The Brain Part 2: Blood Brain Supply & CVA

Question 1

what does the common carotid artery divide into

Answer 1

• internal carotid arteries

- external carotid arteries

Question 2

what does the internal carotid arteries divide into

Answer 2

• anterior cerebral artery
• middle cerebral artery
• posterior cerebral artery

Question 3

describe the vertebral artery + what it divides into

Answer 3

ascends in the neck through openings of cervical vertebrae
divides into:
- cerebellar arteries
- posterior cerebral arteries

Question 4

Describe the circle of willis

Answer 4

Branches of internal carotid arteries + basilar artery join to form the circle

blood is then distributed around the brain

Question 5

describe venous drainage

Answer 5

venous sinuses in the dura mater

• sinuses converge at back of skull
• sigmoid sinus on each side - to the internal jugular vein

Question 6

list the substances that move freely through the blood brain barrier

Answer 6

• blood
• gases
• water
• alcohol
• anaesthetics

Question 7

list the substances that do not move freely through the blood brain barrier

Answer 7

• antibiotics
• other drugs
• glucose
• amino acids (these 2 require carrier proteins to move across)

Question 8

describe the anatomy of the blood brain barrier

Answer 8

lipid nature = water soluble to molecules acting as barrier

• tight junctions seal the pathway
• efflux pumps extrude fat soluble molecules

Question 9

list the components of intracranial pressure within the skull

Answer 9

Brain - 80%
Blood - 12%
CSF - 8%

Question 10

how is cerebral blood flow maintained

Answer 10

• arterioles dilate to increase flow if BP drops

- arterioles constrict if BP constrict

Question 11

what happens when there is > co2 in cerebral Blood flow

Answer 11

= vasodilation to > flow + carry it away

Question 12

cerebrovascular accident

CVA

Answer 12

tissue which has died because blood supply has failed = infarct

Question 13

Describe the features of Transient Ischaemic Attack (TIA)

Answer 13

• mini stroke
• spontaneous blood restore before cell death
• symptoms disappear completely within 24 hours
• increases risk of stroke

Question 14

define thrombosis

Answer 14

obstruction of blood vessel by a clot

Question 15

define embolism

Answer 15

obstruction due to clot from elsewhere in the body

Question 16

how does an occlusive “ischaemic” stroke occur

Answer 16

• thrombosis
  or
• embolism

Question 17

describe the process petechial bleeding

Answer 17

when blood flows through damaged vessels

• depolarisation of neurone
• influx of calcium
• release of neurotransmitters
• further depolarisation + calcium influx

Question 18

what are the 2 major zones of injury within ischaemic tissue

Answer 18

1. Core Ischaemic tissue

2. Ischaemic penumbra

Question 19

Define Ischaemic Penumbra

Answer 19

a rim of mild to moderate ischaemic tissue between tissue that is normally perfused + an area of severe ischaemia. Brain cells remain viable for 7 hours.

Question 20

describe penumbral blood supply

Answer 20

collateral arteries connecting with branches of occluded vessels

• this is where pharmacological interventions are most likely to work

Question 21

define necrosis

Answer 21

severe ischaemia where neurones + glial cells die

• tissues replaced by CSF

Question 22

List the 2 different types of Oedema

Answer 22

1. Cytotoxic (cellular)

2. Vasogenic Oedema

Question 23

describe cytotoxic oedema

Answer 23

• swelling of all cellular elements of the affected area

- cells sweep within minutes

Question 24

describe vasogenic oedema

Answer 24

an increase in ISF due to increased permeability which is a local inflammatory response following damage which takes between hours and days

Question 25

define herniation

Answer 25

when an increase in pressure inside the skull causes a displace of brain tissue

Question 26

where does herniation occur through

Answer 26

occipital foramen or within skull

Question 27

how does herniation cause death

Answer 27

due to compression of blood vessels + structures such as respiratory centres of the brain stem

Question 28

where does bleeding occur within the hemorrhagic stroke

Answer 28

bleeding may occur - within brain - within surrounding meningeal spaces

Question 29

describe the presenting features of a hemorrhagic stroke

Answer 29

- nausea - vomitting - headache if haematoma absorbs; surrounding tissue regains most function

Question 30

where does an intracerebral haemorrhage occur

Answer 30

- basal ganglia - thalamus - cerebellum - pons - brainstem (deep structures)

Question 31

factors which contribute to intracerebral haemorrhage

Answer 31

- compression - increase in ICP = herniation - blood in subarachnoid space

Question 32

describe subarachnoid haemorrhage

Answer 32

"berry" aneurysm ruptures + blood goes into subarachnoid space

Question 33

list the presentation of acute stroke

Answer 33

- alteration in consciousness - headache - aphasia - facial weakness - paralysis - ataxia (poor balance) - visual loss - vertigo, double vision, vomitting

Question 34

list the 3 mechanisms of head injury

Answer 34

1. primary 2. secondary 3. tertiary

Question 35

describe a primary head injury

Answer 35

caused by impact

Question 36

describe what causes a secondary head injury

Answer 36

- cerebral oedema - haematoma - infection - increased ICP

Question 37

describe what causes a tertiary head injury

Answer 37

- hypotension | - respiratory + cardiovascular effects of primary and secondary injuries

Question 38

list the effects of increasing ICP and what part of the brain means is affected

Answer 38

- consciousness = brainstem/cerebral cortex - headache = meninges - vomiting = pressure on emetic centre in medulla

Question 39

list the clinical management of head injuries

Answer 39

- induced coma - oxygen - steroids - diuretics

Question 40

post traumatic amnesia scale

Answer 40

``` < 5 minutes = very mild 5-60 min = mild injury 1-24 hours = moderate 1-7 days = severe > 7 days = very severe ```