chapter 25: blood supply of CNS

Question 1

the brain

Answer 1

• depends on aerobic metabolism of glucose
• most metabolically active organ of the body
• no cerabral circulation –> unconscious in 10 sec

Question 2

CVA=

Answer 2

cerebrovascular accident

occlusion: clot forming will prevent blood from flowing through

Question 3

arterial supply of the brain

Answer 3

internal carotid artery and vertebral artery

Question 4

where does internal carotid artery divide into?

Answer 4

middle cerebral artery

anterior cerebral artery

Question 5

where does vertebral artery divide into?

Answer 5

posteroir cerebral artery

Question 6

arterial circle = circle of Willis

consists of …

Answer 6

anterior communicating artery
anterior cerebral artery
middle cerebral artery
posterior communicating artery
posteroir cerebral artery

Question 7

what does the arterial circle do?

Answer 7

exchange of blood between main arteries through communicating vessels
circle provides alternative route when a clot was to occur

Question 8

venous drainage of the brain stem and cerebellum

Answer 8

• drained by veins that empty into dural venous sinusses
• external venous system with external cerebral veins lie in subarachnoid space
• internal venous system with internal cerebral veins drain central core of cerebellum and are situated beneath corpus callosum

Question 9

venous drainage of the extenal cerebral veins

Answer 9

• superoir cerebral veins empty into superior sagittal sinus
• superficial middle cerebral veins empty into cavernous sinus
• deep middle cerebral vein accompanied by anteroir cerebral vein unite in anterior perforated substance to form basal vein: empty into great cerebral veins

Question 10

venous drainage of internal cerebral veins

Answer 10

froms each lateral ventricle and continues through transverse cerebral fissure
thalamostriate vein and choroidal vein unite to form internal cerebral vein and great cerebral vein
empty in straight sinus

Question 11

blood supply of the spinal cord

Answer 11

blood received by spinal arteries is sufficient for only upper cervical segments of the spinal cord
they are reinforced at intervals

Question 12

blood brain barrier

certain substances fail to pass from blood into CNS although they did to non- nervous tissue

Answer 12

• in the blood substances are bound to plasma protein molecules and they are unable to leave normal cerebral blood vessels
• the brain and spinal cord are separated by endothelium, basal lamina and parivascular end feet of astrocytes

Question 13

the blood brain barrier is formed by …

Answer 13

• internal plamsa membranes of endothelial cells and their tight junctions
• small hydrophobic molecules can diffuse through endothelial cell membranes and cytoplasm. they are not excluded by te brain