In many vertebrates, neurogenesis persists throughout adulthood throughout the CNS. For example, new neurones are continuously born in all brain regions in birds, whilst lizards can very effectively regenerate the retina and spinal cord. In primates, including humans, neurogenesis in the adult is restricted to the hippocampus and subventricular zone. In both locations, the stem elements that produce neurones are astroglia. These 'stem' astrocytes have the morphology, physiology and biochem-ical/immunological markers characteristic for astrocytes: they express GFAP, form vascular endfeet, have negative resting membrane potentials, are nonexcitable, and predominantly express K+ channels. 'Stem' astrocytes differ from 'classical' mature astrocytes by specific expression of the protein nestin (a marker for neural stem cells), and some of them form cilia. Neurones born in the subventricular zone migrate to the olfactory bulb, whereas those produced in the hippocampus remain there and integrate themselves into existing neuronal networks.
'Stem' astrocytes residing in the hippocampus and subventricular zone are multipotent, as they give birth to both neurones and glia; the production of glia or neurones is under control of numerous chemical factors (Figure 7.1).
Was this article helpful?
If Pregnancy Is Something That Frightens You, It's Time To Convert Your Fear Into Joy. Ready To Give Birth To A Child? Is The New Status Hitting Your State Of Mind? Are You Still Scared To Undergo All The Pain That Your Best Friend Underwent Just A Few Days Back? Not Convinced With The Answers Given By The Experts?