Wk2.:intro to the BBB

What is the main function of the blood-brain barrier (BBB)?

To keep the brain's environment stable by controlling what enters from the blood

What four structures protect the brain?

Skull/vertebral column, meninges, CSF, and blood-brain barrier

What are the three meninges (from outer to inner)?

Dura mater, arachnoid mater, pia mater

What is meningitis?

Infection of the meninges

What are the two main fluid compartments of the brain?

CSF compartment (ventricles) and interstitial compartment (around cells)

What is the difference between the blood-CSF barrier and the BBB?

Blood-CSF barrier is at the choroid plexus; BBB is at brain capillaries

What cells line the ventricles and help produce CSF?

Ependymal cells

What structure produces CSF?

Choroid plexus

What is the volume of CSF in the adult brain?

125-150 mL

How does CSF composition compare to blood?

Less K+, more Na+, no protein

What are the functions of CSF?

Shock absorber, allows brain to float, removes waste

Where does CSF drain?

Into subarachnoid space, then via arachnoid villi into dural sinus (venous blood)

What is the BBB made of?

Cerebral microvascular endothelial cells with tight junctions, plus pericytes and astrocyte foot processes

How do brain capillaries differ from general body capillaries?

Brain capillaries have tight junctions (no pores); body capillaries have pores/fenestrations

What must any substance do to cross from blood into brain interstitial fluid?

Pass THROUGH the endothelial cell (not between cells)

Which glial cell helps maintain the BBB?

Astrocyte (foot processes surround capillaries)

What types of substances can cross the BBB easily?

Oxygen, CO2 (diffusion); glucose, amino acids (carrier-mediated); fat-soluble drugs

Why is it difficult to treat brain diseases with drugs?

Most drugs cannot cross the BBB

What are circumventricular organs (CVOs)?

Parts of the brain that are outside the BBB – they sense blood composition

What is the area postrema and what does it do?

A CVO in the medulla; the chemoreceptor trigger zone (CTZ) that detects toxins and causes vomiting

What is the posterior pituitary and why is it outside the BBB?

A CVO that releases hormones (oxytocin, vasopressin) into the blood

What cells isolate CVOs from the rest of the brain?

Tanocytes (tanocytic membrane)

What happens if the BBB fails?

Neurotransmitters, toxins, or K+ fluctuations enter the brain – can cause seizures, inflammation, or neuronal damage

What is the main function of tight junctions in brain capillaries?

To seal endothelial cells together, preventing uncontrolled leakage

What is the primary function of the BBB?

To maintain a stable environment for neurons

Name the three meninges.

Dura mater, arachnoid mater, pia mater

What is meningitis?

Infection of the meninges

Which glial cell helps maintain the BBB?

Astrocyte

Do brain capillaries have pores?

No – they have tight junctions

How does glucose cross the BBB?

Carrier-mediated transport (GLUT1)

What is the area postrema?

A CVO in the medulla that detects toxins and causes vomiting

What does CTZ stand for?

Chemoreceptor trigger zone

What produces CSF?

Choroid plexus (ependymal cells)

What are two circumventricular organs?

Area postrema and posterior pituitary

Why can't most drugs reach the brain?

They cannot cross the BBB

What cells isolate CVOs from the rest of the brain?

Tanocytes