Blood Supply to the Nervous System

Blood Supply to the Nervous System

• 20% of cardiac output and lung oxygen goes to the brain
• Precise regulation of blood delivery is vital
• Monitoring pressure changes in internal carotids is crucial
• Monitoring respiratory gas levels is critical for brain function
• Loss of consciousness occurs within 1 minute without blood supply
• Irreversible brain damage can occur after 5 minutes without blood supply

Blood Supply Pathways

• Internal carotids supply the anterior part of the brain
• Vertebral arteries supply the posterior part of the brain
• Circle of Willis links anterior and posterior circulations
• Vertebral arteries are vulnerable in the neck region

Circle of Willis

• A complex network of arteries at the base of the brain
• Provides alternative pathways for blood flow if one artery is blocked
• Ensures a continued supply to the brain in case of blockage

Arteries of the Brain

• Vertebral arteries
• Basilar artery
• Anterior spinal artery
• Anterior cerebral artery
• Middle cerebral artery
• Posterior cerebral artery

Anterior Spinal Artery Syndrome

• Occurs due to blockage of the anterior spinal artery.
• Initial symptoms include sudden onset, often without warning.
• Symptoms include radicular pain, widespread paralysis, loss of sensation
• Gradual onset of weakness or spasticity, followed by loss of pain and temperature sensation below the level of the injury, with reflexes affected.

Posterior Spinal Artery Syndrome

• Less common than anterior spinal artery syndrome, often from blockage.
• Often related to damage or reduced blood flow to posterior spinal arteries.
• Usually results in the loss of sensation and the impaired coordination and reflexes.

Vertebro-Basilar Insufficiency (VBI)

• Reduced blood flow to the brainstem and cerebellum
• Causes a variety of symptoms including dizziness, headache, visual disturbances
• 'Beauty parlour syndrome' is a less well-known name for VBI

Cranial Nerve involvement

• Certain pontine branches effect cranial nerves V, VI, VII
• Potentially causing paralysis

Venous Drainage of the Brain

• Veins lack valves, draining into sinuses (dural walls)
• Sinuses drain into the internal jugular vein.
• Emissary veins connect scalp and skull veins with dural sinuses.
• Some facial/skull base veins drain into cavernous sinus.

Spinal Cord Circulation

• Posterior spinal artery forms a plexus, with significant collateral supply.
• Anterior spinal artery supplies the anterior two-thirds of the spinal cord.
• Radicular arteries contribute to spinal cord supply.

Cerebrovascular Disorders

• Syncope (fainting): Often related to blood pressure fluctuations.
• Vasospasm: Temporary narrowing of blood vessels (e.g., migraine, TIA)
• Infarction: Blockage of blood flow to the brain (70% of strokes)
• Haemorrhage: Bleeding in the brain (30% of strokes)

Headaches and Blood

• Symptoms of severe headache, stiff neck, altered consciousness, visual problems, and hypertension, may suggest a serious bleed.
• High-risk factors include prior head injuries, and specific medical conditions.
• If these symptoms are present, immediate medical attention is crucial.

Hemorrhages

• Subarachnoid: Burst aneurysms or congenital malformations.
• Subdural: Blooding veins of the brain
• Epidural: Common cause of bleeding middle meningeal artery due to injuries of the head.

Stroke Risk Factors

• High blood pressure
• Diabetes
• Age over 65
• Heart disease
• Oral contraceptives
• Smoking
• Transient Ischemic Attacks (TIAs)
• Symptoms like headaches, neck pain, neuro signs, and fainting.

Explore the essential pathways and mechanisms of blood supply to the brain. Learn about the significance of the Circle of Willis and the impact of arterial blockage on brain function. This quiz will test your knowledge on the critical role of blood flow in maintaining consciousness and preventing irreversible damage.