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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 brain

A
  • Brain is 2% of body weight
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2
Q

what is the glucose, cardiac and oxygen input into the brain

A
  • Receives 15% of cardiac output and uses 20% of total body oxygen and 25% of total body glucose
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3
Q

how much time of anoxia leads to unconsciousness int he brain

A
  • 20 seconds of anoxia leads to unconsciousness

- 5 minutes and greater leads to permanent unconsciousness

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4
Q

describe the blood vessels in the brain

A
  • Arteries – these are thin walled, easily blocked, disorted or ruptured
  • Veins, no valves, thin walled, no muscles of elasticity to help return
    Flow regulation by auto-regulation
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5
Q

describe normotensive cerebral blood flow

A
  • In Normotensive cerebral blood flow – 50ml per 100g of brain tissue per min if cerebral perfusion pressure between 60-160mmHg
  • This causes lower oxygen and higher carbon dioxide which leads to increased flow, only a small amount of increase carbon dioxide causes an increase in flow – relies on gravity to drain venous return out of the skull
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6
Q

what are the two blood supplies to the brain

A

these are the internal carotid (80%) and vertebral arteries (20%)

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7
Q

what is the anterior circulation of the brain and what does it supply

A
  • 80% of the total cerebral blood flow is done by the internal carotids –
  • they carry out the anterior circulation
  • they go through the cavernous sinus
  • provides most of the blood supply to the cerebral cortex
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8
Q

what is the posterior circulation of the Brian

A
  • 20% comes from the vertebral arteries

- this supplies the brainstem, cerebellum and a little part of the cerebral cortex

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9
Q

what is the name of the blood supply to the brain

A

circle of willis

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10
Q

what makes the circle of willis the circle of willis

A
  • They have communicating arteries that communicate between the anterior and posterior system and this creates the circle of willis
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11
Q

normally the collateral..

A

circulation is not open and you do not need it between the two systems
- therefore the anterior and posterior communicating are closed

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12
Q

why is blood from the right side not go into the left side of the brain and vis versa

A
  • It does not transimit across from the right to the left side, this is because the pressure is the same from the right and left side,
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13
Q

when is the anterior communicating artery involved

A
  • when there is a problem with either the right and left cerebral arteries
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14
Q

describe the collateral circulation to the brainstem

A
  • The blood flow already has kind of a collateral circulation, this is because there are right and left vertebral arteries that merge to form the basilar
  • if one vertebral artery is blocked the whole of the brainstems still has a blood stem as it only needs one vertebral artery to supply it (expect the medulla)
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15
Q

how much of the population is the classic circle of willis seen in

A

34.5%

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16
Q

when is collateral circulation open

A

Collateral circulation should only open when there is a pressure difference

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17
Q

what are the things that can go wrong with the blood supply to the brain

A
  • Missing posterior communicating artery – doesn’t affect under normal circulations, only becomes a problem if you are blocking one of the blood supplies
  • Missing or small anterior communicating or anterior cerebral artery
  • Abnormal origin of posterior cerebral arteries from ICA
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18
Q

describe the blood supply to the brain

A
  • you have two vertebral arteries
  • these join together and form a basilar artery
  • the vernetral arteries also give of the posterior spinal and anterior spinal artery
  • they also give of the posterior inferior cerebellar artery (PICA)
  • The basilar artery gives of the anterior inferior cerebellar artery (AICA)
  • The basilar artery gives of the superior cerebellar artery as well
  • the last part of the basilar is the posterior cerebral artery
    (there are three cerebral arteries these are the posterior, middle and anterior)
  • there is a posterior communicating artery between the posterior cerebral artery and middle cerebral artery
  • the internal carotid artery leads into the middle cerebral artery
  • the anterior cerbreral artery branches of these
  • anterior communicating artery connects the two anterior cerebral arteries
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19
Q

what are the four main branches of the ICA internal carotid artery

A
  • ophthalmic
  • posterior communicating
  • middle cerebral artery
  • anterior cerebral artery
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20
Q

what does the ophthalmic artery do

A
  • it supplies the orbit and retina and optic nerve
  • it connects to the external carotid artery
  • it is seen in the ophthalmoscope
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21
Q

what does the posterior communicating artery do

A

– Connects carotid and vertebral artery system

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22
Q

the middle cerebral artery is a continuation of…

A

the ICA

23
Q

what does the middle cerebral artery do

A

– it supplies Basal ganglia and internal capsule (striate arteries), lateral 2/3rds of cortex, lateral wall of the cerebral cortex, internal nucleus frontal, lateral and parietal

24
Q

what does the anterior cerebral artery do and what does it anatomise with

A

– it supplies Internal capsule, medial wall side of frontal and parietal lobes
- supplies the corpus callous .
– Anastomose with MCA
– Anatomise at the top of the lateral wall of the cerebral cortex with the MCA

25
Q

what does the middle cerebral artery give of

A
  • it goes from the partial and temporal and gives of lenticulostraite vessels
26
Q

what do the lenticulostriate vessels supply

A
  • they are the blood supply to nuclei that are involved in movement and coordination, such as the the internal capsule
27
Q

what is the blood supply of the internal capsule

A

lenticulostriate vessels of the MCA

28
Q

what are these areas supplied with

  • primary motor cortex
  • primary somatosensory
A

MCA

29
Q

what does the vertebral arteries supply

A

– Supplied by Dorsal medulla of brainstem – PICA- posterior inferior cerberallar artery

30
Q

when do the vertebral arteries merge into the basilar artery

A

– Merge into the basilar at the medullarypons junction

31
Q

what does the basilar supply

A

– Goes over the Pons and supplies it

– cerebellum

32
Q

where does the basilar artery divide into the posterior cerebral artery

A

at midbrain level

33
Q

what does the posterior cereal artery supply

A

– Inferior and medial aspects of temporal and occipital cortex
– Thalamus and posterior internal capsule supplied by it
– Midbrain

34
Q

describe the superficial venous drainage that happens in the brain

A
  • Superficial cerebral veins cross the subarachnoid space
  • Bridging veins pierce dura as they enter intracranial Dural venous sinuses – mainly superior sagittal sinus they also cross into other Dural sinuses
  • CSF drains back into these
35
Q

what is the main venous drainage in to

A

superior saggiata sinus

36
Q

what are dural sinuses made up of

A

the dura mater

37
Q

what allows the flow of the CSF into the dural sinuses

A
  • Arachnoid granulations allow CSF to flow into venous blood of sinuses but prevent back-flow of blood into sub-arachnoid space
38
Q

what artery goes through the cavernous sinus

A

internal carotid artery

39
Q

what does the cavernous sinus drain

A
  • the base of the skull
40
Q

what happens if the pituitary tumour continues to grow

A
  • Above it is the optic chiasm
  • Between it is the pituitary gland, therefore if you have a pituitary adenoma it pushes out and compresses the optic chiasm, if it continues to grow it will push into the cavernus sinus
  • this can compressor cranial nerve III
41
Q

what helps supply the spinal cord

A
  • there is reinforcing blood vessels that help supply the spinal cord arteries (anterior and posterior spinal arteries)
    • Great segmental medullary artery (artery of Adamkiewicz) on left in 65% of population reinforces circulation to 2/3rds of spinal cord, this happens at around T9-T11, it is the largest of the reinforcing arteries,
42
Q

what is the largest reinforcing artery in the Spinal cord

A

Great segmental medullary artery (artery of Adamkiewicz)

43
Q

what happens during an aortic aneurysm

A
  • Patients undergoing surgery for an aortic aneurysm may lose all sensation and voluntary movement inferior to level of occlusion – due to the reinforcing arteries
  • Severe drop in BP for 3-6 mins may be reduce or stop blood flow from the segmental medullary to anterior spinal artery
44
Q

what are the two types of haemotoma

A

extradura - middle meneigneal artery

subdrua - venous bridging veins

45
Q

what are the major causes of stroke

A 
–	Atherosclerosis
–	Hypertension
–	Aneurysm
–	Elderly
–	Head injury (trauma)
–	Alcoholics
–	Arteriovenous malformation
46
Q

what are the 3 types of cerebral aneurysm

A

– saccular, fusiform, berry

47
Q

describe the statistics of cerebral aneurysm

A
  • Can get subarachnoid
  • 1 in 15 will develop a brain aneurysm
  • Women are at higher risk 3:2
48
Q

what happens if you get a stroke in the anterior cerebral artery

A
  • Contralateral sensorimotor loss below the waist
  • Urinary incontinence
  • Personality defects
  • Split brain syndrome
49
Q

what happens if you get a stroke in the posterior cerebral artery

A
  • Contralateral homonymous hemianopsia
  • Reading and writing deficits
  • Impaired memory
50
Q

what is wallenbrug syndrome

A
  • it is a syndrome that is effected by the lateral medullary PICA
51
Q

describe the symptoms of Wallenberg syndrome

A

– Vertigo, nystagmus, nausea and vomiting, dysarthia, dysphonia, loss of pain and temp in body (contralateral), loss of pain and temp in face (ipsilateral), loss of gag reflex (nucleus ambiguus)
– Horner syndrome (ipsilateral)

52
Q

what are TIAs

A

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

53
Q

what are the warning signs of heart attack or stroke

A

number of TIAs
– 4-8% in 1st month
– 12-13% in 1st year
– 24-29% in 5 years

54
Q

what are the symptoms of TIAs

A 
–	Anterior circulation
•	Motor weakness
•	Hemi-sensory loss
•	Dysarthria
•	Transient monocular blindness
–	Posterior circulation
•	Vertigo
•	Diplopia
•	Ataxia
  • amnesias

Brain and Behaviour (34 decks)

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