Blood Supply

Question 1

What are the demands of the brain in term of Blood and Glucose?

Answer 1

2% of body weight

10-20% of Cardiac output

20% of O₂ Consumption

66% of Liver Glucose

• Basically its very vunerable

Question 2

What are the brains two sources of blood?

Answer 2

Internal Carotid Arteries (Front)

Vertebral Arteries (Back)

Question 3

Where do Cerebral Arteries originate?

Answer 3

The branch off the Circle of Willis

Question 4

What does the External Carotid Supply?

Answer 4

The Face

Question 5

Where doe the Vertebral Arteries originate and how do they snake their way into the brain?

Answer 5

Branch off the Subclavian Arteries

Make their way up through the Transverse foramina in the cervical vertebrae then though the Foramen Magnum

Question 6

Label the Circle of Willis:

Answer 6

Question 7

Where do the Middle Cerebral Arteries travel?

Answer 7

Through the fissure between the Frontal, Parietal and Temporal Lobes

Question 8

What is the significance of the Anterior and Posterior Communicating Arteries making Willis circular?

Answer 8

So if one side gets blocked, there is still another route for blood to travel

Question 9

Name the structures through which Blood leaves the brain:

Answer 9

Cerebral Veins

Venous Sinuses

Dura Mater

Internal Jugular Vein

Question 10

What is the Superior Sagittal Sinus?

Answer 10

A Venous Sinus housed between the two folds of the dura at the top of the brain in the sagittal plane (dur)

The place where CSF drains back into the venous system

Question 11

Where is the Inferior Sagittal Sinus?

Where does it go?

Answer 11

Runs along the bottom of the dural fold

Runs backwards and joins the Superior SS at the
Confluence of the Sinuses

Question 12

Define Stroke:

Answer 12

Rapidly developing focal disturbance of brain function of presumed vascular origin lasting more than 24 hours

Question 13

What are the two main types of stroke and what are there incidences?

Answer 13

Infarction: 85%

Haemorrhagic: 15%

Question 14

Define TIA:

Answer 14

Transient Ischaemic Attack

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

Question 15

What is Infarction?

Answer 15

Degenerative changes that occur in tissue following occlusion of an artery

Question 16

What is Cerebral Ischaemia?
What is it caused by?

Answer 16

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

Due to Hypoxia/Anoxia

Question 17

What are the causes of Occlusions?

Answer 17

Thrombosis:
Formation of a Thrombus (Blood clot)

Embolism:
Plugging of small vessel by material carried from larger vessel (e.g. thromboembolism from heart of atherosclerotic debris from carotid)

Question 18

What is the Epidemiology of Stroke?

Answer 18

3rd most common cause of death (100,000/yr UK)

50% of survivors permanently disabled

Risk Factors:
Age
HPT
Cardiac Disease
Smoking
DM

Question 19

What is the perfusion field of the middle cerebral artery?

Answer 19

Supplies the front 2/3 of the lateral part of the Hemisphere

Question 20

What is the perfusion field of the Posterior Cerebral Artery?

Answer 20

Supplies the medial and lateral 1/3 of the posterior part of the hemisphere

Question 21

What is the Perfusion Field of the Anterior Cerebral Artery?

Answer 21

Supplies the medial part of the hemisphere

Question 22

What is the characteristic set of symptoms in a disturbance of the Anterior Cerebral Artery?

Answer 22

Paralysis of the contralateral leg

Disturbance of intellect, executive function and judgement
(Abulia - absence of willpower)

Loss of appropriate social behaviour

Question 23

What is the characteristic set of symptoms in a disturbance of the Middle Cerebral Artery?

Answer 23

Classic Stroke

Contralateral Hemiplegia - More arms than legs

Contralateral hemisensory defects

Hemianopia - Blindness over half the field of vision

Aphasia (Left sided)

Question 24

What is the characteristic set of symptoms in a disturbance of the Posterior Cerebral Artery?

Answer 24

Visual defects (Occipital lobe):

Homonymous hemianopia - Loss of the same side of vision in both eyes
Visual agnosia - not recognising

Question 25

What are Lacunar Infarcts?

Answer 25

Strokes that cause small holes - Lacunae - to appear in brain tissue when parts of the tissue die

Question 26

Where do Lacunar Infarcts occur? Why?

Answer 26

Deep structures As a result of small-vessel occlusion - the symptoms are therefore totally dependent on the anatomical location

Question 27

What are the four main types of Haemorrhagic stoke? What causes each type?

Answer 27

**Extradural** - Trauma (Immediate effects) **Subdural** - Trauma (Delayed effects) **Subarachnoid** - Ruptured Aneurysms **Intracerebral** - Spontaneous hypertensive rupture of small vessels

Question 28

What is the difference between the Dura in the Skull and Vertebral column?

Answer 28

Vertebral Column has a single layer of dura with fat between bone and dura Skull has two layers of dura (mostly stuck together) - Periosteal and Meningeal

Question 29

What is the name of the fold of Dura that extends between the medial surfaces of the two hemispheres? What structure is it part of?

Answer 29

Falx Cerebri The superior sagittal sinus is on top of it

Question 30

What do you find in the gap of the dural layers? | (not blood)

Answer 30

Arachnoid Granulation - Bursts of subarachnoid space that protrude into the SSS CSF leaks through holes in the arachnoid membrane and enter the SSS

Question 31

What is the reason the onset of symptoms of Extra and Subdural Haemorrhages differ?

Answer 31

Extradural - rupture of **high pressure meningeal artery** Subdural - Rupture of **low pressure Veins** in the skull