Structure and Function - Week 1 Blood Supply to the Brain

Question 1

What are the properties of the brain (2)

Answer 1

High metabolic demand:
- Consumes 20% of total energy supply

Body mass
- Brain – 2% of the body mass

Question 2

Why is blood supply important to the brain? (3)

Answer 2

Neurons don’t store glucose
Loss of blood flow
- 10 sec = Loss of consciousness
- 20 sec = cessation of electrical activity
- 4-8 min = neuronal death

Question 3

Describe cerebral blood flow and metabolism (4)

Answer 3

50ml/100gm/min on avg

Grey matter higher, white matter lower

CBF determined by balance between arterial blood pressure and intracranial pressure

Hypothermia is neuroprotective – better neurological recovery

Question 4

Describe the basic circuit (5)

Answer 4

Aorta —> Arteries —> Arterioles —> Capillaries —> Venules —> Veins —> Vena cava —> Right atrium —> Right ventricle —> Pulmonary artery —> Lung capillary bed —> Pulmonary vein —> Left atrium —> Left ventricle —> Aorta

Question 5

Which arteries arise from the aortic arch? (2)

Answer 5

Left and right subclavian artery

Question 6

Which artery supplies blood to the brain? (1)

Answer 6

Internal carotid artery

Question 7

How do the arteries enter the brain? (1)

Answer 7

Through carotid canal

Question 7

What does the external carotid artery supply? (1)

Answer 7

Face muscles

Question 8

What is the carotid sinus? (4)

Answer 8

Area of bifuraction of external and internal carotid artery
Slight bulge
Has special cells in wall of artery
Senses blood pressure and any changes in blood pressure will trigger feedback loops to return blood pressure back to normal

Question 9

Which artery supplies to the posterior brain? (1)

Answer 9

Basilar artery

Question 10

What are the basilar artery branches? (2)

Answer 10

Anterior inferior cerebellar arteries (AICA)
Superior cerebellar arteries (SCA)
Pontine arteries

Question 11

What are the branches of vertebral artery? (3)

Answer 11

Anterior spinal arteries (ASA)
Posterior spinal arteries (PSA)
Posterior inferior cerebellar arteries (PICA)

Question 12

What joins the internal carotid and basilar arteries? (1)

Answer 12

Circle of Willis

Question 13

Anterior circulation is fed by what? (1)

Answer 13

Carotid artery

Question 14

Posterior circulation is fed by what? (1)

Answer 14

Basilar artery

Question 15

What happens if there is a blockage in an artery (occlusion)? (2)

Answer 15

Quality of pressure changes

The other circulation compensates for the the other to maintain blood supply to the brain (posterior compensates for anterior or anterior compensates for posterior)

Question 15

Why is there an equality of pressure ? (1)

Answer 15

No mixing of anterior and posterior circulations

Question 16

What happens if there is an occlusion in the circle of willis? (1)

Answer 16

Stops blood supply to the brain

Question 17

Describe venous outflow (4)

Answer 17

Deep veins > superficial veins > venous sinuses > jugular

Question 18

How do veins leave the brain? (1)

Answer 18

Through internal jugular vein

Question 19

What happens if the internal jugular vein is blocked? (2)

Answer 19

Start to choke a person/the blood supply
Can stop inflow of air into the lungs

Question 20

What are the large veins called? (1)

Answer 20

Sinus

Question 21

Describe anterior cerebral artery (5)

Answer 21

Smaller branch
Arises at right angles from internal carotid artery
Sits on medial surface of the brain
Supplies majority of corpus callosum

Question 22

Middle cerebral artery (3)

Answer 22

Lateral surface of the brain
75-80% of blood of anterior circulation
Individual differences in parietal supply

Question 23

Posterial cerebral artery (3)

Answer 23

Medial and inferior surface of temporal lobe Occipital 1/5th of corpus callosum (posterior)

Question 24

Supply to deep structures (3)

Answer 24

Perforating arteries All three arteries give off deep branches Right angles to main branch

Question 25

What are watershed zones? (3)

Answer 25

Territories at the border of 2 supply zones Lowest blood supply Vulnerable to ischemia or hypoxia

Question 26

Why is there a blood brain barrier? (1)

Answer 26

Neurons require stable environment

Question 27

What are the three types of fluids in the brain? (6)

Answer 27

Blood - carried into the brain through arterial system Cerebrospinal fluid - nourishing fluid that fills the ventricles of the brain and between the membranes Interstitial fluid - neural cells float around in this

Question 28

What is the neuromuscular unit? (3)

Answer 28

Muscles cells surrounding the arterioles are very closely packed - tight junctions Forms the blood brain barrier

Question 29

What are tight junctions responsible for? (1)

Answer 29

Responsible for implementing rules of entry for substances from the blood into interstitial fluid

Question 30

What is the cerebrospinal fluid (3)

Answer 30

Carries nutritious molecules required for upkeep of neuronal tissue Generated in choroid plexus Absorbed back into the system

Question 31

Rules of entry (3)

Answer 31

Lipid soluble molecules Microorganisms are not permitted Drug entry is limited

Question 32

Exception to the rules of entry (2)

Answer 32

Circumventricular organs 3rd and 4th ventricle

Question 33

What abnormalities can occur in the brain? (3)

Answer 33

Stenosis Aneurysm Arteriovenous malformation

Question 34

What is a stenosis? (1)

Answer 34

Narrowing of inside of a blood vessel

Question 35

What is an aneurysm? (1)

Answer 35

Dilatation of artery wall

Question 36

What is Arteriovenous malformation? (3)

Answer 36

Progressive reduction in size of vessels carrying blood the brain Shunting of smallest vessel/arteries Circulation drawn away from brain tissue and blood drawn from veins to arteries