1.2 Bloody supply

Question 1

Occlusion to BV in the brain for 10 seconds results in what?

Answer 1

unconsciousness

Question 2

How much O2 does brain use?

What % of CO does brain receive?

Answer 2

Brain uses 20% Oxygen

Brain receives 17% Cardiac output

Question 3

Define stroke

Answer 3

Persistent neurological deficit of vascular origin

Question 4

What are the 4 major arteries that supply the brain?

Answer 4

2 Internal Carotid Arteries (80%)

2 Vertebral Arteries (20%)

Question 5

Where do the vertebral arteries arise from and what do they supply?

Describe their pathway and include other arteries they give rise to

Answer 5

Branches of subclavian artery. Supply brainstem and spinal cord, cerebellum, inferior parts of cerebral hemispheres and parts of temporal and occipital lobes

1) ascend through transverse foramina for upper 6 cervical vertebrae
2) enter cranial cavity via foramen magnum
3) unite at lower pons to form Basilar Artery
4) Basilar artery divides into posterior cerebral arteries

Question 6

Where do the Internal Carotid arteries arise from and what does it supply?

Describe their pathway and include other arteries they give rise too

Answer 6

Arises in the neck from common carotid arteries (at C3-C4) and supplies the majority of cerebral hemispheres and eye. (anterior part of brain)

1) enters cranial cavity via carotid canal and then foramen laserum
2) travels through cavernous venous sinus (related closely to CN III,IV, VI)
3) terminates into anterior and middle cerebral arteries (ACA, MCA)

Question 7

List the 5 branches off the Internal carotid artery

Answer 7

1) Ophthalmic
2) Posterior Communicating
3) Anterior Choroidal
4) Anterior Cerebral Artery (ACA)
5) Middle Cerebral Artery (MCA) is direct continuation of ICA

Question 8

How do the vertebral and carotid circulations link each other?

What is this known as?

Answer 8

The Internal carotid (anterior) links to vertebral (posterior) circulation via posterior communicating arteries

Connections between the VA and ICA form the circle of Willis (located on the base of brain)

Question 9

Label the arteries shown on the Circle of Willis below

Answer 9

Question 10

List the exact arteries that comprise the circle of willis and state how they connect

Answer 10

Internal Carotid arteries

• ACA: connect via anterior communicating artery
• MCA: connect to PCA via posterior communicating artery

Vertebral Arteries —> form Basilar Artery

• PCA connect to MCA via posterior communicating artery

Question 11

Where in the brain do the anterior vs posterior circulations primarily supply?

Answer 11

Anterior circulation (ICA, ACA, MCA) supplies the Cerebrum 
Posterior circulation (VA) supplies the meningies and cerebellum

Question 12

Before the vertebral arteries join to form the Basilar Artery, what 3 branch do they give off and what do these supply?

Answer 12

1) Posterior inferior cerebellar arteries (PICA) –> supply parts of the cerebellum
2) Posterior spinal
3) Anterior spinal (only ONE single AS created from a branch from each vertebral artery)

The 1 anterior and 2 posterior arteries supply the spinal cord

Question 13

What branches does the Basilar artery give off? (5)

Answer 13

1) Posterior Cerebral Arteries (PCA)
2) posterior communicating
3) superior cerebellar arteries
4) pontine arteries
5) Anterior inferior cerebellar arteries (AICA)

Question 14

What are the main territories of the brain supplied by the ICA and VB?

State and indicate on the image below (inclue main branches)

Answer 14

Internal carotid: supplies the anterior surface of the brain

• ACA supplies the superior strip
• MCA supplies the superolateral surface

Vertebral branches: supplies occipital part of brain

Question 15

The PCA passes over what structure? What is the clinical revelance of this?

Answer 15

PCA passes over tentorium –> Prone to stretching and compression in raised ICP

Question 16

State which teritory belongs to which artery in this coronal section of the brain

What is the V shape structure in middle and what is its function?

Answer 16

V shape structure in middle is known as the internal capsule This is the place where all the different axons from various regions of the brain come together in tight clusters

Question 17

What arteries supply the spinal cord?

Answer 17

The anterior spinal artery supplies the anterior 2/3

The 2 posterior spinal arteries supply the posterior 1/3

Question 18

List 3 ways arterial supply to the brain can be comprimised

Answer 18

1) Vessel occlusion: embolus or thrombus
2) Haemorrhage: burst aneurysm, degeneration of vessel wall
3) Aneurysm: abnormal dilatation of vessel wall often at sites of branching

Question 19

Compare occlusion of an artery at the surface of the brain to occlusion in the Internal capsule (deeper) in the brain, explain why and the consequences

Answer 19

Chances of oclusion is unlikely in the arteries at the surface of the brain because of collateral circulation.

Size of arteries in the Internal capsule decreases, until we reach end arteries (terminal branches) which are extremely small and have no collateral circulation.

An occlusion here will lead to infarction of that part of the brain, which can subsequently lead to:

• Ischemic Stroke (87%)
• Hemorrhagic stroke (13%)

Question 20

Compare an Ischemic vs Haemorrhagic stroke?

Which produces ‘focal’ vs ‘diffuse’ brain disfunction?

Answer 20

Ischemic: Occlusion to end artery (by clot/thrombus) comprises that region of the brain and causes it to become ischemic ➞ Focal brain disfunction

Hemorrhagic: weakness in vessel wall may cause vessel to rupture leading to a brain bleed which will compress the smaller vessels ➞ Focal brain disfunction

If a Hemorrhagic stroke is large it may leak into the subarachnoid space. This will cause a subarachnoid haemorrhage and increased ICP ➞ Diffuse brain disfunction

Question 21

What is FAST?

What does specific stroke presentation depend on?

Answer 21

Signs of a stroke

• Face: one side of face drooping
• Arm: arm weakness
• Speech: speech difficulties
• Time: time to call for an ambulance

Specific stroke presentation (sign & symptoms) depend on part of brain affected

Question 22

Give 4 consequences of a stroke

Answer 22

1) Hemiplegia, monoplegia, paraplegia (sensory loss and/or motor loss)
2) cranial nerve dysfunction
3) aphasia
4) Memory loss

Question 23

Why will strokes/ neuron damage lead to permanent damage

Answer 23

because neurons are unable to regenerate, hence damage is irreversible

Question 24

An image that represents the body over the surface of the brain is known as a what?

What does it show?

Answer 24

Homunculus: helps link symptom presentation to area of the brain affected

Question 25

Describe the venous drainage of the brain incl structures involved

Answer 25

1) veins run in the subarachnoid space (do NOT follow arterial supply like other parts of the body) 2) drain into dural venous sinuses * endothelial-lined spaces between periosteal and meningeal layers of dura 3) blood in dural sinuses ultimately drains into internal jugular veins 4) IJV \> BCV \> RA

Question 26

What are the 2 layers of the Dura Mater and what is found between layers?

Answer 26

1) The menial layer 2) The periosteal layer The dural venous sinus is located between these layers

Question 27

Where do the dural sinuses join?

Answer 27

Join through the 'straight sinus' at the 'confluence of sinuses'

Question 28

Describe the superficial venous drainage of the brain

Answer 28

Superior cerebral Veins ⬇ Superior Sagittal sinuses ⬇ Straight sinus ➞ confluence ➞ transverse ➞ sigmoid ⬇ Internal jugular veins

Question 29

Describe the venous drainage of the middle and inferior cerebral veins

Answer 29

middle and inferior cerebral veins (deeper part of cerebral hemisphere) ⬇ cavernous sinus (red arrow on image) ⬇ superior and Inferior pertrosal sinuses ⬇ sigmoid sinus

Question 30

What structures do the deep cerebral veins drain and describe the pathway of drainage

Answer 30

Deep cerebral veins = Thalamus, Basal nuclei (deep subcortical structures) ⬇ Cavernous/cerebral venous sinuses ⬇ Petrosal sinuses ➞ sigmoid ⬇ Internal jugular veins

Question 31

Where do the Internal cerebral veins drain?

Answer 31

Internal cerebral veins (under corpus callosum, splenium) ⬇ Unite with opposite side to form the great cerebral vein of Galen (GCV) ⬇ GCV joins with the inferior sagital sinus to form the straight sinus ⬇ confluence ➞ transverse ➞ sigmoid ⬇ Internal jugular

Question 32

Do the dural venous sinuses have valves?

Answer 32

No

Question 33

What cell type lines the ventricular system? What are the contents of this system and where does this drain?

Answer 33

Cell type: Ependymal cells Contents: CSF secreted from the choroid plexus Pathway: CSF drains ➞ subarachnoid space ➞ through arachnoid granulations ➞ dural sinuses

Question 34

How does the ventricular system communicate with the subarachnoid space?

Answer 34

Via 3 foramina in roof of 4th ventricle

Question 35

What is the largest ventricle in the brain? What horns does this contain?

Answer 35

R and L lateral ventricles which partly extend into: * frontal lobe as the ‘frontal horn * occipital lobe as the ‘occipital horn’ * temporal lobe as the ‘temporal horn’

Question 36

What are the 4 ventricles of the brain? Include how each connects to the next and their locations

Answer 36

**R and L lateral ventricles** located in the R and L cerebral hemispheres communicate with the **third ventricle** located down the midline between two thalami via the **interventricular foramen** (of Monro) Third ventricle connects the **fourth ventricle** located in the brainstem at the **cerebral aqueduct**

Question 37

What structure separates the R and L lateral ventricles?

Answer 37

The septum pellucidum

Question 38

Arrangement of ependymal cells covering arterial loops form what structure? label it below

Answer 38

Choroid plexus

Question 39

Label CT

Answer 39

Question 40

Describe the pathway of CSF flow in the brain, begin at lateral ventricles

Answer 40

Question 41

List the 5 subarachnoid cisterns and indicate them on the image below

Answer 41

1) superior 2) cerebellomedullary 3) pontine 4) interpeduncular 5) chiasmatic

Question 42

What is the function of the BBB?

Answer 42

BBB separates brain + cerebrospinal fluid (CSF) from blood AND tightly regulates movement of ions, molecules, cells between blood & brain

Question 43

Describe the organisation (3 layers) of the BBB

Answer 43

1) layer of endothelial cells interconnected through tight junctions, NO fenestrations 2) basement membrane consisting of ➞ basal lamina of astrocytes and basal lamina of endothelial cells 3) protrusions of astrocytes ➞ pedicles, going onto the basal membrane

Question 44

List 3 important functions of the BBB

Answer 44

1) maintains homeostasis in CNS (levels of hormones, nutrients and water) 2) protects brain from endogenous & exogenous toxins (pathogens in blood) 3) prevents escape of neurotransmitters into general circulation

Question 45

Describe the organisation (3 layers) of the Blood-CSF barrier

Answer 45

1) choroidal epithelial cells ➞ secrete CSF, have microvilli Interconnected by tight junctions (which are more permeable than junctions b/w in BBB capillaries) 2) Basement membrane 3) Endothelium of pia mater capillaries containing fenestrations

Question 46

Give one way in which we can get chemicals across the BBB (ie. medicines)

Answer 46

drugs structured to trick the BBB to and allow their passage across the BBB ➞ ‘trojan horse approach’ (drugs fused with chemicals that are able to cross BBB)

Question 47

Compare capillaries in the BBB vs the Blood-CSF Barrier

Answer 47

BBB: non-fenestrated capillaries with tight junctions b/w endothelial cells Blood-CSF Barrier: fenestrated capillaries in choroid plexus

Question 48

List 4 substances that can freely cross the BBB and one substance that can cross via transport

Answer 48

Freely cross: CO2, O2, water and free forms of steroid hormones Transport: glucose

Question 49

What are circumventricular areas /organs (CVOs) of brain? List 4 of these?

Answer 49

Structures of the brain that do NOT have a BBB 1) posterior pituitary (Neurohypophysis) 2) median eminence 3) area prostrema 4) lamina Terminalis