Blood brain barrier and CSF

function of Cerebrospinal fluid (CSF)

gives buoyance to CNS structures

Protects CNS from blows and other trauma

Nourishes brain and carries chemical signals

Blood brain barrier

helps maintain stable environment from brain

separates neurons from some bloodborne substances

Composition of blood brain barrier

• Continuous endothelium (squamous cells) of capillary walls

• Thick basal lamina around capillaries

• Feet of astrocytes

  • They provide signal to endothelium for formation of tight junctions

Functions of blood brain barrier

• Selective barrier that allows

  • Nutrients to move by facilitated diffusion

  • Metabolic wastes, proteins, toxins, most drugs, and small nonessential amino acids to pass

  • Allows any fat-soluble substances to pass, including alcohol, nicotine, and anesthetics 

  • K+ is denied