CSF & Blood Supply to the Brain

Question 1

Blood flow pathway: Internal carotid ==> somatosensory cortex ==> jugular vein

Answer 1

Internal carotid → Anterior cerebral artery → Anterior communicating →superior sagital sinus → confluence of sinuses → transverse sinus → sigmoid sinus → jugular vein

Question 2

Blood flow pathway: “foot” region vs. “hand” regions of somatosensory

Answer 2

• foot = Internal carotid → Anterior cerebral artery → Anterior communicating →superior sagital sinus → confluence of sinuses → transverse sinus → sigmoid sinus → jugular vein
• hand = Internal carotid → middle cerebral artery → superior sagital sinus → confluence of sinuses → transverse sinus → sigmoid sinus → jugular vein

Question 3

Blood flow pathway: left vertebral artery ==> R frontal lobe w/occlusion of an internal carotid

Answer 3

L Verterbral → Basilar → R. Posterior → R. Posterior communicating → R. Anterior

Question 4

Components of the Circle of Willis

Answer 4

Question 5

Meninges layers & characteristics @ CNS

Answer 5

• pia = single cell layer closely covering outside of CNS tissues
• arachanoid = loose, spongy layer between the pia and dura
  
  • filled with CSF
• dura = leathery layer, applied closely to the cranium

Question 6

Meninges layers & characteristics @ Spinal column

Answer 6

• dura = outermost layer, tough protective coating
  
  • epidural space = between dura and bone
    
    • contains adipose tissue + blood vessels
• arachnoid = spiderweb-like
  
  • subarachnoid space = between arachnoid & pia
    
    • contains CSF
• pia = delicate, tightly adhered to spinal cord

Question 7

Ventricles characteristics

Answer 7

• ventricles = fluid-filled spaces inside the brain
  
  • result of brain development from a single, folded neural tube
• lateral, third, & fourth ventricles
• CSF is formed and flows through the ventricles

Question 8

Flow of CSF through the ventricles

Answer 8

• CSF is formed @ lateral ventricles ==> interventricular foramen ==> third ventricle ==> cerebral aqueduct ==> fourth ventricle
• fourth ventricle ==> subarachnoid space via two lateral and one caudal aperature ==> blood via arachnoid granulations

Question 9

Hydrocephalus definition

Answer 9

• increasing intracranial fluid pressure due to retention of CSF
• can be caused by an obstruction of flow w/in the ventricle or a failure to reabsorb CSF

Question 10

Ependymal cells @ ventricles vs. Ependymal cells @ choroid plexus

Answer 10

• ventricular ependymal = leaky
• choroid plexus ependymal cells = tight jxns

Question 11

Location of formation of CSF

Answer 11

• choroid plexus
• capillaries w/in brain lack tight jxns ==> fluid diffuse across pia and actively transported across ependymal cells into CSF

Question 12

Volume/rate of CSF production

Answer 12

• rate = 500 ml/day
• volume @ brain/spinal cord = 125 ml

Question 13

Communicatings vs. Non-communicating hydrocephalus

Answer 13

• communicating = CSF into subarachnoid space but not reabsorped properly
• non-communicating = CSF is obstructed from entering the subarachnoid space (e.g. @ interventricular foramen or cerebral aqueduct)