CNS Circulation, Brainstem, Cranial Nerves & CSF: Key Concepts

What is the importance of vascular supply to the CNS?

The vascular supply is critical for maintaining cellular function by providing a constant supply of oxygen and nutrients, and removing waste products. Deprivation of oxygen can lead to cellular death and neurological damage.

What are the main arteries supplying the cerebral hemispheres and cerebellum?

The internal carotid and vertebral arteries supply the cerebral hemispheres and cerebellum.

What happens to CNS tissue when deprived of oxygen?

CNS tissue can die quickly, within a few minutes, leading to brain damage.

What arteries originate from the vertebral arteries?

The posterior inferior cerebellar artery (PICA) originates from the vertebral arteries.

What arteries arise from the basilar artery?

The anterior inferior cerebellar artery (AICA) and the superior cerebellar artery (SCA) arise from the basilar artery.

What is the function of the posterior inferior cerebellar artery (PICA)?

The PICA supplies the posterior and caudal portion of the cerebellum.

What does the anterior inferior cerebellar artery (AICA) supply?

The AICA supplies the middle portion of the cerebellum.

What is the role of the superior cerebellar artery (SCA)?

The SCA supplies the superior portion of the cerebellum.

What is the Circle of Willis?

The Circle of Willis is formed by communicating arteries that allow blood from the basilar artery and internal carotid arteries to supply the cerebral hemispheres.

Which arteries are part of the Circle of Willis?

The anterior cerebral artery (ACA), middle cerebral artery (MCA), and posterior cerebral artery (PCA) are part of the Circle of Willis.

What does the anterior cerebral artery (ACA) supply?

The ACA supplies the medial surface of the frontal and parietal lobes.

What areas does the middle cerebral artery (MCA) supply?

The MCA supplies the lateral surface of the frontal, parietal, and temporal lobes.

What is significant about the posterior cerebral artery (PCA)?

The PCA supplies the inferior and medial surfaces of the parietal and temporal lobes and the occipital lobe through smaller vessels.

What structures does the vertebral artery supply?

The vertebral artery supplies the cervical spinal cord, medulla, and smaller vessels to the cerebellum.

What does the basilar artery supply?

The basilar artery supplies the pontine nuclei, cerebellum, and descending tracts of corticobulbar, corticospinal, and corticopontine fibers.

What are the consequences of a blockage in the PICA?

A blockage in the PICA would result in ipsilateral problems related to cerebellar function.

Why is it important to know the initials of the arteries supplying the cerebellum?

Knowing the initials is crucial for understanding the implications of occlusions or blockages, as they relate specifically to the cerebellum rather than the cerebral hemispheres.

What are central pattern generators in relation to cranial nerves?

Central pattern generators are neural circuits that produce rhythmic outputs, such as those involved in swallowing and respiration.

What is the role of cranial nerves in the CNS?

Cranial nerves are responsible for various functions, including sensory and motor control of the head and neck.

What is the impact of vascular insufficiency on CNS function?

Vascular insufficiency can lead to impaired oxygen delivery, resulting in neurological deficits and potential cellular death.

What is the significance of the basilar artery in relation to the cerebellum?

The basilar artery is significant as it supplies blood to the cerebellum and its associated structures.

How does the blood supply to the CNS relate to neurological health?

Adequate blood supply is essential for neurological health, as it prevents ischemia and supports cellular metabolism.

What are the neurological symptoms of a blockage in the anterior cerebral artery (ACA)?

A blockage in the ACA will produce neurological symptoms affecting the medial portion of the frontal and parietal lobes, particularly impacting the motor and sensory functions of the legs and trunk on the contralateral side.

What areas of the brain does the anterior cerebral artery (ACA) supply?

The ACA supplies the medial portion of the frontal and parietal lobes.

What is the significance of the motor and sensory homunculus in relation to the ACA?

The motor homunculus is located in the frontal lobe and the sensory homunculus in the parietal lobe, both of which relate to the leg and trunk regions of the body.

What are the effects of a blockage in the middle cerebral artery (MCA)?

A blockage in the MCA will compromise the use of the arm, hand, and oral motor regions on the contralateral side.

What areas of the brain does the middle cerebral artery (MCA) supply?

The MCA supplies the lateral surface of the frontal and parietal lobes.

What disturbances are caused by a blockage of the cerebellar arteries?

A blockage of the cerebellar arteries will produce disturbances in the grading of movement on the ipsilateral side.

What are the two main types of strokes affecting the CNS?

Ischemic strokes and hemorrhagic strokes.

What is an ischemic stroke?

An ischemic stroke occurs when blood flow is blocked, depriving neurological tissue of oxygen, often due to atherosclerosis or thrombosis.

What causes an embolic stroke?

An embolic stroke occurs when a piece of an atheroma or thrombosis breaks off and travels through the bloodstream until it blocks a vessel.

What is a hemorrhagic stroke?

A hemorrhagic stroke occurs when a blood vessel ruptures, leading to bleeding in the CNS and increased intracranial pressure.

What is the risk associated with a hemorrhagic stroke in a closed cranial system?

A hemorrhagic stroke can lead to herniation of the brainstem through the foramen magnum due to increased intracranial pressure.

What is an aneurysm?

An aneurysm is a ballooning or out-pouching of a vessel wall, which is often weaker and may leak or rupture.

How can aneurysms affect individuals?

Aneurysms can be congenital and may never bleed, or they may bleed at any time during a person's life.

What is locked-in syndrome and what causes it?

Locked-in syndrome occurs due to damage to the ventral portion of the pons, interrupting corticospinal and corticobulbar pathways, resulting in the inability to move except for vertical eye gaze.

What pathways remain intact in locked-in syndrome?

The ascending somatosensory pathways and ascending reticular activating pathways remain intact, allowing the person to be conscious but unable to respond.

What is the consequence of cellular death in strokes?

Cellular death occurs in both ischemic and hemorrhagic strokes, with the extent of damage depending on the location and severity of the stroke.

How does the size of a bleed or blockage affect its impact in different brain areas?

A small bleed or blockage in the brainstem may have more devastating effects than the same size bleed or blockage in other areas.

What is the relationship between the lumen of arteries and capillary beds?

The lumen of the arteries decreases in size as you travel towards the capillary bed.

What happens to the brain and cerebrospinal fluid (CSF) during a hemorrhagic stroke?

During a hemorrhagic stroke, blood accumulates in the closed cranial system, potentially leading to increased intracranial pressure and brain herniation.

What is the role of fatty deposits in ischemic strokes?

Fatty deposits (atheroma) can block blood flow, leading to ischemic strokes.

What are the potential consequences of a hemorrhagic stroke?

A hemorrhagic stroke can deprive neurological tissue of oxygen and create a risk for increased intracranial pressure.

What can a burst aneurysm produce?

A hemorrhagic stroke.

What are the three main arteries supplying the spinal cord?

Two posterior spinal arteries and one anterior spinal artery.

What happens to the vascular supply during a spinal cord injury?

The vascular supply is often compromised in addition to the compression or damage to the spinal cord.

What is the consequence of starving spinal cord tissue of blood?

It results in cellular death.

What areas does the posterior spinal artery supply?

The posterior region of the spinal cord, including the dorsal columns and portions of the descending lateral corticospinal tracts.

What does the anterior spinal artery supply?

The anterior or ventral portion of the spinal cord, including the anterior horn cells.

How do the anterior and posterior spinal arteries balance their pressure?

The pressure from the anterior spinal artery and the two posterior spinal arteries is balanced to supply distinct areas of the spinal cord.

What is the arterial vasocorona?

It is the structure through which the posterior and anterior spinal arteries join together to encircle the spinal cord.

What is the role of the spinal artery in relation to peripheral nerves?

The spinal artery follows along the peripheral nerve to supply it along its course.

What is the primary function of cerebrospinal fluid (CSF)?

CSF cushions the brain and spinal cord, providing protection and maintaining homeostasis.

Where is CSF produced?

In the brain by modified ependymal cells in the choroid plexus and around blood vessels along ventricular walls.

What is the pathway of CSF circulation?

From the lateral ventricles to the foramina of Monro, third ventricle, aqueduct of Sylvius, fourth ventricle, foramen of Magendie, and foramina of Luschka, then into the subarachnoid space.

How does CSF move throughout the system?

In a pulsating manner with nearly zero net flow.

How is CSF reabsorbed into the venous system?

Via arachnoid granulations.

What alternative route for CSF reabsorption has been suggested?

CSF flow along cranial nerves and spinal nerve roots into lymphatic channels.

Why is CSF reabsorption via lymphatic channels particularly significant in neonates?

Because arachnoid granulations are sparsely distributed in neonates.

What happens to blood supply at the site of a spinal cord injury?

The site of the lesion may crimp off the blood supply in one area while producing a bleed in another area.

What is the effect of vascular insufficiency in spinal cord injuries?

It may produce selective damage depending on the severity and extent of the injury.

What does the diagram of the vascular supply of the spinal cord depict?

The arrangement of the anterior and posterior spinal arteries and their supply to the spinal cord.

What is the significance of the anterior spinal artery's branch?

It supplies the lateral corticospinal tract.

What is the consistency of the vascular supply arrangement within the spinal cord?

It is a fairly consistent arrangement.

What is the anatomical relationship of the spinal arteries to the meninges?

The diagrams provide a view of where the various vessels are located relative to the meninges of the spinal cord.

What can result from bleeding into the neurological tissue?

Cellular death.

What is the approximate percentage of CSF produced by the choroid plexus?

Approximately 50-70%.

What three protein biomarkers can indicate the presence of Alzheimer's disease according to a 2010 study?

CSF amyloid beta 1-42, total CSF tau protein, and P-Tau181P.

What was the sensitivity and specificity of the biomarker test for Alzheimer's disease in the 2010 study?

The test showed 90% sensitivity but poor specificity, with 36% of control subjects testing positive.

What might explain the low specificity of the Alzheimer's biomarkers in control subjects?

The presence of developing but not yet symptomatic Alzheimer's disease in controls.

Describe the shape and location of the lateral ventricles in the brain.

The lateral ventricles are shaped like a 'C' with a horn at the end.

What is the flow path of cerebrospinal fluid (CSF) from the lateral ventricles to the subarachnoid space?

Lateral ventricles → foramina of Monro → third ventricle → cerebral aqueduct → fourth ventricle → foramen of Magendie and foramina of Luschka → subarachnoid space.

What are the four primary purposes of cerebrospinal fluid (CSF)?

1. Buoyancy, 2. Protection, 3. Chemical stability, 4. Prevention of brain ischemia.

How does CSF provide buoyancy to the brain?

It reduces the effective weight of the brain from about 1400 grams to 25 grams, allowing it to maintain density without being impaired by its own weight.

In what way does CSF protect the brain?

CSF cushions the brain tissue from injury during jolts or impacts.

What can happen if CSF cannot protect the brain during severe impacts?

It can lead to hemorrhaging, brain damage, and sometimes death.

How does CSF contribute to chemical stability in the central nervous system?

CSF rinses metabolic waste from the CNS and regulates the distribution of neuroendocrine factors.

What are the consequences of high glycine concentration in CSF?

It can disrupt temperature and blood pressure control.

What effect does high CSF pH have on a person?

It can cause dizziness and syncope (fainting).

How does CSF help prevent brain ischemia?

By decreasing the amount of CSF in the skull, which lowers intracranial pressure and facilitates blood perfusion.

What happens to CSF circulation if there is a blockage in its flow?

Increased intracranial pressure can occur, which can be fatal.

What is the reabsorption process of CSF after circulation?

CSF is reabsorbed by the arachnoid granulations into the superior sagittal sinus.

What are the three openings through which CSF exits the fourth ventricle?

The paired foramina of Luschka and the single foramen of Magendie.

Where does CSF circulate in relation to the spinal cord?

CSF circulates around the spinal cord and through the central canal of the spinal cord.

What diagrammatic flow path represents the circulation of CSF?

Lateral ventricles → interventricular foramen → third ventricle → cerebral aqueduct → fourth ventricle → foramina of Luschka and Magendie → subarachnoid space → arachnoid villi → superior sagittal sinus.

What is the significance of maintaining constant pressure within the skull and spinal cord?

It is crucial for preventing increased intracranial pressure and ensuring proper brain function.

What condition can result from excessive amounts of cerebrospinal fluid (CSF) within the cranium?

Hydrocephalus.

What are the potential causes of hydrocephalus?

Problems with CSF production, reabsorption, or blockage of circulation.

What degenerative disorder is associated with increased CSF quantities?

Alzheimer's disease.

What is normal pressure hydrocephalus?

A condition where CSF quantity increases due to a decrease in cerebral quantity.

What is increased intracranial pressure (ICP) in relation to CSF?

A condition where there is a blockage in the flow of CSF.

Where are the majority of cranial nerve nuclei located?

In the brainstem.

What is the Roman numeral for cranial nerve I?

CN I: olfactory.

What is the function of cranial nerve II?

CN II: optic, responsible for vision.

What is the function of cranial nerve III?

CN III: oculomotor, responsible for eye movement and pupil constriction.

What is the function of cranial nerve V?

CN V: trigeminal, responsible for facial sensation and mastication.

What is the function of cranial nerve VII?

CN VII: facial, responsible for facial expressions and taste.

What is the function of cranial nerve X?

CN X: vagus, responsible for autonomic functions of the heart and digestive tract.

What are bulbar symptoms?

Problems with cranial nerve function due to brainstem damage.

What are the three main functions of the brainstem?

Conduction, integrative functions, and cranial nerve supply.