Cerebral blood flow

1. Cerebral Blood Flow
Dr. Sara Sadiq
(MBBS, M.Phil)

2. Cerebral Circulation
Four main arteries:
Two internal carotid arteries
Two vertebral arteries
The clinical consequences of
vascular disease in the cerebral
circulation is depend upon which
vessels or combinations of vessels
are involved.

3. Cerebral Circulation
The Circle of Willis is a grouping
of arteries near the base of the
brain which is called the Arterial
Circle of Willis.
The vertebral arteries unite to
form Basilar artery
The basilar artery and the internal
carotid artery form the circle of
Willis

7. Cerebral Blood Flow
Normal blood flow through the brain of the adult person averages
50 to 65 milliliters per 100 grams of brain tissue per minute.
For the entire brain, this amounts to 750 to 900 ml/min, or 15 per
cent of the resting cardiac output.

9. 1. Autoregulation
Cerebral blood flow is “autoregulated” extremely well between arterial
pressure limits of 60 and 140 mm Hg.
The vascular smooth muscle is highly responsive to changes in pressure, a
process called myogenic activity, that contributes to auto-regulation of
cerebral blood flow.
Regulation of Cerebral Blood Flow

10. Regulation of Cerebral Blood Flow
2. Metabolic Factors:
(1) Oxygen concentration (35-40 mmHg)
(2) Carbon dioxide concentration
(3) Hydrogen ion concentration
(Lactic acid, Pyruvic acid)

12. 3. Nervous Regulation
• Strong sympathetic innervation  superior cervical sympathetic ganglia
• The sympathetic nervous system constricts the large- and intermediate-
sized brain arteries enough to prevent the high pressure from reaching
the smaller brain blood vessels. This is important in preventing vascular
hemorrhages into the brain—that is, for preventing the occurrence of
“cerebral stroke.”
Regulation of Cerebral Blood Flow

13. Cerebral Microcirculation

14. Temporary loss of consciousness,
weakness of muscles, and inability to
stand up, caused by sudden loss of
blood flow to the brain.
Fainting is a relatively common
symptom caused by a various factors
relating to changes in blood pressure.
Fainting

16. When the blood supply to a part of the brain is blocked resulting in the death
of an area within the brain.
If a large vessel is blocked the outcome may be rapidly fatal or may lead to
very severe disability.
If smaller blood vessels are blocked the outcome is less severe and recovery
may be good.
Principal types of stroke:
1. Thrombotic
2. Hemorrhagic
3. Embolic
Stroke