fold of dura that extends between the medial surfaces of the two hemispheres?

A

Falx Cerebri

33
Q

Why are extradural haemorrhages more rapid onset than subdural haemorrhages?

A

Extradural haemorrhages are caused by rupture of a meningeal ARTERY (high pressure) whereas subdural haemorrhages are caused by rupture of veins in the skull

34
Q

What is infarction?

A

Degenerative changes which occur in tissue following occlusion of an artery

35
Q

What is cerebral ischaemia?

A

Lack of sufficient blood supply to the nervous tissue resulting in permanent damage if the blood flow is not restored quickly

This is both a BLOOD and OXYGEN supply problem.

36
Q

Which arteries have the largest perfusion fields in the brain?

A

Middle cerebral arteries

37
Q

Which cerebral artery supplies the frontal lobe?

A

Anterior cerebral artery