Blood Supply to the N.S.

What are arteries?

Blood vessels that carry blood AWAY from the heart

What are veins?

Blood vessels that carry blood TO the heart

What are capillaries?

• Simple tubules connecting arteries & veins

• Exchange materials between blood & cells takes place here

What is the tunica intima of arteries?

• Innermost layer

• Single layer of endothelium

• Where arteriosclerosis happens

What is the tunica media in arteries?

• Middle layer

• Mostly smooth muscle

• Elastic area that veins don’t have

• Allow fro vasoconstriction & vasodilation

What is the tunica adventitia of arteries?

• Outermost layer

• Connective tissue or sheath

What are elastic arteries?

• Conduct high-pressure blood from the heart to smaller vessels

• Recoil after being stretched by blood ejected from heart

• Ex: aorta, brachiocephalic trunk, left common carotid, left subclavian

What are muscular arteries?

• Distribute blood to various body regions & organs

• Thick/smooth muscle layer in tunica media (allows for vasoconstriction & vasodilation)

• Ex: femoral artery, brachial artery, most named arteries

What are arterioles?

• Small arteries with narrow lumen & thick muscular walls

• Empty into bed of capillaries

• Regulate BP & control flow into capillaries using smooth muscle & sphincters

What are key characteristics of capillaries?

• Epithelial cells; Continuation of endothelial lining of arteries & veins

• Exchange of nutrients, metabolic waste, and O2 & CO2 take place here

What are venules?

• Smallest veins that unite to form venous plexuses

• Drain capillary beds & joint similar vessels to form small veins

What are medium veins?

• Drain venous plexuses

• Have one-way valves

• Ex: cephalic, saphenous vein

What are large veins?

• Wide bundles of longitudinal smooth muscle

• Tougher & can tolerate more force or pressure

• Well developed tunica adventitia

• Ex: superior & inferior vena cava

What is the aorta?

• Largest blood vessel

• Conducts oxygenated blood from heart to systemic circulation

Which 3 main vessels branch off of the arch of the aorta?

• Brachiocephalic trunk (right side only)

• Left common carotid artery

• Left subclavian artery

Which 4 arteries directly supply the brain from the heart?

• Right vertebral artery

• Left vertebral artery

• Right common carotid artery

• Left common carotid artery

Which posterior arteries join to create the basilar artery?

• Left vertebral artery

• Right vertebral artery

Which anterior arteries bifurcate into the internal carotid?

• Left common carotid

• Right common carotid

What do internal carotid arteries form and what % of blood flow do they supply to the brain?

• They form the internal carotid system (anterior system)

• ~80% of cerebral blood flow

What do vertebral arteries form and what % of blood flow do they supply to the brain?

• They form the basilar artery (posterior system)

• ~20% of cerebral blood flow

Why is a posterior stroke often worse?

It can affect vital functions and lead to life-long disability

What is the Circle of Willis and its purpose?

A ring of arteries at the base of the brain that provides collateral circulation in case of arterial blockage

What arteries make up the Circle of Willis?

• 2 Posterior cerebral arteries

• 2 Posterior communicating arteries

• 2 Internal carotid arteries

• 2 Anterior cerebral arteries

• 1 Anterior communicating artery

Is the middle cerebral artery part of the Circle of Willis?

No

What does the internal carotid system supply?

• Frontal & parietal lobes (anterior/medial/lateral)

• Lateral temporal lobe

• Basal nuclei

• Hypothalamus

What does the anterior cerebral artery (ACA) supply?

• Medial/Superior frontal & parietal lobes

• Pre- & Post-central gyrus

• Corpus callosum

What does the middle cerebral artery (MCA) supply?

• Lateral frontal, parietal, & temporal lobes

• Includes motor & sensory areas

What does the posterior cerebral artery (PCA) supply?

• Occipital lobe

• Medial/Inferior temporal lobes

• Thalamus

ACA stroke symptoms?

• Affects LEs more than UEs

• Medial homunculus

MCA stroke symptoms?

Affects face & UEs more than LEs

PCA stroke symptoms?

• Hemianopsia (visual field cut)

• Visual agnosia (issue with association of visuals)

• Cortical blindness (occipital lobe is dead)

• Memory loss

• Thalamic pain

• Cranial nerve issues (motor issues in eyes)

What symptoms arise from cerebellar artery strokes?

• Ataxia

• Vertigo

• Nausea/Vomiting

• Dysarthria (difficulty speaking)

• Headache

What symptoms can brainstem strokes cause?

• Eye movement/Hearing deficits

• Dysphagia

• Dysarthria

• Paralysis (uni or bilateral)

• Impairs vital functions

What are key structures of the brainstem?

• Reticular formation (arousal)

• Red nucleus

• Spinothalamic tract

• Pyramidal decussation

What are symptoms of PICA stroke/Vertebral Artery Thrombosis/Lateral Medullary Syndrome AKA Wallenburg Syndrome?

• Vertigo

• Nystagmus

• Nausea & Vomiting

• Ipsilateral limb ataxia

• Loss of pain & temperature on ipsilateral face

• Loss of pain & temperature on contralateral body

• Dysphagia & hoarseness

• Hiccups

What brain structure is primarily affected in PICA strokes?

• Lateral medulla

• Inferior cerebellum

What are key signs of AICA syndrome?

• Ipsilateral ataxia

• Vertigo, nystagmus, nausea

• Horner’s syndrome

• Impaired pain/temp

• Unilateral hearing loss

How do PICA and AICA strokes differ?

• AICA stroke includes unilateral hearing loss since it supplies the inner ear

• PICA strokes does NOT include hearing loss but often has hiccups and more prominent swallowing/speech issues

Why do symptoms overlap in ACA/MCA strokes?

• They both supply watershed areas

• Regions at the border of their territories

What are the major spinal arteries?

• Anterior spinal artery = supplies anterior 2/3 of SC

• Posterior spinal artery = supplies posterior 1/3 of SC

What does the anterior spinal artery affect?

• Motor neurons (anterior horn)

• Corticospinal tract (UMNs)

• Spinothalamic tract (pain/temp)

What does the posterior spinal artery affect?

• Dorsal columns (proprioception, 2 point discrimination)

• May spare motor function