MCQ Quiz

Q1. Normal cerebral blood flow (CBF) in an adult is best described as:

25–30 ml/100 g brain/min

50–65 ml/100 g brain/min

90–110 ml/100 g brain/min

150 ml/100 g brain/min

Explanation:
Normal adult CBF is approximately 50–65 ml per 100 g of brain tissue per minute.

Q2. Although the brain constitutes only ~2% of body weight, it receives approximately what percentage of resting cardiac output?

5%

10%

15%

25%

Explanation:
Despite its small mass, the brain receives about 15% of resting cardiac output due to high metabolic demand.

Q3. Cerebral perfusion pressure (CPP) is defined as:

Mean arterial pressure − intracranial pressure

Intracranial pressure − mean arterial pressure

Mean arterial pressure ÷ cerebral vascular resistance

Cerebral blood flow × vascular resistance

Explanation:
CPP represents the pressure gradient driving cerebral blood flow and equals MAP − ICP.

Q4. Cerebral blood flow remains relatively constant due to autoregulation within which MAP range?

40–100 mmHg

50–120 mmHg

70–160 mmHg

60–140 mmHg

Explanation:
Cerebral autoregulation maintains stable CBF between MAP values of approximately 60–140 mmHg.

Q5. A sudden increase in cerebral perfusion pressure triggers which immediate vascular response?

Vasodilation via metabolic control

Vasoconstriction via myogenic reflex

Opening of K⁺ channels

Inhibition of nitric oxide release

Explanation:
Increased CPP stretches vascular smooth muscle, triggering a myogenic vasoconstrictive response.

Q6. A 70% rise in arterial PCO₂ causes approximately what change in cerebral blood flow?

25% increase

50% increase

100% increase

No change

Explanation:
A 70% rise in arterial PCO₂ approximately doubles CBF due to hydrogen ion–mediated vasodilation.

Q7. The primary mechanism by which CO₂ increases cerebral blood flow is:

Increase in hydrogen ion concentration causing vasodilation

Direct relaxation of vascular smooth muscle

Increased oxygen extraction

Activation of sympathetic nerves

Explanation:
CO₂ forms carbonic acid, increasing H⁺ concentration, which directly dilates cerebral vessels.

Q8. Cerebral tissue PO₂ begins to significantly increase CBF when it falls below:

40 mmHg

35 mmHg

25 mmHg

30 mmHg

Explanation:
A drop in cerebral tissue PO₂ below ~30 mmHg triggers vasodilation to preserve oxygen delivery.

Q9. Which substance released from astrocytes causes cerebral vasodilation?

Neuropeptide Y

Nitric oxide

Serotonin

Endothelin-1

Explanation:
Astrocytes release nitric oxide, potassium ions, adenosine, and arachidonic acid metabolites causing vasodilation.

Q10. Mild to moderate sympathetic stimulation of cerebral vessels causes:

Marked reduction in CBF

Complete loss of autoregulation

Little change in CBF

Cerebral hyperperfusion

Explanation:
Autoregulation overrides mild–moderate SNS effects, maintaining near-normal CBF.

Q11. Gray matter has approximately how much greater blood flow than white matter?

Four times

Twice

Equal

Half

Explanation:
Gray matter metabolic rate and capillary density are about four times higher than white matter.

Q12. Brain capillaries are less “leaky” primarily because they are:

Fenestrated

Lined by squamous epithelium

Surrounded by pericytes only

Supported by astrocytic (glial) feet

Explanation:
Astrocytic end-feet support brain capillaries and contribute to the blood–brain barrier.

Q13. The most common pathological cause of ischemic stroke is:

Vasculitis

Arteriosclerotic plaque with thrombosis

Cardioembolic arrhythmia

Venous sinus thrombosis

Explanation:
Most strokes result from arteriosclerotic plaques activating clot formation and blocking arteries.

Q14. Left middle cerebral artery (MCA) occlusion classically causes:

Aphasia and contralateral spastic paralysis

Visual field loss only

Pure sensory stroke

Ipsilateral facial paralysis only

Explanation:
Left MCA infarction affects Broca’s and Wernicke’s areas and motor cortex, causing aphasia and contralateral weakness.

Q15. Posterior cerebral artery occlusion most commonly results in:

Aphasia

Hemiplegia

Contralateral homonymous hemianopia

Loss of pain sensation

Explanation:
PCA infarction damages the occipital cortex, producing visual field defects.

Q16. Total volume of cerebrospinal fluid (CSF) in adults is approximately:

50 mL

150 mL

300 mL

500 mL

Explanation:
The total CSF volume in adults is about 150 mL, despite daily production of ~500 mL.

Q17. CSF is primarily produced by:

Arachnoid villi

Ependymal cells of spinal cord

Cerebral capillaries

Choroid plexuses of the ventricles

Explanation:
CSF is formed mainly by choroid plexuses, especially in the lateral ventricles.

Q18. Which CSF component is approximately 40% lower than plasma?

Potassium

Sodium

Chloride

Bicarbonate

Explanation:
CSF potassium concentration is about 40% lower than plasma, crucial for neuronal stability.

Q19. CSF normally flows into venous sinuses when CSF pressure exceeds venous pressure by:

0.5 mmHg

1.0 mmHg

1.5 mmHg

5 mmHg

Explanation:
Arachnoid villi act as pressure-dependent valves opening at ~1.5 mmHg above venous pressure.

Q20. Non-communicating hydrocephalus is most commonly caused by obstruction at the:

Foramen of Monro

Fourth ventricle outlets