Cerebrovascular System

Question 1

Importance of CVS

Answer 1

Blood supplies brain with nutrition (glucose & oxygen)
Removes carbon dioxide from nerve cells
Brain requires constant and uninterrupted flow

Blood flow interruption:
5-8 seconds = unconsciousness
20-25 seconds = stop electrical activity in area
4-6 minutes = irreversible brain damage

Question 2

Vascular Basics

Answer 2

Arteries carry oxygenated blood to tissues/organs; Veins return depleted blood to heart/lungs
Capillaries perform O2/Co2 gas exchange in lungs (alveolar sacs)

Blood = oxygen supply; dependent upon respiration and circulatory system

Question 3

Vascular Systems in Brain

Answer 3

2 major blood suppliers to brain – carotid (outer) and vertebral (inner) arteries

Carotid: begins with the common carotid; divides into external and internal carotid

Internal carotid forms 2 cortical arteries; close to Broca’s area

• Anterior Cerebral (ACA)
• Middle Cerebral (MCA)

Vertebral Basilar: begins with vertebral artery and merges to form the basilar artery; will join the Circle of Willis
-Basilar splits into the two Posterior Cerebral Arteries (PCA); supplies deep tissues and occipital lobe

Question 4

Circle of Willis

Answer 4

Wreath-shaped circle on ventral side of brain; Cranial nerves wrapped in all these blood vessels

Connects the carotid and the vertebral-basilar systems

Equalizes the blood flow to both sides of the brain; the safety net (compensatory circulation); can make up for blockage to areas above the circle

However, 80% of strokes occur in the circle of Willis; a lot of pressure pushed thru circle opposite a blockage

Question 5

Frontal Lobe Blood Supply

Answer 5

Lateral Surface: Middle Cerebral Artery (MCA)
Medial Surface: Anterior Cerebral Artery (ACA)
Inferior Surface: Middle and Anterior Cerebral Arteries

Important Areas: Broca’s Area, pre-motor cortex

Question 6

Parietal Lobe Blood Supply

Answer 6

Lateral Surface: Middle Cerebral Artery (MCA)
Medial Surface: Anterior Cerebral Artery (ACA)

Important Areas: Primary Motor Cortex, Primary Sensory cortex

Question 7

Temporal Lobe Blood Supply

Answer 7

Lateral Surface: Middle Cerebral Artery (MCA)
Medial Surface: MCA, PCA, posterior communicating & anterior choroidal
Inferior Surface: Posterior Cerebral Artery

Important Areas: Wernicke’s Area, primary auditory cortex

Question 8

Occipital Lobe Blood Supply

Answer 8

Lateral Surface: Posterior Cerebral Artery
Medial Surface: Posterior Cerebral Artery

Important Areas: Primary visual cortex

Question 9

Types of strokes:

Answer 9

Ischemic/Thrombosis – blood clot, stopped bloodflow

Transient Ischemic Attack – similar to ischemic, transient (moving); clot develops but does not completely occlude; holds for a period but then breaks away; often a precursor to a larger stroke

Aneurysm – deformity of vessel; congenital or blockage; pressure causes bulging, ballooning effect; weakens the stretched walls, could lead to rupture; if massive, could be fatal

Hemorrhage –bleeding; caused by aneurysm, trauma (blunt force, penetrating), tumor growth

Question 10

Stroke Warning Signs

Answer 10

Sudden numbness or weakness of face, arm, or leg, especially on one side of the body

Sudden confusion, trouble speaking or understanding

Sudden trouble seeing in one or both eyes

Sudden trouble walking, dizziness, loss of balance or coordination

Sudden severe headache with no known cause

Question 11

Spinal Cord Blood Supply

Answer 11

Anterior and posterior spinal arteries branch off the vertibral artery to supply the spinal cord

Question 12

Thalamus Blood Supply

Answer 12

posteromedial, posterolateral, and choroidal

Question 13

Hypothalamus Blood Supply

Answer 13

anteromedial and posteromedial

Question 14

Caudate Nucleus Blood Supply

Answer 14

anterolateral, medial striate, and lenticulostriate

Question 15

Putamen Blood Supply

Answer 15

lenticulostriate, medial striate, and anterior choroidal

Question 16

Globus Pallidus Blood Supply

Answer 16

anterior choroidal

Question 17

Subthalamus Blood Supply

Answer 17

posteromedial

Question 18

Substantia Nigra Blood Supply

Answer 18

posteromedial

Question 19

Blood-Brain Barrier

Answer 19

Structural property of the CNS vessels formed by closely packed endothelial cells that restrict the passage of most substances to the brain; further aided by end feet of astrocytes outside the capillary

Only lipid soluable substances can cross the BBB; the BBB is not developed in infants

Aneurysm, meningitis, severe infection, sickle cell disease, congenital malformation, tumors, penetrating wounds can degrade the BBB

Question 20

Arteriosclerosis

Answer 20

Narrowing of arterial lumen owing to accumulation of lipids, fatty substances, and cholesterol along walls of blood vessels; also called atherosclerosis

Lumen – the opening in a blood vessel thru which blood flows; lined with endothelium cells which are tightly packed and control what goes in/out; muscles contract/expand

Blood pressure rises in response to plaque build-up

Question 21

Artervenous malformations (AVM)

Answer 21

Congenital vascular disorder – clump of extra venous growth; blood still flows through; higher risk for aneurysm

Smaller malformations may be surgically repaired; larger ones may not