Ventricular system

What are the three important components for controlling the brain extracellular fluid

Ventricular system, cerebrospinal fluid, and blood-brain barrier

What are the two fluid compartments of the brain and where are they located i

Interstitial fluid = in the brain

Cerebrospinal fluid = intraventricular and subarachnoid space

What regulates the homeostasis of the interstitial fluid and the cerebrospinal fluid compartments and the intracellular compartment of brain cells

Blood-brain barrier

Blood-CSF barrier

What forms the blood brain barrier and Blood-CSF barrier

Endothelial cells of capillaries (vascular)

Endothelial cells of choroid plexus

Cerebral ventricles; what are they, where is it located, what are they filled with, what produces/modifies what their filled with

Cerebral ventricle are a series of interconnected cavities

in the core of forebrain and brainstem

Filled with cerebrospinal fluid

produced and modified by choroid plexus

Label this diagram

What connects the two lateral ventricles

Inter-ventricular foramen of Monro

Where does the cerebral aqueduct lead to

The fourth ventricle

Choroid Plexus what is it and where does it get its blood supply from (3)

Network that secretes cerebrospinal fluid

Posterior; Anterior choroidal artery

anterior and posterior inferior cerebellar

What are the cellular make up of the choroid plexus and what do these cellular constituents form

Blood vessels and Pia = form the core of the choroid plexus and choroid epithelium

Choroid epithelium; what is it, what it forms

Specialized cells that secrete CSF to ventricles

Forms a blood-CSF barrier = prevent transport of materials from blood to CSF

How are choroid epithelial cells bound to one another

Tight junctions that separate ECF from CSF

Total CSF production per day

500mL/day

CSF forms in two sequential stages, explain them

• Ultrafiltration of plasma occurs across the capillary wall to ECF below the membran of choroid epithelial cell

• Choroid epithelial cells secrete fluid into the ventricle

CSF production occurs with a net transfer of what

Transfer of NaCl and NaHCO3 from plasma to CSF which drives water movement isosmotically

Name the two processes of how Na is secreted from the plasma to the CSF

Na-K pump in choroid plexus

Na-H and Na-HCO3 transporter

Cerebrospinal Fluid circulation

Lateral Ventricle

Interventricular foramina of Monro

Third ventricle

Cerebral aqueduct of sylvius

Fourth ventricle

Foramina of magendie and luschka

Subarachnoid space

Where is the CSF absorbed?

Venous sinuses through arachnoid granulation

What allows the absorption of CSF to the venous sinuses

Arachnoid granulations = one-way pressure sensitive valves that push CSF from Subarachnoid space to venous blood.

compare and contrast where csf and venous Blood can enter

CSF can cross into venous blood

Blood cant cross the CSF due to CSF having higher pressure than venous blood

The rate of CSF formation is NOT affected by what

CSF pressure

CSF formation remains constant no matter what the CSF pressure is

What happens when CSF pressure exceeds 70 mm H20

CSF absorption increases as CSF pressure go above 70 mm H20

Why does absorption increase when CSF pressure increased

Absorption increases as CSF pressure increases to prevent excess fluid building up in the brain.

Prevents dangerous brain conditions

What does an increase in volume od brain tissue, blood, or CSF cause

Causes an increase in Intracranial pressure could be caused by edema, tumor formation, cerebral abscess, or hematoma

Compare and contrast small and large volume changes in the brain tissue

• Small volume changes can be compensated by reducing intracranial CSF and blood volume without causing much rise in ICP pressure

• Large volumes however cant be compensated by reducing CSF leading to dangerous consequences

When large volume changes in the brain cant be compensated leading to increased ICP pressure, what does this lead to

Brain perfusion decreases leading to death or herniation

How is cerebral perfusion pressure determined

Cerebral perfusion pressure = Mean arterial pressure - intracranial pressure

What is the relationship of intracranial pressure and cerebral perfusion pressure

As ICP increases = CPP decreases meaning less blood is able to enter the brain

Lumbar puncture (spinal tap)

Procedure used to reduce ICP to normal levles

Needle inserted between fourth and fifth lumbar

Normal intracranial pressure in mm CSF or mm Hg

65 - 195 mm CSF

5-15 mm Hg

Papilledema

Optic disc swelling caused by blood build up in the optic disc by increased ICP

Decompressive hemicraniectomy

Surgical procedure that removes part of the skull to relieve brain swelling and increased ICP

Hydrocephalus

Caused by excess CSF in the intracranial cavity

What three conditions cause hydrocephalus

Excess CSF production

Obstruction of flow at any ventricles but ESPECIALLY the narrow joints or subarachnoid space

Decreased reabsorption via the arachnoid granulations

What are the narrow points obstruction can occur causing Hydrocephalus`

Interventricular foramina of Monro, the cerebral aqueduct, or the fourth ventricle

What are the two categories of Hydrocephalus

Communicating hydrocephalus = caused by impaired reabsoprtion of fluid in arachnoid granulations

Noncommunicating hydrocephalus = Caused by obstruction of flow within the ventricle system

Hydrocephalus treatment

• Ventriculostomy = a surgical procedure where a catheter is inserted into the brain’s ventricular system to drain excess cerebrospinal fluid (CSF) and relieve increased intracranial pressure (ICP).

• Ventriculoperitoneal shunt = shunt passes from the ventricle to the skull, uunder the skin and drains into the peritoneal cavity in the abdomen

Location of barrier sites in the CNS. In all these sites what are the physical barriers caused by

• The brain endothelium forming the blood-brain barrier

• The arachnoid epithelium forming middle layer of the meninges

• The choroid plexus epithelium which secretes CSF

Each physical barrier is caused by tight junction

Astrocytic endfeet

Provide a continuous covering of the capillaries and facilitate transport between cells and blood

What molecules readily cross the Blood-Brain-Barrier

CO2, O2, ethanol, caffeine, nicotine, and opioids

Entry into the brain is achieved primarily in three ways; name them

Diffusion of lipid soluble substances

Facilitative and energy dependent receptor-mediated transport

Ion channels and exchangers