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Question 1

What happens if blood flow to the brain stops for 5-10 seconds?

Answer 1

Unconsciousness occurs due to lack of oxygen shutting down brain cell metabolism.

Question 2

What are the four main arteries supplying the brain?

Answer 2

Two carotid and two vertebral arteries.

Question 3

What is the Circle of Willis?

Answer 3

A circular network at the base of the brain formed by the four main arteries.

Question 4

What are pial arteries?

Answer 4

Arteries that branch from the Circle of Willis and travel along the brain surface.

Question 5

What is the Virchow-Robin space?

Answer 5

An extension of the subarachnoid space separating penetrating vessels from brain tissue.

Question 6

Where does exchange of gases and nutrients occur in the brain?

Answer 6

In the capillaries branching from intracerebral arterioles.

Question 7

What is the average cerebral blood flow in adults?

Answer 7

50–65 ml/100 g of brain tissue/min or 750–900 ml/min for the whole brain.

Question 8

What factors regulate cerebral blood flow?

Answer 8

CO2 concentration, H+ concentration, O2 concentration, and substances from astrocytes.

Question 9

How does increased CO2 affect cerebral blood flow?

Answer 9

It increases it by forming carbonic acid, which dissociates to H+, causing vasodilation.

Question 10

What is the relationship between H+ concentration and cerebral blood flow?

Answer 10

Higher H+ leads to vasodilation and increased blood flow, helping remove acids.

Question 11

What is the brain’s O2 utilization rate?

Answer 11

Approximately 3.5 ±0.2 ml O2/100 g brain tissue/min.

Question 12

What Po2 level begins to increase cerebral blood flow?

Answer 12

Below ~30 mm Hg.

Question 13

What Po2 level can cause coma?

Answer 13

Below 20 mm Hg.

Question 14

What are astrocytes?

Answer 14

Star-shaped non-neuronal cells that support neurons and regulate blood flow.

Question 15

How do astrocytes regulate cerebral blood flow?

Answer 15

By releasing vasoactive substances in response to neuronal activity.

Question 16

What are examples of astrocyte-derived vasodilators?

Answer 16

Nitric oxide, arachidonic acid metabolites, K+, adenosine.

Question 17

How is regional cerebral blood flow measured?

Answer 17

By injecting radioactive Xe and detecting flow with scintillation detectors.

Question 18

What happens to blood flow when the hand is clenched?

Answer 18

It increases in the opposite motor cortex.

Question 19

What does reading affect in the brain?

Answer 19

Increases flow in occipital and temporal (language) cortices.

Question 20

What is BOLD fMRI based on?

Answer 20

Differences in magnetic behavior of oxy- and deoxyhemoglobin.

Question 21

What does ASL MRI do?

Answer 21

Provides a more quantitative measure of regional blood flow.

Question 22

What is cerebral autoregulation?

Answer 22

Maintaining stable blood flow between MAPs of 60–150 mm Hg.

Question 23

How does chronic hypertension affect autoregulation?

Answer 23

Shifts it to higher pressures and increases stroke risk if BP drops.

Question 24

What condition during pregnancy impairs autoregulation?

Answer 24

Preeclampsia.

Question 25

What is the role of the sympathetic nervous system in brain circulation?

Answer 25

It constricts large arteries during high MAP to prevent stroke.

Question 26

Where are capillaries denser in the brain?

Answer 26

In gray matter, where metabolic needs are higher.

Question 27

Why are brain capillaries less leaky?

Answer 27

They are supported by glial feet from astrocytes.

Question 28

What happens to arterioles in chronic hypertension?

Answer 28

They thicken and constrict to protect capillaries.

Question 29

What can happen if brain fluid protection fails?

Answer 29

Brain edema, coma, and death.

Question 30

What causes most strokes in elderly people?

Answer 30

Arteriosclerotic plaques in feeder arteries to the brain, which can activate clotting and block blood flow.

Question 31

What causes 25% of strokes?

Answer 31

High blood pressure that causes a blood vessel to burst, leading to hemorrhage and compression of brain tissue.

Question 32

What determines the neurological effects of a stroke?

Answer 32

The specific area of the brain affected by the stroke.

Question 33

What happens if the middle cerebral artery is blocked on the left side?

Answer 33

Loss of Wernicke’s area, Broca’s area, and motor control areas in the left hemisphere, causing speech loss and spastic paralysis on the right side.

Question 34

What happens if a posterior cerebral artery is blocked?

Answer 34

Infarction of the occipital pole and loss of vision in both eyes in the half of the retina on the same side as the stroke.

Question 35

What is the effect of stroke involving the midbrain blood supply?

Answer 35

Blocks nerve conduction between brain and spinal cord, causing sensory and motor abnormalities.

Question 36

What are silent strokes?

Answer 36

Small infarcts or microbleeds in small brain vessels with subtle cognitive decline, detectable by MRI or CT.

Question 37

What percent of people over 80 have had a silent stroke?

Answer 37

Approximately 25%.

Question 38

What is the total volume capacity of the cerebral cavity?

Answer 38

1600 to 1700 ml.

Question 39

How much cerebrospinal fluid (CSF) is in the cerebral cavity?

Answer 39

About 150 ml.

Question 40

Where is cerebrospinal fluid located?

Answer 40

In brain ventricles, cisterns, and subarachnoid space around the brain and spinal cord.

Question 41

What is a major function of cerebrospinal fluid?

Answer 41

To cushion the brain within the skull by allowing it to float.

Question 42

What is contrecoup injury?

Answer 42

Injury on the side opposite the impact due to skull acceleration creating a vacuum that collapses.

Question 43

What areas of the brain are prone to contusions from severe blows?

Answer 43

Poles and inferior surfaces of frontal and temporal lobes.

Question 44

Can coup and contrecoup injuries occur without direct head impact?

Answer 44

Yes, due to rapid acceleration or deceleration such as in shaken baby syndrome or vehicle accidents.

Question 45

How much CSF is formed daily?

Answer 45

About 500 ml/day.

Question 46

What is the main source of CSF?

Answer 46

Choroid plexuses in the ventricles, especially the lateral ventricles.

Question 47

Describe the pathway of CSF flow from the lateral ventricles.

Answer 47

Lateral ventricles → third ventricle → aqueduct of Sylvius → fourth ventricle → foramina of Luschka and Magendie → cisterna magna → subarachnoid space → arachnoidal villi → venous blood.

Question 48

What causes secretion of CSF from the choroid plexus?

Answer 48

Active transport of sodium ions, which draws chloride ions and water by osmosis.

Question 49

What are the ion characteristics of CSF?

Answer 49

Osmotic pressure ~ plasma; Na+ ~ plasma; Cl− 15% > plasma; K+ 40% < plasma; glucose 30% < plasma.

Question 50

What are arachnoidal villi?

Answer 50

Microscopic projections of the arachnoidal membrane into venous sinuses that absorb CSF.

Question 51

What is found in arachnoidal granulations?

Answer 51

Clusters of arachnoidal villi.

Question 52

What can pass through the arachnoidal villi into venous blood?

Answer 52

CSF, proteins, red and white blood cells.

Question 53

What are perivascular spaces?

Answer 53

Spaces between brain vessels and pia mater that follow vessels into the brain.

Question 54

What is the lymphatic function of perivascular spaces?

Answer 54

Transport protein, fluid, and debris from brain tissue to subarachnoid space for removal via arachnoidal villi.

Question 55

What role do perivascular spaces play in brain infection?

Answer 55

They transport dead white blood cells and debris out of the brain.

Question 56

Do humans have true brain lymphatic vessels?

Answer 56

Still uncertain; reported in rodents but not confirmed in humans.