Role of a changing membrane potential (Em) and matching blood flow with neuronal activity

Abstract

It is crucial that blood flow is matched to metabolic activity in the brain. This matching of flow to metabolism is an absolute requirement for survival in that oxygen and glucose are the primary substrates for neuronal tissue; blood is the only source for these nutrients and matching of flow to metabolic activity dictates normal physiologic regulation of brain activity. Blood flow is regulated by changes in vascular diameter which is controlled by the activation state of vascular muscle. The activation of vascular muscle is under the control of membrane potential with fine adjustments made in response to metabolites of neuronal and astrocytic environmental influences. Astrocytes sense neuronal activity, and are intimately involved in the matching of flow by sensing changes in the metabolic state of neurons. This mechanism involves release of dilators at gap junctions of astrocytic foot processes. This chapter focuses on the mechanisms responsible for local control of cerebral blood flow via changes in membrane potential in astrocytes, neurons, and vascular muscle. These cell types form the neurovascular unit and are under the control of local environmental influences, such as H+, K+, oxygen, and CO2 and other factors defined within this chapter.